WO2024154750A1 - Semiconductor element and method for producing same - Google Patents

Abstract

A semiconductor element disclosed in the present description is provided with: an element main body that comprises quantum dots in the surface; and a passivation film that is provided on the surface of the element main body so as to cover the quantum dots. The film thickness of the passivation film is smaller than the height of the projected shapes of the quantum dots. The surface of the passivation film is displaced so as to follow the projected shapes of the quantum dots.

Description

Semiconductor device and manufacturing method thereof

This specification relates to a semiconductor device and a method for manufacturing the same.

As can be seen from Patent Documents 1-7 and Non-Patent Documents 1-15, technology that uses semiconductor elements that contain quantum dots has been attracting attention in recent years. In these semiconductor elements, it is common to coat or passivate the surfaces of the quantum dots in order to passivate the quantum dots and prevent contamination.

For example, Patent Document 1 discloses a semiconductor device that includes an element body having quantum dots on its surface, and a coating film or passivation film that is provided on the surface of the element body and covers the quantum dots. The surface of the coating film or passivation film is almost flat, without following the convex shape of the quantum dots.

JP 2001-237413 A JP 2009-10425 A JP 2011-129733 A Japanese Patent Application Publication No. 5-243209 JP 2006-165537 A JP 2018-82211 A JP 2018-174270 A

K. Nishi, H. Saito, S. Sugou, and J-S. Lee, “A narrow photoluminescence linewidth of 21 meV at 1.35 μm from strain-reduced InAs quantum dots covered by In0.2Ga0.8As grown on GaAs substrates,” Appl. Phys. Lett. 74 (1999) 1111. H. Saito, K. Nishi, and S. Sugou, “Ground-state lasing at room temperature in long-wavelength InAs quantum-dot lasers on InP(311)B substrates,” Appl. Phys. Lett. 78 (2001) 267 . H. Saito, K. Nishi, and S. Sugou, “Influence of GaAs capping on the optical properties of InGaAs/GaAs surface quantum dots with 1.5 μm emission,” Appl. Phys. Lett. 73 (1998) 2742. Z. Z. Sun, S. F. Yoon, W. K. Loke, and C. Y. Liu, “Mechanism of emission-energy tuning in InAs quantum dots using a thin upper confinement layer,” Appl. Phys. Lett. 88 (2006) 203114. Z. Mi, et al., “Growth and characteristics of ultralow threshold 1.45 μm metamorphic InAs tunnel injection quantum dot lasers on GaAs,” Appl. Phys. Lett. 89 (2006) 153109. K. Shimomura and I. Kamiya, “Strain engineering of quantum dots for long wavelength emission: Photoluminescence from self-assembled InAs quantum dots grown on GaAs(001) at wavelengths over 1.55 μm,” Appl. Phys. Lett. 106 (2015) 082103. C. J. Sandroff, R. N. Nottenburg, J.-C. Bischoff, and R. Bhat, “Dramatic enhancement in the gain of a GaAs/AlGaAs heterostructure bipolar transistor by surface chemical passivation,” Appl. Phys. Lett. 51 (1987) 33. B. J. Skromme, C. J. Sandroff, E. Yablonovitch, and T. Gmitter, “Effects of passivating ionic films on the photoluminescence properties of GaAs,” Appl. Phys. Lett. 51 (1987) 2022. Jia-Fa FAN, Haruhiro Oigawa, and Yasuo Nannichi, “The Effect of (NH4)2S Treatment on the Interface Characteristics of GaAs MIS Structures,” J. J. Appl. Phys. 27 (1988) L1331. N. Li, Eric S. Harmon, James Hyland, David B. Sazman, T. P. Ma, Yi Xuan, and P. D. Ye, “Properties of InAs metal-oxide-semiconductor structures with atomic-layer-deposited Al2O3 Dielectric,” Appl. Phys. Lett. 92 (2008) 143507. R. Timm, A. Fian, M. Hjort, C. Thelander, E. Lind, J. N. Andersen, L-E. Wernersson, and A. Mikkelsen, “Reduction of native oxides on InAs by atomic layer deposited Al2O3 and HfO2, ” Appl. Phys. Lett. 97 (2010) 132904. Xiaoye Qin and Robert M. Wallace, “In-situ plasma enhanced atomic layer deposition half cycle study of Al2O3 on AlGaN/GaN high electron mobility transistors,” Appl. Phys. Lett. 107 (2015) 081608. Omer Salihoglu, “Atomic layer deposited passivation layers for superlattice photodetectors,” J. Vac. Sci. Technol. B 32 (2014) 051201. Abhiroop Chellu, Eero Koivusalo, Marianna Raappana, Sanna Ranta, Ville Polojaervi, Antti Tukiainen, Kimmo Lahtonen, Jesse Saari, Mika Valden, Heli Seppaenen, Harri Lipsanen, Mircea Guina and Teemu Hakkarainen, “GaAs surface passivation for InAs/GaAs quantum dot based nanophotonic devices,” Nanotechnology 32 (2021) 130001. H. Mohammadi, Ronel C. Roca, and I. Kamiya, “Anomalous photoluminescence of InAs surface quantum dots: intensity enhancement and strain control by underlying quantum dots,” Nanotechnology 33 (2022) 415204.

