WO2025204466A1 - Light-emitting device - Google Patents

Abstract

[Problem] To provide a light-emitting device that comprises a dielectric reflecting mirror and can facilitate polarization control. [Solution] This light-emitting device comprises a first reflecting mirror that is formed by layering a plurality of types of semiconductor materials that have different refractive indices and has a first surface and a second surface that is on the reverse side from the first surface, a second reflecting mirror that is formed by layering a plurality of types of dielectric materials that have different refractive indices and has a third surface and a fourth surface that is on the reverse side from the third surface, an active layer that is provided between the first surface of the first reflecting mirror and the fourth surface of the second reflecting mirror and emits light when electric power is applied thereto, and an uneven layer that is formed from a dielectric material, is provided on the third surface of the second reflecting mirror, and has an uneven shape at a light emission surface that emits light from the active layer.

Description

Light-emitting device

This disclosure relates to a light-emitting device.

Light-emitting devices such as VCSELs (Vertical-Cavity Surface-Emitting Lasers) are used as light sources for distance measurement sensors and the like. In GaAs-based light-emitting devices, one approach to control polarization is to provide a grating on the surface of a semiconductor DBR (Distributed Bragg Reflector) (Patent Document 1, Non-Patent Document 1).

Japanese Patent Application Publication No. 5-021889

Fundamental, technology and applications of Vertical-Cavity Surface-Emitting Lasers, Michalzik (2013)

On the other hand, the refractive index of a dielectric is smaller than that of a semiconductor, and the difference in refractive index between the dielectric and air is small.
For this reason, even if a grating is provided on the surface of the dielectric DBR used in an InP-based light-emitting device, it has been difficult to control the polarization of the light-emitting device.

This disclosure therefore provides a light-emitting device that uses a dielectric reflector to facilitate polarization control.

A light emitting device according to one aspect of the present disclosure includes a first reflector constructed by laminating multiple types of semiconductor materials with different refractive indices and having a first surface and a second surface opposite the first surface; a second reflector constructed by laminating multiple types of dielectric materials with different refractive indices and having a third surface and a fourth surface opposite the third surface; an active layer disposed between the first surface of the first reflector and the fourth surface of the second reflector and emitting light upon application of electric power; and a concavo-convex layer constructed of a dielectric material and disposed on the third surface of the second reflector, having an uneven shape on the light emitting surface from which light from the active layer is emitted.

The uneven layer has a refractive index equal to or higher than that of the multiple types of dielectric material layers that make up the second reflector.

The refractive index of the dielectric material that makes up the uneven layer is 2 or greater.

The uneven layer is made of the same material as the dielectric material layer with the highest refractive index among the multiple types of dielectric material layers that make up the second reflector.

The dielectric material that constitutes the uneven layer is either TiO ₂ , Ta ₂ O ₅ , SiN or amorphous silicon.

Of the multiple types of dielectric material layers that make up the second reflecting mirror, the dielectric material layer with a low refractive index is SiO ₂ or MgO.

The uneven shape of the uneven layer is composed of multiple grooves extending in a first direction within the light emitting surface, and the period of the uneven shapes arranged in a second direction perpendicular to the first direction within the light emitting surface is equal to or less than the wavelength of the light emitted from the light emitting surface.

The height of the convex portions of the uneven layer's uneven shape is 200 nm ± 60 nm.

The side surfaces between the concave and convex portions of the concave-convex layer are approximately perpendicular or inclined to the light exit surface.

The active layer is made of AlGaInAs, and the wavelength of light emitted from the active layer is 1.2 μm to 2 μm.

The device further includes a plurality of tunnel junction layers disposed between the active layer and the second reflector and separated from the active layer, and the plurality of uneven shapes of the uneven layer are provided corresponding to the plurality of tunnel junction layers.

In a plan view looking in the stacking direction of the multiple types of dielectric materials, the multiple uneven shapes overlap multiple tunnel junction layers.

When viewed in a plan view from the stacking direction of the multiple types of dielectric materials, the multiple uneven shapes and multiple tunnel junction layers have an approximately circular, approximately elliptical, or approximately polygonal shape.

Furthermore, a substrate containing InP is provided on the second surface side of the first reflecting mirror, and the first reflecting mirror has a layered structure of InP and AlGaInAs.

Furthermore, a substrate containing GaAs is provided on the second surface side of the first reflecting mirror, and the first reflecting mirror has a layered structure of GaAs and AlGaAs or AlAs.

1 is a cross-sectional view showing an example of the configuration of a light emitting device according to a first embodiment. FIG. 1 is a plan view showing an example of the configuration of a light emitting device according to a first embodiment. FIG. 4 is a cross-sectional view showing an example of the configuration of a second reflecting mirror and a grating layer. FIG. 1 is a plan view showing the relationship between a grating and a BTJ. FIG. 1 is a plan view showing the relationship between a grating and a BTJ. FIG. 1 is a plan view showing the relationship between a grating and a BTJ. FIG. 1 is a plan view showing the relationship between a grating and a BTJ. 10 is a graph showing the relationship between the refractive index ngr of the grating layer 95, the reflectance R, and the reflectance difference ΔR. 1 is a graph showing the relationship between grating height, reflectivity, and reflectivity difference. FIG. 10 is a cross-sectional view showing an example of the configuration of a grating layer and a second reflecting mirror according to the second embodiment. FIG. 10 is a cross-sectional view showing an example of the configuration of a grating layer and a second reflecting mirror according to the third embodiment. FIG. 10 is a cross-sectional view showing an example of the configuration of a light emitting device according to a fourth embodiment. FIG. 10 is a plan view showing an example of the configuration of a light emitting device according to a fourth embodiment. 5A to 5C are cross-sectional views showing an example of a manufacturing method for the light emitting device according to the embodiment. 15 is a cross-sectional view showing an example of a method for manufacturing the light emitting device, following FIG. 14 . 16 is a cross-sectional view showing an example of a method for manufacturing the light emitting device, following FIG. 15 . 17A to 17C are cross-sectional views showing an example of a method for manufacturing the light emitting device, following FIG. 16 . 18 is a cross-sectional view showing an example of a method for manufacturing the light emitting device, following FIG. 17. 19 is a cross-sectional view showing an example of a method for manufacturing the light emitting device, following FIG. 18 . 19A to 19C are cross-sectional views showing an example of a method for manufacturing the light emitting device. 21 is a cross-sectional view showing an example of a method for manufacturing a light emitting device, following FIG. 20 . 22 is a cross-sectional view showing an example of a method for manufacturing a light emitting device, following FIG. 21. FIG. 11 is a cross-sectional view showing an example of the configuration of a light emitting device according to a fifth embodiment. FIG. 13 is a cross-sectional view showing an example of the configuration of a light emitting device according to a sixth embodiment. FIG. 1 is a block diagram showing an example of a schematic configuration of a vehicle control system. FIG. 4 is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit.

