CN120826501A - Crucible, method for manufacturing β-type gallium trioxide single crystal substrate using the same, and β-type gallium trioxide single crystal substrate - Google Patents

Abstract

The present invention provides a crucible for growing beta-type gallium trioxide single crystals, wherein the crucible has a thickness of 1mm or more and 10mm or less, the maximum inner diameter of the crucible is 100mm or more, the composition of the crucible is stabilized zirconia containing both or either yttrium oxide and calcium oxide, the inner peripheral surface side surface of the crucible is coated with a thermal spray coating film containing both or either rhodium and platinum, the thickness of the thermal spray coating film is 100 [ mu ] m or more and 500 [ mu ] m or less, and the stabilized zirconia contains at least 12.0 mass% or more and 15.5 mass% or less of yttrium oxide or 10.2 mass% or more and 11.4 mass% or less of calcium oxide.

Description

Crucible, method for producing beta-type gallium trioxide single crystal substrate using same, and beta-type gallium trioxide single crystal substrate

Technical Field

The present invention relates to a crucible, a method for producing a beta-type gallium trioxide single crystal substrate using the crucible, and a beta-type gallium trioxide single crystal substrate.

Background

Japanese patent application laid-open publication No. 2016-079080 (patent document 1), japanese patent application laid-open publication No. 2017-193466 (patent document 2), japanese patent application laid-open publication No. 2021-031367 (patent document 3), japanese patent application laid-open publication No. 2021-031379 (patent document 4), japanese patent application laid-open publication No. 2020-059633 (patent document 5), ganchuan et al, japanese society for crystal Growth, vol.44, no.4 (2017), 44-4-03 (non-patent document 1) disclose a method of growing a beta-type gallium (hereinafter also referred to as "beta-Ga ₂O₃") single crystal by using a crucible made of a platinum-rhodium alloy (hereinafter also referred to as "Pt-Rh alloy"), a crucible made of a platinum-iridium alloy (hereinafter also referred to as "Pt-Ir alloy"), a Vertical Boat for a die (Vertical Boat) method, or a limited Edge feed film Growth (EFG, edge-DEFINED FILM-fed Growth method), or the like. Japanese patent application laid-open No. 2000-129465 (patent document 6) discloses a method of coating a surface of a refractory substrate such as ceramic with platinum or a platinum-based alloy by thermal spraying.

Prior art literature

Patent literature

Patent document 1, japanese patent laid-open publication 2016-079080;

patent document 2, japanese patent application laid-open No. 2017-193466;

Patent document 3, japanese patent application laid-open No. 2021-031367;

patent document 4, japanese patent application laid-open No. 2021-031379;

Patent document 5 Japanese patent laid-open No. 2020-059633;

Patent document 6 Japanese patent application laid-open No. 2000-129465.

Non-patent literature

Non-patent document 1, ganchuan et al, japanese society for crystal growth, vol.44, no.4 (2017), 44-4-03.

Disclosure of Invention

The crucible of the invention is a crucible for the growth of beta-type gallium trioxide single crystals. The crucible has a thickness of 1mm to 10mm. The maximum inner diameter of the crucible is more than 100 mm. The composition of the crucible is stabilized zirconia containing both or either of yttria and calcia. The inner peripheral surface of the crucible is coated with a thermal spray film containing rhodium and/or platinum. The thickness of the thermal spray coating film is 100 μm or more and 500 μm or less. The stabilized zirconia contains at least 12.0 mass% or more and 15.5 mass% or less of the yttrium oxide or 10.2 mass% or more and 11.4 mass% or less of the calcium oxide.

Drawings

Fig. 1 is a schematic diagram illustrating main parts of a single crystal growth apparatus used in a method for producing a β -type Ga ₂O₃ single crystal substrate according to the present embodiment and a crucible according to a first embodiment used in the single crystal growth apparatus.

Fig. 2 is an enlarged cross-sectional view of a main part of a crucible illustrating a second embodiment used in the single crystal growth apparatus of fig. 1.

Fig. 3 is an enlarged cross-sectional view of a main part of a crucible illustrating a third embodiment used in the single crystal growth apparatus of fig. 1.

Fig. 4 is an enlarged cross-sectional view of a main part of a crucible illustrating a fourth embodiment used in the single crystal growth apparatus of fig. 1.

Fig. 5 is an enlarged cross-sectional view of a main part of a crucible illustrating a fifth embodiment used in the single crystal growth apparatus of fig. 1.

Fig. 6 is a flowchart showing an example of a method for manufacturing a β -type Ga ₂O₃ single crystal substrate according to the present embodiment.

Fig. 7 is a schematic diagram illustrating a β -type Ga ₂O₃ single crystal substrate according to the present embodiment.

Fig. 8 is an explanatory view illustrating a hall measurement sample prepared using the central portion of the substrate in order to measure the carrier concentration in the β -type Ga ₂O₃ single crystal substrate according to the present embodiment.

Detailed Description

[ Problem to be solved by the invention ]

As disclosed in patent documents 1 to 5, non-patent document 1, and the like, it is known to grow and obtain a β -type Ga ₂O₃ single crystal using a crucible or the like composed of a Pt-Rh alloy or a Pt-Ir alloy. These crucibles made of Pt-Rh alloy, pt-Ir alloy, etc. are expensive, and the reduction of thickness is considered for the purpose of cost reduction. However, since the crucible made of Pt-Rh alloy, pt-Ir alloy, or the like is easily deformed by thermal shrinkage or the like, the crucible is broken or defective due to the β -type Ga ₂O₃ single crystal existing in the crucible at the time of crystal growth or at the time of cooling after crystal growth, and therefore, there is a problem that a desired β -type Ga ₂O₃ single crystal cannot be obtained with good yield. Especially, breakage of the crucible at the time of crystal growth is fatal to obtain a beta-type Ga ₂O₃ single crystal. The method of covering platinum or a platinum-based alloy by thermal spraying disclosed in patent document 6 does not aim to suppress breakage or chipping of a crucible or the like, and therefore does not give any suggestion about the action or effect of preventing breakage of the crucible at the time of crystal growth. Therefore, a crucible using a thin film of pt—rh alloy, pt—ir alloy, or the like has not been obtained, and it has been demanded to develop a β -type Ga ₂O₃ single crystal with a good yield by suppressing at least the occurrence of cracking, chipping, or the like at the time of crystal growth.

In view of the above, an object of the present invention is to provide a crucible capable of suppressing the occurrence of cracking, chipping, and the like at the time of crystal growth, a method for producing a beta-type gallium trioxide single crystal substrate using the same, and a beta-type gallium trioxide single crystal substrate.

[ Effect of the invention ]

According to the present invention, it is possible to provide a crucible capable of suppressing the occurrence of cracking, chipping, and the like in crystal growth, a method for producing a beta-type gallium trioxide single crystal substrate using the crucible, and a beta-type gallium trioxide single crystal substrate.

[ Summary of the embodiments ]

Hereinafter, an outline of the embodiment of the present invention will be described. The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and have completed the present invention. First, the present inventors focused on zirconia, which is a material having low thermal conductivity and stable to temperature change and being not easily deformed, as a material of a crucible to which a vertical boat method is applied. In particular, the inner peripheral surface of the crucible made of zirconia is coated with a thin film containing rhodium or platinum, for example, a thin film made of pt—rh alloy containing Rh, which can withstand the temperature (about 1800 ℃) required for the crystal growth of the β -type Ga ₂O₃ single crystal. Thus, a crucible capable of suppressing at least the occurrence of cracking, chipping, and the like at the time of crystal growth is thought. In addition, in order to obtain the single crystal with good yield, it has been found that the thickness of the crucible and the thickness of the thin film are appropriate, respectively, and the present invention has been achieved.

Next, embodiments of the present invention will be described below.

[1] The crucible according to one embodiment of the present invention is a crucible for growing beta-type gallium trioxide single crystals. The crucible has a thickness of 1mm to 10 mm. The maximum inner diameter of the crucible is more than 100 mm. The composition of the crucible is stabilized zirconia containing both or either of yttria and calcia. The inner peripheral surface of the crucible is coated with a thermal spray film containing rhodium and/or platinum. The thickness of the thermal spray coating film is 100 μm or more and 500 μm or less. The stabilized zirconia contains at least 12.0 mass% or more and 15.5 mass% or less of the yttrium oxide or 10.2 mass% or more and 11.4 mass% or less of the calcium oxide. The crucible having such characteristics can suppress the occurrence of cracking, chipping, and the like at the time of crystal growth.

[2] In the crucible of the above item [1], the thermally sprayed film is preferably composed of a platinum-rhodium alloy containing 10 to 30 mass% of rhodium. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth.

[3] In the crucible of the above [2], the thermally sprayed film preferably has voids. The porosity, which is the volume ratio of the voids in the thermal spray coating film, is preferably 30 to 50% by volume. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth.

[4] In the crucible of [2], the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. Preferably, the thermally sprayed film has pores. The porosity, which is the volume ratio of the voids in the thermal spray coating film, is preferably 10% by volume or more and less than 30% by volume. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth.

[5] In the crucible of the above [3], the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth.

[6] In the crucible of the above item [1], the thermal spray coating film is preferably composed of a first film and a second film. Preferably, the first film is coated on the surface. Preferably, the first film is composed of rhodium or a platinum-rhodium alloy containing rhodium as a main component. Preferably, the second film is coated with the first film. Preferably, the second film is made of platinum or a platinum-rhodium alloy containing platinum as a main component. The thickness of the thermal spray coating film is preferably 100 μm to 500 μm in total of the first film and the second film. This can suppress rhodium from being mixed into the beta-type gallium trioxide single crystal.

[7] In the crucible of the above [6], it is preferable that each of the first film and the second film has pores. Preferably, the first membrane porosity, which is a volume ratio of the pores in the first membrane, and the second membrane porosity, which is a volume ratio of the pores in the second membrane, are both 30 vol% to 50 vol%. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth.

[8] In the crucible of the above [6], the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. Preferably, the first film and the second film each have pores. Preferably, the first membrane porosity, which is a volume ratio of the pores in the first membrane, and the second membrane porosity, which is a volume ratio of the pores in the second membrane, are each 10% by volume or more and less than 30% by volume. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth.

[9] In the crucible of [7], the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth.

[10] A method for producing a beta-type gallium oxide single crystal substrate according to one embodiment of the present invention is a method for producing a beta-type gallium oxide single crystal substrate using the crucible according to any one of the above [1] to [9 ]. The manufacturing method includes a step of preparing the crucible, a step of obtaining a beta-type gallium trioxide single crystal by a vertical boat method using the crucible, and a step of processing the beta-type gallium trioxide single crystal to obtain a beta-type gallium trioxide single crystal substrate having a circular main surface. By the manufacturing method having such characteristics, a β -type gallium oxide single crystal substrate having a good yield and a good product yield can be obtained.

[11] The beta-type gallium oxide single crystal substrate according to one embodiment of the present invention is a beta-type gallium oxide single crystal substrate having a circular main surface. The diameter of the beta-type gallium oxide single crystal substrate is more than 100 mm. The main surface is the (001) plane of the beta-type gallium trioxide single crystal. Or the main surface is a surface having a deviation angle of more than 0 DEG and 10 DEG or less from the (001) plane of the beta-type gallium trioxide single crystal, and a deviation direction of the [010] direction or a direction orthogonal to the [010] direction of the beta-type gallium trioxide single crystal. The above beta-type gallium oxide single crystal substrate contains rhodium and iridium or both. The rhodium concentration and the iridium concentration are each less than 3 mass ppm in glow discharge mass spectrometry analysis. The beta-type gallium oxide single crystal substrate having such characteristics can be excellent in both electrical characteristics and optical characteristics.

[12] The beta-type gallium oxide single crystal substrate according to [11], wherein the beta-type gallium oxide single crystal substrate preferably has a transmittance of 70% or more with respect to light having a wavelength of 400nm or more and 430nm or less. In the hall measurement using the van der waals method, the carrier concentration measured at 25 ℃ is preferably 1×10 ¹⁷cm^-3 or more and 1.0×10 ¹⁹cm^-3 or less. This can provide further excellent electrical characteristics and optical characteristics.

Detailed description of the embodiments

Hereinafter, an embodiment of the present invention (hereinafter, also referred to as "the present embodiment") will be described in further detail, but the present invention is not limited thereto. In the following, the same or corresponding elements in the present specification and drawings may be denoted by the same reference numerals while referring to the drawings, and the same description will not be repeated. In the drawings, the scale of each component shown in the drawings is not necessarily identical to the scale of the actual component, and is appropriately adjusted to facilitate understanding of each component.