In the semiconductor element of Patent Document 1, the coating film cannot be provided to follow the convex shape of the quantum dots, so the stress acting on the quantum dots is non-uniform. This can result in excessive stress acting locally on the quantum dots, causing distortion of the quantum dots. As a result, although the luminous intensity of the quantum dots is ensured, the peak of the luminous wavelength of the quantum dots shifts to the short wavelength side, making it impossible to realize a semiconductor element that exhibits a stable luminous intensity on the long wavelength side. This specification provides technology that can realize a semiconductor element that exhibits a stable luminous intensity on the long wavelength side.

The semiconductor device disclosed in this specification comprises an element body having quantum dots on its surface, and a passivation film provided on the surface of the element body and covering the quantum dots. The surface of the passivation film is displaced to follow the convex shape of the quantum dots.

With the above configuration, the passivation film that covers the surface of the quantum dot can be provided to follow the convex shape of the quantum dot. This makes the stress acting on the quantum dot uniform, and prevents excessive stress from acting locally on the quantum dot. This prevents distortion of the quantum dot, and prevents the peak of the emission wavelength of the quantum dot from shifting to the short wavelength side. In addition, the passivation effect of the passivation film can be obtained, making it possible to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side. This also shows that the loss of carriers (mobile charges) due to the existence of non-radiative recombination processes is suppressed, which is an essential requirement not only for applications to light-emitting elements, but also for applications such as light-receiving elements and sensors.

1 is a diagram illustrating a semiconductor element 2 according to a first embodiment of the present invention; FIG. 2 is a diagram showing a schematic view of an element body 4 with its surface uncoated. FIG. 1 is a diagram illustrating a PEALD apparatus according to a first embodiment. 4 is a flowchart showing a process for forming a passivation film 6 on a surface of an element body 4, which is executed by a control device 38 of the PEALD apparatus according to the first embodiment. FIG. 1 is a diagram illustrating a conventional semiconductor element 102. 4 is a graph showing the results of fluorescence measurements performed on the semiconductor device 2 according to Example 1. FIG. 13 is a diagram illustrating a semiconductor element 202 according to a second embodiment. 11 is a graph showing the results of fluorescence measurements performed on the semiconductor device 202 according to Example 2.

In one or more embodiments, the thickness of the passivation film may be smaller than the height of the convex shape of the quantum dot.

If the passivation film becomes excessively thick compared to the size of the quantum dots, the stress acting on the quantum dots will be excessively large, causing distortion of the quantum dots. With the above configuration, the passivation film can be said to be relatively thin, since the film thickness is smaller than the height of the convex shape of the quantum dots. This makes it possible to prevent the stress acting on the quantum dots from becoming excessively large, thereby preventing distortion of the quantum dots.

In one or more embodiments, the difference between the minimum and maximum thicknesses of the passivation film may be 50% or less of the height of the convex shape of the quantum dot, or even 30% or less, or even 10% or less.

If the difference between the minimum and maximum film thicknesses (hereinafter simply referred to as the "film thickness difference") is large, the stress acting on the quantum dots cannot be made sufficiently uniform, and it may not be possible to sufficiently prevent distortion of the quantum dots. With the above configuration, the film thickness difference is 50% or less of the height of the convex shape of the quantum dots, so it can be said that the film thickness difference is relatively small. As a result, the stress acting on the quantum dots can be made sufficiently uniform, and distortion of the quantum dots can be sufficiently prevented.