Specific embodiments applying this technology will be described in detail below with reference to the drawings. The drawings are schematic or conceptual, and the proportions of each part may not necessarily be the same as those in reality. In the specification and drawings, elements similar to those previously described with reference to the drawings will be designated by the same reference numerals, and detailed descriptions will be omitted where appropriate.

(First embodiment)
Fig. 1 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the first embodiment. Fig. 2 is a plan view showing an example of the configuration of a light-emitting device according to the first embodiment. Fig. 1 shows a cross section taken along line 1-1 in Fig. 2.

The light-emitting device 1 comprises a substrate 10, a first reflecting mirror 20, a first semiconductor layer 30, an active layer 40, a second semiconductor layer 50, a third semiconductor layer 60, a fourth semiconductor layer 70, a fifth semiconductor layer 80, a second reflecting mirror 90, a grating layer 95, a first electrode 100, a second electrode 110, and a protective film 120. The light-emitting device 1 is a semiconductor light-emitting device such as a VCSEL. The light-emitting device 1 emits light by applying power between the first electrode 100 and the second electrode 110, injecting electrons and holes from the first and second semiconductor layers 30, 50 into the active layer 40 and causing the electrons and holes to recombine in the active layer 40. The light is reflected and resonates between the first reflecting mirror 20 and the second reflecting mirror 90, and is emitted as laser light from the second reflecting mirror 90 side.

The substrate 10 may be, for example, a semiconductor substrate such as an n-type InP substrate.

The first reflecting mirror 20 is a so-called DBR (Distributed Bragg Reflector) and is constructed by alternately stacking multiple materials with different refractive indices. For example, the first reflecting mirror 20 has a layered structure of multiple types of semiconductor materials with different refractive indices (e.g., a layered structure of n-type InP and n-type AlGaInAs) epitaxially grown on the substrate 10. The first reflecting mirror 20 has a first surface F1 and a second surface F2 located opposite the first surface F1.

The first semiconductor layer 30 is located between the first reflecting mirror 20 and the second reflecting mirror 90 and is a spacer layer provided on the first reflecting mirror 20. The first semiconductor layer 30 is made of n-type InP or an n-type material lattice-matched to InP (e.g., n-type InGaAsP, n-type AlGaInAs, etc.). The first semiconductor layer 30 may be a single layer of any of the above materials, or a laminate film made of multiple of the above materials.

The active layer 40 is provided between the first semiconductor layer 30 and the second semiconductor layer 50. The active layer 40 receives power from the first and second semiconductor layers 30, 50 and emits light by internally recombining electrons from the first semiconductor layer 30 and holes from the second semiconductor layer 50. The active layer 40 has a multiple quantum well (MQW) structure made of, for example, AlGaInAs, InGaAs, or InGaAsP, and generates light with a wavelength of 1.2 μm to 2 μm.

The second semiconductor layer 50 is a spacer layer located between the first reflecting mirror 20 and the second reflecting mirror 90 and provided on the active layer 40. The second semiconductor layer 50 is made of p-type InP, which is the opposite conductivity type to the first semiconductor layer 30. Therefore, by applying a negative voltage to the first electrode 100 and a positive voltage to the second electrode 110, electrons are supplied from the first semiconductor layer 30 to the active layer 40, and holes are supplied from the second semiconductor layer 50 to the active layer 40. The p-type impurity concentration of the second semiconductor layer 50 is, for example, 5×10 ¹⁷ to 1×10 ¹⁸ /cm ⁻³ .

The third semiconductor layer 60 is provided on the second semiconductor layer 50. The third semiconductor layer 60 is located between the second reflecting mirror 90 and the second semiconductor layer 50. The third semiconductor layer 60 is made of a p-type semiconductor, for example, p ⁺ -type AlGaInAs. The p-type impurity concentration of the third semiconductor layer 60 is higher than that of the second semiconductor layer 50, for example, 5×10 ¹⁹ /cm ⁻³ .

The fourth semiconductor layer 70 is provided on the third semiconductor layer 60. The fourth semiconductor layer 70 is also located between the second reflecting mirror 90 and the second semiconductor layer 50. The fourth semiconductor layer 70 is made of an n-type semiconductor, for example, n ⁺ -type AlGaInAs. The n-type impurity concentration of the fourth semiconductor layer 70 is higher than that of the fifth semiconductor layer 80, for example, 5×10 ¹⁹ /cm ⁻³ .

