Light-emitting device

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device with which it is possible to stably generate high output from a light-emitting element. SOLUTION: A light-emitting device according to the present disclosure comprises: a plurality of active layers and a plurality of tunnel junction layers included in a light-emitting element; an anode electrode electrically connected to the light-emitting element; and a cathode electrode electrically connected to the light-emitting element. The light emission diameter of the light-emitting element is 30 μm or more. The temperature at which an oscillation wavelength of the light-emitting element and a gain peak wavelength of the plurality of active layers match is 50°C or less.

Description

Light-emitting device

[0001] The present disclosure relates to a light emitting device.

[0002] Surface-emitting lasers, such as vertical cavity surface-emitting lasers (VCSELs), are known as one type of semiconductor laser. Generally, in a light-emitting device using a surface-emitting laser, a plurality of light-emitting elements are formed in a two-dimensional array on the front or back surface of a substrate.

[0003] Japanese Patent Application Laid-Open No. 2022-098436

[0004] DB Young et al., “Enhanced performance of offset-gain high-barrier vertical-cavity surface-emitting lasers”, IEEE Journal of Quantum Electrons, vol.29, no.6, pp.2013-2022

[0005] There is a growing need for VCSELs capable of high peak power operation for LiDAR (Light Detection and Ranging). For example, reports and new product announcements regarding a type of VCSEL known as a multi-junction VCSEL (MJ-VCSEL) have been rapidly increasing in recent years. This type of VCSEL has multiple active layers stacked in series using multiple tunnel junction (TJ) layers. It is suitable for short-pulse, high-peak drive, such as LiDAR drive. The more the number of stacks, the higher the output efficiency (slope efficiency: SE) relative to the injected current. However, MJ-VCSELs have the problem of being prone to non-unimodal oscillation transverse modes compared to conventional VCSELs without TJ layers. It has been reported that even commonly used MJ-VCSELs with an OA (Optical Aperture) diameter of less than 30 μm exhibit a doughnut-shaped near-field pattern.

[0006] On the other hand, in order to realize a high-output VCSEL array, it is effective to increase the light-emitting area (filling factor: FF) of the VCSEL across the entire chip. The FF can be increased by increasing the OA diameter. However, as the OA diameter increases, the number of transverse modes that can exist in the VCSEL increases, making the non-single-peaked oscillation described above more likely to occur. Depending on the driving conditions, the near-field and far-field patterns of the VCSEL may no longer meet the requirements for a LiDAR light source.

[0007] Based on the above explanation, in order to realize a high peak power VCSEL array for LiDAR, it is effective to form an MJ-VCSEL with a large number of stacks, a high SE, and a large OA diameter. However, in this case, it may not be possible to obtain the near-field and far-field patterns that are desirable as a light source for LiDAR.

[0008] Therefore, the present disclosure provides a light emitting device capable of stably generating high output from a light emitting element.

[0009] A light-emitting device according to a first aspect of the present disclosure includes a plurality of active layers and a plurality of tunnel junction layers included in a light-emitting element, an anode electrode electrically connected to the light-emitting element, and a cathode electrode electrically connected to the light-emitting element, wherein the light-emitting element has an emission diameter of 30 μm or more, and the temperature at which the oscillation wavelength of the light-emitting element matches the gain peak wavelength of the plurality of active layers is 50°C or less. This enables the light-emitting element to stably generate high output power. For example, when forming an MJ-VCSEL with a large number of stacks, a high SE, and a large OA diameter, it becomes possible to stably generate high output power from the light-emitting element even if the relationship between the oscillation wavelength and the gain peak wavelength changes with temperature.

[0010] The light emitting device according to the first aspect may further include a plurality of oxide layers and a plurality of non-oxide layers included in the light emitting element, and each non-oxide layer may be provided within a corresponding oxide layer, thereby enabling, for example, an oxidation confinement structure to be realized by these oxide layers and non-oxide layers.

[0011] In this first aspect, the number of the oxide layers may be equal to or greater than the number of the active layers, thereby making it possible to realize an oxide confinement structure using a large number of oxide layers, for example.

[0012] In this first aspect, the diameter of each of the non-oxidized layers may be different, which makes it possible to reduce, for example, the adverse effects of stress at the tip of the oxide layer.

[0013] In this first aspect, each active layer may include a non-insulating region and an insulating region provided around the non-insulating region, thereby making it possible to reduce non-radiative recombination in each active layer by the insulating region, for example.

[0014] In this first aspect, the insulating region may be provided near an end face of each active layer and may contain impurity atoms, thereby making it possible to reduce non-radiative recombination near the end face of each active layer by the insulating region formed by implanting impurity atoms.

[0015] In this first aspect, the distance between the end face of each active layer and the boundary between the insulating region and the non-insulating region may be 1 μm or more, which makes it possible to ensure, for example, a sufficiently wide insulating region.

[0016] In this first aspect, the light emitting element may emit light such that the light intensity at the boundary between the insulating region and the non-insulating region is less than 10% of the peak light intensity, thereby making it possible to sufficiently reduce non-radiative recombination in each active layer, for example.

[0017] In addition, in this first aspect, the light emitting element may have an intra-cavity structure, which makes it possible to improve the performance of the light emitting element, for example.

[0018] In this first aspect, the shape of the light-emitting region of the light-emitting element may be circular or polygonal in plan view, which makes it possible to easily arrange a plurality of light-emitting elements in an array, for example.

[0019] In this first aspect, the half-width of the gain spectrum observed when the plurality of active layers are simultaneously excited may be greater than 25 nm, thereby making it possible to realize, for example, a high-output light-emitting device.

[0020] In addition, in this first aspect, the output of the light-emitting element is represented by Po [W], the number of the active layers is represented by Na [pieces], and the light-emitting area of ​​the light-emitting element is represented by Se [cm ２ ], Na≧0.0144×Po ０．４９１ ×Se －０．４８８ This may enable realization of a high-output light-emitting element, for example.

[0021] In addition, in this first aspect, the output of the light-emitting element is represented by Po [W], the number of the active layers is represented by Na [pieces], and the light-emitting area of ​​the light-emitting element is represented by Se [cm ２ ], Na≧0.0171×Po ０．４９１ ×Se －０．４８８ This may enable realization of a high-output light-emitting element, for example.

[0022] In addition, in this first aspect, the output of the light-emitting element is represented by Po [W], the number of the active layers is represented by Na [pieces], and the light-emitting area of ​​the light-emitting element is represented by Se [cm ２ ], Na≧0.0203×Po ０．４９１ ×Se －０．４８８ This may enable realization of a high-output light-emitting element, for example.