In the present specification, the expression "a to B" means the upper limit and the lower limit of the range (that is, a is not lower than a and B is not lower than B), and when a is not a unit and only B is a unit, the unit of a is the same as the unit of B. Further, in the case where the compound or the like is represented by a chemical formula in the present specification, the atomic ratio is not particularly limited, and any conventionally known atomic ratio is included, and the present invention is not necessarily limited to the stoichiometric range.

In the present specification, "yield" refers to a ratio at which a beta-type gallium trioxide single crystal can be grown to a desired thickness in a crucible without causing breakage or chipping of the crucible. In the present specification, "product yield" refers to a ratio of the mass of the beta-type gallium trioxide single crystal ingot after crystal growth in the crucible to the mass of a portion of the substrate that can be evaluated as a good product by the evaluation method described later, excluding first a region where a desired diameter cannot be obtained when processing the beta-type gallium trioxide single crystal substrate due to breakage or chipping of the crucible during cooling. Further, it can be evaluated that the larger the value of the "product yield" of the single crystal is, the less breakage, chipping, or the like is generated in the crucible in which the single crystal is grown. In the present specification, the term "main component" means a component contained in an amount exceeding 95 mass% in a composition such as an alloy.

In the present specification, the "maximum inner diameter" of a crucible means an inner diameter of the crucible at a position where the inner diameter of a ring appearing as a cross section perpendicular to the axial direction of a cylindrical crucible is maximum when the inner diameter of the ring is compared in the axial direction of the crucible. In the present invention, the crucible preferably has a structure including a cylindrical seed crystal housing portion, an increased diameter portion connected to the seed crystal housing portion, and a straight cylindrical portion connected to the increased diameter portion, for example, as will be described later. In the crucible of this type, the "maximum inner diameter" means the inner diameter of the straight tube portion.

In the present specification, the "main surface" of the β -type gallium oxide single crystal substrate means both of the two circular surfaces of the β -type gallium oxide single crystal substrate. In the above-mentioned beta-type gallium oxide single crystal substrate, it is within the technical scope of the present invention to satisfy the scope of the claims of the present invention in at least either of the two surfaces. In addition, in the present specification, the "face" used in the term "in-plane" means "main face". Further, when the diameter of the β -type gallium oxide single crystal substrate is "100mm", the diameter is about 100mm (about 95 to 105 mm), or 4 inches. When the diameter is "150mm", the diameter is about 150mm (145 to 155 mm), or 6 inches. The diameter can be measured by using a conventionally known outer diameter measuring instrument such as a vernier caliper.

In the crystallographic descriptions in this specification, the individual crystal directions are represented by [ ], the crystal direction group by < >, the individual crystal planes by (), and the crystal plane group by { }, respectively. In addition, a crystallographic index negative is usually expressed by labeling "- (bars)" above the number, and a negative sign is labeled before the number in this specification.

[ Crucible ]

The crucible of the present embodiment is a crucible for growing a beta-type gallium trioxide single crystal (beta-type Ga ₂O₃ single crystal). The crucible has a thickness of 1mm to 10 mm. The maximum inner diameter of the crucible is more than 100 mm. The composition of the crucible is stabilized zirconia containing both or either of yttria and calcia. The inner peripheral surface of the crucible is coated with a thermal spray coating film containing rhodium (Rh) and/or platinum (Pt). For example, the thermally sprayed film is preferably composed of a platinum-rhodium alloy (Pt-Rh alloy) containing 10 mass% or more and 30 mass% or less of Rh. The thickness of the thermal spray coating film is 100 μm or more and 500 μm or less. The stabilized zirconia contains at least 12.0 mass% or more and 15.5 mass% or less of the yttrium oxide or 10.2 mass% or more and 11.4 mass% or less of the calcium oxide. The crucible having such characteristics can suppress the occurrence of cracking, chipping, and the like at the time of crystal growth.

As described above, the crucible is a crucible for growing a beta-type Ga ₂O₃ single crystal. The crucible is used for growing and obtaining a β -type Ga ₂O₃ single crystal, and is applied to a single crystal growing apparatus shown in fig. 1, for example. The crucible of the present embodiment will be described in detail below by describing the single crystal growth apparatus shown in fig. 1. Fig. 1 is a schematic diagram illustrating main parts of a single crystal growth apparatus used in a method for producing a β -type Ga ₂O₃ single crystal substrate according to the present embodiment and a crucible according to a first embodiment used in the single crystal growth apparatus.

As shown in fig. 1, the single crystal growth apparatus 100 includes the crucible 5, a crucible holding table 6 for holding the crucible 5, and a heating device 7 for heating the crucible 5. Further, the single crystal growth apparatus 100 may have a closed vessel 9 for accommodating itself. The size, material, and the like of the closed vessel 9 are not particularly limited as long as they can house the single crystal growth apparatus 100 and the like and have a function of preventing invasion of impurities from the outside.

The crucible 5 includes a cylindrical seed crystal accommodating portion 51, a diameter-increased portion 52 connected to the seed crystal accommodating portion 51, and a straight cylindrical portion 53 connected to the diameter-increased portion 52. The seed crystal housing portion 51 has a cylindrical shape, and is open on the side connected to the enlarged diameter portion 52, and has a hollow portion with a bottom wall formed on the side opposite to the enlarged diameter portion 52. The seed crystal housing portion 51 can house and hold the seed crystal 8a in the hollow portion. The diameter-increasing portion 52 has a truncated cone shape that increases in diameter upward in the axial direction of the crucible 5, and is connected to the seed receiving portion 51 on the small diameter side of the diameter-increasing portion 52. The straight tube portion 53 has a hollow cylindrical shape, and is connected to the large diameter side of the diameter-increased portion 52. The diameter increasing portion 52 and the straight tube portion 53 have a function of holding a bulk of a gallium oxide bulk (specifically, polycrystalline Ga ₂O₃. Hereinafter, also referred to as "Ga ₂O₃ bulk") inside thereof. The diameter-increased portion 52 and the straight tube portion 53 have a function of growing a β -type Ga ₂O₃ single crystal as a crystal by solidifying a gallium trioxide melt as described later.

< Thickness and maximum inner diameter >

The crucible 5 has a thickness of 1mm to 10 mm. More specifically, the side wall portion 5a of each of the seed crystal accommodating portion 51, the diameter increasing portion 52, and the straight tube portion 53 of the crucible 5 has a thickness of 1mm or more and 10mm or less. The seed crystal accommodating portion 51, the diameter increasing portion 52, and the side wall portion 5a of the straight tube portion 53 of the crucible 5 each preferably have a thickness of 5mm to 10 mm. Further, the maximum inner diameter of the crucible 5 is 100mm or more. More specifically, the inner diameter of the straight tube portion 53 of the crucible 5 is preferably 100mm or more. The inner diameter of the straight tube portion 53 of the crucible 5 is also preferably 150mm or more. The upper limit of the maximum inner diameter of the crucible 5 is not particularly limited, and is 165mm, for example.

When the thickness of the crucible 5 is less than 1mm, breakage or chipping of the crucible 5 at the time of crystal growth may not be sufficiently suppressed. The crucible 5 may also be deformed during crystal growth. In the case where the thickness of the crucible 5 exceeds 10mm, the adverse effect of the cost increase of the crucible 5 may exceed the effect of cost reduction or the like obtained by suppressing breakage or chipping of the crucible 5 at the time of crystal growth. When a large-diameter β -type Ga ₂O₃ single crystal substrate having a diameter of 4 inches or 6 inches is produced by setting the maximum inner diameter of the crucible 5 to 100mm or more, breakage and chipping of the crucible 5 can be suppressed.

< Composition of crucible > stabilized zirconia

The crucible 5 has a composition of stabilized zirconia (hereinafter, also referred to as "stabilized ZrO ₂") containing both or either of yttria (ytria: Y ₂O₃) and calcia (calcia: caO). The composition of crucible 5 is preferably stabilized ZrO ₂ comprising either Y ₂O₃ or CaO. Specifically, the stabilized ZrO ₂ contains at least 12.0 mass% or more and 15.5 mass% or less of Y ₂O₃, or 10.2 mass% or more and 11.4 mass% or less of CaO. By setting the composition of the crucible 5 to the stable ZrO ₂ having a low thermal conductivity as described above, crystal defects generated during crystal growth can be easily repelled to the outer peripheral side of the crystal, and polycrystallization of the β -type Ga ₂O₃ single crystal during crystal growth can be prevented. "stabilized ZrO ₂" refers to ZrO ₂ in which a high-temperature phase (typically a solid solution of cubic or tetragonal crystals) becomes stable at room temperature by adding Y ₂O₃, caO, magnesium oxide (MgO), aluminum oxide (aluminum: al ₂O₃) or the like to ZrO ₂. The oxides dissolved in the stabilized ZrO ₂ are not limited to Y ₂O₃, caO, mgO, and Al ₂O₃.

< Thermally sprayed film >

(Composition)

The inner peripheral surface of the crucible is coated with a thermal spray coating film containing either or both of Rh and Pt. For example, the thermally sprayed film is preferably composed of a pt—rh alloy containing 10 mass% or more and 30 mass% or less of Rh. For example, in the crucible 5 according to the first embodiment shown in fig. 1, the thermally sprayed film 5b composed of a platinum-rhodium alloy (Pt-Rh alloy) containing 10 mass% or more and 30 mass% or less of Rh is coated. The thermally sprayed film 5b has a thickness of 100 μm or more and 500 μm or less. The thermally sprayed film 5b preferably covers the entire surface of the inner peripheral surface side of the crucible 5. However, even if a part of the surface is not covered with the thermally sprayed film 5b or the composition of the thermally sprayed film 5b is partially different, it does not depart from the scope of the present invention.

The thermal spraying can be performed by a conventionally known method, for example, plasma spraying. For example, the thermal spraying can be performed by heating the Pt-Rh alloy to form molten particles or particles close thereto (for example, particle diameter: 45 to 300 μm) and supplying the thermal spraying material to the inner peripheral surface side of the side wall portion 5a from a direction inclined by 30 to 45 DEG with respect to the axial direction of the crucible 5 using a thermal spraying nozzle as the spraying material. In this case, the distance from the tip of the nozzle to the inner peripheral surface side of the crucible 5 is preferably 20 to 120mm, for example, in the direction in which the tip of the thermal spraying nozzle is oriented. Further, by controlling the supply speed of the thermally sprayed material, the thickness of the thermally sprayed film 5b can be determined. For example, the supply rate of the deposition material may be 50 to 75 g/min. The porosity described later can be determined by controlling the angle of the thermal spraying nozzle and the thermal spraying material supply speed. By increasing the particle diameter of the thermal spraying material, the surface roughness Rz described later can be increased.

By setting the Rh content in the pt—rh alloy constituting the thermally sprayed film 5b to 10 mass% or more, cracking and chipping of the crucible 5 at the time of crystal growth can be more sufficiently suppressed. By setting the Rh content in the pt—rh alloy constituting the thermally sprayed film 5b to 30 mass% or less, cracking and chipping of the crucible 5 at the time of crystal growth can be sufficiently suppressed without increasing the cost of the crucible 5. The thermally sprayed film 5b is more preferably composed of a pt—rh alloy containing 20 mass% or more and 30 mass% or less of Rh.

If the thickness of the thermally sprayed film 5b is less than 100 μm, the thermally sprayed film 5b may be peeled off from the side wall portion 5a, and breakage or chipping of the crucible 5 at the time of crystal growth may not be sufficiently suppressed. In the case where the thickness of the thermally sprayed film 5b exceeds 500 μm, the adverse effect of the cost increase of the crucible 5 may exceed the effect of cost reduction and the like obtained by suppressing breakage, chipping of the crucible 5 at the time of crystal growth. The thickness of the thermal spray coating film 5b is preferably 200 μm or more and 500 μm or less.

The thickness of the thermal spray coating film was measured according to JIS H8401:1999 (thickness test method of thermal spray coating product). Specifically, the difference between the crucible thickness before thermal spraying and the crucible thickness after thermal spraying can be determined by a direct method using a micrometer (for example, product name (product number): "U-shaped micrometer PMU100-25", manufactured by Sanfeng Co., ltd., or product name (product number): "laser digital micrometer LSM-501S", manufactured by Sanfeng Co., ltd.). The Rh concentration in the Pt-Rh alloy can be determined at the time of preparation of the thermal spray material.

(Pore space)

The thermally sprayed film preferably has pores. The volume ratio of the voids in the thermal spray coating film, that is, the porosity, is preferably 30% by volume or more and 50% by volume or less. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth. Fig. 2 is an enlarged cross-sectional view of a main part of a crucible illustrating a second embodiment used in the single crystal growth apparatus of fig. 1. In the crucible of the second embodiment shown in fig. 2, the thermally sprayed film 5b present on the inner peripheral surface side of the side wall portion 5a has a void 5c. The volume ratio of the voids 5c to the thermally sprayed film 5b, that is, the porosity, is preferably 30% by volume or more and 50% by volume or less.