The third and fourth semiconductor layers 60, 70 form a highly doped buried tunnel junction (BTJ). Hereinafter, the third and fourth semiconductor layers 60, 70 will also be referred to as BTJs 60, 70. The current between the electrodes 100, 110 flows concentratedly through the BTJs 60, 70 and is constricted. This allows the BTJs 60, 70 to promote light emission in the active layer 40 directly below them.

When viewed from the stacking direction (Z direction), the multiple BTJs 60, 70 overlap with the multiple gratings GR of the second reflecting mirror 90, as shown in Figure 2. Note that the stacking direction (Z direction) is also the direction in which current flows through the BTJs 60, 70 and the direction in which light resonates between the first reflecting mirror 20 and the second reflecting mirror 90.

In the first embodiment, as shown in FIG. 2, multiple divided BTJs 60, 70 are provided for one active layer 40, and laser light is emitted from each BTJ 60, 70 via a grating GR (multi-emitter structure). In FIG. 2, six BTJs 60, 70 are provided, but the number of BTJs 60, 70 is not limited.

As shown in FIG. 1 , the fifth semiconductor layer 80 is provided on the second semiconductor layer 50 and the BTJs 60 and 70. The fifth semiconductor layer 80 covers the BTJs 60 and 70. The fifth semiconductor layer 80 is made of an n-type semiconductor, for example, n-type InP. The n-type impurity concentration of the fifth semiconductor layer 80 is lower than that of the fourth semiconductor layer 70, for example, 5×10 ¹⁷ to 1×10 ¹⁸ /cm ⁻³ . A reverse bias is applied to the pn junction between the fifth semiconductor layer 80 and the second semiconductor layer 50 when a negative voltage is applied to the first electrode 100 and a positive voltage is applied to the second electrode 110. Therefore, no current flows through the pn junction between the fifth semiconductor layer 80 and the second semiconductor layer 50.

The second reflecting mirror 90 is provided above the BTJs 60 and 70 (in the Z direction). The second reflecting mirror 90 is a dielectric DBR and is configured by alternately stacking multiple types of dielectric materials with different refractive indices. For example, the second reflecting mirror 90 has a layered structure of multiple dielectric materials (e.g., a layered structure of _SiO2 or MgO _{with TiO2} , _Ta2O3 , SiN, or amorphous silicon). That is, the second reflecting mirror 90 is a dielectric DBR containing a dielectric material. The dielectric material in this disclosure refers to a dielectric material other than a single-crystal semiconductor obtained by epitaxial growth _on a semiconductor substrate such as GaAs or InP, and includes, for example, _SiO2 , _TiO2 , _Ta2O3 , SiN, MgO, and amorphous semiconductor materials. The second reflecting mirror 90 also has a third surface F3 and a fourth surface F4 located on the opposite side of the third surface F3.

A grating layer 95 serving as a concave-convex layer is provided on the third surface F3 of the second reflecting mirror 90. The grating layer 95 has a refractive index equal to or higher than that of the multiple dielectric materials constituting the second reflecting mirror 90. Furthermore, the grating layer 95 is preferably composed of a material with a refractive index of 2 or higher. The material of the grating layer 95 may be the same as the dielectric material with the higher refractive index among the dielectric materials constituting the second reflecting mirror 90. For example, if the second reflecting mirror 90 is a laminated film of SiO ₂ and TiO ₂ , the grating layer 95 may be composed of TiO _2. The material of the grating layer 95 may be a material different from the dielectric material constituting the second reflecting mirror 90. For example, if the second reflecting mirror 90 is a laminated film of SiO ₂ and TiO ₂ , the grating layer 95 may be composed of amorphous silicon.

The grating layer 95 has an uneven surface (hereinafter referred to as the grating) GR on its surface F5. The surface F5 of the grating layer 95 is the light emission surface from which the laser light is emitted. The grating GR is provided at the position from which the laser light is emitted, and the laser light passes through the grating GR before being emitted to the outside. A more detailed configuration of the grating GR will be described later.

In this embodiment, light is generated by applying power to the active layer 40, which is located between the first surface F1 of the first reflecting mirror 20 and the fourth surface F4 of the second reflecting mirror 90. The light oscillates in the resonator between the first reflecting mirror 20 and the second reflecting mirror 90, and is emitted as laser light from the surface F5 of the second reflecting mirror 90. At this time, the polarization of the laser light can be controlled to one direction by the grating GR.

The first electrode 100 is provided on the first semiconductor layer 30 and is electrically connected to the first semiconductor layer 30. The first electrode 100 is made of a conductive metal such as Ti, Pt, or Au, an AuGe/Ni/Au laminate film, or a PdGe/Ni/Au laminate film. The first electrode 100 is provided around the active layer 40 via a protective film 120. The first electrode 100 is electrically insulated from components other than the first semiconductor layer 30 by the protective film 120.

The second electrode 110 is provided on the fifth semiconductor layer 80 and is electrically connected to the fourth semiconductor layer 70 via the fifth semiconductor layer 80. The second electrode 110 is also made of a conductive metal such as Ti, Pt, or Au, an AuGe/Ni/Au laminate film, or a PdGe/Ni/Au laminate film. The second electrode 110 may be made of the same material as the first electrode 100. The second electrode 110 is provided around the second reflecting mirror 90. The second electrode 110 may be in contact with the second reflecting mirror 90. The second electrode 110 is electrically insulated from components other than the fifth semiconductor layer 80 by a protective film 120.

The first and second electrodes 100, 110 do not overlap with the BTJs 60, 70 when viewed from the Z direction. Therefore, the first and second electrodes 100, 110 do not obstruct the laser light emitted from the second reflector 90.