[0023] In addition, in this first aspect, the temperature at which the oscillation wavelength and the gain peak wavelength coincide may be equal to or lower than 30° C. This makes it possible to realize, for example, a high-output light-emitting device.

[0024] The light emitting device according to the first aspect may further include a plurality of light emitting elements including the light emitting element, thereby making it possible to realize a light emitting device in which, for example, these light emitting elements are arranged in an array.

[0025] In this first aspect, the plurality of light-emitting elements may be arranged in a one-dimensional array or a two-dimensional array, thereby making it possible to realize a light-emitting device that is suitable for applications such as LiDAR, for example, by using the light-emitting elements arranged in an array.

[0026] In this first aspect, the anode electrode and the cathode electrode may function as a common anode electrode and a common cathode electrode for the plurality of light-emitting elements, thereby making it possible to reduce the number of anode electrodes and cathode electrodes, for example.

[0027] In this first aspect, the plurality of light-emitting elements may be electrically connected to a plurality of different anode electrodes and / or a plurality of different cathode electrodes, which makes it possible to provide a different anode electrode for each light-emitting element or a different cathode electrode for each light-emitting element, for example.

[0028] In this first aspect, the pitch between the light-emitting elements may be equal to or greater than 0.6 of the width of the light-emitting region of each light-emitting element, thereby making it possible to ensure a sufficient pitch between the light-emitting elements, for example.

[0029] FIG. 1 is a cross-sectional view showing the structure of the light emitting device of the first embodiment. FIG. 2 is a plan view showing the structure of the light emitting device of the first embodiment. FIG. 3 is a graph for explaining the operation of the light emitting device of the first embodiment. FIG. 4 is another graph for explaining the operation of the light emitting device of the first embodiment. FIG. 5 is another graph for explaining the operation of the light emitting device of the first embodiment. FIG. 6 is a cross-sectional view (1 / 4) showing a method for manufacturing the light emitting device of the first embodiment. FIG. 7 is a cross-sectional view (2 / 4) showing a method for manufacturing the light emitting device of the first embodiment. FIG. 8 is a cross-sectional view (3 / 4) showing a method for manufacturing the light emitting device of the first embodiment. FIG. 9 is a cross-sectional view (4 / 4) showing a method for manufacturing the light emitting device of the first embodiment. FIG. 10 is a cross-sectional view showing the structure of the light emitting device of the second embodiment. FIG. 11 is a cross-sectional view showing the structure of the light emitting device of the second embodiment. FIG. 12 is a cross-sectional view showing the structure of the light emitting device of the third embodiment. FIG. 13 is a plan view showing the structure of the light emitting device of the third embodiment. FIG. 14 is a cross-sectional view showing the structure of the light emitting device of the fourth embodiment. FIG. 15 is a plan view showing the structure of the light emitting device of the fourth embodiment. FIG. 16 is a cross-sectional view showing the structure of the light emitting device of the fifth embodiment. FIG. 17 is a plan view showing the structure of the light emitting device of the fifth embodiment. FIG. 18 is a block diagram showing an example of the configuration of a distance measuring device of the sixth embodiment. FIG. 19 is a diagram for explaining the STL system of the sixth embodiment. Fig. 10 is a block diagram showing the configuration of a vehicle according to a seventh embodiment Fig. 11 is a plan view showing a sensing area of ​​the vehicle according to the seventh embodiment.

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0031] First Embodiment FIG. 1 is a cross-sectional view showing the structure of a light emitting device according to a first embodiment.

[0032] The light emitting device of this embodiment is a surface emission type VCSEL light emitting device, and includes one light emitting element shown in Fig. 1. This light emitting element corresponds to a VCSEL light emitting element.

[0033] The light emitting device of this embodiment includes, as components of the light emitting element, a substrate 1, an n-type contact layer 2, an n-type DBR (Distributed Bragg Reflector) 3, a laminated film 4, a p-type DBR 5, and a p-type contact layer 6. The light emitting device of this embodiment further includes a p-type electrode 11, an n-type electrode 12, a passivation film 13, an AR (Anti-Reflection) coating film 14, an anode electrode 15, and a cathode electrode 16. The laminated film 4 also includes a plurality of active layers 4a, a plurality of oxide layers 4b, a plurality of non-oxide layers 4b', and a plurality of tunnel junction (TJ) layers 4c.

[0034] 1 shows X, Y, and Z axes that are perpendicular to each other. The X and Y directions correspond to the lateral (horizontal) direction, and the Z direction corresponds to the longitudinal (vertical) direction. The +Z direction corresponds to the upward direction, and the −Z direction corresponds to the downward direction. The −Z direction may or may not strictly coincide with the direction of gravity.

[0035] The light emitting device of this embodiment will be described in detail below with reference to Fig. 1. In this description, Fig. 2 will also be referred to as appropriate. Fig. 2 is a plan view showing the structure of the light emitting device of the first embodiment. Fig. 1 shows a vertical cross section taken along line AA' shown in Fig. 2.

[0036] [Substrate 1] The substrate 1 is a semiconductor substrate such as a GaAs (gallium arsenide) substrate. In this embodiment, the substrate 1 is an n-type GaAs substrate having a thickness of approximately 100 μm. In FIG. 1 , the surface S1 of the substrate 1 is the upper surface of the substrate 1, and the back surface S2 of the substrate 1 is the lower surface of the substrate 1. Furthermore, in FIG. 1 , the X and Y directions are parallel to the surface S1 and back surface S2 of the substrate 1, and the Z direction is perpendicular to the surface S1 and back surface S2 of the substrate 1.

[0037] [N-Type Contact Layer 2] The n-type contact layer 2 is formed on the substrate 1. In Fig. 1, the n-type contact layer 2 serves as an underlying layer for the n-type electrode 12. The n-type contact layer 2 is, for example, a semiconductor layer such as an n-type GaAs layer. The n-type contact layer 2 is also called an n-type current injection layer.

[0038] [n-Type DBR 3] The n-type DBR 3 is formed on the n-type contact layer 2 and is included in the mesa M of the light-emitting device. As shown in FIG. 2 , the mesa M of this embodiment has a circular shape in a planar view. The diameter of the mesa M in a planar view is, for example, 40 μm. The mesa M is an example of a light-emitting region of the light-emitting device of the present disclosure. The n-type DBR 3 is, for example, an n-type semiconductor layer.