In one or more embodiments, at least a portion of the passivation film may have an amorphous structure.

Generally, when comparing the same materials, a crystalline structure is less flexible than an amorphous structure. For this reason, if the passivation film does not have an amorphous structure (i.e., if the passivation film is composed only of a crystalline structure), the stress acting on the quantum dots becomes large. This may cause distortion in the quantum dots, and the peak of the emission wavelength of the quantum dots may shift to the short wavelength side. As a result, it becomes difficult to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side. In contrast, according to the above configuration, at least a part of the passivation film has an amorphous structure, so the stress acting on the quantum dots is reduced. This makes it possible to suppress distortion in the quantum dots, and therefore to suppress the shift of the peak of the emission wavelength of the quantum dots to the short wavelength side. Therefore, it is possible to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side.

Furthermore, when the crystalline structures of the quantum dots and the passivation film come into contact at the interface between them, a lattice mismatch occurs at the interface between them due to the difference in lattice constants between the crystalline structures of the two. The lattice mismatch may cause distortion in the quantum dots, and the peak of the emission wavelength of the quantum dots may shift to the short wavelength side. As a result, it becomes difficult to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side. According to the above configuration, at least a part of the passivation film has an amorphous structure. In the region where the crystalline structure of the quantum dots and the amorphous structure of the passivation film come into contact with each other, lattice mismatch does not occur, and the number of dangling bonds of atoms is significantly reduced. Therefore, the region where lattice mismatch occurs at the interface between the quantum dots and the passivation film can be reduced. Therefore, it is possible to suppress the occurrence of distortion and non-radiative recombination sites in the quantum dots, and therefore it is possible to suppress the shift of the peak of the emission wavelength of the quantum dots to the short wavelength side. This makes it possible to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side.

In one or more embodiments, the passivation film may be made of a material capable of forming the amorphous structure under temperature conditions of 300°C or less.

In the process of forming the passivation film, interdiffusion of materials may occur between the quantum dots and the layer adjacent to the quantum dots (for example, the base layer of the device body or the passivation film). If interdiffusion of materials occurs actively, the dot size of the quantum dots is reduced. As a result, the peak of the emission wavelength of the quantum dots shifts to the short wavelength side, making it difficult to realize a semiconductor device that exhibits stable emission intensity on the long wavelength side. In addition, the higher the temperature, the more active the interdiffusion of materials. Therefore, from the viewpoint of suppressing interdiffusion of materials, it is preferable to form the passivation film under low temperature conditions. According to the above configuration, a material that can form an amorphous structure under temperature conditions of 300° C. or less is used for the passivation film. In other words, the passivation film according to the present application can be formed under temperature conditions of 300° C. or less. Therefore, since it is possible to suppress the active interdiffusion of materials, it is possible to suppress the peak of the emission wavelength of the quantum dots from shifting to the short wavelength side. This makes it possible to realize a semiconductor device that exhibits stable emission intensity on the long wavelength side.

In one or more embodiments, the _passivation film may include any one of _Al2O3 and ZnO.

Although the details will be described later, the results of fluorescence measurement have already been obtained when either _Al2O3 or ZnO is used as the passivation film. Therefore, according to the above configuration, the fluorescence characteristics of the semiconductor element are known, which makes _it easy to put the semiconductor element into practical use.

In one or more embodiments, the thickness of the passivation film may be in the range of 0.3 nm or more and less than 1000 nm.

If the passivation film is excessively thick, the stress acting on the quantum dots will be large, causing distortion of the quantum dots. From this perspective, it is preferable that the thickness of the passivation film is less than 1000 nm. On the other hand, if the passivation film is excessively thin, it may not be possible to completely cover the surface of the element body. From this perspective, it is preferable that the thickness of the passivation film is 0.3 nm or more. According to the above configuration, the thickness of the passivation film is 0.3 nm or more and less than 1000 nm. As a result, it is possible to completely cover the surface of the element body while suppressing distortion of the quantum dots.

In one or more embodiments, the quantum dots may be made of any one of a III-V group semiconductor, a II-VI group semiconductor, and a IV group semiconductor.

With the above configuration, the passivation film of the present application can be applied to various types of quantum dots.