The protective film 120 covers the side surfaces of the active layer 40, the second semiconductor layer 50, and the fifth semiconductor layer 80, and also covers a portion of the top surface of the fifth semiconductor layer 80. This allows the protective film 120 to protect the structure of the active layer 40, the second semiconductor layer 50, and the fifth semiconductor layer 80, and to prevent the first and second electrodes 100, 110 from short-circuiting to unintended components. The protective film 120 is made of an insulating material such as SiO ₂ or SiN, for example.

Figure 3 is a cross-sectional view showing an example configuration of the second reflector 90 and grating layer 95.

The second reflecting mirror 90 is a laminated film of a first material 91 and a second material 92. The first material 91 is made of, for example, a low-refractive-index dielectric material (e.g., _SiO2 or MgO) having a refractive index of less than 2. The second material 92 is made of, for example, a high-refractive-index material (e.g., _TiO2 , _Ta2O3 , SiN, or amorphous silicon) having _a refractive index of 2 or more.

The grating layer 95 is formed on the first material 91 and is made of a high refractive index material (for example, TiO ₂ , Ta ₂ O ₃ , SiN, or amorphous silicon). The grating GR is an uneven shape formed on the surface F5 of the grating layer 95.

The uneven shape of the grating GR is formed by providing multiple grooves on the surface F5 of the grating layer 95. The multiple grooves extend in the Y direction of the surface F5 of the grating layer 95.

4 to 7 are plan views showing the relationship between the grating GR and the BTJ. The grating GR is configured with multiple grooves extending in the Y direction and arranged at approximately equal intervals in the X direction. Therefore, the uneven shape of the grating GR appears repeatedly and periodically in the X direction.
The region where the grating GR is provided has a shape that overlaps with the BTJs 60 and 70 in a plan view seen from the Z direction. For example, the outer shapes of the grating GR and the BTJs 60 and 70 may be substantially circular. The outer shapes of the grating GR and the BTJs 60 and 70 are not particularly limited, and may be substantially elliptical or substantially polygonal.

Furthermore, as shown in Figure 4, in plan view from the Z direction, the area of the grating GR may be approximately the same size as the corresponding BTJs 60 and 70.

Furthermore, as shown in Figure 5, in plan view from the Z direction, the area of the grating GR may be larger than the corresponding BTJs 60 and 70.

Furthermore, as shown in Figure 6, in a plan view seen from the Z direction, the area of the grating GR may be slightly smaller than the corresponding BTJs 60 and 70. The area of the grating GR only needs to cover half or more of the center of the corresponding BTJs 60 and 70.

Furthermore, as shown in Figure 7, the grating GR may be composed of gratings GR1 and GR2 with different periods. In a plan view seen from the Z direction, grating GR1 is provided in the center of BTJs 60 and 70 where the laser light intensity is high. Grating GR2 is provided around grating GR1 where the laser light intensity is low. The period (pitch) of the concave-convex pattern of grating GR1 is wider than the period (pitch) of the concave-convex pattern of grating GR2.

The extension direction (Y direction) of the grooves of the grating GR can be any direction, but it is preferable that it be, for example, the crystal direction [011] or the crystal direction [01-1] of the substrate 10.

The period Pgr of the uneven shape of the grating GR shown in Figure 3 is equal to or less than the wavelength λ of the laser light generated by the light-emitting device 1 and emitted from the surface F5. For example, if the light-emitting device 1 is an InP-based VCSEL with an oscillation wavelength of 1450 nm, the period Pgr of the grating GR is set to, for example, 700 nm. This prevents the laser light from being diffracted by the grating GR, enabling the laser light to be extracted with high efficiency.

Figure 8 is a graph showing the relationship between the refractive index ngr of the grating layer 95, the reflectivity R, and the reflectivity difference ΔR. In this graph, Rx represents the reflectivity of the grating layer 95 for light polarized in the X direction. Ry represents the reflectivity of the grating layer 95 for light polarized in the Y direction. ΔR represents the reflectivity difference Ry-Rx. The larger ΔR is, the greater the difference in threshold gain for laser oscillation for the polarization components of the laser light in the X and Y directions. This means that the larger ΔR is, the more advantageous it is to control the polarization of the laser light.

From this graph, it was found that the greater the refractive index of the grating layer 95, the greater the ΔR. In other words, the greater the refractive index of the grating layer 95, the more advantageous it is for controlling the polarization of laser light. Conversely, it was found that when the refractive index of the grating layer 95 approaches the refractive index of air, which is 1, it becomes disadvantageous for controlling the polarization of laser light.

Typically, the threshold gain of a VCSEL is around 1%. The ΔR required for polarization control is preferably around 1%, but it is thought that at least half of that, 0.5%, is preferable. Referring to Figure 8, in order for ΔR to be 0.5% or more, the refractive index ngr of the grating layer 95 is preferably 2 or more.

When the grating layer 95 is made of _SiO2 (n=1.45), ΔR is 0.06%, which is considered to make it difficult to control the polarization of the laser light. On the other hand, when the grating layer 95 is made of _TiO2 (n=2.25), ΔR is approximately 0.9%, which is a large difference from the refractive index of air, which is considered to make it easier to control the polarization of the laser light.

The graph in FIG. 8 was created by a wave optics simulation using the finite element method. In the simulation, the fifth semiconductor layer 80 was n-type InP. The second reflecting mirror 90 was a laminated film of SiO ₂ with a film thickness of λ/4n and TiO ₂ with a film thickness of λ/4n. λ was set to 1450 nm, and n is the refractive index of each material at λ. The grating layer 95 was TiO ₂ with a film thickness of λ/2n, and had a grating GR on the surface F5. The period Pgr of the grating GR was 700 nm, and the height of the grating GR was 200 nm. The widths of the recesses and protrusions of the grating GR were approximately equal, and the duty of the uneven shape (the ratio of the width of the recesses to the width of the protrusions) was set to 50%.