The porosity was measured according to JIS K7112:1999A method (substitution method in water). Specifically, the measured densities of the thermal spray films were first calculated by measuring the densities of the crucible before and after thermal spraying. The composition of the thermal spray film was determined by using an energy dispersive X-ray device (SEM-EDX: scanning Electron Microscope-ENERGY DISPERSIVE X-ray Spectroscppy) attached to a transmission electron microscope, and the ideal density was calculated from the composition. The porosity can be obtained by multiplying the measured density by the ideal density x 100.

Since the crucible of the second embodiment is formed of the above-mentioned stable ZrO ₂, deformation due to thermal shrinkage is not originally easy at the time of crystal growth and at the time of cooling after crystal growth. However, even when the side wall portion 5a is pressed by the β -type Ga ₂O₃ single crystal present in the crucible due to some thermal contraction of the crucible, particularly, when the crucible is cooled after crystal growth, the pores 5c included in the thermal spray film 5b are crushed, and thus, the occurrence of cracking, chipping, and the like of the crucible can be suppressed. In the case where the porosity is less than 30% by volume, the effect of suppressing breakage or chipping of the crucible may be insufficient by crushing only the pores 5 c. In the case where the above-described porosity exceeds 50% by volume, it may become difficult to thermally spray such a thermally sprayed film 5b on the side wall portion 5 a.

(Surface roughness)

The surface roughness Rz of the inner peripheral surface side surface of the crucible is preferably 300 μm or more and 500 μm or less. In this case too, it is preferable that the thermally sprayed film has pores. The volume ratio of the voids in the thermal spray coating film, that is, the porosity, is preferably 10% by volume or more and less than 30% by volume. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth. Fig. 3 is an enlarged cross-sectional view of a main part of a crucible illustrating a third embodiment used in the single crystal growth apparatus of fig. 1. In the crucible according to the third aspect shown in fig. 3, the surface roughness Rz of the inner peripheral surface side surface of the side wall portion 5a is 300 μm or more and 500 μm or less. The thermally sprayed film 5b present on the inner peripheral surface side of the side wall portion 5a has a void 5c. The porosity, which is the volume ratio of the voids 5c in the thermally sprayed film 5b, is 10% by volume or more and less than 30% by volume. The surface roughness Rz of the inner peripheral surface side surface of the side wall portion 5a is preferably 300 μm or more and 400 μm or less.

The method for measuring the surface roughness Rz of the inner peripheral surface side surface of the side wall 5a is as follows. That is, the surface roughness Rz can be measured by obtaining the maximum height (Rz) specified in JIS B0601:2001 on the surface on the inner peripheral surface side of the side wall 5 a. For example, a surface roughness meter (product name (product number): "surface roughness meter SV-2100M4", manufactured by Sanfeng Co., ltd.) or a product name (product number): "surface roughness meter SURFCOM TOUCH 550", manufactured by Tokyo precision Co., ltd.) was used. The surface roughness Rz can be measured by providing a measuring means inside the crucible and measuring the roughness by using a display/control means. The method for measuring the porosity can be the same as that of the thermal spray coating film of the crucible according to the second embodiment.

Since the crucible of the third embodiment is formed of the above-mentioned stable ZrO ₂, deformation due to thermal shrinkage is not originally easy at the time of crystal growth and at the time of cooling after crystal growth. However, even when the crucible is pressed against the side wall portion 5a by the β -type Ga ₂O₃ single crystal present in the crucible due to some thermal contraction occurring particularly at the time of cooling after crystal growth, the occurrence of cracking, chipping, and the like of the crucible can be suppressed by the convex portions present on the inner peripheral surface side of the side wall portion 5a being compressively broken due to the surface roughness thereof. Further, the voids 5c included in the thermal spray film 5b are compressed and broken, whereby the occurrence of cracking, chipping, and the like of the crucible can also be suppressed. When the surface roughness Rz is less than 300 μm, the effect of suppressing breakage or chipping of the crucible due to the compression fracture of the convex portion may be insufficient. When the surface roughness Rz exceeds 500 μm, the strength of the crucible itself may be lowered, which may cause breakage of the convex portion during crystal growth or the like, and may cause breakage or chipping of the crucible. Further, when the porosity is less than 10% by volume, the effect of suppressing breakage or chipping of the crucible by the compression fracture of the pores 5c may be insufficient.

In the crucible according to the second aspect, the surface roughness Rz of the surface is also preferably 300 μm or more and 500 μm or less. This can further suppress the occurrence of cracking, chipping, and the like at the time of crystal growth due to the presence of the protrusions and the pores 5c on the surface. The surface roughness Rz of 300 μm or more can sufficiently suppress cracking and chipping of the crucible due to crushing of the convex portion. The surface roughness Rz of 500 μm or less can sufficiently suppress cracking and chipping of the crucible at the time of crystal growth or the like without reducing the strength of the crucible itself. The crucible according to the second aspect may have a surface roughness Rz of 300 μm or more and 500 μm or less, which is similar to the porosity of 30% by volume or more and 50% by volume or less in the crucible according to the third aspect.

(First film and second film)

The thermally sprayed film is preferably composed of a first film and a second film. The first film is preferably coated on the surface. The first film is preferably composed of Rh or a pt—rh alloy containing Rh as a main component. The second film is preferably coated with the first film. The second film is preferably made of Pt or a pt—rh alloy containing Pt as a main component. The thickness of the thermal spray coating film is preferably 100 μm to 500 μm in total of the first film and the second film. This can suppress the mixing of Rh into the β -type Ga ₂O₃ single crystal, in addition to the effect of suppressing the occurrence of cracking, chipping, and the like at the time of crystal growth.

Fig. 4 is an enlarged cross-sectional view of a main part of a crucible illustrating a fourth embodiment used in the single crystal growth apparatus of fig. 1. In the crucible of the fourth embodiment shown in fig. 4, the thermally sprayed film is composed of the first film 5b1 and the second film 5b 2. The first film 5b1 covers the inner peripheral surface side surface of the side wall portion 5 a. The first film 5b1 is composed of Rh or a pt—rh alloy containing Rh as a main component, and preferably composed of Rh, for example. The second film 5b2 covers the first film 5b1. The second film 5b2 is made of Pt or a pt—rh alloy containing Pt as a main component, and is preferably made of Pt, for example. The thickness of the thermal spray coating film is 100 μm to 500 μm in total of the first film 5b1 and the second film 5b 2. The thickness of the thermal spray coating film is more preferably 100 μm or more and 300 μm or less in terms of the total of the first film 5b1 and the second film 5b 2. When the total thickness of the first film 5b1 and the second film 5b2 is less than 100 μm, the first film 5b1 and the second film 5b2 may be peeled off from the side wall portion 5a, and the effect of suppressing breakage or chipping of the crucible 5 when the thermally sprayed film is formed by the first film 5b1 and the second film 5b2 may be insufficient. If the total thickness of the first film 5b1 and the second film 5b2 exceeds 500 μm, the adverse effect of the increase in the cost of the crucible 5 may exceed the effect of cost reduction or the like obtained by suppressing breakage or chipping of the crucible 5 at the time of crystal growth. The method for measuring the thickness of the first film and the second film can be the same as the method for measuring the thickness of the thermal spray film of the crucible according to the first aspect.

As shown in fig. 4, the first film 5b1 and the second film 5b2 each preferably have pores 5c. The volume ratio of the pores 5c in the first film 5b1, that is, the first film porosity, and the volume ratio of the pores 5c in the second film 5b2, that is, the second film porosity, are each preferably 30% by volume or more and 50% by volume or less. This can further suppress the occurrence of cracking, chipping, and the like at the time of crystal growth due to the above-described action of the pores 5c. The method for measuring the porosity of the first film and the porosity of the second film can be the same as the method for measuring the porosity of the thermal spray coating film of the crucible according to the second embodiment.

In the crucible according to the fourth aspect, the thermal spray coating film is composed of the first film 5b1 and the second film 5b 2. The first film 5b1 is made of Rh or a pt—rh alloy containing Rh as a main component, and the second film 5b2 is made of Pt or a pt—rh alloy containing Pt as a main component. The first film 5b1 covers the inner peripheral surface side surface of the side wall portion 5a, and the second film 5b2 covers the first film 5b1. Therefore, rh in the thermal spray film does not directly contact the β -type Ga ₂O₃ single crystal in the crucible or is very slight even in contact, and thus, it is possible to suppress Rh from being mixed into the β -type Ga ₂O₃ single crystal at the time of crystal growth or the like.

Here, in the crucible of the fourth embodiment, the thermally sprayed film is composed of the first film 5b1 and the second film 5b 2. Therefore, by considering the first film 5b1 and the second film 5b2 in combination, the thermal spray film can be a thermal spray film composed of a pt—rh alloy containing Rh in an amount of 10 mass% or more and 30 mass% or less. For example, in the crucible according to the fourth aspect, the thermal spray film may be composed of a first film 5b1 and a second film 5b2, the first film 5b1 being composed of Rh, the second film 5b2 being composed of Pt, and the thickness of the first film 5b1 being one third of the thickness of the second film 5b 2. Thus, the crucible according to the fourth aspect can contain a thermal spray film made of a pt—rh alloy containing 10 mass% or more and 30 mass% or less of Rh. As described above, the thickness of the thermal spray coating film is 100 μm or more and 500 μm or less in total of the first film 5b1 and the second film 5b 2.

Further, in the crucible in which the thermally sprayed film is composed of the first film and the second film, the surface roughness Rz of the surface on the inner peripheral surface side is preferably 300 μm or more and 500 μm or less. In this case, it is also preferable that the first film and the second film each have pores. The volume ratio of the pores in the first film, that is, the first film porosity, and the volume ratio of the pores in the second film, that is, the second film porosity, are each preferably 10% by volume or more and less than 30% by volume. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth. Fig. 5 is an enlarged cross-sectional view of a main part of a crucible illustrating a fifth embodiment used in the single crystal growth apparatus of fig. 1. In the crucible according to the fifth aspect shown in fig. 5, the surface roughness Rz of the inner peripheral surface side surface of the side wall portion 5a is 300 μm or more and 500 μm or less. The first film 5b1 and the second film 5b2 present on the inner peripheral surface side of the side wall portion 5a have pores 5c, respectively. The volume ratio of the pores 5c in the first film 5b1 and the second film 5b2, that is, the first film porosity and the second film porosity, is 10% by volume or more and less than 30% by volume, respectively. The surface roughness Rz of the inner peripheral surface side surface of the side wall portion 5a is preferably 300 μm or more and 400 μm or less.

According to the crucible of the fifth aspect, the occurrence of cracking, chipping, and the like at the time of crystal growth can be further suppressed based on the presence of the convex portion and the void 5c of the surface on the inner peripheral surface side, as in the crucible of the third aspect. Further, like the crucible of the fourth embodiment, rh in the thermal spray film is not in direct contact with the β -type Ga ₂O₃ single crystal in the crucible or is in very slight contact with it, and thus it is possible to suppress the mixing of Rh into the β -type Ga ₂O₃ single crystal at the time of crystal growth or the like.

In the crucible according to the fourth aspect, the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. This can further suppress the occurrence of cracking, chipping, and the like during crystal growth due to the presence of the protrusions and pores 5c on the surface. The crucible according to the fourth aspect has the same structure in which the surface roughness Rz of the surface is 300 μm or more and 500 μm or less as that of the crucible according to the fifth aspect in which the first film porosity and the second film porosity are 30% by volume or more and 50% by volume or less, respectively.

< Crucible holding table >

As shown in fig. 1, the single crystal growing apparatus 100 has a crucible holding table 6 that holds a crucible 5. The crucible holding table 6 contacts the bottom of the crucible 5 and holds the crucible 5. The crucible holding table 6 sometimes has a cylindrical appearance. The material of the crucible holding table 6 is not particularly limited, and quartz, alumina, zirconia, silicon carbide, or the like can be used, for example. The outer diameter of the crucible holding table 6 is also dependent on the diameter of the crucible 5 that it supports, and is, for example, 75mm or more and 200mm or less.

(Heating device)

The heating device 7 is provided for heating the crucible 5. The heating device 7 may be, for example, a conventionally known electric heater (hereinafter, also simply referred to as "heater"). For example, two heaters may be provided and disposed so that the two heaters surround the outer periphery of the crucible 5. The output of the heaters may sometimes each be independently controlled. In particular, each heater is sometimes divided into a plurality of portions in a direction perpendicular to the axis of the crucible 5, thereby forming a multi-stage structure. In this case, the output of the heater of each portion constituting the plurality of stages is preferably independently controlled. This allows the temperature of the content in the crucible 5 to be finely adjusted in the axial direction of the crucible 5. For example, by independently controlling the output of the heater of each portion constituting the plurality of stages to heat the diameter-increased portion 52 and the straight tube portion 53, the growth rate of the crystal grown at the diameter-increased portion 52 and the straight tube portion 53, respectively, can be stabilized.