Another semiconductor element disclosed in this specification comprises an element body having quantum dots on a surface thereof, and a passivation film provided on the surface of the element body and covering the quantum dots. At least a portion of the passivation film has an amorphous structure.

The method for manufacturing a semiconductor device disclosed in this specification includes the steps of preparing a device body having quantum dots on its surface, and forming a passivation film on the surface of the device body to cover the quantum dots. At least a portion of the passivation film has an amorphous structure.

Generally, when comparing the same materials, a crystalline structure is less flexible than an amorphous structure. For this reason, if the passivation film does not have an amorphous structure (i.e., if the passivation film is composed only of a crystalline structure), the stress acting on the quantum dots will be large. This may cause distortion in the quantum dots, and the peak of the emission wavelength of the quantum dots may shift to the short wavelength side. As a result, it becomes difficult to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side. In contrast, according to the above method, a passivation film having at least a part of an amorphous structure can be formed, so that the stress acting on the quantum dots can be reduced. This makes it possible to suppress the occurrence of distortion in the quantum dots, and therefore to suppress the shift of the peak of the emission wavelength of the quantum dots to the short wavelength side. Therefore, it is possible to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side.

Furthermore, when the crystal structures of the quantum dots and the passivation film come into contact at the interface between them, a lattice mismatch occurs at the interface between them due to the difference in lattice constants between the two crystal structures. The lattice mismatch may cause distortion in the quantum dots, and the peak of the emission wavelength of the quantum dots may shift to the short wavelength side. As a result, it becomes difficult to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side. According to the above method, a passivation film having at least a part of an amorphous structure is formed. In the region where the crystal structure of the quantum dots and the amorphous structure of the passivation film come into contact with each other, no lattice mismatch occurs. Therefore, the region where lattice mismatch occurs at the interface between the quantum dots and the passivation film can be reduced. Therefore, it is possible to suppress distortion in the quantum dots, and therefore to suppress the peak of the emission wavelength of the quantum dots from shifting to the short wavelength side. This makes it possible to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side.

In one or more embodiments, the step of forming the passivation film may include a step of growing the passivation film at a rate of 0.05 ML/s (monolayer per second) or less.

If the growth rate of the passivation film is too fast, the thickness of the passivation film may become non-uniform. For example, when the passivation film is grown by a method such as epitaxial growth, the growth rate of the passivation film is at least 0.06 ML/s, so the thickness of the passivation film may become non-uniform. In this case, the stress acting on the quantum dots becomes non-uniform, and excessive stress acts locally on the quantum dots. This may cause distortion in the quantum dots, and the peak of the emission wavelength of the quantum dots may shift to the short wavelength side. As a result, it becomes difficult to realize a semiconductor element that exhibits stable emission intensity on the long wavelength side. In contrast, according to the above method, the growth rate of the passivation film is 0.05 ML/s or less, so the thickness of the passivation film is relatively uniform. As a result, the stress acting on the quantum dots is uniform, and the effect of excessive stress locally on the quantum dots is suppressed. This prevents the quantum dots from being distorted, and prevents the peak emission wavelength of the quantum dots from shifting to the shorter wavelength side. This makes it possible to realize a semiconductor device that exhibits stable emission intensity on the longer wavelength side.

In one or more embodiments, the step of forming the passivation film may include a step of growing the passivation film under a temperature condition of 300°C or less.

In the process of growing the passivation film, interdiffusion of materials may occur between the quantum dots and layers adjacent to the quantum dots (for example, the underlayer of the device body or the passivation film). If interdiffusion of materials occurs actively, the dot size of the quantum dots is reduced. As a result, the peak of the emission wavelength of the quantum dots shifts to the short wavelength side, making it difficult to realize a semiconductor device that exhibits stable emission intensity on the long wavelength side. In addition, the higher the temperature, the more active the interdiffusion of materials. Therefore, from the viewpoint of suppressing interdiffusion of materials, it is preferable to grow the passivation film under low temperature conditions. According to the above method, the passivation film is grown under temperature conditions of 300° C. or less. Therefore, since it is possible to suppress the interdiffusion of materials from occurring actively, it is possible to suppress the shift of the peak of the emission wavelength of the quantum dots to the short wavelength side. This makes it possible to realize a semiconductor device that exhibits stable emission intensity on the long wavelength side.