Figure 9 is a graph showing the relationship between grating height Hgr, reflectance R, and reflectance difference ΔR. This graph was created using a simulation under the same conditions as the simulation in Figure 8. This graph shows that ΔR becomes small whether the grating GR height Hgr is too low or too high. The grating GR height Hgr at which ΔR is maximized is approximately 200 nm. If the ΔR required for polarization control is 0.5%, then it can be seen that the grating GR height Hgr should preferably be approximately 140 nm to 260 nm (200 nm ± 60 nm).

As described above, the grating layer 95 is preferably made of a material with a refractive index of 2 or higher. Furthermore, the period of the unevenness of the grating GR is preferably equal to or less than the wavelength λ of the laser light. Furthermore, the height Hgr of the convex portions of the grating GR (depth of the concave portions) is preferably 200 nm ± 60 nm. This enables the light-emitting device 1 to effectively control the polarization of the laser light in one direction (for example, the Ry direction).

Second Embodiment
FIG. 10 is a cross-sectional view showing an example configuration of the grating layer and second reflector according to the second embodiment. The side surfaces of the concave or convex portions of the grating GR may be perpendicular to the surface F5, or may be inclined as shown in FIG. 10 . Even if the side surfaces of the concave or convex portions of the grating GR are formed in a forward tapered shape, the effect of the present technology is not lost. By forming the side surfaces of the concave or convex portions of the grating GR in a tapered shape in the process of forming the grating GR, in-plane variation in the shape of the grating GR is suppressed, improving yield. Other configurations of the second embodiment may be similar to those of the first embodiment. Therefore, the second embodiment can also achieve the same effects as the first embodiment.

(Third embodiment)
FIG. 11 is a cross-sectional view showing an example configuration of a grating layer and a second reflecting mirror according to the third embodiment. In the third embodiment, the inclination of the taper of the side surface of the grating GR is opposite to that of the second embodiment. That is, the side surface of the concave or convex portion of the grating GR is formed in an inverse tapered shape. In this way, even if the inclination of the taper of the side surface of the grating GR is opposite to that of the second embodiment, the effect of the present technology is not lost. The other configurations of the third embodiment may be the same as those of the second embodiment. Therefore, the third embodiment can obtain the same effect as that of the second embodiment.

(Fourth embodiment)
FIG. 12 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the fourth embodiment. FIG. 13 is a plan view showing an example of the configuration of a light-emitting device according to the fourth embodiment. In the fourth embodiment, one BTJ 60, 70 and one grating GR are provided for one active layer 40 (jingle emitter structure). The other configurations of the fourth embodiment may be the same as those of the first embodiment. Therefore, the fourth embodiment can achieve the same effects as the first embodiment. The number of BTJs 60, 70 and the number of gratings GR provided for one active layer 40 are not limited.

(Method for manufacturing a light-emitting device)
Next, a method for manufacturing the light emitting device 1 according to the above embodiment of the present disclosure will be described.

Figures 14 to 22 are cross-sectional views showing an example of a method for manufacturing a light-emitting device according to the above embodiment.

First, as shown in FIG. 14, an MOCVD (Metal Organic Chemical Vapor Deposition) method is used to epitaxially grow an n-type InP buffer layer (not shown), a first reflecting mirror 20 (e.g., a stacked film of n-type InP and n-type AlGaInAs), a first semiconductor layer 30 (n-type InP), an active layer (e.g., a multiple quantum well layer having well layers of AlGaInAs and barrier layers of AlGaInAs) 40, a second semiconductor layer (e.g., p-type InP) 50, a third semiconductor layer (e.g., p ⁺ -type AlGaInAs) 60, and a fourth semiconductor layer (n + -type AlGaInAs) 70 in this order on a substrate (e.g., n ^- type InP).

The thickness of each layer of the first reflecting mirror 20 is, for example, λ/(4n). Here, when λ = 1450 nm, the refractive indices of InP and AlGaInAs are 3.18 and 3.45, respectively. Therefore, the thicknesses of the n-type InP layer and the n-type AlGaInAs layer are, for example, 114 nm and 105 nm. Silicon is used as the n-type impurity, and magnesium is used as the p-type impurity. The active layer 40 (e.g., an AlGaInAs/AlGaInAs multiple quantum well) has well and barrier layers whose compositions and thicknesses are designed to achieve an emission wavelength of 1450 nm. Introducing opposing strains of approximately 0.5% into the well and barrier layers is preferable for improving device characteristics. The impurity of the third semiconductor layer 60 constituting the BTJ is preferably carbon, which is difficult to diffuse. The impurity concentrations of the third and fourth semiconductor layers 60 and 70 may each be 5×10 ¹⁹ cm ⁻³ . The impurity concentration of the other semiconductor layers may be 5×10 ¹⁷ cm ⁻³ to 1×10 ¹⁸ cm ⁻³ .

Next, as shown in Figure 15, the material of the BTJs 60, 70 is processed using lithography and wet etching. In the etching process, the BTJs 60, 70 are wet-etched using a mixed aqueous solution containing sulfuric acid and hydrogen peroxide. The shape of the BTJs 60, 70 as viewed from the Z direction may be circular, elliptical, or polygonal. When the BTJs 60, 70 are circular as viewed from the Z direction, their diameter is, for example, approximately 10 μm. The spacing between multiple BTJs 60, 70 is preferably 50 μm or more to suppress thermal interference. In Figure 15, two BTJs 60, 70 are formed, but as mentioned above, there is no limit to the number of BTJs 60, 70 per active layer 40.

