Light-emitting element and production method

Abstract

[Problem] To improve luminous efficiency, heat dissipation and etching selectivity. [Solution] A light emitting element includes a first reflecting mirror and a second reflecting mirror arranged apart along an optical axis, and two or more laminated semiconductor layers arranged between the first reflecting mirror and the second reflecting mirror. Each of the two or more laminated semiconductor layers has a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type arranged apart along the optical axis, an active layer arranged between the first semiconductor layer and the second semiconductor layer, and a tunnel junction layer arranged between two of the laminated semiconductor layers that are adjacent to each other in a lamination direction. The two or more laminated semiconductor layers have two or more kinds of the second semiconductor layers different from each other in material and dopant.

Description

Light-emitting device and manufacturing method

[0001] The present disclosure relates to light emitting devices and methods of manufacture.

[0002] In recent years, infrared VCSELs (Vertical Cavity Surface Emitting Lasers) have been developed for the purposes of 3D sensing and facial recognition. Currently, 940 nm band VCSELs using GaAs-based materials are mainly used, but longer wavelengths are desired in the future, and VCSELs using InP-based materials suitable for wavelengths of 1.3 μm or longer are attracting attention. In particular, the 1.4 μm band is an eye-safe band where the damage threshold for the eye is significantly increased, and has the advantage of suppressing noise due to the low background light from sunlight.

[0003] Furthermore, even higher efficiency and higher output are desired for sensing VCSELs. One configuration that can achieve this is a multi-junction VCSEL (also called a cascade type or multi-junction type) that has multiple tunnel junctions and active layer regions. For example, multi-junction VCSELs using InP-based materials have been proposed (see Patent Documents 1 and 2).

[0004] Japanese Patent Application Laid-Open No. 2006-351798

[0005] In InP-based materials, Zn, Mg, Be, Cd, etc. are used as dopants to form p-type semiconductor layers. However, these elements have the problem of easily diffusing from the p-type semiconductor layer during the process of growing the active layer at high temperatures. If these elements diffuse into the tunnel junction layer or the active layer, problems such as an increase in driving voltage or deterioration of light-emitting characteristics may occur.

[0006] On the other hand, when C-doped AlGaInAs is used as the p-type semiconductor layer, the diffusion of the dopant can be suppressed. However, when the above-mentioned AlGaInAs is used, there are problems such as a deterioration in heat dissipation properties or difficulty in selective etching during device fabrication, which limits the manufacturing process.

[0007] In Patent Document 1, a p-type semiconductor layer is used as a tunnel junction layer, but it is not used as a semiconductor layer that confines carriers in the active layer, which causes a problem of increased carrier overflow. Furthermore, there is no disclosure of a method for suppressing dopant diffusion from p-type semiconductor layers other than the tunnel junction layer.

[0008] Patent Document 2 discloses a technique of using Al(Ga)As as a current confinement layer in a GaAs-based VCSEL. However, in an InP-based VCSEL, Al(Ga)As cannot be grown due to the difference in lattice constant.

[0009] Therefore, the present disclosure provides a light emitting device and a manufacturing method thereof that can improve the light emitting efficiency, heat dissipation, and etching selectivity.

[0010] In order to solve the above-mentioned problems, according to the present disclosure, there is provided a light-emitting device comprising: a first reflecting mirror and a second reflecting mirror arranged to be spaced apart along an optical axis; and two or more laminated semiconductor layers arranged between the first reflecting mirror and the second reflecting mirror, wherein each of the two or more laminated semiconductor layers has: a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type arranged to be spaced apart along the optical axis; an active layer arranged between the first semiconductor layer and the second semiconductor layer; and a tunnel junction layer arranged between two of the laminated semiconductor layers adjacent to each other in the stacking direction, and the two or more laminated semiconductor layers have two or more types of second semiconductor layers each made of a different material and dopant.

[0011] Of the two or more laminated semiconductor layers, the second semiconductor layer in the laminated semiconductor layer located closest to the second reflector may contain a dopant that diffuses more easily than the second semiconductor layers in the other laminated semiconductor layers, and may have a higher thermal conductivity and a larger etching selectivity than the second semiconductor layers in the other laminated semiconductor layers.

[0012] The second semiconductor layer in the laminated semiconductor layer disposed closest to the second reflector includes InP doped with at least one of Zn, Mg, Be, and Cd, and the second semiconductor layer in the other laminated semiconductor layer includes Al doped with C. x Ga y In 1-x-y As (0≦x, 0≦y, 1−x−y≦1).

[0013] The two or more types of second semiconductor layers may have a third semiconductor layer and a fourth semiconductor layer stacked in each of the two or more laminated semiconductor layers, the third semiconductor layer being positioned closer to the second reflecting mirror than the fourth semiconductor layer, and the third semiconductor layer may contain a dopant that diffuses more easily than the fourth semiconductor layer, and may have a higher thermal conductivity and an etching selectivity than the fourth semiconductor layer.

[0014] The third semiconductor layer has InP doped with at least one of Zn, Mg, Be, and Cd, and the fourth semiconductor layer has Al doped with C. x Ga y In 1-x-y As (0≦x, 0≦y, 1−x−y≦1).

[0015] At least one of the first semiconductor layer, the active layer, the second semiconductor layer, and the tunnel junction layer may have a current confinement structure formed by implanting impurity ions.

[0016] The semiconductor device may include: a fifth semiconductor layer of a first conductivity type that is disposed between the second semiconductor layer in the laminated semiconductor layer that is disposed closest to the second reflector among the two or more laminated semiconductor layers and the second reflector; and a first buried tunnel junction layer that is provided inside the fifth semiconductor layer and that is in contact with the second semiconductor layer in the laminated semiconductor layer that is disposed closest to the second reflector among the two or more laminated semiconductor layers.

[0017] The semiconductor device may further include at least one second buried tunnel junction layer provided inside the first semiconductor layer in contact with the second semiconductor layer in each of the two or more laminated semiconductors and in contact with the second semiconductor layer.

[0018] The semiconductor device may include: a stacked body having the two or more stacked semiconductor layers; and a resistor surrounding the stacked body in the stacking direction and concentrating current inside the stacked body.

[0019] The semiconductor device may further include a contact layer that is arranged between the second reflector and one of the two or more laminated semiconductor layers that is located closest to the second reflector, and that supplies current to the active layer and is made of a transparent electrode that transmits light emitted from the active layer.

[0020] The first reflecting mirror comprises an InP substrate and an Al layer laminated on the InP substrate. x Ga y In 1-x-y As (0≦x, 0≦y, 1−x−y≦1) layer, In x Ga 1-x As y P 1-y (0≦x, 0≦y, 1−x≦1, 1−y≦1) layer, or Al x In 1-x The semiconductor layer may include at least one of an As (0≦x, 1−x≦1) layer and an InP layer.

[0021] The first reflecting mirror comprises a GaAs substrate and an Al layer laminated on the GaAs substrate. x Ga 1-x The semiconductor layer may include an As (0≦x, 1−x≦1) layer and a GaAs layer.

[0022] Light emitted from the active layer and resonated in the first reflecting mirror and the second reflecting mirror may be transmitted through the second reflecting mirror and then emitted.

[0023] Light emitted from the active layer and resonated in the first reflecting mirror and the second reflecting mirror may be transmitted through the first reflecting mirror and then emitted.

[0024] The first reflecting mirror and the second reflecting mirror may form at least a part of a resonator that resonates light emitted from the active layer, the active layer may be disposed at an antinode of a standing wave of light resonated in the resonator, and the tunnel junction layer may be disposed at a node of the standing wave.

[0025] The light emitting device may further include a plurality of light emitting units each having the first reflecting mirror, the second reflecting mirror, and the two or more laminated semiconductor layers, and each having a different optical axis for emitting light.

[0026] It may also be a VCSEL (Vertical Cavity Surface Emitting Laser).

[0027] The present disclosure also provides a method for manufacturing a light-emitting element, the method comprising the steps of: forming a first reflecting mirror on a substrate; stacking two or more laminated semiconductor layers, each including a first semiconductor layer of a first conductivity type, an active layer, and a second semiconductor layer of a second conductivity type, with a tunnel junction layer sandwiched between the two or more laminated semiconductor layers, the two or more laminated semiconductor layers having two or more types of second semiconductor layers different from each other in material and dopant, the two or more types of second semiconductor layers having a third semiconductor layer and a fourth semiconductor layer stacked in each of the two or more laminated semiconductor layers, the third semiconductor layer being disposed in a laminated semiconductor layer formed last, the third semiconductor layer containing a dopant that diffuses more easily than the fourth semiconductor layer, and having a higher thermal conductivity and an etching selectivity than the fourth semiconductor layer; forming a first buried tunnel junction layer on the two or more laminated semiconductor layers, the first buried tunnel junction layer having an area smaller than that of the laminated semiconductor layers; forming a fifth semiconductor layer of the first conductivity type on the first buried tunnel junction layer; and forming a second reflecting mirror on the fifth semiconductor layer.

[0028] The method may include a step of thinning the first substrate after stacking the laminated semiconductor layer on the first substrate, and a step of forming the first reflecting mirror on a second substrate and then bonding the first reflecting mirror to the thinned surface of the first substrate.

[0029] The present disclosure also provides a process for manufacturing a light-emitting device, which includes repeating two or more steps of forming a laminated semiconductor layer, forming a buried tunnel junction layer on the laminated semiconductor layer, and implanting impurity ions into a portion of the surface of the laminated semiconductor layer where the buried tunnel junction layer is not located.