In one or more embodiments, the process for forming the passivation film may be a process using atomic layer deposition, and may include a process for sequentially supplying multiple precursors to the surface of the element body and reacting the multiple precursors with each other.

Atomic layer deposition involves repeatedly performing a cycle of growing a passivation film by reacting multiple precursors with each other at the molecular level. This allows the thickness of the passivation film to be adjusted at the molecular level, so the passivation film can be formed to mimic the convex shape of the quantum dots. Furthermore, atomic layer deposition allows the passivation film to be grown in an amorphous form. Therefore, in a semiconductor element coated with atomic layer deposition, the stress acting on the quantum dots is reduced. This prevents the quantum dots from being distorted, and prevents the peak of the quantum dot's emission wavelength from shifting to the short wavelength side. This allows a semiconductor element to be realized that exhibits stable emission intensity on the long wavelength side.

In one or more embodiments, the plurality of precursors may include a material that acts as a reducing agent for native oxides present on the surface of the element body.

Natural oxides may form on the surface of the element body. If natural oxides remain on the surface of the element body, the effect of covering the quantum dots with a coating layer may not be properly achieved. In contrast, according to the above method, the multiple precursors contain a material that acts as a reducing agent on the natural oxides. Therefore, in the second step, the natural oxides present on the surface of the element body are reduced (i.e., removed) before the passivation film is formed. Therefore, the effect of covering the quantum dots with a coating layer is properly achieved.

In one or more embodiments, the precursors may include at least one of TMA (trimethylaluminum) and DEZ (diethylzinc).

(Example 1; Semiconductor element 2)
1, a semiconductor device 2 of this embodiment includes an element body 4 and a passivation film 6. The element body 4 includes a GaAs substrate 8, a GaAs buffer layer 10, an InAs/GaAs carrier supply layer 12, a GaAs spacer layer 14, and an InAs quantum dot layer 16.

FIG. 2 shows the device body 4 before the passivation film 6 is formed. The device body 4 is mainly fabricated based on molecular beam epitaxy (MBE). The method of fabricating the device body 4 includes the steps of setting the GaAs substrate 8 in an MBE apparatus (not shown), heating the GaAs substrate 8 and removing the oxide film present on the GaAs substrate 8, and growing a GaAs buffer layer 10, an InAs/GaAs carrier supply layer 12, a GaAs spacer layer 14, and an InAs quantum dot layer 16, in that order, on the GaAs substrate 8.

The GaAs buffer layer 10 is provided from the viewpoint of improving crystallinity. The GaAs buffer layer 10 is provided with a film thickness of approximately 100 nm. The InAs/GaAs carrier supply layer 12 is provided to increase the emission intensity (for details, see Non-Patent Document 10).

In the process of growing the InAs quantum dot layer 16, InAs is deposited on the GaAs spacer layer 14 in an amount equivalent to 2.8 ML (monolayer). As a result, a layer (also called a wetting layer) having a composition of In _x Ga _1-x As (x=0.67) is formed with a thickness of 1 ML, and quantum dots 16a having a convex shape protruding from the surface of the wetting layer are formed by themselves. It is known that the height of the convex shape of the quantum dots 16a is about 2 nm to 10 nm.

The quantum dots 16a are also called surface quantum dots because they are located on the outermost surface of the element body 4. When the quantum dots 16a are on the outermost surface, an electronic state called a surface state is formed on the surface of the quantum dots 16a. It is known that the surface state is a factor that reduces the luminous intensity of the quantum dots 16a. In response to this, a method called surface passivation has been proposed. Passivation is a method of chemically treating the surface of an uncoated material to inactivate the surface state, which is a type of defect. For example, it has been reported that for III-V semiconductors, surface termination with a material containing VI group atoms, such as ammonium sulfide or sulfide, has resulted in an increase in luminous intensity and an improvement in the gain of bipolar transistors.

It is also known that when the quantum dots 16a are exposed to the atmosphere, components in the atmosphere are adsorbed to or react with the quantum dots 16a, thereby contaminating the quantum dots 16a. For example, when the quantum dots 16a react with oxygen and moisture in the atmosphere, natural oxides (oxides of In and As) are formed on the surface of the quantum dots 16a. It is also known that natural oxides are a factor that reduces the luminescence intensity of the quantum dots 16a.