Although not shown, the single crystal growth apparatus 100 may have a thermocouple that can measure the temperature of the crucible 5 heated by the heater. The thermocouples may be arranged outside the crucible 5 in plural numbers in the axial direction. The thermocouple can employ, for example, a well-known temperature monitor.

[ Method for producing beta-type gallium oxide single crystal substrate ]

The method for producing a β -type gallium oxide single crystal substrate (β -type Ga ₂O₃ single crystal substrate) according to the present embodiment is preferably, for example, a β -type Ga ₂O₃ single crystal substrate using the above-described crucible. That is, the production method preferably includes a step of preparing the crucible, a step of obtaining a β -type gallium trioxide single crystal (β -type Ga ₂O₃ single crystal) by a Vertical Boat (Vertical Boat) method using the crucible, and a step of processing the β -type Ga ₂O₃ single crystal to obtain a β -type Ga ₂O₃ single crystal substrate having a circular main surface. By the method for producing a β -type Ga ₂O₃ single crystal substrate having such characteristics, breakage and defect of the crucible at the time of crystal growth or the like are reduced, and thus a β -type Ga ₂O₃ single crystal substrate can be obtained with good yield.

Fig. 6 is a flowchart showing an example of a method for manufacturing a β -type Ga ₂O₃ single crystal substrate according to the present embodiment. The method for producing a β -type Ga ₂O₃ single crystal substrate according to the present embodiment preferably includes, for example, a β -type Ga ₂O₃ single crystal production step S100 and a β -type Ga ₂O₃ single crystal substrate production step S200 shown in the flowchart of fig. 6. Referring to fig. 6, the method for producing a β -type Ga ₂O₃ single crystal substrate according to the present embodiment more specifically preferably includes a step of preparing a single crystal growth apparatus (first step: preparation step S110) as a β -type Ga ₂O₃ single crystal production step S100, the single crystal growth apparatus including at least a cylindrical crucible and a heating device disposed so as to surround an outer periphery of the crucible. In the preparation step S110, it is preferable to prepare a seed crystal or a bulk Ga ₂O₃ block in addition to the single crystal growth apparatus and the crucible constituting the same.

The β -type Ga ₂O₃ single crystal production step S100 preferably includes a step of storing the seed crystal in the bottom of the crucible and storing the Ga ₂O₃ block in a portion above the seed crystal in the crucible (second step: raw material loading step S120). In the raw material charging step S120, the Ga ₂O₃ block is preferably stored in a portion above the seed crystal in the crucible. The β -type Ga ₂O₃ single crystal production step S100 preferably includes a step of heating the crucible by the heating device to melt a part of the Ga ₂O₃ block and the seed crystal to obtain a Ga ₂O₃ melt, and bringing the Ga ₂O₃ melt into contact with the remainder of the seed crystal (third step: raw material melting step S130). Further, the β -type Ga ₂O₃ single crystal production step S100 preferably includes a step of obtaining a β -type Ga ₂O₃ single crystal by growing a crystal from the Ga ₂O₃ melt on the remaining portion of the seed crystal (fourth step: ga ₂O₃ single crystal growth step S140).

The method for producing a β -type Ga ₂O₃ single crystal substrate according to the present embodiment may include a dicing step, an outer periphery polishing step, and a polishing step, which will be described later, as the β -type Ga ₂O₃ single crystal substrate production step S200. In the β -type Ga ₂O₃ single crystal substrate manufacturing step S200, the β -type Ga ₂O₃ single crystal substrate can be obtained by sequentially performing the above steps.

The steps included in the method for producing a β -type Ga ₂O₃ single crystal substrate according to the present embodiment will be described below with reference to fig. 1 and 6. According to the above method for producing a β -type Ga ₂O₃ single crystal substrate, first, a β -type Ga ₂O₃ single crystal is grown by the vertical boat method using the crucible 5 shown in fig. 1 applied to the single crystal growth apparatus 100. As the crucible 5, any one of the above-described first to fifth aspects can be used. Hereinafter, the vertical boat method is abbreviated as VB method. The VB method includes a vertical Bridgman method and a vertical temperature gradient solidification method.

< Beta-Ga ₂O₃ Single Crystal production Process S100>

(Preparation step S110)

As shown in fig. 1 and 6, first, in the β -type Ga ₂O₃ single crystal production step S100, a step of preparing the single crystal growth apparatus 100 (preparation step S110) is performed, and the single crystal growth apparatus 100 includes at least a cylindrical crucible 5 and a heating device 7 disposed so as to surround the outer periphery of the crucible 5. In the preparation step S110, it is preferable to prepare the seed crystal 8a and the bulk Ga ₂O₃ bulk, respectively, in addition to the single crystal growth apparatus 100 for producing the β -type Ga ₂O₃ single crystal 81. The seed crystal 8a is composed of a β -type Ga ₂O₃ single crystal. The Ga ₂O₃ block is sometimes composed of polycrystalline Ga ₂O₃. The seed crystal 8a and the bulk Ga ₂O₃ block may be prepared by a conventionally known method or may be prepared by obtaining a commercially available product.

In the preparation step S110, any of the crucibles according to the first to fifth aspects described above may be prepared as the crucible 5. The crucibles according to the first to fifth aspects can each have the above-described features by using a conventionally known method. That is, by a conventionally known method, the crucible 5 having the thickness of the side wall portion 5a of 1 to 10mm and the inner diameter of the straight tube portion 53 of 100mm or more can be manufactured. In this case, the composition of the crucible 5 may be made of, for example, Y ₂O₃ containing at least 12.0 mass% or more and 15.5 mass% or less, or stabilized ZrO ₂ containing 10.2 mass% or more and 11.4 mass% or less of CaO.

Further, for example, by plasma spraying the crucible 5 using the prepared spray material under the following conditions, the inner peripheral surface side surface of the side wall portion 5a can be coated with the thermal spray film 5 b.

Thermal spraying material, pt-Rh alloy containing 10-30 mass% Rh

The particle diameter of the thermal spraying material is 45-300 mu m

The feeding speed of the thermal spraying material is 50-75 g/min

The direction of the thermal spraying nozzle is 30-45 DEG relative to the axial direction of the crucible

The distance between the thermal spraying nozzle and the surface of the side wall of the crucible on the inner peripheral surface side is 20-120 mm.

By controlling the supply speed of the thermal spraying material, the thickness of the thermal spraying film 5b can be set to, for example, 100 to 500 μm. By controlling the angle of the spray nozzle and the spray material supply speed, the porosity of the thermally sprayed film 5b can be adjusted to 10 to 50% by volume. By controlling the particle diameter of the sputtering material, the surface roughness Rz of the inner peripheral surface side surface of the side wall portion 5a in the crucible 5 can be adjusted to 300 to 500 μm.

Here, in the case of preparing the crucible according to the fourth aspect and the crucible according to the fifth aspect, as the sputtering material, a first sputtering material composed of Rh or a pt—rh alloy containing Rh as a main component and having a particle diameter of 45 to 300 μm, and a second sputtering material composed of a pt—rh alloy containing Pt as a main component and having a particle diameter of 45 to 300 μm can be used. In this case, by performing plasma spraying using the first spraying material, the inner peripheral surface side surface of the side wall portion 5a of the crucible 5 can be covered with the first film. Further, by performing plasma spraying using the second spraying material, the first film can be coated with the second film. At this time, by controlling the supply rates of the first and second deposition materials, the angle of the deposition nozzle, and the particle diameters of the first and second deposition materials, the thicknesses of the first and second films, the first and second film porosities, and the surface roughness Rz of the inner peripheral surface side surface of the side wall portion 5a of the crucible 5 can be adjusted.

(Raw material charging step S120)

The raw material charging step S120 is a step of storing the seed crystal in the bottom of the crucible and storing a bulk Ga ₂O₃ block in a portion above the seed crystal in the crucible. In the raw material charging step S120, it is preferable to store a bulk Ga ₂O₃ block and also a solid B ₂O₃ in a portion above the seed crystal 8a in the crucible 5. The purpose of the raw material charging step S120 is to enclose various raw materials for crystal growth using the single crystal growth apparatus 100 in a crucible. In the raw material charging step S120, first, a seed crystal 8a made of a β Ga ₂O₃ single crystal is charged into the hollow portion of the seed crystal housing portion 51 of the crucible 5. Next, a plurality of block-shaped Ga ₂O₃ blocks composed of polycrystalline Ga ₂O₃ are packed in the diameter increasing portion 52 and the straight tube portion 53 of the crucible 5, and stacked. In the raw material charging step S120, a predetermined amount of Sn or Si is preferably added when a plurality of bulk Ga ₂O₃ blocks are charged into the crucible 5. Thus, from the β -type Ga ₂O₃ single crystal 81 obtained in the β -type Ga ₂O₃ single crystal production step S100, a β -type Ga ₂O₃ single crystal substrate containing Sn or Si as a dopant is obtained. When adding Sn or Si, the amount of the dopant is preferably adjusted so that the concentration of the dopant is, for example, 1.0x10 ¹⁸cm^-3(5.0×10¹⁷cm^-3 or more and 4.0x10 ¹⁹cm^-3 or less in the β -type Ga ₂O₃ single crystal substrate.

(Raw material melting Process S130)

The raw material melting step S130 is a step of melting a part of the seed crystal and the bulk Ga ₂O₃ by heating the crucible using the heating device to obtain a Ga ₂O₃ melt, and bringing the Ga ₂O₃ melt into contact with the remainder of the seed crystal. The purpose of the raw material melting step S130 is to melt a portion of the seed crystal 8a and the bulk of Ga ₂O₃ when the single crystal growth apparatus 100 is used to grow a crystal, so that the remainder of the seed crystal 8a is brought into contact with the Ga ₂O₃ melt 82. In this way, in the Ga ₂O₃ single crystal growth step S140, which is the next step, the β -type Ga ₂O₃ single crystal 81 can be grown on the remaining portion of the seed crystal 8 a. Specifically, in the raw material melting step S130, the crucible 5 in which the seed crystal 8a and the Ga ₂O₃ block are housed is supported by the crucible holding table 6. Then, an electric current is supplied to the heating device 7 to heat the crucible 5. Thereby, the Ga ₂O₃ block is melted to obtain a Ga ₂O₃ melt 82. Next, a part of the seed crystal 8a is also melted, and at the interface thereof, the remaining part of the seed crystal 8a is in contact with the Ga ₂O₃ melt 82.

(Ga ₂O₃ Single Crystal growth Process S140)

The Ga ₂O₃ single crystal growth step S140 is a step of growing a crystal from the Ga ₂O₃ melt on the remaining portion of the seed crystal to obtain a β -type Ga ₂O₃ single crystal. In the Ga ₂O₃ single crystal growth step S140, for example, the crucible 5 is gradually lowered (toward the seed crystal storage portion 51) along the axis of the crucible 5 with respect to the heating device 7, whereby a temperature gradient is formed in the crucible 5 such that the temperature on the seed crystal 8a side is low and the temperature on the Ga ₂O₃ melt 82 side is high. This solidifies the Ga ₂O₃ melt 82 in contact with the seed crystal 8a, and the β -type Ga ₂O₃ single crystal 81 can be continuously grown from the Ga ₂O₃ melt 82 on the remaining portion of the seed crystal 8 a. At this time, for example, the temperature of the Ga ₂O₃ melt 82 side is 1800 to 1820 ℃. The temperature gradient at the interface between the Ga ₂O₃ melt 82 and the growing beta-type Ga ₂O₃ single crystal 81 is, for example, 3-8 ℃/cm. The speed at which the crucible 5 is lowered in the axial direction is not particularly limited, and may be, for example, 0.1 to 2 mm/hr.

In the Ga ₂O₃ single crystal growth step S140, the crucible 5 is gradually lowered down along the axis of the crucible 5 with respect to the heating device 7, whereby the interface between the β -type Ga ₂O₃ single crystal 81 and the Ga ₂O₃ melt 82 is raised toward the Ga ₂O₃ side of the liquid, and the Ga ₂O₃ melt 82 is solidified as the β -type Ga ₂O₃ single crystal 81. Thus, the crystal growth of the β -type Ga ₂O₃ single crystal 81 continues until the solidification of the Ga ₂O₃ melt 82 remaining in the straight tube portion 53 of the crucible 5 ends. In this way, an ingot of the β -type Ga ₂O₃ single crystal 81 can be obtained.