[0030] FIG. 1 is a cross-sectional view showing a light-emitting device according to a first embodiment of the present disclosure. FIG. 2 is a view showing a first epitaxial growth step according to the first embodiment of the present disclosure. FIG. 3 is a view showing a second epitaxial growth step according to the first embodiment of the present disclosure. FIG. 4 is a view showing a hard mask formation step according to the first embodiment of the present disclosure. FIG. 5 is a view showing an ion implantation step according to the first embodiment of the present disclosure. FIG. 6 is a view showing a recovery annealing step according to the first embodiment of the present disclosure. FIG. 7 is a cross-sectional view showing a light-emitting device according to a second embodiment of the present disclosure. FIG. 8 is a view showing an epitaxial growth step according to the second embodiment of the present disclosure. FIG. 9 is a view showing a selective etching step according to the second embodiment of the present disclosure. FIG. 10 is a view showing an ion implantation step according to the second embodiment of the present disclosure. FIG. 11 is a view showing a regrowth step of a semiconductor layer and a contact layer according to the second embodiment of the present disclosure. FIG. 12 is a cross-sectional view showing a light-emitting device according to a third embodiment of the present disclosure. FIG. 13 is a view showing a light-emitting device according to a fourth embodiment of the present disclosure. FIG. 14 is a view showing an etching step according to the fourth embodiment of the present disclosure. FIG. 15 is a view showing a resistor embedding step according to the fourth embodiment of the present disclosure. FIG. 16 is a view showing a regrowth step of a semiconductor layer and a contact layer according to the fourth embodiment of the present disclosure. FIG. 17 is a cross-sectional view showing a light-emitting device according to a fifth embodiment of the present disclosure. FIG. 18 is a cross-sectional view showing a light-emitting device according to a sixth embodiment of the present disclosure. FIG. 19 is a cross-sectional view showing a light-emitting device according to a seventh embodiment of the present disclosure. 13 is a diagram illustrating an epitaxial growth process of a light-emitting element according to a seventh embodiment of the present disclosure. FIG. 14 is a diagram illustrating a process of forming a current confinement structure according to a seventh embodiment of the present disclosure. FIG. 15 is a diagram illustrating a process of temporarily bonding a support substrate according to a seventh embodiment of the present disclosure. FIG. 16 is a diagram illustrating a process of removing a semiconductor wafer according to a seventh embodiment of the present disclosure. FIG. 17 is a diagram illustrating a process of forming a first reflecting mirror and a substrate according to a seventh embodiment of the present disclosure. FIG. 18 is a diagram illustrating a process of permanently bonding a first reflecting mirror and a substrate according to a seventh embodiment of the present disclosure. FIG. 19 is a cross-sectional view showing a light-emitting element according to an eighth embodiment of the present disclosure. FIG. 20 is a cross-sectional view showing a light-emitting element according to a ninth embodiment of the present disclosure. FIG. 21 is a block diagram illustrating an example configuration of a distance measuring system according to a tenth embodiment of the present disclosure. FIG. 22 is an explanatory diagram of an STL system. FIG. 23 is an explanatory diagram illustrating the distance measuring principle of the STL system. FIG. 24 is a block diagram illustrating an example of the general configuration of a vehicle control system. FIG. 25 is an explanatory diagram illustrating an example of the installation positions of an outside vehicle information detection unit and an imaging unit.

[0031] Hereinafter, embodiments of a light-emitting device and a manufacturing method thereof will be described with reference to the drawings. The following description will focus on the main components of the light-emitting device and the manufacturing method thereof, but the light-emitting device and the manufacturing method thereof may include components and functions that are not shown or described. The following description does not exclude components and functions that are not shown or described.

[0032] First Embodiment Fig. 1 is a cross-sectional view showing a light-emitting element 1 according to a first embodiment of the present disclosure. The light-emitting element 1 in Fig. 1 is, for example, a VCSEL. The light-emitting element 1 is used for various purposes, such as a light source for optical communication or a light source for distance measurement.

[0033] The light-emitting element 1 includes a substrate 2, a first reflecting mirror 3, a second reflecting mirror 4, a plurality of stacked semiconductor layers 5, a semiconductor layer (fifth semiconductor layer) 6, a contact layer 7, and electrodes 11 and 12. In addition to the above, the light-emitting element 1 may include an insulating protective film, which is not shown in FIG.

[0034] The first reflecting mirror 3, the second reflecting mirror 4, the plurality of laminated semiconductor layers 5, and the semiconductor layer 6 are stacked on the substrate 2. More specifically, the first reflecting mirror 3 is stacked on the substrate 2, and the second reflecting mirror 4 is disposed spaced apart from the first reflecting mirror 3 along the optical axis AX. In addition, the plurality of laminated semiconductor layers 5 and the semiconductor layer 6 are disposed in this order from the first reflecting mirror 3 side between the first reflecting mirror 3 and the second reflecting mirror 4.

[0035] The light-emitting element 1 emits laser light L from the end face (light-emitting surface A1) of the second reflecting mirror 4 opposite to the substrate 2. In this specification, the light-emitting element 1 is also referred to as a front-side emission VCSEL. Note that the light-emitting element 1 may also be a back-side emission VCSEL that emits laser light L from the substrate 2 side.

[0036] Each of the plurality of laminated semiconductor layers 5 includes an active layer 21, a semiconductor layer (first semiconductor layer) 22, a semiconductor layer (second semiconductor layer) 23, and a tunnel junction layer 24. The light-emitting element 1 includes the plurality of tunnel junction layers 24, and is therefore also called a multi-junction structure.

[0037] 1 has a three-layer (3-stack) structure having three laminated semiconductor layers 5. The light-emitting element 1 may have a two-layer structure or a four-layer or more structure.

[0038] The substrate 2 is, for example, an InP substrate, and more specifically, an n-InP substrate doped with S. In this specification, a semiconductor material X doped with a dopant Y may be referred to as X:Y.

[0039] The substrate 2 may be a semi-insulating InP:Fe substrate other than the n-InP:S substrate. The substrate 2 has a thickness sufficient to maintain the mechanical strength when the light emitting element 1 is bonded to other members.

[0040] The first reflecting mirror 3 reflects light generated in the active layer 21 that propagates in the opposite direction to the emission direction of the laser light. The first reflecting mirror 3 is, for example, a semiconductor DBR (Distributed Bragg Reflector) and is made of semiconductor materials (for example, AlGaInAs / InP) having two or more different refractive indices. x Ga y In 1-x-y As (0≦x, 0≦y, 1−x−y≦1) layer, In x Ga 1-x As y P 1-y (0≦x, 0≦y, 1−x≦1, 1−y≦1) layer, or Al x In 1-x It can be composed of at least one As (0≦x, 1−x≦1) layer and an InP layer.

[0041] The first reflecting mirror 3 includes a non-doped layer or an undoped layer (hereinafter simply referred to as a non-doped layer) in part. In order to reduce the optical absorption loss of the laser light as much as possible, it is desirable that all layers of the first reflecting mirror 3 are non-doped layers, or that several layers on the outermost surface facing the second reflecting mirror 4 are doped with n-type (first conductivity type) impurities, and that most of the other layers are non-doped layers.

[0042] The second reflecting mirror 4 reflects light that propagates in the emission direction of the laser light out of the light emitted from the active layer 21. The second reflecting mirror 4 is, for example, a dielectric DBR, and is made of TiO2 / SiO2 or the like.

[0043] The active layer 21 emits and amplifies spontaneously emitted light. The active layer 21 has a quantum well (QW) structure in which quantum well layers with small band gaps and barrier layers with large band gaps are alternately stacked. The structure of the active layer 21 is not limited to the above, and may be a quantum dot (QDs) structure or a quantum wire structure. The active layer 21 is made of, for example, AlGaInAs. The active layer 21 may be made of any semiconductor material containing at least one of Al, Ga, or In as a group 3 element and at least one of As, P, N, or Sb as a group 5 element. The active layer 21 is configured as, for example, a non-doped layer, but may be partially doped. The active layer 21 is disposed between the semiconductor layers 22 and 23.

[0044] The semiconductor layers 22 and 23 are used to confine charges in the active layer 21. The semiconductor layer 22 is an n-type semiconductor layer and is made of, for example, n-InP:Si or n-AlGaInAs:Si.

[0045] The semiconductor layer 23 is a p-type (second conductivity type) semiconductor layer. The light-emitting element 1 has two or more types of semiconductor layers 23 each made of a different material and dopant. The two or more types of semiconductor layers 23 include a semiconductor layer (third semiconductor layer) 23 a and a semiconductor layer (fourth semiconductor layer) 23 b having a dopant with lower thermal diffusivity than the dopant of the semiconductor layer 23 a.

[0046] The semiconductor layer 23a is made of, for example, p-InP as a semiconductor material, and is doped with at least one of Zn, Mg, Be, and Cd (for example, Mg) as a dopant.

[0047] The semiconductor layer 23b is made of p-Al x Ga y In 1-x-yThe semiconductor layer 23b has p-AlGaInAs (0≦x, 0≦y, 1−x−y≦1), more specifically, p-AlGaInAs or p-AlInAs, etc. The semiconductor layer 23b is doped with, for example, C as a dopant.

[0048] The semiconductor layer 22, the semiconductor layer 23a, and the semiconductor layer 23b may be partially non-doped.

[0049] The tunnel junction layer 24 injects charges into the active layer 21 via a tunnel junction. The tunnel junction layer 24 is disposed between two stacked semiconductor layers 5 adjacent to each other in the stacking direction. The tunnel junction layer 24 has a semiconductor layer 27a configured as an n-type highly doped layer (heavily doped n-type layer) and a semiconductor layer 27b configured as a p-type highly doped layer (heavily doped p-type layer).

[0050] The semiconductor layer 27a is made of Al doped with at least one of Si, Te, S, Sn, and Se. x Ga y In 1-x-y As (0≦x, 0≦y, 1−x−y≦1), or In doped with at least one of Si, Te, S, Sn, and Se x Ga 1-x As y P 1-y (0≦x, 0≦y, 1−x≦1, 1−y≦1), etc. More specifically, the semiconductor layer 27a is made of, for example, InP:Si+, AlGaInAs:Si+, or the like.

[0051] The semiconductor layer 27b is an In doped with at least one of Zn, Mg, Be, and Cd. x Ga 1-x As y P 1-y (0≦x, 0≦y, 1−x≦1, 1−y≦1), or Al doped with at least one of Zn, Mg, Be, Cd, or C. x Ga y In 1-x-y As (0≦x, 0≦y, 1−x−y≦1), etc. More specifically, the semiconductor layer 27b is made of, for example, AlInAs:C+ or AlGaInAs:C+.