16, a fifth semiconductor layer 80 is formed by MOCVD on the second semiconductor layer 50 and the fourth semiconductor layer 70. The fifth semiconductor layer 80 is, for example, n-type InP and has an impurity concentration of 1×10 ¹⁸ cm ⁻³ .

Next, as shown in FIG. 17, lithography and dry etching are used to expose portions of the top surfaces of the first semiconductor layer 30 and the substrate 10.

Next, as shown in FIG. 18, a material for the protective film 120 is deposited using the CVD method so as to cover the upper surfaces of the fifth semiconductor layer 80 and the first semiconductor layer 30, as well as the side surfaces of the fifth semiconductor layer 80, the second semiconductor layer 50, the active layer 40, the first semiconductor layer 30, and the first reflecting mirror 20. The material for the protective film 120 is, for example, a silicon nitride film.

Next, the material of the protective film 120 is processed using lithography and etching techniques. This creates openings in the areas where the first electrode 100, second electrode 110, and second reflector 90 will be formed.

Next, the material for the first and second electrodes 100, 110 is deposited on the first semiconductor layer 30, the fifth semiconductor layer 80, and the protective film 120. The material for the first and second electrodes 100, 110 is, for example, a conductive metal such as Ti, Pt, or Au.

Next, the material of the first and second electrodes 100, 110 is processed using lithography and etching techniques. As a result, as shown in FIG. 18, the first electrode 100 is formed on the first semiconductor layer 30, and the second electrode 110 is formed on the fifth semiconductor layer 80. At this time, the material of the second electrode 110 in the region where the second reflector 90 is to be formed is removed.

19, a material for the second reflector 90 (e.g., a stacked film of _SiO2 and _Ti2O2 ) is formed on the fifth semiconductor layer 80 and the second electrode _110. The film thicknesses of the _SiO2 film and the _Ti2O2 film are λ/(4n). Here, when λ=1450 nm, the refractive indices of _SiO2 and _Ti2O2 are 1.45 and 2.15, respectively. Therefore, the film thicknesses _of the _SiO2 film and _{the Ti2O2} film are, for example, 250 nm _and 169 nm, respectively.

Next, the material of the grating layer 95 (for example, TiO ₂ ) is epitaxially grown to a thickness of λ/(2n) on the third surface F3 of the second reflecting mirror 90. Here, when λ=1450 nm, the refractive index of TiO ₂ is 2.25. Therefore, the thickness of the grating layer 95 is, for example, 337 nm.

Next, using lithography technology, a resist film ER for electron beam lithography is applied onto the grating layer 95. Next, using an electron beam lithography device, an electron beam is irradiated onto the recessed areas where the grating GR will be formed. Next, the resist film ER is developed, and the resist film ER in the recessed areas of the grating GR is removed, as shown in Figure 20.

Next, as shown in FIG. 21, the grating layer 95 is processed by dry etching using the resist film ER as a mask. The depth of the grooves in the recesses of the grating layer 95 may be, for example, approximately 200 nm. The grooves may be limited to within the grating layer 95, or may extend to the second reflector 90.

Next, as shown in Figure 22, the resist film ER is removed. The substrate 10 is then diced into individual semiconductor chips, which are then mounted on a heat sink or wiring board. Metal wires are bonded to the first and second electrodes 100, 110, completing the light-emitting device 1.

Fifth Embodiment
23 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the fifth embodiment. In the fifth embodiment, the substrate 11 is made of, for example, GaAs. In this case, the first reflecting mirror 21 is made of, for example, a laminated film of GaAs and AlAs. The other configurations of the fifth embodiment may be the same as those of the first embodiment. Therefore, the fifth embodiment can achieve the same effects as the first embodiment.

In the fifth embodiment, a sacrificial layer (e.g., an n-type InGaAs layer) (not shown) is epitaxially grown on the InP substrate 10. Each layer above the first semiconductor layer 30 in the first embodiment is epitaxially grown on the sacrificial layer.

Separately, a first reflector 21 (e.g., a stacked film of GaAs and AlGaAs or AlAs) is epitaxially grown on the GaAs substrate 11.

Next, the InP substrate 10 and sacrificial layer are removed.

Next, each layer above the first semiconductor layer 30 according to the first embodiment is attached to the GaAs substrate 11 and the first reflector 21.

Then, the light-emitting device 1 according to the fifth embodiment is completed through the steps described with reference to Figures 15 to 22.

Sixth Embodiment
FIG. 24 is a cross-sectional view showing an example of the configuration of a light-emitting device according to the sixth embodiment. In the sixth embodiment, instead of defining the light-emitting region by processing the BTJs 60 and 70, the light-emitting region is defined by forming a non-conductive region 140 in a portion of the third semiconductor layer 60, the fourth semiconductor layer 70, and the active layer 40. The non-conductive region 140 is formed by ion implantation of impurity ions (e.g., hydrogen ions, helium ions, or boron ions) into a portion of the third semiconductor layer 60, the fourth semiconductor layer 70, and the active layer 40. The non-conductive region 140 is non-conductive, and current flows intensively in the active layer 40 other than the non-conductive region 140. In this way, the non-conductive region 140 functions as a current confinement layer, concentrating the laser light at the position of the grating GR. As a result, polarization control of the laser light is facilitated.

The other configurations of the sixth embodiment may be the same as those of the first embodiment. Therefore, the sixth embodiment can achieve the same effects as the first embodiment.

(Example of application to a moving object)
The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of moving body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

Figure 25 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology disclosed herein can be applied.

The vehicle control system 12000 includes multiple electronic control units connected via a communication network 12001. In the example shown in FIG. 25, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside vehicle information detection unit 12030, an inside vehicle information detection unit 12040, and an integrated control unit 12050. The functional configuration of the integrated control unit 12050 also includes a microcomputer 12051, an audio/video output unit 12052, and an in-vehicle network I/F (Interface) 12053.