< Beta-Ga ₂O₃ Single Crystal substrate manufacturing Process S200>

As shown in fig. 6, the method for producing the β -type Ga ₂O₃ single crystal substrate includes a step of processing the β -type Ga ₂O₃ single crystal obtained in the Ga ₂O₃ single crystal growth step S140 to obtain a β -type Ga ₂O₃ single crystal substrate having a circular main surface (β -type Ga ₂O₃ single crystal substrate production step S200). The β -type Ga ₂O₃ single crystal substrate manufacturing process S200 includes the following dicing process, peripheral polishing process, and these processes are sequentially performed, whereby a β -type Ga ₂O₃ single crystal substrate can be obtained.

The dicing step is a step of slicing an ingot of β -type Ga ₂O₃ single crystal taken out of a crucible to obtain a β -type Ga ₂O₃ single crystal substrate so that the ingot becomes a wafer having a predetermined thickness. The outer periphery polishing step is a step of polishing the outer periphery of the wafer to obtain a β -type Ga ₂O₃ single crystal substrate having a circular main surface. The outer periphery polishing step may include, for example, a step of chamfering. As the cutting step and the peripheral polishing step, a conventionally known cutting method and a conventionally known peripheral polishing method can be used. The polishing step is a step of mirror-forming a central portion of the main surface. As the polishing step, a conventionally known polishing method can be used. The center portion can have a surface roughness Ra of 10nm or less, for example, as defined in JIS B0681-2:2018, by a polishing step.

< Effect >

By performing the above steps, the β -type Ga ₂O₃ single crystal substrate according to the present embodiment can be manufactured. In the method for producing a β -type Ga ₂O₃ single crystal substrate, since the β -type Ga ₂O₃ single crystal is produced using any one of the crucibles according to the first to fifth aspects, breakage and chipping of the crucible during crystal growth or the like can be reduced. Therefore, the β -type Ga ₂O₃ single crystal substrate can be obtained with good yield.

[ Beta-type gallium trioxide single crystal substrate ]

The β -type gallium oxide single crystal substrate (β -type Ga ₂O₃ single crystal substrate) of the present embodiment is a β -type Ga ₂O₃ single crystal substrate having a circular main surface. The diameter of the beta Ga ₂O₃ single crystal substrate is more than 100 mm. The main surface is the (001) plane of the β -type Ga ₂O₃ single crystal. Alternatively, the main surface is a surface having a deviation angle of from the (001) plane of the β -type Ga ₂O₃ single crystal of more than 0 ° and 10 ° or less, and a deviation direction of the [010] direction or a direction orthogonal to the [010] direction of the β -type tri-Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single-crystal substrate contains both or either rhodium (Rh) and iridium (Ir). The concentration of Rh and the concentration of Ir are both less than 3 mass ppm in Glow DISCHARGE MASS Spectrometry (GDMS). Since the β -type Ga ₂O₃ single crystal substrate having such characteristics contains very little Rh and Ir, it can be excellent in both electrical characteristics and optical characteristics.

The present inventors focused on making the concentrations of rhodium and iridium in the above-mentioned substrate extremely small, which may be contained in a β -type Ga ₂O₃ single crystal substrate and not be homogeneous with gallium (Ga), and thus may prevent good electrical and optical characteristics in the above-mentioned substrate. Specifically, when a β -type Ga ₂O₃ single crystal for obtaining a β -type Ga ₂O₃ single crystal substrate is produced, rh and Ir are not brought into direct contact with the β -type Ga ₂O₃ single crystal and a Ga ₂O₃ melt as a raw material thereof. More specifically, for example, a β -type Ga ₂O₃ single crystal is produced using the crucible of the fifth embodiment, and a β -type Ga ₂O₃ single crystal substrate is obtained from the β -type Ga ₂O₃ single crystal. Thus, the present invention has been completed in view of the fact that a β -type Ga ₂O₃ single crystal substrate in which the concentration of Rh and the concentration of Ir are both less than 3 mass ppm is provided.

< Diameter >

Fig. 7 is a schematic diagram illustrating a β -type Ga ₂O₃ single crystal substrate according to the present embodiment. In the β -type Ga ₂O₃ single crystal substrate 1 shown in FIG. 7, the diameter is 100mm or more. In particular, the diameter of the β -type Ga ₂O₃ single crystal substrate 1 is preferably 100mm or more and 155mm or less. The β -type Ga ₂O₃ single-crystal substrate 1 having a diameter of 100mm or more and 155mm or less is particularly preferably 101.6mm or 152.4mm in diameter, in other words, preferably 4 inches or 6 inches in diameter. Thus, the β -type Ga ₂O₃ single crystal substrate having a large diameter of 100mm or more and 155mm or less can be excellent in both electrical characteristics and optical characteristics. Here, the diameter OF the β -type Ga ₂O₃ single crystal substrate is obtained based on the circular shape before forming OF the above-described OF, IF, and the like even in the case where the above-described main surface is not formed into a geometrically circular shape due to the influence OF a positioning side (hereinafter, referred to as "OF"), an instruction side (hereinafter, referred to as "IF"), and the like. As described above, the diameter of the β -type Ga ₂O₃ single crystal substrate can be measured by using a conventionally known outer diameter measuring instrument such as a vernier caliper. In addition, in this specification, definition of "circular shape" representing the shape of the main surface will be described later.

< Major surface >

(Circular shape)

The β -type Ga ₂O₃ single crystal substrate 1 has the circular main surface 10 as described above. In the present specification, the "circular shape" indicating the shape OF the main surface includes, in addition to the geometric circular shape, a shape in the case where the main surface is not formed into the geometric circular shape due to at least any one OF a Notch (OF), or IF being formed in the outer periphery OF the main surface 10. Here, the "shape in the case where the main surface does not form a geometrically circular shape" refers to a shape in the case where the length OF a line segment extending from any point on the outer periphery OF the main surface 10 to the center OF the main surface is shortened among line segments extending from any point on the grooves, OF, and IF to the center OF the main surface. Further, the "shape in the case where the main surface does not form a geometrically circular shape" also includes a shape in which the lengths of line segments extending from any point on the outer periphery of the main surface 10 to the center of the main surface 10 are not necessarily all the same due to the shape of the β -type Ga ₂O₃ single crystal as the raw material of the β -type Ga ₂O₃ single crystal substrate 1. In this case, the center of the main surface 10 means the position of the center of gravity, and the diameter of the β -type Ga ₂O₃ single crystal substrate 1 means the length of the longest line segment among line segments extending from any point on the outer periphery of the β -type Ga ₂O₃ single crystal substrate 1 through the center of the main surface 10 to other points on the outer periphery.

(Beta-type Ga ₂O₃ monocrystal (001) face)

The main surface 10 is the (001) plane of the β -type Ga ₂O₃ single crystal. Alternatively, the main surface 10 is a surface having a deviation angle of more than 0 ° and 10 ° or less from the (001) plane of the β -type Ga ₂O₃ single crystal, and a [010] direction or a deviation direction of a direction orthogonal to the [010] direction of the β -type tri-Ga ₂O₃ single crystal. Thus, a β -type Ga ₂O₃ single crystal substrate 1 having the (001) plane or the like of the β -type Ga ₂O₃ single crystal as the main surface 10 can be provided, which is widely used for forming optical devices, electronic devices, and the like.

Here, in the present specification, the crystal plane of the main surface 10 has an accuracy error of ±0.5°. For example, in the case where the main surface 10 is the "(001) plane" of the β -type Ga ₂O₃ single crystal, this means that the main surface 10 may be a (001) positive (just) plane, or the main surface 10 may be a plane having an off angle of-0.5 to +0.5° from the (001) plane. The angle and direction of deviation of the main surface 10 of the β -type Ga ₂O₃ single crystal substrate 1 from the (001) plane can be measured by using a conventionally known crystal orientation measuring apparatus (for example, trade name (product number): FSASIII ", manufactured by the company, ltd.).

< Rhodium (Rh) and Ir (Ir) >

The β -type Ga ₂O₃ single-crystal substrate contains both or either rhodium (Rh) and iridium (Ir). The concentration of Rh and the concentration of Ir are both less than 3 mass ppm in GDMS. The concentration of Rh and the concentration of Ir in the GDMS are each preferably 1 mass ppm or less, more preferably 0.1 mass ppm or less, and still more preferably 0.01 mass ppm or less. The lower limit of the concentration of Rh and the concentration of Ir is not detected in GDMS. The β -type Ga ₂O₃ single crystal substrate is excellent in both electrical characteristics and optical characteristics by having less than 3 mass ppm of Rh and Ir.

The above-mentioned Rh and Ir are known as elements that can be contained in the β -type Ga ₂O₃ single crystal substrate. On the other hand, for example, when the β -type Ga ₂O₃ single crystal substrate is obtained by using the crucible of the fifth aspect and the method for producing the β -type Ga ₂O₃ single crystal substrate, both the Rh concentration and the Ir concentration can be easily reduced to less than 3 mass ppm in GDMS, based on the material of the crucible and the structure of the thermal spray film composed of the first film and the second film. This can provide a β -type Ga ₂O₃ single crystal substrate excellent in both electrical characteristics and optical characteristics with good yield.

(Glow discharge Mass Spectrometry (GDMS))

Hereinafter, a method for measuring the concentrations of Rh and Ir in the β -type Ga ₂O₃ single crystal substrate using Glow Discharge Mass Spectrometry (GDMS) will be described. GDMS is a method of measuring constituent elements in an ionized analysis sample by a mass spectrometer by sputtering the surface of the analysis sample in a high-purity argon atmosphere using the analysis sample as a cathode and generating glow discharge plasma. Thus, impurity elements including Rh and Ir, excluding Ga and O, contained in the β -type Ga ₂O₃ single crystal substrate can be qualitatively and quantitatively determined. As the ion source of the above-mentioned GDMS, any one of a flat cell and a needle cell (pin-SHAPED CELL) is used. The needle-shaped discharge cell can be applied to a sample that can be formed into a strip shape having a square of about 2mm and a length of 20 mm. Specifically, the method can be used for analyzing Si single crystals, gallium arsenide (GaAs) single crystals, indium phosphide (InP) single crystals, and the like, which can be used for producing a sample by cleavage. The sheet-like discharge cell can be applied to a sample to be analyzed which can be formed into a disk shape having a diameter of about 10mm, and can be used, for example, in analyzing polycrystal. In short, from the viewpoint of avoiding contamination of the analysis sample with impurity elements from the outside, it is preferable to select either one of the sheet-like discharge cell and the needle-like discharge cell as the ion source of the above-mentioned GDMS. Since the β -type Ga ₂O₃ single crystal substrate can produce a needle-shaped analysis sample using the cleavage direction as the longitudinal direction, it is preferable to produce a needle-shaped cell-shaped analysis sample from the β -type Ga ₂O₃ single crystal substrate as an ion source for GDMS.

The above GDMS can be performed, for example, in the following manner. First, a β -type Ga ₂O₃ single crystal substrate was obtained by a manufacturing method described later. Further, a bar-shaped Ga ₂O₃ analysis sample having a square 2mm and a length of 20mm was prepared by using the cleavage direction as the longitudinal direction of the β -type Ga ₂O₃ single crystal substrate, and was placed in a sample placement unit attached to the apparatus described below. Here, the sample placement portion is preferably cleaned by a conventional method and pre-sputtered for 60 minutes to prevent foreign matter from being mixed and to remove foreign matter. The analysis value at the time of pre-sputtering was used as a background value.

Next, the Ga ₂O₃ analysis sample placed on the sample placement surface can be subjected to GDMS under the following conditions. In addition, rh and Ir, which are elements other than Ga and O in the constituent elements of the Ga ₂O₃ analysis sample, can be calculated as semi-quantitative values by correcting the ionic strength ratio of Ga to Rh or the ionic strength ratio of Ga to Ir by the Relative Sensitivity Factor (RSF), respectively. The relative sensitivity coefficient may be a value built in software attached to the following device.

Device for glow discharge Mass Spectrometry (trade name (product number): manufactured by VG-9000,VG Elemental Co.)

Ion source needle discharge cell (liquid nitrogen cooling for analysis)

Discharge area 10mm in diameter

Discharge gas high purity argon (6N stage)

Discharge conditions 2MA,1kV (constant current mode)

Detector Faraday cup and multiplier

Mass spectrum resolution m/delta m (high resolution mode) above 4000

As described above, by analyzing the Ga ₂O₃ analysis sample, rh and Ir contained in the β -type Ga ₂O₃ single crystal substrate can be qualitatively and quantitatively determined. The lower limit concentration of the present GDMS is preferably 0.01 mass ppm.