[0052] The laminated semiconductor layer 5 includes a semiconductor layer 22, an active layer 21, a semiconductor layer 23, a semiconductor layer 27b, and a semiconductor layer 27a stacked in this order from the first reflecting mirror 3 side. The plurality of laminated semiconductor layers 5 includes a laminated semiconductor layer (first laminated semiconductor layer) 5a including the semiconductor layer 23a and a laminated semiconductor layer (second laminated semiconductor layer) 5b including the semiconductor layer 23b.

[0053] The semiconductor layer 6 is an n-type semiconductor layer, and is made of n-InP:Si or the like, similar to the semiconductor layer 22. In this specification, the semiconductor layer 6 may be described as part of the laminated semiconductor layer 5.

[0054] The contact layer 7 is disposed on the semiconductor layer 6 so as to surround the second reflecting mirror 4. The contact layer 7 is made of, for example, n-InGaAs:Si+. The contact layer 7 is connected to the electrode 11 and supplies the current of the electrode 11 to the active layer 21.

[0055] Furthermore, a portion of the laminated semiconductor layer 5 includes a region (first region) 25 that has been made highly resistive (semi-insulating) by ion implantation, and a region (second region) 26 that has higher conductivity than region 25. Region 25 is formed in semiconductor layers 23 and 27b, which are p-type semiconductor layers. Region 26 is formed in semiconductor layers 6, 22, and 27a, which are n-type semiconductor layers.

[0056] The region 25 is disposed in the outer peripheral portion of the laminated semiconductor layer 5 away from the center of the optical axis AX. The region 25 functions as a current confinement by restricting the diffusion of current. A part of the region 26 is used as a current path for supplying current from the electrode 11 to the active layer 21.

[0057] The electrode 11 is also called an upper electrode, and the electrode 12 is also called a lower electrode. The electrodes 11 and 12 are made of a metal (for example, Au, Pt, or Ti).

[0058] When a voltage is applied between the electrodes 11 and 12, a current flows between the electrodes 11 and 12. As a result, charges are injected into the active layer 21 via the tunnel junction layer 24. As a result, spontaneous emission of light occurs from the active layer 21.

[0059] The first reflecting mirror 3 and the second reflecting mirror 4 constitute at least a part of a resonator 13 that resonates light generated in the active layer 21. Spontaneous emission light generated in the active layer 21 travels in the stacking direction of the light-emitting element 1 and is reflected by the first reflecting mirror 3 and the second reflecting mirror 4. Because the first reflecting mirror 3 and the second reflecting mirror 4 are configured to reflect light having a predetermined resonance wavelength λ, the component of the spontaneous emission light having the resonance wavelength λ generates a standing wave (also called resonance) within the resonator 13 and is amplified by the active layer 21. When the charge injected into the active layer 21 exceeds a predetermined threshold, the light that forms the standing wave undergoes laser oscillation and passes through the second reflecting mirror 4, and laser light is emitted from the light-emitting surface A1.

[0060] The active layer 21 is preferably disposed at an antinode of the standing wave of light resonated in the resonator 13. On the other hand, the tunnel junction layer 24 with a high impurity concentration is preferably disposed at a node of the standing wave of light to suppress a decrease in laser output due to light absorption (free carrier absorption). The antinode of the standing wave is, for example, a position xλ / 2 (x is an integer equal to or greater than 1) from the interface between the second reflecting mirror 4 and the laminated semiconductor layer 5. The node of the standing wave is, for example, a position xλ / 2+λ / 4 (x is an integer equal to or greater than 0) from the interface. For example, the above condition can be satisfied by arranging the laminated semiconductor layer 5 at a constant period (for example, a period equal to an integer multiple of λ / 2). In this specification, the space in which the standing wave of light resonated in the resonator 13 exists is also referred to as an optical field, and the node of the standing wave is also referred to as a minimum region of the optical field, and the antinode of the standing wave is also referred to as a maximum region of the optical field.

[0061] As described above, the light-emitting element 1 according to the first embodiment of the present disclosure is an InP-based multi-junction VCSEL formed using an InP substrate 2. In InP semiconductor materials, C dopants exhibit n-type or semi-insulating characteristics, so C cannot be used as a p-type dopant. For this reason, Zn, Mg, Be, Cd, or the like (e.g., Mg) are used as p-type dopants for InP semiconductor materials. However, these elements have the problem of being prone to diffusion during high-temperature growth.

[0062] In order to improve the crystallinity, it is generally desirable to grow the AlGaInAs active layer 21 at a higher temperature than an InP semiconductor layer, etc. In this case, the Mg and other elements may diffuse into the tunnel junction layer 24 or the active layer 21, etc. This may cause problems such as an increase in the driving voltage of the light-emitting element 1 or a deterioration in the light-emitting characteristics.

[0063] On the other hand, if AlGaInAs:C is used in all p-type semiconductor layers, dopant diffusion can be prevented, but AlGaInAs has a lower thermal conductivity than InP, which causes a problem of deterioration in the heat dissipation of the light-emitting element 1. In addition, AlGaInAs cannot be selectively etched by wet etching, which causes a problem of limitations on the manufacturing process of the light-emitting element 1.

[0064] The light-emitting device 1 according to the first embodiment of the present disclosure is characterized in that it can solve the above-mentioned problems. Figures 2A to 2E are diagrams illustrating the manufacturing process of the light-emitting device 1 according to the first embodiment of the present disclosure.

[0065] 2A is a diagram showing a first epitaxial growth step of the light-emitting element 1. In FIG. 2A, metal organic chemical vapor deposition (MOCVD, or MOVPE), molecular beam epitaxy (MBE), or the like is used. In FIG. 2A, first, a first reflecting mirror 3 is formed on a substrate 2. Then, a semiconductor layer 22, an active layer 21, a semiconductor layer 23b, and a tunnel junction layer 24 are grown on the first reflecting mirror 3, thereby forming a first laminated semiconductor layer 5b. Then, a second laminated semiconductor layer 5 is formed on the laminated semiconductor layer 5b.

[0066] In the second laminated semiconductor layer 5, the active layer 21 is grown at a high temperature. At this time, if a dopant such as Mg is used in the previously formed p-type semiconductor layer, there is a risk of the dopant diffusing. In contrast, the semiconductor layer 23b according to the first embodiment of the present disclosure is composed of p-AlGaInAs:C, p-AlInAs:C, or the like, which uses C as a dopant. Therefore, the semiconductor layer 23b can suppress the diffusion of the dopant.

[0067] When forming three or more laminated semiconductor layers 5, another laminated semiconductor layer 5 is formed on the second laminated semiconductor layer 5.

[0068] 2A shows a state in which one or more (two in the example of FIG. 2A) laminated semiconductor layers 5b have been formed, excluding the laminated semiconductor layer 5a that is to be formed last, among the plurality of laminated semiconductor layers 5. Also, in FIG. 2A, of the laminated semiconductor layers 5a, the semiconductor layer 22 and the active layer 21a have been formed. The active layer 21a in FIG. 2A is the active layer 21 that is to be formed last.

[0069] 2B is a diagram showing a second epitaxial growth step of the light-emitting element 1. In Fig. 2B, the semiconductor layer 23a and the tunnel junction layer 24, which are the remaining parts of the laminated semiconductor layer 5a, are formed by metal organic vapor phase epitaxy, molecular beam epitaxy, or the like, as in Fig. 2A. Also, in Fig. 2B, the semiconductor layer 6 and the contact layer 7 are formed.

[0070] 2B and subsequent steps, there is no process for forming the active layer 21. Therefore, the semiconductor layer 23a can be made of p-InP:Mg or the like using Mg or the like as a dopant.

[0071] As described above, the laminated semiconductor layer 5 a according to the first embodiment of the present disclosure is disposed at the position farthest from the substrate 2 and closest to the second reflecting mirror 4 among the plurality of laminated semiconductor layers 5 .

[0072] 2C is a diagram showing a process of forming a hard mask 31. In FIG. 2C, the semiconductor wafer 30 formed in FIG. 2B is taken out of the furnace, and a hard mask 31 is formed on the outermost surface of the semiconductor wafer 30. The hard mask 31 is made of, for example, SiO ２The hard mask 31 is formed by evaporation, sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), etc. A photolithography process (photolithography process) is used to form the pattern of the hard mask 31, and wet etching, reactive ion etching (RIE), etc. are used for etching.

[0073] 2D is a diagram showing an ion implantation process. Ions (impurity ions) 33 such as H or He are implanted into regions 32 of the semiconductor wafer 30 where the hard mask 31 is not formed. As a result, carriers in the semiconductor layer in the regions 32 are deactivated, making the semiconductor layer semi-insulating.

[0074] 2E is a diagram showing a recovery annealing step. In FIG. 2E, after the hard mask 31 is removed, a conductivity recovery annealing is performed. Since the p-type semiconductor layer (i.e., semiconductor layers 23 and 27b) and the n-type semiconductor layer (i.e., semiconductor layers 6, 22, and 27a) have different easiness of conductivity recovery by annealing, by selecting appropriate conditions, the p-type semiconductor layer can remain semi-insulating while the n-type semiconductor layer can recover conductivity. This allows regions 25 and 26 to be formed, and region 25 can form a current confinement structure.

[0075] In the steps from Fig. 2E onwards, a device structure is fabricated on the semiconductor wafer 30 that has undergone recovery annealing. The electrodes 11 and 12, the protective film (not shown in Fig. 1), and the second reflecting mirror 4 are formed by evaporation, sputtering, chemical vapor deposition, atomic layer deposition, etc. Furthermore, pattern formation by a photolithography process or the like, and etching by wet etching or reactive ion etching, etc., are also performed. Through these steps, the light-emitting element 1 shown in Fig. 1 is formed.