[0039] [Stacked Film 4] The stacked film 4 includes a plurality of active layers 4a, a plurality of oxide layers 4b, and a plurality of TJ layers 4c stacked in this order in the Z direction, and is included in the mesa M of the light-emitting element. These layers are stacked in the Z direction in the following order: active layer 4a, oxide layer 4b, TJ layer 4c, active layer 4a, oxide layer 4b, TJ layer 4c, ...

[0040] The stacked film 4 shown in FIG. 1 includes five active layers 4a, five oxide layers 4b, and four TJ layers 4c. However, the number of active layers 4a in the stacked film 4 may be any number other than five, for example, 3 to 20. The same applies to the number of oxide layers 4b and the number of TJ layers 4c in the stacked film 4. In this embodiment, if the number of active layers 4a is Na, the number of oxide layers 4b is also Na, and the number of TJ layers 4c is Na-1. Note that the number of oxide layers 4b in this embodiment may be the same as the number of active layers 4a as shown in FIG. 1, or may be greater than the number of active layers 4a. The number of active layers 4a is also called the "stack number," and the number of TJ layers 4c is also called the "TJ number."

[0041] Each active layer 4a has a quantum well structure, specifically including multiple quantum well layers and multiple barrier layers alternately stacked to have compressive strain. Each oxide layer 4b is formed, for example, by steam oxidation of an AlAs (aluminum arsenic) layer. Each TJ layer 4c is formed, for example, from a material capable of forming a TJ layer for an MJ-VCSEL.

[0042] As shown in FIG. 1 , the stacked film 4 further includes a plurality of non-oxide layers 4b', the number of which is equal to the number of oxide layers 4b. Each non-oxide layer 4b' is formed within a corresponding oxide layer 4b and is surrounded by this oxide layer 4b in a ring-shaped configuration in plan view. Conversely, each oxide layer 4b is formed around a corresponding non-oxide layer 4b' and surrounds this non-oxide layer 4b' in a ring-shaped configuration in plan view. In this embodiment, each non-oxide layer 4b' has a substantially circular shape in plan view, and each oxide layer 4b has a substantially annular shape in plan view. Like the oxide layers 4b, the non-oxide layers 4b' are stacked in the Z direction in the following order: active layer 4a, non-oxide layer 4b', TJ layer 4c, active layer 4a, non-oxide layer 4b', TJ layer 4c, ...

[0043] Hereinafter, a certain oxidized layer 4b and a corresponding non-oxidized layer 4b' will be referred to as a "pair of oxidized layer 4b and non-oxidized layer 4b'." The pair of oxidized layer 4b and non-oxidized layer 4b' is formed, for example, by forming an AlAs layer on a certain active layer 4a and then steam-oxidizing a portion of the AlAs layer. In this case, the oxidized portion of the AlAs layer becomes the oxidized layer 4b, and the non-oxidized portion of the AlAs layer becomes the non-oxidized layer 4b'. The oxidized layer 4b and non-oxidized layer 4b' may be a fully oxidized portion of the AlAs layer and a partially inoxidized portion of the AlAs layer. In this embodiment, the pair of oxidized layer 4b and non-oxidized layer 4b' is formed by steam-oxidizing the AlAs layer from the side surface (end face of the AlAs layer) of the mesa M after the mesa M is formed.

[0044] FIG. 1 shows the light-emitting diameter D of the light-emitting element of this embodiment. The light-emitting diameter D roughly corresponds to the diameter of the laser light generated by the light-emitting element of this embodiment. The light-emitting diameter D of this embodiment is determined based on the diameter (OA diameter) of the plurality of non-oxide films 4b′. The light-emitting diameter D of this embodiment is 30 μm or more, e.g., 30 μm. However, it may be larger to improve output, e.g., 40 μm or 50 μm. In this embodiment, the diameter of each non-oxide film 4b′ is set large, resulting in a large light-emitting diameter D. Note that when the planar shape of the non-oxide layer 4b′ is other than circular, the light-emitting diameter D is determined based on the length of the longest dividing line (a line parallel to the XY plane) passing through the center of gravity of the planar shape of the non-oxide layer 4b′.

[0045] The difference between the radius of the inner side surface and the radius of the outer side surface of each oxide layer 4b is called the oxidation length of each oxide layer 4b. The diameter of the outer side surface of each oxide layer 4b corresponds to the diameter of the mesa M. On the other hand, the diameter of the inner side surface of each oxide layer 4b corresponds to the diameter of the corresponding non-oxide layer 4b'. In this embodiment, the oxidation lengths of the multiple oxide layers 4b are different for each oxide layer 4b, and as a result, the diameters of the multiple non-oxide layers 4b' are different for each non-oxide layer 4b'. This makes it possible to reduce the adverse effects of stress at the tips (inner side surfaces) of these oxide layers 4b. This is because stress within the mesa M is greater at the tips of these oxide layers 4b. According to this embodiment, by dispersing the positions of the tips of these oxide layers 4b, it is possible to suppress cracks within the mesa M and improve the reliability of the mesa M.

[0046] [P-Type DBR 5] The p-type DBR 5 is formed on the laminated film 4 and is included in the mesa M of the light emitting device. The p-type DBR 3 is, for example, a p-type semiconductor layer.

[0047] [P-Type Contact Layer 6] The p-type contact layer 6 is formed on the p-type DBR 5 and is included in the mesa M of the light-emitting device. In FIG. 1, the p-type contact layer 6 serves as an underlying layer for the p-type electrode 11. The p-type contact layer 6 is, for example, a semiconductor layer such as a p-type polysilicon layer. The p-type contact layer 6 is also called a p-type current injection layer.

[0048] [P-type electrode 11] The p-type electrode 11 is formed on the p-type contact layer 6. In plan view, the p-type electrode 11 has a circular shape, but the diameter of the p-type electrode 11 is set to be smaller than the diameter of the p-type contact layer 6. The p-type electrode 11 is, for example, a p-type semiconductor layer.

[0049] [N-Type Electrode 12] The n-type electrode 12 is formed on the n-type contact layer 2. In plan view, the n-type electrode 12 has a shape that annularly surrounds the mesa M. The n-type electrode 12 is, for example, an n-type semiconductor layer.