(Transmittance and Carrier concentration)

In the β -type Ga ₂O₃ single crystal substrate, the transmittance for light having a wavelength of 400nm to 430nm is preferably 70% or more. In the hall measurement using the van der waals method, the carrier concentration measured at 25 ℃ is preferably 1×10 ¹⁷cm^-3 or more and 1.0×10 ¹⁹cm^-3 or less. This can provide further excellent electrical characteristics and optical characteristics.

As described above, in the β -type Ga ₂O₃ single crystal substrate, the transmittance for light having a wavelength of 400nm or more and 430nm or less is preferably 70% or more. The transmittance is more preferably 75% or more, and still more preferably 80% or more. The ideal value of the upper limit of the transmittance is 100%. The transmittance can be obtained by measuring the transmittance of light to the β -type Ga ₂O₃ single crystal substrate using an ultraviolet-visible infrared spectrophotometer or the like. Hereinafter, a specific procedure for obtaining the transmittance will be described with reference to fig. 7.

First, for example, a β -type Ga ₂O₃ single crystal substrate 1 is obtained based on the above-described production method. From this β -type Ga ₂O₃ single crystal substrate 1, rectangular slices 10a (for example, 600 μm in thickness) having a size of 20mm in the vertical direction x 20mm in the horizontal direction centered on the center O (for example, the center O of the main surface 10) were prepared, and samples for transmittance measurement were obtained. Next, light having a wavelength of 400nm or more and 430nm or less (for example, a wavelength of 427 nm) is vertically incident on the rectangular slice 10a with respect to the center of the rectangular slice 10a using an ultraviolet-visible infrared spectrophotometer (trade name (product number): "U-4000", manufactured by Hitachi high-tech Co., ltd.). This enables measurement of the transmittance of the light in the β -type Ga ₂O₃ single crystal substrate 1.

(Carrier concentration)

In the present embodiment, in the hall measurement using the van der waals method, the carrier concentration measured at 25 ℃ is preferably 1×10 ¹⁷cm^-3 or more and 1.0×10 ¹⁹cm^-3 or less. Specifically, in the hall measurement using the van der waals method, which uses the center of the β -type Ga ₂O₃ single crystal substrate as a measurement target, the carrier concentration obtained at 25 ℃ is preferably 1×10 ¹⁷cm^-3 or more and 1.0×10 ¹⁹cm^-3 or less. In the case where the carrier concentration is less than 1.0x10 ¹⁷cm^-3, the current may not be conducted when the semiconductor element is fabricated, and the element may not operate. When the carrier concentration exceeds 1.0X10 ¹⁹cm^-3, it is suggested that the crystal contains 1.0X10 ¹⁹cm^-3 or more inactive impurities, which may adversely affect the operation of the device. The carrier concentration is particularly preferably 5.0X10 ¹⁷cm^-3 or more and 3.8X10 ¹⁸cm^-3 or less. Thus, the n-type β -type Ga ₂O₃ single-crystal substrate can have excellent electrical characteristics that can be widely used in various electronic devices and optical devices. The carrier concentration can be obtained by the following measurement method.

The step of obtaining the carrier concentration will be specifically described below with reference to fig. 7 and 8. Fig. 8 is an explanatory view illustrating a hall measurement sample prepared using the central portion of the substrate in order to measure the carrier concentration in the β -type Ga ₂O₃ single crystal substrate according to the present embodiment. First, as shown in fig. 7, a single β -type Ga ₂O₃ single crystal substrate 1 is obtained, for example, based on the above-described production method. Rectangular slices 10a (for example, 600 μm thick) having a size of 4mm in the vertical direction x 4mm in the horizontal direction centered on the center O (for example, the center O of the main surface 10) are produced from the center portion of the β -type Ga ₂O₃ single crystal substrate 1. Next, as shown in fig. 8, electrodes 21 made of an alloy containing gold and titanium are formed at four corners of the rectangular slice 10a (surface to be measured), thereby obtaining a sample for hall measurement. Here, the shape of the electrode 21 is not limited to the rectangular shape shown in the drawings, and may be a sector shape or a circular shape. The carrier concentration of the rectangular slice 10a having the electrode 21 can be obtained by applying hall measurement by the van der waals method in an environment of 25 ℃. In the present specification, the carrier concentration obtained based on the rectangular slice as the measurement target is defined as the carrier concentration of the β -type Ga ₂O₃ single crystal substrate measured at 25 ℃.

< Use >

The β -type Ga ₂O₃ single crystal substrate of the present embodiment is more excellent in both electrical characteristics and optical characteristics, and thus can be used as a substrate for forming optical devices and electronic devices. In particular, a β -type Ga ₂O₃ single crystal substrate is preferably used as a substrate for forming an electronic device on the basis of good electrical characteristics.

Examples

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In this example, a β -type Ga ₂O₃ single crystal substrate was produced in accordance with the flow chart shown in fig. 6 using the single crystal production apparatus shown in fig. 1 and using a crucible having the main portions shown in fig. 2 to 5, respectively. In the following description, samples 101 to 115, 201 to 213, and 301 to 313 are examples. Samples 10A to 10C and samples 20A to 20C are comparative examples.

The "crystal outer diameter" of the β -type Ga ₂O₃ single crystal in each sample below refers to the crystal outer diameter obtained by the following method. That is, the outer diameters of the ingot at three points, i.e., a position (hereinafter, also referred to as "measurement point 1") corresponding to the boundary between the enlarged diameter portion and the straight tube portion, a position (hereinafter, also referred to as "measurement point 2") 10mm down from the crystal growth end side of the ingot, and an intermediate position (hereinafter, also referred to as "measurement point 3") between the measurement point 1 and the measurement point 2, were obtained, respectively, in the ingot of the β -type Ga ₂O₃ single crystal taken out from the crucible, and the average value thereof was defined as "crystal outer diameter".

[ Production of Ga ₂O₃ monocrystal substrate ]

< Sample 10A >

According to the method disclosed in patent document 1, an attempt is made to produce a β -type Ga ₂O₃ single crystal by using the vertical bridgman (VB: vertical Bridgeman) method, with the growth direction being the [001] direction. When the β -type Ga ₂O₃ single crystal was obtained, a crucible made of a pt—rh alloy containing 30 mass% of Rh was used. The inner diameter of the straight tube portion of the crucible was 105mm. Further, the thickness of the side wall portion of the crucible was 0.2. Mu.m, and the surface roughness Rz of the inner peripheral surface side surface of the side wall portion was 20. Mu.m. However, since the crucible is broken during crystal growth, the β -type Ga ₂O₃ single crystal cannot be obtained, and thus the β -type Ga ₂O₃ single crystal substrate of sample 10A cannot be obtained.

< Sample 10B >

The β -type Ga ₂O₃ single crystal was produced by the same method as that for obtaining the β -type Ga ₂O₃ single crystal substrate of sample 10A, with the growth direction being the [001] direction. In this test example, breakage of the crucible was not found. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 120mm. Further, the cutting step, the outer periphery polishing step, and the polishing step are sequentially performed on the β -type Ga ₂O₃ single crystal. In this manner, a β -type Ga ₂O₃ single crystal substrate of sample 10B was obtained. The β -type Ga ₂O₃ single crystal substrate of sample 10B had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 10B was 25 mass ppm in the above GDMS, and the concentration of Ir was 0.02 mass ppm in the above GDMS.

< Sample 10C >

Except that the thickness of the side wall portion of the crucible was set to 1.0mm, a β -type Ga ₂O₃ single crystal was produced in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of sample 10A, with the growth direction being the [001] direction. In this test example, breakage of the crucible was not found. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 108mm. Further, the cutting step, the outer periphery polishing step, and the polishing step are sequentially performed on the β -type Ga ₂O₃ single crystal. In the above manner, a β -type Ga ₂O₃ single crystal substrate of sample 10C was obtained. The β -type Ga ₂O₃ single crystal substrate of sample 10C had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 10C was 45 mass ppm in the GDMS, and the concentration of Ir was 0.02 mass ppm in the GDMS.

< Sample 101>

(Preparation step S110)

First, the single crystal growth apparatus 100, the seed crystal 8a composed of the β -type Ga ₂O₃ single crystal, and the bulk Ga ₂O₃ polycrystal are prepared by a conventionally known method or by obtaining a commercially available product. As the crucible 5 constituting the single crystal growth apparatus 100, a crucible having a side wall portion 5a composed of stabilized ZrO ₂ having a purity of 89.2 mass% containing CaO of 10.8 mass% and having a thickness of 3mm, and a thermally sprayed film 5b having a thickness of 500 μm was used. More specifically, the inner diameter of the straight cylindrical portion of the crucible 5 is 105mm. Further, the surface roughness Rz of the inner peripheral surface side surface of the side wall portion 5a was 20 μm. The composition of the thermally sprayed film 5b was a pt—rh alloy containing 30 mass% of Rh, and the porosity of the thermally sprayed film 5b was 10%.

(Raw material charging step S120 and raw material melting step S130)

Next, by a conventionally known method, the seed crystal 8a is housed in the seed crystal housing portion 51 of the crucible 5, and the bulk Ga ₂O₃ polycrystal is housed in a portion above the seed crystal 8 a. Specifically, a plurality of block-shaped Ga ₂O₃ polycrystal is stored in the diameter increasing portion 52 and the straight tube portion 53 and stacked. Next, the crucible 5 containing the seed crystal 8a and the bulk Ga ₂O₃ polycrystal therein is supported by the crucible holding table 6. Then, a current is supplied to the heating device 7 and the crucible 5 is heated to dissolve the Ga ₂O₃ polycrystal and a part of the seed crystal 8a, respectively, to prepare a Ga ₂O₃ melt 82. Next, the remaining portion of the seed crystal 8a is brought into contact with the Ga ₂O₃ melt 82 at the interface thereof.

(Ga ₂O₃ Single Crystal growth Process S140)

Next, the crucible 5 is gradually lowered (toward the bottom) along the axis of the crucible 5 with respect to the heating device 7, whereby a temperature gradient is formed in the crucible 5 in which the temperature on the seed crystal 8a side is low and the temperature on the Ga ₂O₃ melt 82 side is high. Thus, the beta-type Ga ₂O₃ single crystal 81 grown with the growth direction being the [001] direction was obtained from the Ga ₂O₃ melt 82 in the remainder on the seed crystal 8a side. Further, this operation was continued until the lowering distance reached 100mm. The temperature of the interface between the growing beta-type Ga ₂O₃ single crystal 81 and the Ga ₂O₃ melt 82 is 1800-1820 ℃. The temperature gradient in the interface was set to 5℃/cm. The speed at which the crucible 5 was lowered in its axial direction was set to 1 mm/hr. In this manner, an ingot of β -type Ga ₂O₃ single crystal was obtained. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

(Ga ₂O₃ Single Crystal substrate manufacturing Process S200)

Finally, the ingot of the β -type Ga ₂O₃ single crystal obtained in the Ga ₂O₃ single crystal growth step S140 is processed in each of the cutting step, the outer periphery polishing step, and the polishing step, whereby a β -type Ga ₂O₃ single crystal substrate is obtained. First, in the dicing step, the ingot is sliced into wafers having a thickness of 700 μm by a conventionally known method. In the outer periphery polishing step, the outer periphery of the wafer is polished by a conventionally known method to perform chamfering processing, thereby obtaining a wafer having a main surface constituted by a central portion and an outer periphery portion surrounding the outer periphery of the central portion. Further, in the polishing step, the center portion is polished by a conventionally known polishing method, and the surface roughness Ra defined in JIS B0681-2:2018 is set to 8nm at the center portion.

In the above manner, a β -type Ga ₂O₃ single crystal substrate of sample 101 was produced. The β -type Ga ₂O₃ single crystal substrate of sample 101 has a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 101 was 15 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 102>

In the preparation step, a crucible having a porosity of 20% in the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 101. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 102 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 102 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 102 was 20 mass ppm in the above GDMS, and the concentration of Ir was 0.01 mass ppm in the above GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 103>

In the preparation step, a crucible having a porosity of 30% in the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 101. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 103 was obtained from the β -type Ga ₂O₃ single crystal. The diameter of the β -type Ga ₂O₃ single crystal substrate of sample 103 was 101.6mm, and the thickness was 650. Mu.m. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 103 was 18 mass ppm in the above GDMS, and the concentration of Ir was 0.01 mass ppm in the above GDMS.