Therefore, a passivation film is provided on the surface of the element body 4 for the purpose of passivating the surface quantum dots and preventing contamination. When the element body 4 is removed from the MBE apparatus immediately after being produced by the MBE apparatus, the quantum dots 16a are temporarily exposed to the atmosphere, and some natural oxide is generated on the surface of the quantum dots 16a. For this reason, it has been common in the past to form a passivation film using the MBE apparatus after the element body 4 is produced and before the element body 4 is removed from the MBE apparatus.

However, in this embodiment, the element body 4 produced by the MBE apparatus is removed from the MBE apparatus and transferred to a PEALD apparatus 20 (plasma-assisted atomic layer deposition apparatus) shown in Figure 3. A passivation film 6 is formed on the surface of the element body 4 using the PEALD apparatus 20.

The PEALD apparatus 20 includes an ALD chamber 22, a stage 24, a heater 26, a sensor 28, a first precursor supply device 30, a second precursor supply device 32, a supply passage 34, a discharge passage 36, and a control device 38. The stage 24, the heater 26, and the sensor 28 are provided in the ALD chamber 22. The heater 26 can heat the element body 4 placed on the stage 24. In this embodiment, the sensor 28 is an optical sensor. The sensor 28 can, for example, measure the temperature of the element body 4 or image the element body 4. The first precursor supply device 30 and the second precursor supply device 32 are each connected to a supply passage 34. The first precursor supply device 30 can supply a first precursor to the ALD chamber 22 via the supply passage 34. The first precursor in this embodiment is TMA (trimethylaluminum). The second precursor supply device 32 can supply a second precursor to the ALD chamber 22 through the supply passage 34. The second precursor in this embodiment is O (oxygen). A vacuum pump (not shown) is provided in the middle of the exhaust passage 36. The vacuum pump can purge the ALD chamber 22. The control device 38 is composed of a ROM, a RAM, etc., and has a memory in which a predetermined program is stored. The control device 38 executes various processes related to the operation of the PEALD device 20 according to the predetermined program. The process for forming a passivation film 6 on the surface of the element body 4, which is executed by the control device 38, will be described below.

(Process for forming a passivation film 6 on the surface of the element body 4; FIG. 4)
In S2, the control device 38 uses the heater 26 to increase the temperature of the element body 4 to about 200° C. Note that until the series of processes shown in Fig. 4 is completed, the control device 38 continues to maintain the temperature of the element body 4 at about 200° C. by the heater 26. After S2, the process proceeds to S4.

In S4, the control device 38 supplies TMA gas to the ALD chamber 22 using the first precursor supply device 30. This causes an oxidation-reduction reaction between the native oxide present on the surface of the quantum dots 16a and the TMA. The native oxide is reduced and removed, and the TMA is oxidized to produce Al oxide (Al ₂ O ₃ ). In this process, the quantum dots 16a are passivated. After S4, the process proceeds to S6.

In S6, the control device 38 alternately supplies TMA gas and O plasma to the ALD chamber 22 using the first precursor supply device 30 and the second precursor supply device 32. The supply cycle in S6 includes supplying TMA gas in a pulsed manner for 0.06 seconds, purging for 5 seconds, supplying O plasma for 25 seconds, and purging for 5 seconds. The control device 38 repeats the above supply cycle a predetermined number of times. In this process, TMA and O are alternately deposited on the surface of the element body 4, and an oxidation-reduction reaction occurs between TMA and O. As a result, the passivation film 6 made of Al ₂ O ₃ grows on the surface of the element body 4 at a rate of approximately 0.02 ML/s to 0.03 ML/s. Since the temperature of the element body 4 is relatively low at approximately 200° C., at least a part of the passivation film 6 is made of Al ₂ O ₃ having an amorphous structure. After S6, the process of FIG. 4 ends.

Note that the parameters related to the series of processes shown in FIG. 4 (e.g., the heating temperature of the heater 26, the supply time of each precursor, and the purge time) may be changed by the user as appropriate.

(Features of Semiconductor Element 2)
As shown in FIG. 1, the passivation film 6 is provided with a substantially uniform thickness t1 so as to follow the convex shape of the quantum dots 16a. The thickness t1 indicates the thickness in the direction along the stacking direction of the layers 10, 12, 14, and 16 of the semiconductor element 2. In this embodiment, the difference between the minimum and maximum values of the thickness t1 is 50% or less of the height of the convex shape of the quantum dots 16a. Although the thickness t1 does not strictly take a constant value, the difference between the minimum and maximum values is very small. For this reason, in this specification, the thickness t1 may be expressed by a single numerical value rather than a numerical range. This single numerical value is any numerical value that exists between the minimum and maximum values of the thickness t1.