[0050] [Passivation Film 13] The passivation film 13 is formed on the side surfaces and upper surfaces of the mesa M, the n-type contact layer 2, the p-type electrode 11, and the n-type electrode 12. However, the passivation film 13 has openings on the upper surface of the p-type electrode 11 and the upper surface of the n-type electrode 12. The passivation film 13 is, for example, an insulating film such as a SiN (silicon nitride) film.

[0051] [AR Coating Film 14] The AR coating film 14 is formed on the rear surface S2 of the substrate 1. The AR coating film 14 of this embodiment is made of a material that does not absorb light having a wavelength corresponding to the oscillation wavelength of the light-emitting element of this embodiment.

[0052] [Anode Electrode 15] The anode electrode 15 is formed on the p-type electrode 11 through an opening in the passivation film 13 and is electrically connected to the light-emitting element of this embodiment. In plan view, the anode electrode 15 has a circular shape (see FIG. 2 ), but the diameter of the anode electrode 15 is set to be smaller than the diameter of the p-type electrode 11. The anode electrode 15 is a metal electrode formed by, for example, a plating method.

[0053] [Cathode Electrode 16] The cathode electrode 16 is formed on the n-type electrode 12 through the opening in the passivation film 13 and is electrically connected to the light-emitting element of this embodiment. In plan view, the cathode electrode 16 has a shape that surrounds the mesa M in an annular shape (see FIG. 2). The cathode electrode 16 is a metal electrode formed by, for example, plating.

[0054] 2 shows the planar shapes of the passivation film 13, the anode electrode 15, and the cathode electrode 16. The passivation film 13 includes a portion 13a formed on the top and side surfaces of the mesa M, a portion 13b formed on the top surface of the n-type contact layer 2 inside the anode electrode 15, and a portion 13c formed on the top surface of the n-type contact layer 2 outside the anode electrode 15. In addition, as shown in FIG. 2, the cathode electrode 16 has an inner side surface having a circular planar shape and an outer side surface having a rectangular planar shape.

[0055] In this embodiment, the temperature at which the oscillation wavelength of the light-emitting device and the gain peak wavelength of the multiple active layers 4a coincide is 50°C or lower. The gain peak wavelength is the peak wavelength of the gain spectrum observed when all of these active layers 4a are excited simultaneously. The light-emitting device of this embodiment is configured so that the temperature at which the oscillation wavelength and the gain peak wavelength coincide is 50°C or lower. The temperature at which these wavelengths coincide may be even lower, for example, 30°C or lower or 10°C or lower. Furthermore, the light-emitting device of this embodiment may be configured so that the half-width of the gain spectrum observed when all of these active layers 4a are excited simultaneously is greater than 25 nm. Further details of the oscillation wavelength and the gain peak wavelength will be described later. The gain peak wavelength is also referred to as the PL peak wavelength.

[0056] FIG. 3 is a graph for explaining the operation of the light emitting device of the first embodiment.

[0057] FIG. 3A is a graph showing the relationship between the above-mentioned oscillation wavelength and gain peak wavelength. The coordinate axes in FIG. 3A represent wavelength. Curve S represents the above-mentioned gain spectrum, and point P represents the peak of the gain spectrum. Wavelength L1 represents the wavelength at the peak of the gain spectrum, i.e., the gain peak wavelength. Wavelength L2 represents the wavelength at which the gain spectrum is zero. Wavelength difference L represents the difference between wavelengths L1 and L2 (L = L2 - L1). Region R represents the mode existence range of the light-emitting device of this embodiment. The right end W of region R represents the wavelength of the lowest-order mode of the light-emitting device of this embodiment, i.e., the oscillation wavelength. Thus, the oscillation wavelength is the wavelength at the right end W of region R, and the gain peak wavelength is the wavelength at point P on curve S. Note that the wavelength difference L in this embodiment is, for example, 20 to 30 nm. The same applies to FIGS. 3B and 3C.

[0058] 3A shows the relationship between the oscillation wavelength and the gain peak wavelength when the temperature of the light-emitting device of this embodiment is T1 (high temperature). In FIG. 3A, point P is located on the long wavelength side (right side) of region R. FIG. 3B shows the relationship between the oscillation wavelength and the gain peak wavelength when the temperature of the light-emitting device of this embodiment is T2 (room temperature). In FIG. 3B, point P is located within region R. FIG. 3C shows the relationship between the oscillation wavelength and the gain peak wavelength when the temperature of the light-emitting device of this embodiment is T3 (low temperature). In FIG. 3C, point P is located on the short wavelength side (left side) of region R.

[0059] FIG. 4 is another graph for explaining the operation of the light emitting device of the first embodiment.

[0060] 4 shows the relationship between the oscillation wavelength and the gain peak wavelength when the temperature of the light-emitting device of this embodiment is T. In FIG. 4, point P is located at the right end W of region R. This indicates that the oscillation wavelength and the gain peak wavelength coincide at temperature T. The light-emitting device of this embodiment is configured so that temperature T is 50° C. or less (T≦50° C.).

[0061] The relationship between the oscillation wavelength and the gain peak wavelength will be further explained below with reference to FIGS. 3A, 3B, 3C, and 4. FIG.

[0062] As a result of experiments, it was found that when an MJ-VCSEL with a large number of stacks and a large OA diameter is formed, the near-field and far-field pattern characteristics are generally more likely to be unsuitable for LiDAR applications than a VCSEL with a small number of stacks or a small OA diameter designed with the same temperature T shown in FIG. 4 . Specifically, it was found that the near-field and far-field patterns become donut-shaped. Therefore, when the temperature T was lowered as described above, it was found that the near-field and far-field patterns became unimodal, and the near-field and far-field pattern characteristics became suitable for LiDAR applications. Lowering the temperature T has a physical significance as explained below.

[0063] As the OA diameter increases, the number of transverse modes that can exist in the VCSEL increases. In this case, the oscillation wavelengths of these modes are densely distributed on the coordinate axis (wavelength axis) of the graph, and behave as if they have broad oscillation wavelength characteristics. Of these oscillation wavelengths, the oscillation wavelength on the longest wavelength side is the oscillation wavelength of the lowest-order mode, and the other oscillation wavelengths are oscillation wavelengths of higher-order modes. In this embodiment, as described above, the oscillation wavelength of the lowest-order mode is treated as the oscillation wavelength of the light-emitting element of this embodiment.