The drivetrain control unit 12010 controls the operation of devices related to the vehicle's drivetrain in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a driveforce generating device such as an internal combustion engine or drive motor that generates vehicle driveforce, a driveforce transmission mechanism that transmits driveforce to the wheels, a steering mechanism that adjusts the vehicle's steering angle, and a braking device that generates vehicle braking force.

The body system control unit 12020 controls the operation of various devices installed in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 accepts these radio waves or signal inputs and controls the vehicle's door lock device, power window device, lamps, etc.

The outside vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, the outside vehicle information detection unit 12030 is connected to an imaging unit 12031. The outside vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal according to the amount of light received. The imaging unit 12031 can output the electrical signal as an image, or as distance measurement information. Furthermore, the light received by the imaging unit 12031 may be visible light, or may be invisible light such as infrared light.

The in-vehicle information detection unit 12040 detects information inside the vehicle. Connected to the in-vehicle information detection unit 12040 is, for example, a driver state detection unit 12041 that detects the driver's state. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the driver's level of fatigue or concentration based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

The microcomputer 12051 can calculate control target values for the driving force generating device, steering mechanism, or braking device based on information inside and outside the vehicle acquired by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, or vehicle lane departure warning.

In addition, the microcomputer 12051 controls the driving force generating device, steering mechanism, braking device, etc. based on information about the vehicle's surroundings acquired by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040, thereby enabling cooperative control aimed at autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation.

In addition, the microcomputer 12051 can output control commands to the body system control unit 12020 based on information outside the vehicle acquired by the vehicle exterior information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the vehicle exterior information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

The audio/video output unit 12052 transmits at least one audio and/or video output signal to an output device capable of visually or audibly notifying vehicle occupants or the outside of the vehicle of information. In the example of FIG. 25, an audio speaker 12061, a display unit 12062, and an instrument panel 12063 are exemplified as output devices. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

Figure 26 shows an example of the installation position of the imaging unit 12031.

In FIG. 26, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly capture images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly capture images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly captures images of the rear of the vehicle 12100. The imaging unit 12105 provided on the top of the windshield inside the vehicle cabin is mainly used to detect leading vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

Note that Figure 26 shows an example of the imaging ranges of imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by imaging units 12101 to 12104, an overhead image of vehicle 12100 viewed from above can be obtained.

At least one of the image capturing units 12101 to 12104 may have a function for acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera consisting of multiple image capturing elements, or an image capturing element having pixels for phase difference detection.

For example, based on distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km/h or higher). Furthermore, the microcomputer 12051 can set the inter-vehicle distance that should be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control) and automatic acceleration control (including follow-up start control). In this way, cooperative control can be performed for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation.

For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can classify and extract three-dimensional object data regarding three-dimensional objects into categories such as motorcycles, standard vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects, and use this data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into those that are visible to the driver of the vehicle 12100 and those that are difficult to see. The microcomputer 12051 then determines the collision risk, which indicates the risk of collision with each obstacle, and when the collision risk is equal to or exceeds a set value and a collision is possible, it can provide driving assistance to avoid a collision by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or evasive steering via the drivetrain control unit 12010.

At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether or not a pedestrian is present in the images captured by the image capturing units 12101 to 12104. The recognition of such a pedestrian is performed, for example, by a procedure of extracting feature points in the images captured by the image capturing units 12101 to 12104 as infrared cameras, and a procedure of performing pattern matching processing on a series of feature points that indicate the outline of an object to determine whether or not it is a pedestrian.
When the microcomputer 12051 determines that a pedestrian is present in the images captured by the imaging units 12101 to 12104 and recognizes the pedestrian, the audio/video output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio/video output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

The above describes an example of a vehicle control system to which the technology disclosed herein can be applied. The technology disclosed herein can be applied to, for example, a laser oscillator device for distance measurement used in the image capture unit 12031, etc., among the configurations described above.

This technology can be configured as follows:

(1)
a first reflecting mirror configured by laminating a plurality of types of semiconductor materials having different refractive indices, the first reflecting mirror having a first surface and a second surface opposite to the first surface;
a second reflecting mirror configured by laminating a plurality of types of dielectric materials having different refractive indices, the second reflecting mirror having a third surface and a fourth surface located on the opposite side of the third surface;
an active layer that is provided between the first surface of the first reflecting mirror and the fourth surface of the second reflecting mirror and that emits light when electric power is applied thereto;
a concavo-convex layer made of a dielectric material, provided on the third surface of the second reflector, and having a concavo-convex shape on a light emitting surface through which light from the active layer is emitted.

(2)
The light emitting device according to (1), wherein the uneven layer has a refractive index equal to or higher than that of the plurality of types of dielectric material layers constituting the second reflecting mirror.

(3)
The light emitting device according to (1) or (2), wherein the refractive index of the dielectric material constituting the uneven layer is 2 or more.

(4)
The light-emitting device according to (2), wherein the uneven layer is made of the same material as the dielectric material layer having a higher refractive index among the plurality of types of dielectric material layers constituting the second reflector.

(5)
The light emitting device according to any one of (1) to (4), wherein the dielectric material constituting the uneven layer is any one of TiO ₂ , Ta ₂ O ₅ , SiN, and amorphous silicon.

(6)
The light emitting device according to any one of (1) to (5), wherein the low refractive index dielectric material layer among the plurality of types of dielectric material layers constituting the second reflecting mirror is SiO ₂ or MgO.