[0076] 1 shows an example in which one of the plurality of semiconductor layers 23 that is closest to the second reflecting mirror 4 is the semiconductor layer 23a. However, without being limited to this, two or more of the plurality of semiconductor layers 23 that are arranged near the second reflecting mirror 4 may be the semiconductor layer 23a.

[0077] As described above, in the light-emitting element 1 according to the first embodiment of the present disclosure, the semiconductor layer 23a, which is formed last among the multiple p-type semiconductor layers 23, is formed of InP:Mg or the like, and the other semiconductor layer 23b is formed of AlGaInAs:C or the like. The semiconductor layer 23b uses C, which is difficult to thermally diffuse, as a dopant. This prevents the dopant from diffusing from the semiconductor layer 23b during the growth process of the active layer 21, which is performed after the formation of the semiconductor layer 23b, and prevents deterioration of the power characteristics and light-emitting characteristics of the light-emitting element 1.

[0078] The semiconductor layer 23a contains a dopant such as Mg, which is easily thermally diffused. However, after the formation of the semiconductor layer 23a, there is no process of growing the active layer 21 or the like at high temperatures, so the diffusion of the dopant can be prevented. Furthermore, by forming the semiconductor layer 23a from an InP-based material, the thermal conductivity can be improved compared to when the semiconductor layer 23a is formed from AlGaInAs or the like, and the heat dissipation performance of the light-emitting element 1 can be improved. Furthermore, InP can be selectively etched by wet etching, which allows for greater flexibility in the manufacturing process of the light-emitting element 1 compared to when the semiconductor layer 23a is formed from AlGaInAs or the like.

[0079] That is, the light emitting element 1 according to the first embodiment of the present disclosure can improve the light emitting efficiency, heat dissipation, and etching selectivity.

[0080] 3 is a cross-sectional view showing a light-emitting element 1a according to a second embodiment of the present disclosure. The light-emitting element 1a differs from the light-emitting element 1 shown in FIG. 1 in that, instead of the tunnel junction layer 24, a tunnel junction layer (first buried tunnel junction layer) 24a is embedded in the semiconductor layer 6a and in contact with the semiconductor layer 23a within the laminated semiconductor layer 5a.

[0081] 3 also has a region (third region) 32a that is made highly resistive (semi-insulating) by ion implantation. Region 32a differs from region 25 in FIG. 1 in that it is also formed in semiconductor layers 22 and 27a, which are n-type semiconductor layers.

[0082] 4A to 4D are diagrams illustrating a manufacturing process of a light-emitting element 1a according to a second embodiment of the present disclosure. FIG. 4A is a diagram illustrating an epitaxial growth process for the light-emitting element 1a. In FIG. 4A, similar to FIG. 2B, a first reflecting mirror 3, one or more laminated semiconductor layers 5b, and a laminated semiconductor layer 5a are formed on a substrate 2. On the other hand, in FIG. 4A, a contact layer 7 is not formed. Furthermore, the semiconductor layer 6a is formed as a semiconductor layer 6b having a relatively thin film thickness, which is obtained by subtracting the film thickness formed by regrowth described below.

[0083] 4B is a diagram showing a selective etching step. As in FIG. 2C, the semiconductor wafer 30a formed in FIG. 4A is taken out of the furnace, and a hard mask 31 is formed on the semiconductor layer 6b. Subsequently, in FIG. 4B, the semiconductor layer 6b and the tunnel junction layer 24a are etched by selective wet etching. In FIG. 4B, the etching is stopped at the semiconductor layer 23a arranged below the tunnel junction layer 24a.

[0084] As a comparative example, the semiconductor layer 23a disposed below the tunnel junction layer 24a may be made of p-AlGaInAs:C or p-AlInAs:C, similar to the semiconductor layer 23b. In this example, the material system is the same as that of the AlGaInAs active layer 21 and the p-type highly doped semiconductor layer 27b, and therefore selective etching is not possible.

[0085] In contrast, the semiconductor layer 23a according to the second embodiment of the present disclosure is made of an InP material such as p-InP:Mg, and therefore is made of a different material from the active layer 21 and the semiconductor layer 27b, and can have a sufficiently higher selectivity than the semiconductor layer 23b, etc. This allows etching to be stopped accurately at the interface between the tunnel junction layer 24a and the semiconductor layer 23a.

[0086] 4C is a diagram showing an ion implantation step in which ions 33a are implanted into a region 32a of the semiconductor wafer 30a where the hard mask 31 is not formed. As a result, carriers in the semiconductor layer in the region 32a are deactivated, resulting in semi-insulation.

[0087] The ions 33a in Fig. 4C are different from the ions 33 in Fig. 2D. The ions 33a are at least one ion of O, B, Fe, Ru, or Cr (for example, O).

[0088] 4D is a diagram showing a regrowth step of the semiconductor layer 6 a and the contact layer 7. In FIG. 4D, after the hard mask 31 is removed, the semiconductor wafer 30 a is placed in the furnace again, and the semiconductor layer 6 a is formed by regrowth of the semiconductor layer 6 b, and the contact layer 7 is also formed.

[0089] 4D and subsequent steps, a device structure is fabricated in the same manner as in the first embodiment, thereby forming the light emitting element 1a shown in FIG.

[0090] 3, the semiconductor layer 6a has a low contact resistance at the interface 6c with the tunnel junction layer 24a, allowing current to diffuse, but the contact resistance is high at the regrowth interface in other regions, preventing current diffusion. Furthermore, the bulk resistance of the ion-implanted region 32a is also high, preventing current diffusion. In other words, the difference between the contact resistance and bulk resistance limits current diffusion, allowing the tunnel junction layer 24a and region 32a to form a current confinement structure.

[0091] 4A to 4D, recovery annealing is not performed. It is known that the ion implantation process using ions 33a such as oxygen (O) in FIG. 4C does not easily restore conductivity by annealing, and region 32a can have a higher resistance than region 25 in FIG.

[0092] That is, the region 32a can be made completely semi-insulating. As a result, the light emitting element 1a in Fig. 3 can have a much lower leakage current than the light emitting element 1 in Fig. 1, and can further improve the power characteristics.

[0093] In this way, in the light-emitting device 1 a according to the second embodiment of the present disclosure, the buried tunnel junction layer can be formed by utilizing the selective etching property of the semiconductor layer 23 a, thereby improving the robustness of the current confinement structure and the power characteristics compared to the light-emitting device 1 shown in FIG.

[0094] Third Embodiment FIG. 5 is a cross-sectional view showing a light-emitting element 1b according to a third embodiment of the present disclosure. The light-emitting element 1b differs from the light-emitting element 1 of FIG. 1 in that it includes a contact layer 7a made of a transparent electrode. The contact layer 7a is made of, for example, IWO (W-doped In2O3) or ITiO (Ti-doped In2O3). The contact layer 7a is connected to, for example, the electrode 11 and supplies current to the active layer 21. The contact layer 7a also transmits light emitted from the active layer 21. The contact layer 7a is disposed between the laminated semiconductor layer 5a and the second reflector 4. The contact layer 7a is formed in a device structure fabrication process after the ion implantation process shown in FIG. 2D and other figures.

[0095] The light-emitting element 1b also has a region 32b that has been made highly resistive by ion implantation. The region 32b is formed in the semiconductor layer 6 and in part of the plurality of laminated semiconductor layers 5. Ions 33a similar to those in FIG. 4C can be implanted into the region 32b, and the region 32b can also be made completely semi-insulating. This allows the light-emitting element 1b to have an extremely low leakage current, similar to the light-emitting element 1a in FIG. 3.

[0096] In this way, the light-emitting element 1b according to the third embodiment of the present disclosure can improve power characteristics in the same way as the light-emitting element 1a of Figure 3, thanks to the contact layer 7a made of a transparent electrode and the region 32b made highly resistive by ion implantation.

[0097] 5 does not require the recovery annealing step of Fig. 2E and the step of forming the buried tunnel junction layer of Fig. 4B, etc. This simplifies the manufacturing process and reduces manufacturing costs.

[0098] Fourth Embodiment Fig. 6 is a cross-sectional view showing a light-emitting device 1c according to a fourth embodiment of the present disclosure. The light-emitting device 1c of Fig. 6 differs from the light-emitting device 1 of Fig. 1 in that a resistor (semi-insulating layer) 41 is embedded in place of the region 25, etc. The resistor 41 is made of a semiconductor such as InP:Fe, InP:Ru, InP:Cr, or InP:C. The resistor 41 may also be made of an insulator such as SiO2. The resistor 41 is arranged to surround the periphery in the stacking direction of a stack 42 having two or more stacked semiconductor layers 5.

[0099] In the light-emitting device 1c of Figure 6, the resistor 41 allows current to be concentrated inside the stack 42, forming a current confinement structure. Furthermore, the InP:Fe or other materials used in the resistor 41 are binary materials and therefore have higher thermal conductivity than alloy materials such as AlGaInAs. This improves the heat dissipation of the light-emitting device 1c and reduces its thermal resistance. Furthermore, since InP-based materials have a lower refractive index than AlGaInAs or other materials, the light confinement in the planar direction of the substrate 2 can be improved, resulting in improved light-emitting characteristics compared to the light-emitting device 1 of Figure 1 and other light-emitting devices.

[0100] 7A to 7C are diagrams illustrating a manufacturing process of a light-emitting device 1c according to a fourth embodiment of the present disclosure. First, as a pre-step shown in FIGS. 7A to 7C, epitaxial growth similar to that shown in FIG. 4A is performed. As a result, a first reflecting mirror 3, one or more laminated semiconductor layers 5b, 5a, and a semiconductor layer 6b are formed on the substrate 2. The semiconductor layer 6b is formed to a relatively thin film thickness, subtracting the film thickness formed by regrowth described below.

[0101] 7A is a diagram showing an etching process. First, the semiconductor wafer 30a formed in FIG. 4A is taken out of the furnace, and a hard mask 31 is formed on the semiconductor layer 6b. Next, in FIG. 7A, the semiconductor layer 6b and the portions of the plurality of laminated semiconductor layers 5 that are not protected by the hard mask 31 are etched by wet etching or dry etching. In FIG. 7A, etching is performed up to the front and rear of the semiconductor layer 22 disposed on the first reflecting mirror 3.