[0064] Regarding the relative relationship between the lasing wavelength and the gain peak wavelength, when the gain peak wavelength is longer than the lasing wavelength, as shown in Figure 3A, lower-order mode oscillation occurs preferentially over higher-order mode oscillation, resulting in desirable lasing. On the other hand, when the gain peak wavelength is shorter than the lasing wavelength, as shown in Figures 3B and 3C, higher-order mode oscillation occurs preferentially over lower-order mode oscillation, resulting in undesirable lasing. Furthermore, when the wavelengths are significantly different, as shown in Figure 3C, lower-order mode oscillation does not occur, and both the near-field and far-field patterns exhibit a lack of intensity in the central portion. Since this type of lasing mode selection is more likely to occur with a larger number of stacks, this problem becomes more pronounced when the number of stacks is increased to achieve a high SE. A VCSEL in this state is not suitable for many industrial applications and requires improvement. Specifically, it is desirable that, over the entire range of guaranteed operating temperatures of the light-emitting device, 1) the gain peak wavelength is longer than the oscillation wavelength, 2) the gain peak wavelength is equal to the oscillation wavelength, or 3) the gain peak wavelength is shorter than the oscillation wavelength with a small difference between these wavelengths. In other words, it is desirable that the state shown in Figure 3C does not appear over the entire range of guaranteed operating temperatures of the light-emitting device.

[0065] On the other hand, in this embodiment, both the resonant wavelength of the light-emitting element and the wavelength characteristics of the material gain of the light-emitting element are temperature-dependent. For example, as the temperature of the light-emitting element increases, the above-mentioned oscillation wavelength and gain peak wavelength become longer. Specifically, the amount of shift of the oscillation wavelength per 1°C temperature increase is approximately 0.07 nm / K, and the amount of shift of the gain peak wavelength per 1°C temperature increase is approximately 0.30 nm / K. Therefore, as the temperature of the light-emitting element increases, the oscillation wavelength becomes slightly longer and the gain peak wavelength becomes significantly longer. Furthermore, the relative relationship between the oscillation wavelength and the gain peak wavelength changes at a rate of 0.23 nm / K per 1°C temperature increase.

[0066] The left-pointing arrows in Figures 3A to 3C indicate how the oscillation wavelength and gain peak wavelength shorten as the temperature of the light-emitting element decreases. At this time, when the temperature of the light-emitting element decreases, the oscillation wavelength shortens slightly, and the gain peak wavelength shortens significantly. Therefore, while the gain peak wavelength is longer than the oscillation wavelength in Figure 3A, the gain peak wavelength is shorter than the oscillation wavelength in Figures 3B and 3C. In other words, the relative relationship between these wavelengths is reversed. Therefore, malfunction of the light-emitting element, in which low-order mode oscillation does not occur, is more likely to occur when the temperature of the light-emitting element decreases.

[0067] Therefore, the light-emitting element of this embodiment is designed so that malfunctions of the light-emitting element are unlikely to occur even at the lowest temperature at which the light-emitting element can be used. In this embodiment, the lowest temperature is assumed to be -40°C. In this embodiment, the gain peak wavelength at -40°C is set to be shorter than the oscillation wavelength by a value of 20 nm or less. That is, the gain peak wavelength is set to be shorter than the oscillation wavelength, and the difference between the gain peak wavelength and the oscillation wavelength is set to be 20 nm or less. The reason for this is that when the wavelength difference L is 20 to 30 nm as described above, if the difference between the gain peak wavelength and the oscillation wavelength is set to be 20 nm or less, the oscillation wavelength will be shorter than wavelength L2 even at -40°C, and the lowest-order mode oscillation will occur even at -40°C.

[0068] In this case, when the temperature of the light-emitting device rises from -40°C to 50°C, the relative relationship between the oscillation wavelength and the gain peak wavelength changes by approximately 20 nm. This is because the change in the relative relationship is given by 0.23 nm / K x 90°C = 20.7 nm. Therefore, if the gain peak wavelength at -40°C is set to be 20 nm shorter than the oscillation wavelength, the gain peak wavelength at 50°C will coincide with the oscillation wavelength. This is the reason why the light-emitting device of this embodiment is configured so that the temperature at which the oscillation wavelength and the gain peak wavelength coincide is 50°C or lower. As a result, the gain peak wavelength at -40°C is shorter than the oscillation wavelength by 20 nm or less. To further reduce the likelihood of malfunction of the light-emitting device, the light-emitting device of this embodiment may be configured so that the temperature at which the oscillation wavelength and the gain peak wavelength coincide is 30°C or lower or 10°C or lower.

[0069] Here, the difference Δλ between the oscillation wavelength and the gain peak wavelength will be described (difference Δλ = oscillation wavelength - gain peak wavelength). When a light-emitting element is frequently used at a certain temperature, it is desirable for the absolute value of the difference Δλ at that temperature to be small. Therefore, it is assumed that a light-emitting element is designed so that the difference Δλ is zero when the temperature of the light-emitting element is room temperature. However, taking into consideration that the laser characteristics deteriorate with increasing temperature and that the light-emitting element generates heat when driven, the light-emitting element of this embodiment is designed so that the difference Δλ is zero when the temperature of the light-emitting element is higher than room temperature. For example, the temperature at which the difference Δλ becomes zero is set to the upper limit temperature at which the light-emitting element can be used. This is because light-emitting elements generally operate at temperatures higher than room temperature due to heat generation by the light-emitting element. In this embodiment, the difference Δλ at room temperature is set to, for example, approximately +5 nm. It is desirable to use the light-emitting element at a temperature at which the difference Δλ is between -6 nm and +6 nm.

[0070] FIG. 5 is another graph for explaining the operation of the light emitting device of the first embodiment.

[0071] Fig. 5A shows the relationship between the OA diameter and PCE (power conversion efficiency) when the light-emitting element has an output of 2 W. Fig. 5A shows this relationship for various values ​​of the number of active layers 4a (number of stacks). Fig. 5A shows that the PCE increases as the number of active layers 4a increases.

[0072] FIG. 5B shows the relationship between the OA diameter and the PCE when the light-emitting device has an output of 20 W. FIG. 5B also shows these relationships for various values ​​of the number of active layers 4 a. As with FIG. 5A, FIG. 5B shows that the PCE increases as the number of active layers 4 a increases. FIG. 5B also shows that it is easy to increase the PCE even when the OA diameter is large. From this, it is considered that the need for the light-emitting device of this embodiment increases when the light-emitting device has a high output and a large OA diameter.

[0073] FIG. 6 is another graph for explaining the operation of the light emitting device of the first embodiment.