< Sample 104>

In the preparation step, a crucible having a thickness of 200 μm is prepared for the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a, and an ingot of a β -type Ga ₂O₃ single crystal is obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 101. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 104 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 104 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of the sample 104 was 17 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 105>

In the preparation step, a crucible having a thickness of 200 μm is prepared for the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a, and an ingot of a β -type Ga ₂O₃ single crystal is obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 102. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 105 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 105 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 105 was 25 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 106>

In the preparation step, a crucible having a thickness of 200 μm is prepared for the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a, and an ingot of a β -type Ga ₂O₃ single crystal is obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 103. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 106 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 106 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of the sample 106 was 40 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 107>

In the preparation step, a crucible having a surface roughness Rz of 100 μm on the inner peripheral surface side of the side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 104. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 107 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 107 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 107 was 28 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 108>

In the preparation step, a crucible having a surface roughness Rz of 100 μm on the inner peripheral surface side of the side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 105. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 108 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 108 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 108 was 15 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 109>

In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 104. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 109 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 109 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 109 was 22 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 110>

In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 105. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 110 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 110 has a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 110 was 25 mass ppm in the above GDMS, and the concentration of Ir was 0.02 mass ppm in the above GDMS.

< Sample 111>

In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining a β -type Ga ₂O₃ single crystal substrate of the sample 106. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 111 was obtained from the β -type Ga ₂O₃ single crystal. The diameter of the β -type Ga ₂O₃ single crystal substrate of sample 111 was 101.6mm, and the thickness was 650. Mu.m. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 111 was 27 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 112>

An ingot of β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of sample 111. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 112 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 112 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 112 was 20 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 113>

In the preparation step, a crucible having the inner peripheral surface side of the side wall portion 5a covered with a thermal spray film composed of the following first film 5b1 and second film 5b2 was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 109. That is, in the preparation step of this test example, the surface of the crucible 5 on the inner peripheral surface side of the side wall portion 5a was coated with the first film 5b1 composed of Rh and having a first film porosity of 30% and a thickness of 50 μm by spraying the first spraying material. Further, the first film 5b1 was coated with the second film 5b2 composed of Pt, having a second film porosity of 30% and a thickness of 150 μm by spraying the second spray material onto the first film 5b1.

The crystal outer diameter of the β -type Ga ₂O₃ single crystal thus obtained was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 113 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 113 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 113 is less than 0.01 mass ppm in the GDMS, and the concentration of Ir is less than 0.01 mass ppm in the GDMS.

< Sample 114>

An ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of sample 113. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 114 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 114 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of the sample 114 was 0.08 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 115>

An ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of sample 113. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 115 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 115 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 115 was 2.9 mass ppm in the GDMS, and the concentration of Ir was 0.01 mass ppm in the GDMS.

< Sample 20A and sample 20B >

Except that the inner diameter of the straight cylindrical portion of the crucible used for obtaining the above-mentioned Ga ₂O₃ single crystal was set to 156mm, the production of β -type Ga ₂O₃ single crystal substrates of sample 20A and sample 20B was attempted by the same procedure as the method for obtaining β -type Ga ₂O₃ single crystal substrates of sample 10A and sample 10B, respectively. However, since the above crucible was broken at the time of crystal growth, β -type Ga ₂O₃ single crystal substrates of the samples 20A and 20B could not be obtained.

< Sample 20C >

Beta-type Ga ₂O₃ single crystals were produced in the same manner as the method for producing beta-type Ga ₂O₃ single crystal substrates of sample 20A and sample 20B, except that the thickness of the side wall portion of the crucible was 1.0mm, and the growth direction was the [001] direction. In this test example, breakage of the crucible was not found. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 165mm. Further, the cutting step, the outer periphery polishing step, and the polishing step are sequentially performed on the β -type Ga ₂O₃ single crystal. In the above manner, a β -type Ga ₂O₃ single crystal substrate of sample 20C was obtained. The β -type Ga ₂O₃ single crystal substrate of sample 20C had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 20C was 38 mass ppm in the GDMS, and the concentration of Ir was 0.01 mass ppm in the GDMS.

< Sample 201>

In the preparation step, a crucible having an inner diameter of 156mm in the straight tube portion was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining a β -type Ga ₂O₃ single crystal substrate of sample 101. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 201 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 201 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 201 was 15 mass ppm in the above-described GDMS, and the concentration of Ir was 0.01 mass ppm in the above-described GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 202>

In the preparation step, a crucible having a porosity of 20% in the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 201. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 202 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 202 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 202 was 20 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth by heating, but breakage was found at the time of cooling after crystal growth.

< Sample 203>

In the preparation step, a crucible having a porosity of 30% in the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 201. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 203 was obtained from the β -type Ga ₂O₃ single crystal. The diameter of the β -type Ga ₂O₃ single crystal substrate of sample 203 was 152.4mm and the thickness was 650. Mu.m. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 203 was 23 mass ppm in the above GDMS, and the concentration of Ir was 0.01 mass ppm in the above GDMS.

< Sample 204>

In the preparation step, a crucible having a thickness of 200 μm is prepared for the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a, and an ingot of a β -type Ga ₂O₃ single crystal is obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 201. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 204 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 204 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 204 was 27 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 205>

In the preparation step, a crucible having a thickness of 200 μm is prepared for the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a, and an ingot of a β -type Ga ₂O₃ single crystal is obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 202. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of the sample 205 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 205 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 205 was 15 mass ppm in the above-described GDMS, and the concentration of Ir was 0.02 mass ppm in the above-described GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 206>

In the preparation step, a crucible having a thickness of 200 μm is prepared for the thermally sprayed film 5b on the inner peripheral surface side of the coated side wall portion 5a, and an ingot of a β -type Ga ₂O₃ single crystal is obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 203. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 206 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 206 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 206 was 35 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 207>

In the preparation step, a crucible having a surface roughness Rz of 100 μm on the inner peripheral surface side of the side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 204. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of the sample 207 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 207 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 207 was 18 mass ppm in the above GDMS, and the concentration of Ir was 0.01 mass ppm in the above GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 208>

In the preparation step, a crucible having a surface roughness Rz of 100 μm on the inner peripheral surface side of the side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 205. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 208 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 208 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of the sample 208 is 25 mass ppm in the GDMS, and the concentration of Ir is less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 209>

In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 204. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 209 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 209 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 209 was 32 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 210>

In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface side of the side wall portion 5a was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 205. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of the sample 210 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 210 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 210 was 26 mass ppm in the GDMS, and the concentration of Ir was 0.02 mass ppm in the GDMS.

< Sample 211>

In the preparation step, a crucible having the inner peripheral surface side of the side wall portion 5a covered with a thermal spray film composed of the following first film 5b1 and second film 5b2 was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 209. That is, in the preparation step of this test example, the surface of the crucible 5 on the inner peripheral surface side of the side wall portion 5a was coated with the first film 5b1 composed of Rh and having a first film porosity of 30% and a thickness of 50 μm by spraying the first spraying material. Further, the first film 5b1 was coated with the second film 5b2 composed of Pt, having a second film porosity of 30% and a thickness of 150 μm by spraying the second spray material onto the first film 5b1.

The crystal outer diameter of the β -type Ga ₂O₃ single crystal thus obtained was 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 211 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 211 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 211 was 0.02 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 212>

An ingot of β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of sample 211. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 212 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 212 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 212 is less than 0.01 mass ppm in the GDMS, and the concentration of Ir is less than 0.01 mass ppm in the GDMS.

< Sample 213>

An ingot of β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of sample 211. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal is 157.1mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 213 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 213 had a diameter of 152.4mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 213 was 2.8 mass ppm in the GDMS, and the concentration of Ir was 0.01 mass ppm in the GDMS.

< Sample 301>

In the preparation step S110, an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining a β -type Ga ₂O₃ single crystal substrate of the sample 101 except that the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 11 mass% of Rh, using the side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% containing 13.8 mass% of Y ₂O₃ and having a thickness of 9mm, as the crucible 5 constituting the single crystal growth apparatus 100. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 301 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 301 has a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 301 was 14 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 302>

In the preparation step S110, an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining a β -type Ga ₂O₃ single crystal substrate of the sample 102 except that the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 11 mass% of Rh, using the side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% containing 13.8 mass% of Y ₂O₃ and having a thickness of 9mm, as the crucible 5 constituting the single crystal growth device 100. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 302 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 302 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 302 was 21 mass ppm in the above GDMS, and the concentration of Ir was 0.01 mass ppm in the above GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 303>

In the preparation step S110, an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining a β -type Ga ₂O₃ single crystal substrate of sample 103 except that the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 11 mass% of Rh, using the side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% containing 13.8 mass% of Y ₂O₃, and having a thickness of 9mm, as the crucible 5 constituting the single crystal growth apparatus 100. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 303 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 303 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 303 was 19 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 304>

In the preparation step S110, as the crucible 5 constituting the single crystal growth apparatus 100, a side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% and containing 13.8 mass% of Y ₂O₃ was used, and the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 11 mass% of Rh, except that an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as in the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 104. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 304 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 304 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 304 was 18 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 305>

In the preparation step S110, an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining a β -type Ga ₂O₃ single crystal substrate of the sample 105 except that the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 11 mass% of Rh, using the side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% containing 13.8 mass% of Y ₂O₃ and having a thickness of 9mm, as the crucible 5 constituting the single crystal growth apparatus 100. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of the sample 305 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 305 has a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 305 was 24 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 306>

In the preparation step S110, as the crucible 5 constituting the single crystal growth apparatus 100, a side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% and containing 13.8 mass% of Y ₂O₃ was used, and the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 10 mass% of Rh, except that an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as in the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 106. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of the sample 306 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 306 has a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of the sample 306 was 22 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 307>

In the preparation step S110, as the crucible 5 constituting the single crystal growth apparatus 100, a side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% and containing 13.8 mass% of Y ₂O₃ was used, and the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 10 mass% of Rh, except that an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as in the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 107. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 307 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 307 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the β -type Ga ₂O₃ single crystal substrate of sample 307 was 25 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 308>

In the preparation step S110, as the crucible 5 constituting the single crystal growth apparatus 100, a side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% and containing 13.8 mass% of Y ₂O₃ was used, and the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 10 mass% of Rh, except that an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as in the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 108. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 308 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 308 has a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 308 was 17 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS. In addition, regarding the crucible 5, breakage was not found at the time of crystal growth, but breakage was found at the time of cooling after crystal growth.

< Sample 309>

In the preparation step S110, as the crucible 5 constituting the single crystal growth apparatus 100, a side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% and containing 13.8 mass% of Y ₂O₃ was used, and the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 10 mass% of Rh, except that an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 109. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 309 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of sample 309 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 309 was 21 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 310>

In the preparation step S110, an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 110 except that the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 10 mass% of Rh, using the side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% containing 13.8 mass% of Y ₂O₃ and having a thickness of 9mm, as the crucible 5 constituting the single crystal growth device 100. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of the sample 310 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 310 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 310 was 26 mass ppm in the GDMS, and the concentration of Ir was 0.01 mass ppm in the GDMS.

< Sample 311>

In the preparation step S110, as the crucible 5 constituting the single crystal growth apparatus 100, a side wall portion 5a composed of stabilized ZrO ₂ having a purity of 86.2 mass% and containing 13.8 mass% of Y ₂O₃ was used, and the composition of the thermal spray film 5b covering the inner peripheral surface side of the side wall portion 5a of the crucible 5 was changed to a pt—rh alloy containing 10 mass% of Rh, except that an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as in the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 111. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of the sample 311 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 311 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 311 was 14 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 312>

An ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of sample 311. The crystal outer diameter of the beta-type Ga ₂O₃ single crystal was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of sample 312 was obtained from the β -type Ga ₂O₃ single crystal. The beta Ga ₂O₃ single crystal substrate of sample 312 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of sample 312 was 13 mass ppm in the GDMS, and the concentration of Ir was less than 0.01 mass ppm in the GDMS.

< Sample 313>

In the preparation step, a crucible having the inner peripheral surface side of the side wall portion 5a covered with a thermal spray film composed of the following first film 5b1 and second film 5b2 was prepared, and an ingot of a β -type Ga ₂O₃ single crystal was obtained in the same manner as the method for obtaining the β -type Ga ₂O₃ single crystal substrate of the sample 309. That is, in the preparation step of this test example, the surface of the crucible 5 on the inner peripheral surface side of the side wall portion 5a was coated with the first film 5b1 composed of Rh and having a first film porosity of 30% and a thickness of 50 μm by spraying the first spraying material. Further, the first film 5b1 was coated with the second film 5b2 composed of Pt, having a second film porosity of 30% and a thickness of 150 μm by spraying the second spray material onto the first film 5b1.

The crystal outer diameter of the β -type Ga ₂O₃ single crystal thus obtained was 105.8mm. Further, a β -type Ga ₂O₃ single crystal substrate of the sample 313 was obtained from the β -type Ga ₂O₃ single crystal. The β -type Ga ₂O₃ single crystal substrate of the sample 313 had a diameter of 101.6mm and a thickness of 650 μm. The concentration of Rh in the beta Ga ₂O₃ single crystal substrate of the sample 313 is less than 0.01 mass ppm in the GDMS, and the concentration of Ir is less than 0.01 mass ppm in the GDMS.