[0102] Fig. 7B is a diagram showing a step of embedding the resistor 41. In Fig. 7B, the semiconductor wafer 30a is again placed in the furnace, and the resistor 41 is embedded by regrowth in the portion etched in Fig. 7A.

[0103] 7C is a diagram showing a regrowth step of the semiconductor layer 6b and the contact layer 7. In Fig. 7C, the semiconductor wafer 30a is taken out of the furnace, and the hard mask 31 is removed. Thereafter, the semiconductor wafer 30a is placed back into the furnace, and the semiconductor layer 6b is regrown to form the semiconductor layer 6, and the contact layer 7 is also formed.

[0104] 7C and subsequent steps, a device structure is fabricated in the same manner as in the first embodiment of the present disclosure, thereby forming the light emitting device 1c of FIG.

[0105] As described above, the light-emitting element 1c according to the fourth embodiment of the present disclosure can form a current confinement structure by embedding the resistor 41, which is a semi-insulating layer. Furthermore, since the resistor 41 can be formed of a material with high thermal conductivity and low refractive index, the light-emitting element 1c can have a higher laser output and higher power efficiency than the light-emitting element 1 shown in FIG.

[0106] Fifth Embodiment Fig. 8 is a cross-sectional view showing a light-emitting device 1d according to a fifth embodiment of the present disclosure. The light-emitting device 1a in Fig. 3 shows an example in which a buried tunnel junction layer is formed in the semiconductor layer 6 that is the outermost surface of the light-emitting device 1a. In contrast, the light-emitting device 1d in Fig. 8 differs from the light-emitting device 1a in Fig. 3 in that a buried tunnel junction layer is disposed between two laminated semiconductor layers 5.

[0107] 8 has a tunnel junction layer (second buried tunnel junction layer) 24b buried inside the semiconductor layer 22. The tunnel junction layer 24b is disposed so as to be in contact with the semiconductor layer 23. The light emitting element 1d may have a structure in which one or more other tunnel junction layers 24b are buried in one or more other semiconductor layers 22. Furthermore, the light emitting element 1d may have a structure in which the tunnel junction layer 24a is buried inside the semiconductor layer 6, which is the outermost surface, similar to the light emitting element 1a of FIG.

[0108] The tunnel junction layer 24b in FIG. 8 can be formed by a process similar to that for forming the tunnel junction layer 24a shown in FIGS. 4A to 4D. In FIG. 4D, the contact layer 7 is not formed, and the laminated semiconductor layer 5, such as the active layer 21, is formed on the semiconductor layer 22 in which the tunnel junction layer 24b is embedded, thereby forming the light-emitting element 1d in FIG. 8. The ion implantation in FIG. 4C may be performed when forming the tunnel junction layer 24a, which is disposed on the outermost surface. Alternatively, the ion implantation may be performed each time the tunnel junction layer 24a or 24b is formed. Because the tunnel junction layer 24b is formed before the tunnel junction layer 24a, the tunnel junction layer 24b may be referred to as the first tunnel junction layer and the tunnel junction layer 24a may be referred to as the second tunnel junction layer in this specification.

[0109] When a buried tunnel junction layer is disposed between two laminated semiconductor layers 5, a semiconductor layer 23 d (see FIG. 9 ) for etching stop may be disposed in a part of the semiconductor layer 22 disposed between the buried tunnel junction layer and the active layer 21, as in the sixth embodiment described later.

[0110] 3, when the number of laminated semiconductor layers 5 (hereinafter also referred to as the number of periods of the multi-junction) is large, it is difficult to uniformly implant ions into all of the laminated semiconductor layers 5 in a single ion implantation, and it may not be possible to form a current confinement structure that can sufficiently reduce leakage current. Furthermore, with ion implantation alone, it is difficult to create a difference in refractive index in the planar direction of the substrate 2, resulting in poor light confinement.

[0111] To address the above-mentioned problems, the light emitting device 1d uses the tunnel junction layer 24b disposed between the two laminated semiconductor layers 5, thereby making it possible to improve the current confinement and light confinement properties.

[0112] 8, ion implantation can be performed multiple times, for example, for each formation of the tunnel junction layer 24 a or 24 b, which allows ions to be implanted uniformly into the multiple laminated semiconductor layers 5, thereby further improving the current confinement property.

[0113] 9 is a cross-sectional view showing a light-emitting element 1e according to a sixth embodiment of the present disclosure. The light-emitting element 1e in FIG. 9 differs from the light-emitting element 1 in FIG. 1 in that the p-type semiconductor layer 23 is formed of multiple layers.

[0114] The light-emitting element 1e includes one or more semiconductor layers 23c and a stacked semiconductor layer (third stacked semiconductor layer) 5c including the semiconductor layer 23c. The semiconductor layer 23c is a p-type semiconductor layer composed of at least two or more types of semiconductor materials and a dopant.

[0115] The semiconductor layer 23c is a semiconductor layer (fourth semiconductor layer) 23e formed immediately after the formation of the active layer 21. ... x Ga y In 1-x-y It is desirable to use p-AlGaInAs:C (0≦x, 0≦y, 1-x-y≦1), more specifically, p-AlGaInAs:C or p-AlInAs:C. Furthermore, it is desirable to use p-InP:X (X=Zn, Mg, Be, Cd) or the like for the semiconductor layer (third semiconductor layer) 23d formed immediately before the formation of the tunnel junction layer 24. That is, the semiconductor layer 23d contains a dopant that is more easily diffused than the semiconductor layer 23e, and has a high thermal conductivity and a high etching selectivity. This can mitigate the influence of the diffusion of dopants such as Mg, and can improve the heat dissipation of the light-emitting element 1e.

[0116] All of the plurality of semiconductor layers 23 in the light-emitting element 1e may be semiconductor layers 23c. Furthermore, some of the plurality of semiconductor layers 23 may be formed of a single layer of semiconductor layer 23a or 23b. When some of the semiconductor layers 23 are formed of a single layer of semiconductor layer 23a or 23b, it is desirable to use semiconductor layer 23b on the side closer to the first reflecting mirror 3 and semiconductor layer 23a on the side closer to the second reflecting mirror 4 in order to mitigate the effects of dopant diffusion. Furthermore, when the manufacturing process includes the selective etching step shown in FIG. 4B or the like, it is desirable to use semiconductor layer 23a or semiconductor layer 23c containing p-InP:X (X = Zn, Mg, Be, Cd) or the like for the semiconductor layer 23 disposed closest to the second reflecting mirror 4.

[0117] In this way, the influence of dopant diffusion can be alleviated and the heat dissipation of the light emitting element 1 e can be improved by forming a part of the semiconductor layer 23 with multiple layers. The configuration of the light emitting element 1 e according to the sixth embodiment of the present disclosure can be applied to any of the first to fifth embodiments.

[0118] Seventh Embodiment Fig. 10 is a cross-sectional view showing a light-emitting device 1f according to a seventh embodiment of the present disclosure. The light-emitting device 1f in Fig. 10 differs from the light-emitting device 1 in Fig. 1 in that it has a first reflecting mirror 3a and a substrate (second substrate) 2a formed of a semiconductor material other than an InP-based material. The first reflecting mirror 3a and the substrate 2a are bonded to a substrate (first substrate) 2b on which the laminated semiconductor layer 5 is arranged, at a surface A2.

[0119] It is generally known that the thermal conductivity of semiconductors deteriorates when they are mixed crystals. In particular, AlGaInAs, which is an InP-based material, has low thermal conductivity. Therefore, the first reflecting mirror 3 made of AlGaInAs / InP shown in Figure 1 cannot sufficiently reduce the thermal resistance of the light-emitting element 1, and there is a problem in that the characteristics of the material system cannot be fully utilized.

[0120] In contrast, the first reflecting mirror 3a in FIG. 10 is made of, for example, Al x Ga 1-x The first reflecting mirror 3a is made of an As (0≦x, 1−x≦1) layer and a GaAs layer. More specifically, the first reflecting mirror 3a is made of, for example, AlGaAs / GaAs. This reduces the thermal resistance of the light-emitting element 1f, enabling higher laser output and improved power efficiency.

[0121] The first reflecting mirror 3a may be made of another material, such as AlInN / GaN. AlInN / GaN can reduce thermal resistance, similar to AlGaAs / GaAs. AlGaAs / GaAs has better heat dissipation properties than AlInN / GaN, can reduce manufacturing costs, and is highly practical, making it a suitable material for the first reflecting mirror 3a.

[0122] The substrate 2a in Fig. 10 is, for example, a GaAs substrate. The light emitting element 1f in Fig. 10 shows an example having two laminated semiconductor layers 5, but the light emitting element 1f may have a configuration having three or more laminated semiconductor layers 5.

[0123] 11A to 11F are diagrams illustrating a manufacturing process of a light-emitting device 1f according to a seventh embodiment of the present disclosure. Fig. 11A is a diagram illustrating an epitaxial growth process for the light-emitting device 1f. In Fig. 11A, similar to Fig. 2B and the like, a plurality of laminated semiconductor layers 5, a semiconductor layer 6, and a contact layer 7 are formed on a substrate 2c, which is an InP substrate. Also, in Fig. 11A, a semiconductor layer (etching stop layer) 51 used for etching stop is formed.

[0124] 11B is a diagram showing a process for forming a current confinement structure 52. In FIG. 11B, a current confinement structure 52 is formed by, for example, ion implantation shown in FIG. 2D and recovery annealing shown in FIG. 2E.

[0125] The epitaxial growth step shown in FIG. 11A and the step of forming the current confinement structure shown in FIG. 11B may be any of the manufacturing steps shown in the first to sixth embodiments.