[0074] The horizontal axis of Fig. 6 indicates the number of active layers 4a (number of stacks) in the light-emitting element, and the vertical axis of Fig. 6 indicates the minimum emitter area (light-emitting area) at which the PCE of the light-emitting element becomes 30%. Fig. 6 shows the relationship between the number of stacks of the light-emitting element and the light-emitting area when the light-emitting element has an output of 2 W, 5 W, 10 W, 20 W, and 50 W. Fig. 6 shows a region R1 where the PCE is greater than 30% and a region R2 where the PCE is less than 30% when the light-emitting element has an output of 50 W.

[0075] The plots and approximation curves in FIG. 6 were calculated using the equation shown in FIG. 6. In this equation, η ＰＣＥ represents the PCE [%] of the light-emitting element, Po represents the output [W] of the light-emitting element, and Na represents the number of stacked light-emitting elements [units]. ｏｎ represents the on-voltage [V] of one active layer 4a, and V ＴＪ represents the on-voltage [V] of one TJ layer 4c. ＳＥ represents the output efficiency of the light-emitting element [W / A], and ρ represents the resistance per area of ​​the light-emitting element [Ω cm ２ ], and Se represents the light-emitting area of ​​the light-emitting element [cm ２ ].

[0076] In this embodiment, since it is desirable to increase the number of stacks while avoiding malfunctions, it is desirable for the light-emitting element to operate within region R1 where the PCE is greater than 30% when the output of the light-emitting element is 50 W. This also applies when the output of the light-emitting element is 2 W, 5 W, 10 W, or 20 W.

[0077] Therefore, using the formula shown in FIG. 6, when the output of the light emitting element is 2 W, Na≧2.13×10 －３ ×Se －０．４８８ Similarly, when the output of the light emitting element is 5 W, the light emitting element satisfies the condition Na≧3.31×10 －３ ×Se －０．４８８ Similarly, when the output of the light emitting element is 10 W, the light emitting element satisfies the condition Na≧4.66×10 －３ ×Se －０．４８８Similarly, when the output of the light emitting element is 20 W, the light emitting element satisfies the condition Na≧6.53×10 －３ ×Se －０．４８８ Similarly, when the output of the light emitting element is 50 W, the light emitting element satisfies the condition Na≧1.02×10 －２ ×Se －０．４８８ It is desirable to meet the following conditions.

[0078] These conditions can be abstracted by using a variable "Po." For example, if a light emitting element satisfies Na≧0.0144×Po ０．４９１ ×Se －０．４８８ If the above condition is satisfied, the PCE can be made larger than 30% regardless of whether the output of the light-emitting element is 2 W, 5 W, 10 W, 20 W, or 50 W.

[0079] The PCE value may be a value other than 30%, for example, 35% or 40%. ０．４９１ ×Se －０．４８８ If the above formula is satisfied, the PCE can be made larger than 35% regardless of whether the output of the light-emitting device is 2 W, 5 W, 10 W, 20 W, or 50 W. ０．４９１ ×Se －０．４８８ If the above condition is satisfied, the PCE can be made larger than 40% regardless of whether the output of the light-emitting element is 2 W, 5 W, 10 W, 20 W, or 50 W.

[0080] 7 to 10 are cross-sectional views showing a method for manufacturing the light emitting device of the first embodiment.

[0081] First, the n-type contact layer 2, n-type DBR 3, stacked film 4, p-type DBR 5, and p-type contact layer 6 are formed in this order on the surface S1 of the substrate 1 ( FIG. 7A ). The stacked film 4 is formed to include multiple active layers 4a, multiple non-oxide layers 4b', and a TJ layer 4c. These layers are stacked in the Z direction in the following order: active layer 4a, non-oxide layer 4b', TJ layer 4c, active layer 4a, non-oxide layer 4b', TJ layer 4c, ... Each non-oxide layer 4b' is, for example, an AlAs layer.

[0082] Next, the p-type electrode 11 is formed on the p-type contact layer 6 (FIG. 7B). In this embodiment, the p-type electrode 11 is formed by forming a material for the p-type electrode 11 on the upper surface of the p-type contact layer 6 and processing this material into a circular shape.

[0083] Next, the p-type contact layer 6, the p-type DBR 5, the stacked film 4, and the n-type DBR 3 are processed by lithography and etching (FIG. 8A), thereby forming a mesa M including the n-type DBR 3, the stacked film 4, the p-type DBR 5, and the p-type contact layer 6.

[0084] Next, a portion of each non-oxidized layer 4b' is oxidized with steam from the side surface of the mesa M (FIG. 8A). As a result, a portion of each non-oxidized layer 4b' is transformed into an oxidized layer 4b, and the remaining portion of each non-oxidized layer 4b' is surrounded by the oxidized layer 4b in a ring shape.

[0085] Next, the n-type electrode 12 is formed on the n-type contact layer 2 (FIG. 8B). The n-type electrode 12 of this embodiment is formed by forming a material for the n-type electrode 12 on the upper surface of the n-type contact layer 2 or the like, and then processing this material into a shape that surrounds the mesa M in an annular shape.

[0086] Next, a passivation film 13 is formed on the side and top surfaces of the mesa M, the n-type contact layer 2, the p-type electrode 11, and the n-type electrode 12 (FIG. 9A). Next, openings are formed in the passivation film 13 on the top surfaces of the p-type electrode 11 and the n-type electrode 12 by lithography and etching (FIG. 9B).

[0087] Next, an anode electrode 15 is formed on the p-type electrode 11, and a cathode electrode 16 is formed on the n-type electrode 12 ( FIG. 10A ). In this embodiment, the anode electrode 15 and the cathode electrode 16 are formed by plating the materials for the anode electrode 15 and the cathode electrode 16 on the upper surfaces of the p-type electrode 11 and the n-type electrode 12, and then processing the materials into the anode electrode 15 and the cathode electrode 16.

[0088] Next, the rear surface S2 of the substrate 1 is ground, and then the AR coating film 14 is formed on the rear surface S2 of the substrate 1 (FIG. 10B). In this manner, the light emitting device shown in FIGS.

[0089] As described above, the light-emitting device of this embodiment includes multiple active layers 4 a and multiple TJ layers 4 c, has an emission diameter of 30 μm or more, and is configured so that the temperature at which the oscillation wavelength of the light-emitting device and the gain peak wavelength of these active layers 4 a coincide is 50° C. or less. Therefore, according to this embodiment, it is possible to stably generate high output power from the light-emitting device. For example, when forming an MJ-VCSEL with a large number of stacks, a high SE, and a large OA diameter, it is possible to stably generate high output power from the light-emitting device even if the relationship between the oscillation wavelength and the gain peak wavelength changes with temperature.