The film thickness t1 can be changed as appropriate by adjusting the number of times the supply cycle is repeated in the process shown in S6 of FIG. 4. This allows the film thickness t1 to be adjusted to be within a range of 0.3 nm or more and less than 1000 nm, for example. Alternatively, the film thickness t1 can be adjusted to be smaller than the height of the convex shape of the quantum dots 16a.

As a comparison with the semiconductor element 2, FIG. 5 shows a semiconductor element 102 having a passivation film 106 formed according to a conventional method (MBE). The passivation film 106 is provided with a non-uniform thickness without following the convex shape of the quantum dots 16a. In addition, since MBE is used, the passivation film 106 is composed almost entirely of a crystalline structure.

Figure 6 shows the results of fluorescence measurements carried out to verify the effect of the passivation film 6. Fluorescence measurements were carried out in the cases where the passivation film 6 was not provided, where the thickness t1 of the passivation film 6 was 10 nm, and where the thickness t1 of the passivation film 6 was 30 nm. In the fluorescence measurements, the semiconductor element 2 was excited with laser light having a wavelength of 740 nm and an intensity of approximately 14 W/cm2 at a temperature of 4 K, and the resulting fluorescence was detected by an InGaAs element through a spectroscope.

From Figure 6, it can be seen that the intensity of the emission wavelength of the quantum dots 16a increases by providing the passivation film 6. In particular, when the thickness t1 of the passivation film 6 is 30 nm, the intensity of the emission wavelength of the quantum dots 16a increases with almost no change in the spectral distribution of the emission wavelength of the quantum dots 16a. Note that when the thickness t1 of the passivation film 6 is 10 nm, the peak of the emission wavelength of the quantum dots 16a shifts to the longer wavelength side.

The phenomenon in which the intensity of the emission wavelength of the quantum dots 16a increases around 1500 nm-1600 nm due to the provision of the passivation film 6 is thought to be caused by impurities and defects in the passivation film 6. These impurities and defects are removed as the film formation continues. For this reason, when the thickness t1 of the passivation film 6 is 30 nm, the above phenomenon is less noticeable compared to when the thickness t1 of the passivation film 6 is 10 nm.

(Example 2; Semiconductor element 202)
7, the semiconductor element 202 of this embodiment has substantially the same configuration as the semiconductor element 2 (see FIG. 1) of Example 1. The semiconductor element 202 has an element body 4 in common with Example 1, and also has a passivation film 206 different from that of Example 1. The passivation film 206 will be described below.

The passivation film 206 is formed using a PEALD apparatus 20 (see FIG. 3). In this embodiment, DEZ (diethylzinc) is used instead of TMA as the first precursor. The passivation film 206 is formed by a process substantially similar to the series of processes shown in FIG. 4. In this process, the passivation film 206 made of ZnO grows on the surface of the element body 4.

As shown in FIG. 7, the passivation film 206 has a shape substantially similar to that of the passivation film 6 (see FIG. 1). The passivation film 206 is provided with a substantially uniform thickness t2 so as to imitate the convex shape of the quantum dots 16a. In this specification, the thickness t2 may also be expressed by a single numerical value. Furthermore, at least a portion of the passivation film 206 has an amorphous structure.

Figure 8 shows the results of fluorescence measurements carried out to verify the effect of the passivation film 206. Fluorescence measurements were carried out for the following cases: when the passivation film 206 was not provided; when the thickness t2 of the passivation film 206 was 2 nm; when the thickness t2 of the passivation film 206 was 10 nm; and when the thickness t2 of the passivation film 206 was 30 nm. In the fluorescence measurements, the semiconductor element 202 was excited with laser light having a wavelength of 740 nm and an intensity of approximately 14 W/cm2 at a temperature of 4 K, and the resulting fluorescence was detected by an InGaAs element through a spectroscope.