[0126] 11C is a diagram showing a temporary bonding step of a support substrate. In FIG. 11C, the semiconductor wafer 30b formed in FIG. 11B and other steps is temporarily bonded to a support substrate 54 outside a furnace via a temporary bonding layer 53. For example, wax or epoxy resin is used for the temporary bonding layer 53. For example, a sapphire substrate is used for the support substrate 54.

[0127] 11D is a diagram showing a removal step of the semiconductor wafer 30b. In FIG. 11D, the substrate 2c is removed down to the semiconductor layer 51 from the semiconductor wafer 30b temporarily bonded to the support substrate 54. The removal step of the substrate 2c and the semiconductor layer 51 uses, for example, grinding, polishing, chemical mechanical polishing (CMP), dry etching, wet etching, or the like. As a result, the substrate 2b is formed by thinning the substrate 2c.

[0128] 11E is a diagram showing a process for forming the first reflecting mirror 3a and the substrate 2a. Separately from the semiconductor wafer 30b formed in FIGS. 11A to 11D, the first reflecting mirror 3a is formed on the substrate 2a by epitaxial growth or the like. The process in FIG. 11E may be performed either before or after the processes in FIGS. 11A to 11D, or may be performed simultaneously.

[0129] Fig. 11F is a diagram showing the main bonding process of the first reflecting mirror 3a and the substrate 2a. In Fig. 11F, the first reflecting mirror 3a and the substrate 2a formed in Fig. 11E are bonded to the semiconductor wafer 30b formed in Fig. 11D from the thinned surface A2 side of the substrate 2b. Hydrophilic bonding, room temperature bonding, or the like is used to bond the semiconductor wafer 30b and the substrate 2a.

[0130] 11F and subsequent steps, the temporary bonding layer 53 and the support substrate 54 are removed, and a device structure is fabricated in the same manner as in the first embodiment. Note that some or all of the steps for fabricating the device structure may be performed before the temporary bonding step in FIG. 11C.

[0131] As described above, the light-emitting device 1f according to the seventh embodiment of the present disclosure has a first reflecting mirror 3a and a substrate 2a formed of a semiconductor material other than an InP-based material bonded to a semiconductor wafer 30b. This allows the thermal resistance of the light-emitting device 1f to be lowered compared to the light-emitting device 1 of FIG. 1, thereby achieving higher laser light output and improved power efficiency. The configuration and manufacturing process of the light-emitting device 1f according to the seventh embodiment of the present disclosure can be applied to any of the first to sixth embodiments.

[0132] Eighth Embodiment Fig. 12 is a cross-sectional view showing a light-emitting device 1g according to an eighth embodiment of the present disclosure. The light-emitting device 1g in Fig. 12 differs from the light-emitting device 1 in Fig. 1 in that it emits laser light from the bottom surface A3 of the substrate 2. In this specification, the light-emitting device 1g is also referred to as a back-emission VCSEL.

[0133] The light emitting element 1g of Fig. 12 has an anti-reflection film 60 on the bottom surface of the substrate 2. The light emitting element 1g also has an electrode 11a arranged to cover the surface of the semiconductor layer 6. The light emitting element 1g of Fig. 12 emits laser light having a wavelength longer than that absorbed by the first reflecting mirror 3 and the substrate 2. It is desirable to use a semi-insulating substrate for the substrate 2 of Fig. 12 in order to suppress free carrier absorption in the substrate 2. Light resonated in the resonator 13 passes through the substrate 2, the first reflecting mirror 3, and the anti-reflection film 60 and is emitted.

[0134] The light-emitting element 1g is suitable for coupling to a waveguide. Alternatively, the light-emitting element 1g may be used in a MEMS (Micro Electro Mechanical Systems) device, a flip chip, or the like. The configuration of the light-emitting element 1g according to the eighth embodiment of the present disclosure can be applied to any of the first to seventh embodiments.

[0135] 13 is a cross-sectional view showing a light-emitting element 1h according to a ninth embodiment of the present disclosure. The light-emitting element 1h in FIG. 13 has a plurality of light-emitting portions (light-emitting portions) 70. Each of the plurality of light-emitting portions 70 has a plurality of laminated semiconductor layers 5a or 5b, a semiconductor layer 6, a contact layer 7, a second reflecting mirror 4, and electrodes 11 and 12, and emits light along different optical axes. In this specification, the light-emitting element 1h is also referred to as an array-type element.

[0136] The light-emitting element 1h in Fig. 13 has a plurality of different light-emitting portions 70 on a single substrate 2 (semiconductor chip). Each light-emitting portion 70 can be driven independently or in conjunction with other light-emitting portions 70. The light-emitting element 1h can produce high-power laser light using a single semiconductor chip. The light-emitting element 1h is suitable for applications such as LiDAR (Light Detection and Ranging).

[0137] Tenth Embodiment Fig. 14 is a block diagram showing an example configuration of a distance measuring system 80 according to a tenth embodiment of the present disclosure. The distance measuring system 80 in Fig. 14 measures the distance to an arbitrary subject S by irradiating the subject S with light and receiving the reflected light. The distance measuring system 80 includes a light emitting device 81, a driving unit 82, a power supply circuit 83, a light emitting side optical system 84, a light receiving side optical system 85, a light receiving device 86, a signal processing unit 87, a control unit 88, and a temperature detection unit 89.

[0138] The light emitting device 81 emits light from a plurality of light sources. The light emitting device 81 has a light emitting element 1 (or 1a to 1h) according to the present disclosure as each light source. The light emitting device 81 is configured such that a plurality of light emitting elements (or light emitting units 70) are arranged in a predetermined pattern, such as a matrix.

[0139] The driving unit 82 is configured to have a power supply circuit 83 for driving the light emitting device 81. The power supply circuit 83 generates a power supply voltage for the driving unit 82 based on an input voltage from, for example, a battery (not shown) or the like provided in the distance measuring system 80. The driving unit 82 drives the light emitting device 81 based on the power supply voltage.

[0140] Light emitted from the light-emitting device 81 is irradiated onto a subject (object) S, which is the distance measurement target, via a light-emitting side optical system 84. The light thus irradiated is reflected from the subject S and enters the light-receiving surface of a light-receiving device 86 via a light-receiving side optical system 85.

[0141] The light receiving device 86 is a light receiving element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and receives reflected light from the subject S that enters through the light receiving side optical system 85 as described above, converts it into an electrical signal, and outputs it.

[0142] The light receiving device 86 performs processes such as CDS (Correlated Double Sampling) and AGC (Automatic Gain Control) on the electrical signal obtained by photoelectrically converting the received light, and then performs A / D (Analog / Digital) conversion on the electrical signal, and outputs the resulting digital data to a signal processing unit 87 at a subsequent stage.

[0143] Furthermore, the light receiving device 86 of this example outputs a frame synchronization signal to the driving unit 82. This enables the driving unit 82 to cause the light emitting element of the light emitting device 81 to emit light at a timing according to the frame period of the light receiving device 86.

[0144] The signal processing unit 87 is configured as a signal processor, for example, a DSP (Digital Signal Processor), etc. The signal processing unit 87 performs various signal processes on the digital signal input from the light receiving device 86.

[0145] The control unit 88 is configured with, for example, a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., or an information processing device such as a DSP, and controls the drive unit 82 for controlling the light-emitting operation of the light-emitting device 81, and controls the light-receiving operation of the light-receiving device 86.

[0146] The control unit 88 has a function as a distance measurement unit 88a. The distance measurement unit 88a measures the distance to the subject S based on a signal input via the signal processing unit 87 (i.e., a signal obtained by receiving reflected light from the subject S). The distance measurement unit 88a in this example measures the distance to each part of the subject S in order to be able to identify the three-dimensional shape of the subject S. Note that the specific distance measurement method in the distance measurement system 80 will be described again later.

[0147] The temperature detection unit 89 detects the temperature of the light-emitting device 81. The temperature detection unit 89 may be configured to detect temperature using, for example, a diode. In this example, information about the temperature detected by the temperature detection unit 89 is supplied to the drive unit 82, which enables the drive unit 82 to drive the light-emitting device 81 based on the temperature information.

[0148] The distance measurement method used in the distance measurement system 80 may be, for example, a STL (Structured Light) method or a ToF (Time of Flight) method.

[0149] The STL method is a method for measuring distance based on an image of a subject S illuminated with light having a predetermined light / dark pattern, such as a dot pattern or a grid pattern.

[0150] Fig. 15A is an explanatory diagram of the STL method. In the STL method, pattern light Lp having a dot pattern such as that shown in Fig. 15A is irradiated onto a subject S. The pattern light Lp is divided into a plurality of blocks BL, and a different dot pattern is assigned to each block BL (dot patterns are arranged not to overlap between blocks BL).

[0151] 15B is an explanatory diagram of the distance measurement principle of the STL method. In this example, a wall W and a box BX placed in front of it are considered as the subject S, and pattern light Lp is irradiated onto the subject S. "G" in the diagram schematically represents the angle of view of the light receiving device 86.

[0152] In addition, "BLn" in the figure denotes the light of a certain block BL in the pattern light Lp, and "dn" denotes the dot pattern of the block BLn projected on the light-receiving image by the light-receiving device 86.

[0153] Here, if there is no box BX in front of the wall W, the dot pattern of the block BLn is projected at the position "dn'" in the figure in the received light image. In other words, the position at which the pattern of the block BLn is projected in the received light image differs depending on whether the box BX is present or not, and specifically, the pattern is distorted.

[0154] The STL method is a method for determining the shape and depth of the subject S by utilizing the fact that the irradiated pattern is distorted by the object shape of the subject S. Specifically, it is a method for determining the shape and depth of the subject S from the way the pattern is distorted.

[0155] When the STL system is employed, for example, a global shutter type IR (Infrared) light receiving unit is used as the light receiving device 86. In the case of the STL system, the distance measuring unit 88a controls the drive unit 82 so that the light emitting device 81 emits pattern light, detects distortion of the pattern in the image signal obtained via the signal processing unit 87, and calculates the distance based on the distortion of the pattern.