[0090] Second Embodiment FIG. 11 is a cross-sectional view showing the structure of a light emitting device according to a second embodiment.

[0091] The light emitting device of this embodiment will be described in detail below with reference to Fig. 11. In this description, Fig. 12 will also be referred to as appropriate. Fig. 12 is a plan view showing the structure of the light emitting device of the second embodiment. Fig. 11 shows a vertical cross section taken along line BB' shown in Fig. 12.

[0092] The light-emitting device of this embodiment is a surface-emitting VCSEL light-emitting device and includes a plurality of light-emitting elements arranged in a two-dimensional array. FIG. 12 shows seven mesas M constituting seven light-emitting elements. These light-emitting elements correspond to VCSEL light-emitting elements. As shown in FIG. 12, these light-emitting elements form a triangular lattice-shaped light-emitting element array. Each mesa M of this embodiment has a hexagonal shape in plan view. The shape of each mesa M in plan view may be a polygon other than a hexagon (e.g., a triangle or a rectangle). The diameter of the circumscribing circle of each mesa M in plan view is, for example, 50 μm or more.

[0093] FIG. 11 shows an XZ cross section of one of these light-emitting elements. The components shown in FIG. 11 are generally the same as those shown in FIG. 1 . However, the light-emitting device of this embodiment does not include an n-type electrode 12 or an AR coating film 14, but includes a cathode electrode 16 on the rear surface S2 of the substrate 1. The cathode electrode 16 of this embodiment functions as a cathode electrode common to the multiple light-emitting elements. On the other hand, as shown in FIGS. 11 and 12 , the anode electrode 15 of this embodiment includes a portion 15a formed on the upper surfaces of the multiple mesas M, a portion 15b formed on the side surfaces of the multiple mesas M, and a portion 15c formed on the upper surface of the n-type contact layer 2. Therefore, the anode electrode 15 of this embodiment functions as an anode electrode common to the multiple light-emitting elements. The anode electrode 15 and cathode electrode 16 of this embodiment can simultaneously drive these light-emitting elements to emit light.

[0094] Furthermore, the n-type DBR 3 of this embodiment is provided between the substrate 1 and the n-type contact layer 2, rather than between the n-type contact layer 2 and the laminated film 4. This structure is called an intra-cavity structure. This makes it possible to improve the stress resistance of the mesa M. As shown in FIG. 11 , the n-type DBR 3 of this embodiment is provided outside the mesa M, rather than inside it.

[0095] The stacked film 4 of this embodiment includes multiple active layers 4a, one oxide layer 4b, one non-oxide layer 4b', and multiple TJ layers 4c. In FIG. 11 , the stacked film 4 includes five active layers 4a and four TJ layers 4c arranged alternately along the Z direction, with oxide layers 4b and non-oxide layers 4b' on the active layers 4a and TJ layers 4c. The non-oxide layers 4b' are formed within the oxide layers 4b and are surrounded by the oxide layers 4b in a ring-like shape in plan view. The non-oxide layers 4b' have a generally hexagonal shape in plan view, and the oxide layers 4b have a generally hexagonal ring-like shape in plan view. The emission diameter D of this embodiment, like the emission diameter D of the first embodiment, is determined based on the dimensions of the non-oxide layers 4b'. The emission diameter D of this embodiment is 30 μm or more, e.g., 50 μm.

[0096] As shown in FIG. 11 , the mesa M of this embodiment includes a non-implantation region Q1 provided in the center of the mesa M and an implantation region Q2 provided near the side surface of the mesa M. The implantation region Q2 is a region into which predetermined impurity atoms are implanted, and the non-implantation region Q1 is a region into which the impurity atoms are not implanted. The implantation region Q2 of this embodiment is formed by implanting impurity atoms into a portion of the mesa M from the side surface of the mesa M. Therefore, the implantation region Q2 is formed around the non-implantation region Q1 and surrounds the non-implantation region Q1 in a ring shape in a plan view. Note that the implantation region Q2 may be a region into which predetermined impurity atoms are sufficiently implanted, and the non-implantation region Q1 may be a region into which the impurity atoms are not sufficiently implanted.

[0097] The non-implanted region Q1 and the implanted region Q2 are formed in the stacked film 4, the p-type DBR 5, and the p-type contact layer 6. Each diffusion layer 4a includes the non-implanted region Q1 in the central portion of the diffusion layer 4a and the implanted region Q2 near the end face of the diffusion layer 4a, and is partially insulated by impurity atoms. In each diffusion layer 4a, the non-implanted region Q1 is a non-insulating region, and the implanted region Q2 is an insulating region.

[0098] The stacked film 4 of this embodiment includes only one oxide layer 4b. A structure in which the stacked film 4 includes only one oxide layer 4b or no oxide layer 4b is effective in reducing stress within the mesa M. However, adopting such a structure can cause non-radiative recombination problems near the end faces of each active layer 4a. Therefore, the stacked film 4 of this embodiment includes implantation regions Q2 (insulating regions) near the end faces of each diffusion layer 4a. This prevents carriers from reaching the end faces of each diffusion layer 4a, thereby reducing non-radiative recombination near the end faces of each active layer 4a. Note that a mesare-less structure may be adopted when the stacked film 4 includes no oxide layer 4b.

[0099] The distance between the side surface of the mesa M and the boundary between the non-implanted region Q1 and the implanted region Q2 is set to, for example, 1 μm or more. This makes it possible to ensure a sufficiently wide implanted region Q2. Furthermore, the light emitting device of this embodiment may be configured to emit light such that the light intensity at the boundary between the non-implanted region Q1 and the implanted region Q2 is less than 10% of the peak light intensity. This makes it possible to sufficiently reduce the non-radiative recombination described above.

[0100] 3 to 6 also apply to this embodiment. In this embodiment, the difference Δλ at room temperature is set to, for example, approximately ±0 nm.

[0101] Like the light-emitting device of the first embodiment, the light-emitting device of this embodiment includes a plurality of active layers 4 a and a plurality of TJ layers 4 c, has an emission diameter of 30 μm or more, and is configured so that the temperature at which the oscillation wavelength of the light-emitting device coincides with the gain peak wavelength of these active layers 4 a is 50° C. or less. Therefore, according to this embodiment, like the first embodiment, it is possible to stably generate high output from the light-emitting device.