Table 1, table 2 and Table 3 show the structures (inner diameter, composition, surface roughness Rz, thickness of side wall portion, composition of thermal spray film, porosity and thickness, etc.) of the crucible for producing the β -type Ga ₂O₃ single crystal substrates of samples 10A to 10C, 101 to 115, 20A to 20C, 201 to 213, and 301 to 313, respectively. In tables 1 to 3, the composition, porosity and thickness of the thermal spray coating film when it is a single layer are shown in the column of "thermal spray coating film (innermost layer: second film)".

TABLE 1

TABLE 1

TABLE 2

TABLE 2

TABLE 3

TABLE 3 Table 3

[ Evaluation ]

< Product yield >

The following method was used to obtain the yield of the β -type Ga ₂O₃ single crystal used to obtain the β -type Ga ₂O₃ single crystal substrates of samples 10B to 10C, samples 101 to 115, 20C, 201 to 213, and 301 to 313. As described above, the "product yield" refers to a ratio of the mass of the ingot of the β -type Ga ₂O₃ single crystal after crystal growth in the crucible to the mass of the portion of the substrate that can be evaluated as a good product by the evaluation method described later, excluding a region where a desired diameter cannot be obtained when processing into the β -type gallium trioxide single crystal substrate due to breakage or chipping of the crucible or breakage or chipping of the crystal upon cooling. The better the product yield of the single crystal, the less the occurrence of cracking, chipping, or the like in the crucible in which the single crystal is grown can be evaluated.

First, an ingot of β -type Ga ₂O₃ single crystal of each sample was taken out of a crucible, and a disk-shaped measurement sample (thickness: 1 mm) having a (001) surface was prepared by cutting out each of the ingot at the measurement point 1 and the measurement point 2 as a position for measuring the outer diameter of the crystal. Further, the main surface of the measurement sample was polished, and etching using conventionally known molten potassium hydroxide was performed.

Then, the entire surface of the measurement sample was observed with a differential interference microscope (trade name: LV-150, manufactured by Nikon, inc.), and the number of crystal defects occurring in one field of view of the differential interference microscope was counted for each field of view, and whether or not polycrystallization had occurred was determined. In this case, the observation with the differential interference microscope was performed at a magnification of 10 times. Thus, the differential interference microscope had a single field of view of 10mm×10mm, and the number of crystal defects per field of view was directly determined as a density (cm ^-2). The crystal defects are "pits" which appear as etching holes in the main surface by the etching. The pits described above are not technically synonymous with dislocations, but can be considered equivalent to dislocations in the art. The "dislocation" refers to a "threading dislocation" existing in the beta-type Ga ₂O₃ single crystal, and is considered to be one mode of crystal defect.

Next, when no polycrystallization was observed in the measurement sample, the measurement sample was evaluated as good. On the other hand, when at least polycrystallization is observed in the measurement sample, the measurement sample is evaluated as defective. For the ingot from which the measurement sample evaluated as defective was cut, a new measurement sample was cut at a position 10mm away from the measurement point 1 or the measurement point 2, which is a position from which the measurement sample was cut, toward the measurement point 3, and the observation was performed on the new measurement sample using the differential interference microscope. This operation is repeated until the measurement sample is judged to be good.

Finally, the volume of the ingot was obtained from the length (height) of the ingot enclosed by the position where the measurement sample determined to be good was cut out from the ingot and the diameter (i.e., 101.6mm or 152.4 mm) of the β -type Ga ₂O₃ single crystal substrate of each sample, and the mass of the ingot (hereinafter, also referred to as "good quality") that could be a product was obtained by converting the volume. Next, the ratio of the quality of the good product to the quality of the region sandwiched between the measurement point 1 and the measurement point 2 in the ingot was determined and used as "product yield". The results are shown in tables 4,5 and 6.

[ Measurement of activation Rate ]

The carrier concentrations of the samples 10B to 10C, 101 to 115, 20C, 201 to 213, and 301 to 313 were obtained by performing the above measurement method on the samples for hall measurement prepared by using the central portions of the substrates. Further, the impurity concentration of Sn or Si in the β -type Ga ₂O₃ single crystal substrate was determined by Glow Discharge Mass Spectrometry (GDMS). The activation rate of each sample was calculated by dividing the carrier concentration of each sample by the impurity concentration obtained by GDMS. The results are shown in tables 4, 5 and 6.

[ Measurement of transmittance ]

The transmittance of the β -type Ga ₂O₃ single crystal substrates of samples 10B to 10C, samples 101 to 115, 20C, 201 to 213, and 301 to 313 was obtained by performing the above-described measurement method on the transmittance measurement samples prepared by using the central portions of the substrates. The results are shown in tables 4, 5 and 6.

TABLE 4

TABLE 4 Table 4

Regarding "crucible breakage", NG indicates that breakage was observed at the time of crystal growth, and G indicates that breakage was not observed.

* Indicating cracking upon cooling after crystal growth.

TABLE 5

TABLE 5

Regarding "crucible breakage", NG indicates that breakage was observed at the time of crystal growth, and G indicates that breakage was not observed.

* Indicating cracking upon cooling after crystal growth.

TABLE 6

TABLE 6

Regarding "crucible breakage", NG indicates that breakage was observed at the time of crystal growth, and G indicates that breakage was not observed.

* Indicating cracking upon cooling after crystal growth.

[ Inspection ]

According to table 4, the product yields of the β -type Ga ₂O₃ single crystal substrates of samples 101 to 115 were better than those of the β -type Ga ₂O₃ single crystal substrates of samples 10B to 10C. Therefore, it was possible to evaluate that the crucible for producing the β -type Ga ₂O₃ single crystal substrates of samples 101 to 115 was more capable of suppressing the occurrence of cracking and chipping during crystal growth than the crucible for producing the β -type Ga ₂O₃ single crystal substrates of samples 10B to 10C. According to table 5, the yield of the β -type Ga ₂O₃ single crystal substrate of samples 201 to 213 was better than that of the β -type Ga ₂O₃ single crystal substrate of sample 20C. Therefore, it was possible to evaluate that the crucible for producing the β -type Ga ₂O₃ single crystal substrate of samples 201 to 213 was more capable of suppressing the occurrence of cracking and chipping during crystal growth than the crucible for producing the β -type Ga ₂O₃ single crystal substrate of sample 10C. According to table 6, the yield of β -type Ga ₂O₃ single crystal substrates of samples 301 to 313 was as good as that of β -type Ga ₂O₃ single crystal substrates of samples 101 to 115. Therefore, it was possible to evaluate that the crucible for producing the β -type Ga ₂O₃ single crystal substrates of samples 301 to 313 can suppress the occurrence of cracking and chipping during crystal growth.

Particularly, the β -type Ga ₂O₃ single crystal substrates of samples 113 to 115, samples 211 to 213, and the β -type Ga ₂O₃ single crystal substrate of sample 313 were also superior in activation rate and transmittance to other samples. Therefore, the β -type Ga ₂O₃ single crystal substrates of samples 113 to 115, 211 to 213, and 313 can be evaluated, and a compound semiconductor substrate excellent in both electrical characteristics and optical characteristics can be provided.

Although the embodiments and examples of the present invention have been described above, the configuration of appropriately combining the above-described embodiments and examples is originally intended.

The presently disclosed embodiments and examples are considered in all respects as illustrative and not restrictive. The scope of the present invention is expressed not by the above-described embodiments and examples but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Description of the reference numerals

100 Parts OF a single crystal growth apparatus, 5 parts OF a crucible, 51 parts OF a seed crystal storage portion, 52 parts OF a diameter-increasing portion, 53 parts OF a straight cylindrical portion, 5a parts OF a side wall, 5b parts OF a thermal spray film, 5b1 parts OF a first film, 5b2 parts OF a second film, 5c parts OF a pore, 6 parts OF a crucible holding table, 7 parts OF a heating device, 8a parts OF a seed crystal, 81 parts OF beta Ga ₂O₃ single crystal, 82 parts OF a gallium oxide melt (Ga ₂O₃ melt), 9 parts OF a closed container, 1 parts OF beta gallium oxide single crystal substrate (beta Ga ₂O₃ single crystal substrate), 10 parts OF a main surface, 10a parts OF a rectangular slice, O parts OF a center, a positioning edge, 21 parts OF an electrode, 100 parts OF beta Ga ₂O₃ single crystal production process, 110 parts OF a preparation process, 120 parts OF a raw material storage process, 130 parts OF a raw material melting process, 140 parts OF a Ga ₂O₃ single crystal growth process, and 200 parts OF beta Ga ₂O₃ single crystal substrate production process.

Claims (12)

1. A crucible for growing beta-type gallium trioxide single crystals,

The crucible has a thickness of 1mm or more and 10mm or less,

The maximum inner diameter of the crucible is more than 100mm,

The composition of the crucible is stabilized zirconia comprising either or both yttria and calcia,

The inner peripheral surface of the crucible is coated with a thermal spraying film containing rhodium and/or platinum,

The thickness of the thermal spray coating film is 100 μm or more and 500 μm or less,

The stabilized zirconia contains at least 12.0 mass% or more and 15.5 mass% or less of the yttrium oxide or 10.2 mass% or more and 11.4 mass% or less of the calcium oxide.

2. The crucible of claim 1, wherein the thermally sprayed film is composed of a platinum-rhodium alloy containing 10 mass% or more and 30 mass% or less of rhodium.

3. The crucible of claim 2, wherein,

The thermally sprayed film has an aperture that,

The porosity, which is the volume ratio of the pores in the thermal spray coating film, is 30 to 50% by volume.

4. The crucible of claim 2, wherein,

The surface roughness Rz of the surface is 300-500 μm,

The thermally sprayed film has an aperture that,

The volume ratio of the voids in the thermal spray coating film, that is, the porosity, is 10% by volume or more and less than 30% by volume.

5. A crucible as claimed in claim 3, wherein the surface has a surface roughness Rz of 300 μm or more and 500 μm or less.

6. The crucible of claim 1, wherein,

The thermal spray coating film is composed of a first film and a second film,

The first film coats the surface,

The first film is composed of rhodium or a platinum-rhodium alloy containing rhodium as a main component,

The second film covers the first film,

The second film is composed of platinum or a platinum-rhodium alloy containing platinum as a main component,

The thickness of the thermal spray coating film is 100 [ mu ] m to 500 [ mu ] m based on the total of the first film and the second film.

7. The crucible of claim 6, wherein,

The first membrane and the second membrane each have pores,

The volume ratio of the pores in the first film, i.e., the first film porosity, and the volume ratio of the pores in the second film, i.e., the second film porosity, are both 30% by volume or more and 50% by volume or less.

8. The crucible of claim 6, wherein,

The surface roughness Rz of the surface is 300-500 μm,

The first membrane and the second membrane each have pores,

The volume ratio of the pores in the first film, i.e., the first film porosity, and the volume ratio of the pores in the second film, i.e., the second film porosity, are each 10% by volume or more and less than 30% by volume.

9. The crucible as recited in claim 7, wherein the surface has a surface roughness Rz of 300 μm or more and 500 μm or less.

10. A method for producing a beta-type gallium trioxide single crystal substrate using the crucible according to any one of claims 1 to 9,

The manufacturing method comprises the following steps:

A step of preparing the crucible;

a step of obtaining a beta-type gallium oxide single crystal by a vertical boat method using the crucible;

And a step of processing the beta-type gallium trioxide single crystal to obtain a beta-type gallium trioxide single crystal substrate having a circular main surface.

11. A beta-type gallium oxide single crystal substrate having a main surface of circular shape,

The diameter of the beta-type gallium oxide single crystal substrate is more than 100mm,

The main surface is the (001) plane of the beta-type gallium trioxide single crystal, or

The main surface is a surface having a deviation angle of more than 0 DEG and 10 DEG or less from the (001) surface of the beta-type gallium trioxide single crystal and a deviation direction of the [010] direction or a direction orthogonal to the [010] direction of the beta-type gallium trioxide single crystal,

The beta gallium oxide single crystal substrate comprises either or both rhodium and iridium,

The concentration of rhodium and the concentration of iridium are both less than 3 mass ppm in glow discharge mass spectrometry analysis.

12. The beta gallium oxide single crystal substrate according to claim 11, wherein,

The beta-type gallium oxide single crystal substrate has a transmittance of 70% or more for light having a wavelength of 400nm or more and 430nm or less,

In Hall measurement by Van der Waals method, the carrier concentration measured at 25 ℃ is 1×10 ¹⁷cm^-3 or more and 1.0×10 ¹⁹cm^-3 or less.