[0156] Next, the ToF method is a method for measuring the distance to an object by detecting the time of flight (time difference) of light emitted from the light-emitting device 81, reflected by the object, and reaching the light-receiving device 86.

[0157] When the so-called direct ToF (dToF) method is adopted as the ToF method, a SPAD (Single Photon Avalanche Diode) is used as the light receiving device 86, and the light emitting device 81 is pulse-driven. In this case, the distance measuring unit 88a calculates the time difference between the light emitted from the light emitting device 81 and the light received by the light receiving device 86, based on a signal input via the signal processing unit 87, and calculates the distance to each part of the subject S based on the time difference and the speed of light.

[0158] In addition to dToF, it is also possible to adopt the so-called indirect ToF (iToF) method (indirect method), which calculates the distance to the subject S based on the phase difference between the irradiated light and the reflected light, as the ToF method.

[0159] By using the light emitting element 1 (or 1a to 1h) according to the present disclosure as the light emitting device 81, the cost of the distance measuring system 80 can be reduced and power consumption can be suppressed.

[0160] Eleventh Embodiment A light-emitting element 1 (or 1a to 1h) according to the present disclosure and a light-receiving element may be integrated on a Si substrate to form a ToF module configuration. This allows the light-emitting element and the light-receiving element to be integrated into a single chip, thereby achieving a smaller and less costly distance measuring device. The light-receiving element may be made of, for example, InGaAs or SiGe, which has sensitivity in the long wavelength band. In addition to the light-receiving element, any circuit such as a signal processing circuit may be integrated on the Si substrate.

[0161] (Application Examples) 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.

[0162] FIG. 16 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 according to the present disclosure can be applied.

[0163] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 16, 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. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (interface) 12053.

[0164] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0165] The body system control unit 12020 controls the operation of various devices equipped 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 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0166] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. 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.

[0167] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0168] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. 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 degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0169] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the 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 inter-vehicle distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane departure warning, etc.

[0170] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0171] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside 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 outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0172] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying information to vehicle occupants or the outside of the vehicle. In the example of Fig. 16, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0173] FIG. 17 is a diagram showing an example of the installation position of the imaging unit 12031.

[0174] In FIG. 17, a vehicle 12100 has imaging units 12101, 12102, 12103, 12104, and 12105 as the imaging unit 12031.

[0175] 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 acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The forward images acquired by the imaging units 12101 and 12105 are mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0176] 17 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0177] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0178] For example, based on the 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, in particular, 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 a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which runs autonomously without relying on driver operation.

[0179] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0180] 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 a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0181] The above describes an example of a vehicle control system to which the technology according to the present disclosure can be applied. The technology according to the present disclosure can be applied to, for example, the imaging unit 12031 among the above-described configurations. Specifically, the light-emitting element 1 according to the present disclosure may be provided together with the imaging unit 12031. By applying the technology according to the present disclosure to the imaging unit 12031, the light-emitting efficiency of the light-emitting unit can be increased and the signal-to-noise (S / N) ratio of the imaging unit 12031 of the vehicle 12100 can be improved.

[0182] The present technology may have the following configurations: (1) A light-emitting device comprising: a first reflecting mirror and a second reflecting mirror spaced apart along an optical axis; and two or more laminated semiconductor layers disposed between the first reflecting mirror and the second reflecting mirror, wherein each of the two or more laminated semiconductor layers has: a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type spaced apart along the optical axis; an active layer disposed between the first semiconductor layer and the second semiconductor layer; and a tunnel junction layer disposed between two of the laminated semiconductor layers adjacent in the stacking direction, wherein the two or more laminated semiconductor layers have two or more types of second semiconductor layers each made of a different material and dopant. (2) The light-emitting device according to (1), wherein the second semiconductor layer in a laminated semiconductor layer disposed closest to the second reflecting mirror among the two or more laminated semiconductor layers contains a dopant that diffuses more easily than the second semiconductor layers in the other laminated semiconductor layers, and has a higher thermal conductivity and a larger etching selectivity than the second semiconductor layers in the other laminated semiconductor layers. (3) The second semiconductor layer in the laminated semiconductor layer disposed closest to the second reflector has InP doped with at least one of Zn, Mg, Be, and Cd, and the second semiconductor layer in the other laminated semiconductor layer has Al doped with C. x Ga y In 1-x-y (4) The light-emitting device according to any one of (1) to (3), wherein the two or more types of second semiconductor layers have a third semiconductor layer and a fourth semiconductor layer stacked in each of the two or more laminated semiconductor layers, the third semiconductor layer is disposed closer to the second reflecting mirror than the fourth semiconductor layer, and the third semiconductor layer contains a dopant that diffuses more easily than the fourth semiconductor layer, and has a higher thermal conductivity and a higher etching selectivity than the fourth semiconductor layer. (5) The third semiconductor layer has InP doped with at least one of Zn, Mg, Be, and Cd, and the fourth semiconductor layer has Al doped with C. x Ga y In 1-x-yAs (0≦x, 0≦y, 1−x−y≦1). (6) The light-emitting device according to any one of (1) to (5), wherein at least one of the first semiconductor layer, the active layer, the second semiconductor layer, and the tunnel junction layer has a current confinement structure formed by implantation of impurity ions. (7) The light-emitting device according to (6), wherein the impurity ions include at least one of B, O, Fe, Ru, and Cr. (8) The light-emitting device according to any one of (1) to (7), comprising: a fifth semiconductor layer of a first conductivity type disposed between the second semiconductor layer in the laminated semiconductor layer disposed closest to the second reflecting mirror among the two or more laminated semiconductor layers and the second reflecting mirror; and a first buried tunnel junction layer provided inside the fifth semiconductor layer and in contact with the second semiconductor layer in the laminated semiconductor layer disposed closest to the second reflecting mirror among the two or more laminated semiconductor layers. (9) The light-emitting device according to any one of (1) to (8), further comprising at least one second buried tunnel junction layer provided inside the first semiconductor layer in contact with the second semiconductor layer in each of the two or more laminated semiconductors and in contact with the second semiconductor layer. (10) The light-emitting device according to (6), further comprising: a stacked body having the two or more laminated semiconductor layers; and a resistor surrounding the stacked body in a stacking direction and concentrating current inside the stacked body. (12) The light-emitting device according to (11), further comprising: InP doped with at least one of Fe, Ru, Cr, and C. (13) The light-emitting device according to any one of (1) to (7), (11) and (12), further comprising a contact layer arranged between the second reflector and a laminated semiconductor layer arranged closest to the second reflector among the two or more laminated semiconductor layers, the contact layer being made of a transparent electrode that supplies current to the active layer and transmits light emitted from the active layer. (14) The first reflector is formed of an InP substrate and an Al layer laminated on the InP substrate. x Ga y In 1-x-yAs (0≦x, 0≦y, 1−x−y≦1) layer, In x Ga 1-x As y P 1-y (0≦x, 0≦y, 1−x≦1, 1−y≦1) layer, or Al x In 1-x (15) The light-emitting device according to any one of (1) to (13), including at least one of an As (0≦x, 1−x≦1) layer and an InP layer. (15) The first reflecting mirror is formed of a GaAs substrate and an Al layer stacked on the GaAs substrate. x Ga 1-x (16) The light-emitting device according to any one of (1) to (15), wherein light emitted in the active layer and resonated in the first reflecting mirror and the second reflecting mirror is transmitted through the second reflecting mirror and emitted. (17) The light-emitting device according to any one of (1) to (15), wherein light emitted in the active layer and resonated in the first reflecting mirror and the second reflecting mirror is transmitted through the first reflecting mirror and emitted. (18) The light-emitting device according to any one of (1) to (17), wherein the active layer includes at least one of a quantum well, a quantum wire, or a quantum dot. (19) The light-emitting device according to any one of (1) to (18), wherein the active layer includes at least one of Al, Ga, or In, and at least one of As, P, N, or Sb. (20) The tunnel junction layer is made of Al doped with at least one of Zn, Mg, Be, Cd, and C. x Ga y In 1-x-y As (0≦x, 0≦y, 1-xy≦1), or In doped with at least one of Zn, Mg, Be, and Cd x Ga 1-x As y P 1-y (0≦x, 0≦y, 1-x≦1, 1-y≦1) and Al doped with at least one of Si, Te, S, Sn, and Se. x Ga y In 1-x-yAs (0≦x, 0≦y, 1-xy≦1), or In doped with at least one of Si, Te, S, Sn, and Se x Ga 1-x As y P 1-y(0≦x, 0≦y, 1-x≦1, 1-y≦1). (21) The light-emitting device according to any one of (1) to (20), wherein the first reflecting mirror and the second reflecting mirror form at least a part of a resonator that resonates light emitted from the active layer, the active layer is disposed at an antinode of a standing wave of light resonated in the resonator, and the tunnel junction layer is disposed at a node of the standing wave. (22) The light-emitting device according to any one of (1) to (21), further comprising a plurality of light-emitting units that have the first reflecting mirror, the second reflecting mirror, and the two or more stacked semiconductor layers, and that emit light with different optical axes. (23) The light-emitting device according to any one of (1) to (22), which is a VCSEL (Vertical Cavity Surface Emitting Laser). (24) A distance measurement system comprising: a light-emitting element according to any one of (1) to (23); and a distance measurement unit that measures a distance to an object to be measured based on light emitted from the light-emitting element and light reflected from the object to be measured. (25) A method for manufacturing a light-emitting element, comprising: a step of forming a first reflecting mirror on a substrate; and a step of stacking, on the first reflecting mirror, two or more laminated semiconductor layers, each including a first semiconductor layer of a first conductivity type, an active layer, and a second semiconductor layer of a second conductivity type, with a tunnel junction layer sandwiched between each of the two or more laminated semiconductor layers, the two or more laminated semiconductor layers having two or more types of second semiconductor layers different from each other in material and dopant, the two or more types of second semiconductor layers having a third semiconductor layer and a fourth semiconductor layer stacked in each of the two or more laminated semiconductor layers, the third semiconductor layer being disposed in the laminated semiconductor layer formed last, the third semiconductor layer containing a dopant that diffuses more easily than the fourth semiconductor layer and having a higher thermal conductivity and an etching selectivity than the fourth semiconductor layer; and a step of forming a second reflecting mirror on the two or more laminated semiconductor layers.(26) A method for manufacturing a light-emitting element, comprising: forming a first reflecting mirror on a substrate; stacking two or more laminated semiconductor layers, each including a first semiconductor layer of a first conductivity type, an active layer, and a second semiconductor layer of a second conductivity type, with a tunnel junction layer sandwiched between the two or more laminated semiconductor layers, the two or more laminated semiconductor layers having two or more types of second semiconductor layers different from each other in material and dopant, the two or more types of second semiconductor layers having a third semiconductor layer and a fourth semiconductor layer stacked in each of the two or more laminated semiconductor layers, the third semiconductor layer being disposed in a laminated semiconductor layer formed last, the third semiconductor layer containing a dopant that diffuses more easily than the fourth semiconductor layer and having a higher thermal conductivity and an etching selectivity than the fourth semiconductor layer; forming a first buried tunnel junction layer on the two or more laminated semiconductor layers, the first buried tunnel junction layer having an area smaller than that of the laminated semiconductor layers; forming a fifth semiconductor layer of the first conductivity type on the first buried tunnel junction layer; and forming a second reflecting mirror on the fifth semiconductor layer. (27) A method for manufacturing a light-emitting element according to (25) or (26), comprising the steps of: laminating the laminated semiconductor layer on a first substrate, and then thinning the first substrate; and forming the first reflecting mirror on a second substrate, and then bonding the first reflecting mirror to the thinned surface of the first substrate. (28) A method for manufacturing a light-emitting element, comprising the steps of: forming a laminated semiconductor layer, forming a buried tunnel junction layer on the laminated semiconductor layer, and implanting impurity ions into a portion of the surface of the laminated semiconductor layer where the buried tunnel junction layer is not located, repeated two or more times.