(7)
the uneven shape of the uneven layer is formed by a plurality of grooves extending in a first direction in the light emitting surface,
The light emitting device according to any one of (1) to (6), wherein the period of the uneven shape arranged in the light emitting surface in a second direction perpendicular to the first direction is equal to or less than the wavelength of light emitted from the light emitting surface.

(8)
The light-emitting device according to any one of (1) to (7), wherein the height of the convex portions of the concave-convex shape of the concave-convex layer is 200 nm±60 nm.

(9)
The light emitting device according to any one of (1) to (8), wherein a side surface between the concave and convex portions of the concave-convex shape of the concave-convex layer is substantially perpendicular or inclined to the light emitting surface.

(10)
the active layer is made of AlGaInAs,
The light emitting device according to any one of (1) to (9), wherein the wavelength of light from the active layer is 1.2 μm to 2 μm.

(11)
a plurality of tunnel junction layers provided between the active layer and the second reflector and separated with respect to the active layer;
The light emitting device according to any one of (1) to (10), wherein the plurality of concave-convex shapes of the concave-convex layer are provided corresponding to the plurality of tunnel junction layers.

(12)
The light emitting device according to (11), wherein, in a plan view seen from a stacking direction of the plurality of types of dielectric materials, the plurality of concave and convex shapes overlap the plurality of tunnel junction layers, respectively.

(13)
The light-emitting device according to (11) or (12), wherein, in a planar view seen from the stacking direction of the plurality of types of dielectric materials, the plurality of uneven shapes and the plurality of tunnel junction layers have a substantially circular, substantially elliptical, or substantially polygonal shape.

(14)
a substrate including InP and provided on the second surface side of the first reflecting mirror;
The light emitting device according to any one of (1) to (13), wherein the first reflecting mirror has a layered structure of InP and AlGaInAs.

(15)
a substrate including GaAs and provided on the second surface side of the first reflecting mirror;
The light emitting device according to any one of (1) to (13), wherein the first reflecting mirror has a layered structure of GaAs and AlGaAs or AlAs.

Note that this disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of this disclosure. Furthermore, the effects described in this specification are merely examples and are not limiting, and other effects may also be present.

REFERENCE SIGNS LIST 1 Light emitting device 10 Substrate 20 First reflecting mirror 30 First semiconductor layer 40 Active layer 50 Second semiconductor layer 60 Third semiconductor layer 70 Fourth semiconductor layer 80 Fifth semiconductor layer 90 Second reflecting mirror 95 Grating layer 100 First electrode 110 Second electrode 120 Protective film GR Grating

Claims (15)

a first reflecting mirror configured by laminating a plurality of types of semiconductor materials having different refractive indices, the first reflecting mirror having a first surface and a second surface opposite to the first surface;
a second reflecting mirror configured by laminating a plurality of types of dielectric materials having different refractive indices, the second reflecting mirror having a third surface and a fourth surface located on the opposite side of the third surface;
an active layer that is provided between the first surface of the first reflecting mirror and the fourth surface of the second reflecting mirror and that emits light when electric power is applied thereto;
a concavo-convex layer made of a dielectric material, provided on the third surface of the second reflector, and having a concavo-convex shape on a light emitting surface through which light from the active layer is emitted. The light-emitting device described in claim 1, wherein the uneven layer has a refractive index equal to or higher than that of the multiple types of dielectric material layers that constitute the second reflector. The light-emitting device of claim 1, wherein the refractive index of the dielectric material constituting the uneven layer is 2 or greater. The light-emitting device described in claim 2, wherein the uneven layer is made of the same material as the dielectric material layer having the highest refractive index among the multiple types of dielectric material layers constituting the second reflector. 2. The light emitting device according to claim 1, wherein the dielectric material constituting _the uneven layer is any one of _TiO2 , _Ta2O5 , SiN, and amorphous silicon. 2. The light emitting device according to claim 1, wherein the dielectric material layer having a low refractive index among the plurality of types of dielectric material layers constituting the second reflecting mirror is _SiO2 or MgO. the uneven shape of the uneven layer is formed by a plurality of grooves extending in a first direction in the light emitting surface,
The light emitting device according to claim 1 , wherein the period of the concave and convex shapes arranged in the light emitting surface in a second direction perpendicular to the first direction is equal to or less than the wavelength of light emitted from the light emitting surface. The light-emitting device of claim 1, wherein the height of the convex portions of the concave-convex shape of the concave-convex layer is 200 nm ± 60 nm. The light-emitting device of claim 1, wherein the side surfaces between the concave and convex portions of the concave-convex shape of the concave-convex layer are approximately perpendicular or inclined to the light-emitting surface. the active layer is made of AlGaInAs,
2. The light emitting device according to claim 1, wherein the wavelength of light from said active layer is 1.2 μm to 2 μm. a plurality of tunnel junction layers provided between the active layer and the second reflector and separated with respect to the active layer;
The light emitting device according to claim 1 , wherein the plurality of concave-convex shapes of the concave-convex layer are provided corresponding to the plurality of tunnel junction layers. The light-emitting device of claim 11, wherein, in a plan view seen from the stacking direction of the plurality of types of dielectric materials, the plurality of uneven shapes overlap the plurality of tunnel junction layers. The light-emitting device of claim 11, wherein, in a plan view seen from the stacking direction of the plurality of types of dielectric materials, the plurality of concave-convex shapes and the plurality of tunnel junction layers have a substantially circular, substantially elliptical, or substantially polygonal shape. a substrate including InP and provided on the second surface side of the first reflecting mirror;
The light emitting device according to claim 1 , wherein the first reflecting mirror has a layered structure of InP and AlGaInAs. a substrate including GaAs and provided on the second surface side of the first reflecting mirror;
2. The light emitting device according to claim 1, wherein the first reflecting mirror has a layered structure of GaAs and AlGaAs or AlAs.