From Figure 8, it can be seen that when the film thickness t2 of the passivation film 206 is 10 nm or 30 nm, the intensity of the emission wavelength of the quantum dots 16a increases. Furthermore, when the passivation film 206 is provided, there is a slight tendency toward shorter wavelengths compared to when the passivation film 206 is not provided. In other words, the peak of the emission wavelength of the quantum dots 16a shifts to the shorter wavelength side. This tendency is caused by the generation of ZnO microcrystals in the process of forming the passivation film 206. However, the shift width of the peak of the emission wavelength of the quantum dots 16a is limited to about 100 nm.

The phenomenon in which the intensity of the emission wavelength of the quantum dots 16a increases in the range of 1400 nm to 1600 nm due to the provision of the passivation film 206 is thought to be due to impurities and defects in the passivation film 206.

(Modification)
As long as the surface of the passivation film 6 is displaced so as to follow the convex shape of the quantum dots 16a, the passivation film 6 (or the passivation film 206) does not need to have an amorphous structure.

If the passivation film 6 (or the passivation film 206) has an amorphous structure, the surface of the passivation film 6 does not need to be displaced to follow the convex shape of the quantum dots 16a.

The passivation film 6 (or the passivation film 206) may be made of a material other than Al ₂ O ₃ and ZnO. For example, a material capable of forming an amorphous structure at low temperatures may be used.

The difference between the minimum and maximum values of film thickness t1 (or film thickness t2) may exceed 50% of the height of the convex shape of quantum dot 16a.

The film thickness t1 (or film thickness t2) may be greater than the height of the convex shape of the quantum dot 16a.

The first precursor may be other than TMA and DEZ. The first precursor may be a metal or a non-metal. In one aspect, the first precursor may be selected from among materials with strong reducing power.

The second precursor may be other than O. The second precursor may be a metal or a non-metal. For example, the second precursor may be N (nitrogen).

The PEALD apparatus 20 may include additional precursor supply devices, such as a third precursor supply device, so that the PEALD apparatus 20 may grow a passivation film by reacting three or more precursors with each other.

The technical elements described in this specification or drawings exert technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving any one of those objectives is itself technically useful.

Claims (15)

An element body having quantum dots on a surface thereof;
a passivation film provided on the surface of the element body and covering the quantum dots;
Equipped with
The surface of the passivation film is displaced so as to conform to the convex shape of the quantum dot.
Semiconductor element. The semiconductor element of claim 1, wherein the thickness of the passivation film is smaller than the height of the convex shape of the quantum dot. The semiconductor element according to claim 1, wherein the difference between the minimum and maximum film thicknesses of the passivation film is 50% or less of the height of the convex shape of the quantum dot. The semiconductor element of claim 1, wherein at least a portion of the passivation film has an amorphous structure. The semiconductor element according to claim 4, wherein the passivation film is made of a material capable of forming the amorphous structure under temperature conditions of 300°C or less. The semiconductor device according to claim 5 , wherein the passivation film is made of one of Al ₂ O ₃ and ZnO. The semiconductor element according to claim 1, wherein the thickness of the passivation film is in the range of 0.3 nm or more and less than 1000 nm. The semiconductor device according to claim 1, wherein the quantum dots are made of one of a group III-V semiconductor, a group II-VI semiconductor, and a group IV semiconductor. An element body having quantum dots on a surface thereof;
a passivation film provided on the surface of the element body and covering the quantum dots;
It is equipped with
At least a portion of the passivation film has an amorphous structure.
Semiconductor element. A method for manufacturing a semiconductor device, comprising the steps of:
Providing a device body having quantum dots on a surface thereof;
forming a passivation film on the surface of the element body to cover the quantum dots;
Equipped with
At least a portion of the passivation film has an amorphous structure.
Production method. The manufacturing method according to claim 10, wherein the step of forming the passivation film includes a step of growing the passivation film at a rate of 0.05 ML/s or less. The manufacturing method according to claim 10, wherein the step of forming the passivation film includes a step of growing the passivation film under a temperature condition of 300°C or less. The manufacturing method according to claim 10, wherein the step of forming the passivation film is a step using atomic layer deposition, and includes a step of supplying multiple precursors to the surface of the element body in sequence and reacting the multiple precursors with each other. The manufacturing method according to claim 13, wherein the plurality of precursors include a material that acts as a reducing agent for the native oxide present on the surface of the element body. The method of claim 14, wherein the plurality of precursors includes at least one of TMA and DEZ.

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