[0183] The aspects of the present disclosure are not limited to the individual embodiments described above, but include various modifications that may be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present disclosure, which is derived from the contents defined in the claims and their equivalents.

[0184] 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h Light emitting element, 2, 2a, 2b, 2c Substrate, 3, 3a First reflector, 4 Second reflector, 5, 5a, 5b, 5c Laminated semiconductor layer, 6, 6a, 6b Semiconductor layer, 6c Interface, 7, 7a Contact layer, 11, 11a, 12 Electrode, 13 Resonator, 21, 21a Active layer, 22, 23, 23a, 23b, 23c, 23d, 23e, 27a, 27b, 51 Semiconductor layer, 24, 24a, 24b Tunnel junction layer, 25, 26, 32, 32a, 32b Region, 30, 30a, 30b Semiconductor wafer, 31 Hard mask, 33, 33a Ion, 41 Resistor, 42 Laminated body, 52 Current confinement structure, 53 temporary bonding layer, 54 support substrate, 60 anti-reflection film, 70 light emitting section, 80 distance measuring system, 81 light emitting device, 82 driving section, 83 power supply circuit, 84 light emitting side optical system, 85 light receiving side optical system, 86 light receiving device, 87 signal processing section, 88 control section, 88a distance measuring section, 89 temperature detection section

Claims

1. A light-emitting device comprising: a first reflecting mirror and a second reflecting mirror arranged to be spaced apart along an optical axis; and two or more laminated semiconductor layers arranged between the first reflecting mirror and the second reflecting mirror, wherein each of the two or more laminated semiconductor layers has: a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type arranged to be spaced apart along the optical axis; an active layer arranged between the first semiconductor layer and the second semiconductor layer; and a tunnel junction layer arranged between two of the laminated semiconductor layers adjacent in the stacking direction, wherein the two or more laminated semiconductor layers have two or more types of second semiconductor layers each made of a different material and dopant.

2. The light-emitting element according to claim 1, wherein, of the two or more laminated semiconductor layers, the second semiconductor layer in the laminated semiconductor layer located closest to the second reflector contains a dopant that diffuses more easily than the second semiconductor layers in the other laminated semiconductor layers, and has a higher thermal conductivity and a larger etching selectivity than the second semiconductor layers in the other laminated semiconductor layers.

3. The second semiconductor layer in the laminated semiconductor layer located closest to the second reflector has InP doped with at least one of Zn, Mg, Be, and Cd, and the second semiconductor layer in the other laminated semiconductor layer has Al doped with C. x Ga y In 1-x-y The light-emitting device according to claim 2 , wherein As (0≦x, 0≦y, 1−x−y≦1).

4. The light-emitting element according to claim 1, wherein the two or more types of second semiconductor layers have a third semiconductor layer and a fourth semiconductor layer stacked in each of the two or more laminated semiconductor layers, the third semiconductor layer is located closer to the second reflecting mirror than the fourth semiconductor layer, and the third semiconductor layer contains a dopant that diffuses more easily than the fourth semiconductor layer, and has a higher thermal conductivity and a higher etching selectivity than the fourth semiconductor layer.

5. The third semiconductor layer has InP doped with at least one of Zn, Mg, Be, and Cd, and the fourth semiconductor layer has Al doped with C. x Ga y In 1-x-y The light-emitting device according to claim 4 , wherein As (0≦x, 0≦y, 1−x−y≦1).

6. The light-emitting element according to claim 1, wherein at least one of the first semiconductor layer, the active layer, the second semiconductor layer, and the tunnel junction layer has a current confinement structure formed by implanting impurity ions.

7. The light-emitting element according to claim 1, comprising: a fifth semiconductor layer of a first conductivity type, which is disposed between the second semiconductor layer in the laminated semiconductor layer that is disposed closest to the second reflecting mirror among the two or more laminated semiconductor layers, and the second reflecting mirror; and a first buried tunnel junction layer that is provided inside the fifth semiconductor layer and is in contact with the second semiconductor layer in the laminated semiconductor layer that is disposed closest to the second reflecting mirror among the two or more laminated semiconductor layers.

8. The light-emitting element according to claim 1, further comprising at least one second buried tunnel junction layer provided inside the first semiconductor layer that contacts the second semiconductor layer in each of the two or more laminated semiconductors and in contact with the second semiconductor layer.

9. The light-emitting element according to claim 1, comprising: a stacked body having the two or more stacked semiconductor layers; and a resistor surrounding the stacked body in the stacking direction and concentrating current inside the stacked body.

10. The light-emitting element according to claim 1, further comprising a contact layer arranged between the second reflector and one of the two or more laminated semiconductor layers that is positioned closest to the second reflector, the contact layer being made of a transparent electrode that supplies current to the active layer and transmits light emitted by the active layer.

11. The first reflecting mirror comprises an InP substrate and an Al layer laminated on the InP substrate. x Ga y In 1-x-y As (0≦x, 0≦y, 1−x−y≦1) layer, In x Ga 1-x As y P 1-y (0≦x, 0≦y, 1−x≦1, 1−y≦1) layer, or Al x In 1-x 2. The light-emitting device of claim 1, comprising: at least one As (0≦x, 1−x≦1) layer; and an InP layer.

12. The first reflecting mirror is made of a GaAs substrate and an Al layer laminated on the GaAs substrate. x Ga 1-x 2. The light-emitting device according to claim 1, comprising: an As (0≦x, 1−x≦1) layer; and a GaAs layer.

13. The light emitting device according to claim 1, wherein light emitted from the active layer and resonated in the first reflecting mirror and the second reflecting mirror is transmitted through the second reflecting mirror and emitted.

14. The light emitting device according to claim 1, wherein light emitted from the active layer and resonated in the first reflecting mirror and the second reflecting mirror is transmitted through the first reflecting mirror and then emitted.

15. The light-emitting device according to claim 1, wherein the first reflecting mirror and the second reflecting mirror constitute at least a part of a resonator that resonates light emitted from the active layer, the active layer is disposed at an antinode of a standing wave of light resonated in the resonator, and the tunnel junction layer is disposed at a node of the standing wave.

16. The light-emitting element according to claim 1, further comprising a plurality of light-emitting sections each having the first reflecting mirror, the second reflecting mirror, and the two or more laminated semiconductor layers, and each having different optical axes for emitting light.

17. The light-emitting device according to claim 1, which is a VCSEL (Vertical Cavity Surface Emitting Laser).

18. A method for manufacturing a light-emitting element, comprising the steps of: forming a first reflecting mirror on a substrate; stacking two or more laminated semiconductor layers, each including a first semiconductor layer of a first conductivity type, an active layer, and a second semiconductor layer of a second conductivity type, with a tunnel junction layer sandwiched between each of the two or more laminated semiconductor layers, the two or more laminated semiconductor layers having two or more types of second semiconductor layers different from each other in material and dopant, the two or more types of second semiconductor layers having a third semiconductor layer and a fourth semiconductor layer stacked in each of the two or more laminated semiconductor layers, the third semiconductor layer being disposed in the laminated semiconductor layer formed last, the third semiconductor layer containing a dopant that diffuses more easily than the fourth semiconductor layer and having a higher thermal conductivity and etching selectivity than the fourth semiconductor layer; forming a first buried tunnel junction layer on the two or more laminated semiconductor layers, the first buried tunnel junction layer having an area smaller than that of the laminated semiconductor layers; forming a fifth semiconductor layer of a first conductivity type on the first buried tunnel junction layer; and forming a second reflecting mirror on the fifth semiconductor layer.

19. A method for manufacturing a light-emitting element as described in claim 18, comprising the steps of: laminating the laminated semiconductor layer on a first substrate, and then thinning the first substrate; and forming the first reflecting mirror on a second substrate, and then bonding the first reflecting mirror to the thinned surface of the first substrate.

20. A process for manufacturing a light-emitting element, comprising the steps of forming a laminated semiconductor layer, forming a buried tunnel junction layer on the laminated semiconductor layer, and implanting impurity ions into a portion of the surface of the laminated semiconductor layer where the buried tunnel junction layer is not located, the steps being repeated two or more times.

Images