[0102] The light emitting device of this embodiment can be manufactured by the method shown in Figures 7 to 10, similar to the light emitting device of the first embodiment. However, it is necessary to add modifications to the method due to the difference between the structure shown in Figure 1 and the structure shown in Figure 11. For example, when manufacturing the light emitting device of this embodiment, impurity atoms are implanted in the step of Figure 8A. The above also applies to each embodiment described later.

[0103] Furthermore, as shown in Fig. 12, the light emitting device of this embodiment includes a light emitting element array including a plurality of light emitting elements. In this embodiment, the pitch between the light emitting elements is set to 0.6 or more of the width of the mesa M of each light emitting element. This width is, for example, the length of the longest dividing line passing through the center of gravity of the planar shape of the mesa M. Furthermore, in this embodiment, the pitch between the light emitting elements may be set to 0.7 or more of the width of the mesa M of each light emitting element. The same applies to each embodiment described below.

[0104] Third Embodiment FIG. 13 is a cross-sectional view showing the structure of a light emitting device according to a third embodiment.

[0105] The light emitting device of this embodiment will be described in detail below with reference to Fig. 13. In this description, Fig. 14 will also be referred to as appropriate. Fig. 14 is a plan view showing the structure of the light emitting device of the third embodiment. Fig. 13 shows a vertical cross section taken along line CC' shown in Fig. 14.

[0106] The light-emitting device of this embodiment is a surface-emitting VCSEL light-emitting device and includes a plurality of light-emitting elements arranged in a one-dimensional array. Figure 14 shows four mesas M constituting four light-emitting elements. Each mesa M of this embodiment has a quadrilateral (rectangular) shape in plan view. The shape of each mesa M in plan view may be another quadrilateral (e.g., square). The length of the long side of each mesa M in plan view is, for example, 100 μm or more, and the length of the short side of each mesa M in plan view is, for example, 40 μm or more.

[0107] FIG. 13 shows an XZ cross section of one of these light-emitting elements. The components shown in FIG. 13 are generally the same as those shown in FIG. 1. However, the light-emitting device of this embodiment does not include an n-type electrode 12 or an AR coating film 14, but includes a cathode electrode 16 on the rear surface S2 of the substrate 1. The cathode electrode 16 of this embodiment functions as a cathode electrode common to the multiple light-emitting elements. On the other hand, as shown in FIGS. 13 and 14, the light-emitting device of this embodiment includes multiple anode electrodes 15 separated for each individual light-emitting element, and the multiple light-emitting elements are electrically connected to different anode electrodes 15. The multiple anode electrodes 15 and cathode electrodes 16 of this embodiment enable these light-emitting elements to emit light by individually driving them.

[0108] The stacked film 4 of this embodiment includes a plurality of active layers 4a, a plurality of oxide layers 4b, a plurality of non-oxide layers 4b', and a plurality of TJ layers 4c. The shape of each non-oxide layer 4b' is generally rectangular in plan view, and the shape of each oxide layer 4b is generally a rectangular ring in plan view. The emission diameter D of this embodiment is determined based on the dimensions of these non-oxide layers 4b'. The emission diameter D of this embodiment is 30 μm or more, for example, 100 μm.

[0109] 3 to 6 also apply to this embodiment. In this embodiment, the difference Δλ at room temperature is set to, for example, about −5 nm.

[0110] Like the light-emitting devices of the first and second embodiments, the light-emitting device of this embodiment includes a plurality of active layers 4 a and a plurality of TJ layers 4 c, has an emission diameter of 30 μm or more, and is configured so that the temperature at which the oscillation wavelength of the light-emitting device coincides with the gain peak wavelength of these active layers 4 a is 50° C. or less. Thus, according to this embodiment, like the first and second embodiments, it is possible to stably generate high output from the light-emitting device.

[0111] In this embodiment, only the cathode electrode 16 is shared by a plurality of light-emitting elements, but instead, only the anode electrode 15 may be shared by a plurality of light-emitting elements.

[0112] Fourth Embodiment FIG. 15 is a cross-sectional view showing the structure of a light emitting device according to a fourth embodiment.

[0113] The light emitting device of this embodiment will be described in detail below with reference to Fig. 15. In this description, Fig. 16 will also be referred to as appropriate. Fig. 16 is a plan view showing the structure of the light emitting device of the fourth embodiment. Fig. 15 shows a vertical cross section taken along line DD' shown in Fig. 16.

[0114] The light-emitting device of this embodiment is a back-emitting VCSEL light-emitting device and includes a plurality of light-emitting elements arranged in a two-dimensional array. Figure 16 shows 16 mesas M constituting 16 light-emitting elements. However, since the laminated film 4 of each light-emitting element of this embodiment is formed outside the mesa M, the structure of each light-emitting element of this embodiment is also called a mesa-less structure. Although mesas M that do not include the laminated film 4 are often not called mesas, they will be referred to as mesas in this embodiment for convenience. Each mesa M of this embodiment has a square shape in plan view. The length of one side of each mesa M in plan view is, for example, 50 μm or more.

[0115] FIG. 15 shows an XZ cross section of one of these light-emitting elements. The components shown in FIG. 15 are generally the same as those shown in FIG. 1. However, the light-emitting device of this embodiment does not include an n-type electrode 12 or an AR coating film 14, but includes a cathode electrode 16 on the rear surface S2 of the substrate 1. The cathode electrode 16 of this embodiment functions as a cathode electrode common to the multiple light-emitting elements. On the other hand, as shown in FIGS. 15 and 16, the light-emitting device of this embodiment includes four anode electrodes 15 separated for each individual light-emitting element row, and the four light-emitting element rows are electrically connected to different anode electrodes 15. Each light-emitting element row includes four light-emitting elements. These anode electrodes 15 and cathode electrodes 16 of this embodiment enable these light-emitting element rows to emit light by individually driving them, and also enable the four light-emitting elements in each light-emitting element row to emit light by simultaneously driving them.

[0116] Furthermore, the n-type DBR 3 of this embodiment is provided between the substrate 1 and the n-type contact layer 2, rather than between the n-type contact layer 2 and the laminated film 4. This structure is called an intra-cavity structure, which makes it possible to improve the stress resistance of the mesa M. Similarly, the p-type DBR 5 of this embodiment is provided between the p-type contact layer 6 and the p-type electrode 11, rather than between the laminated film 4 and the p-type contact layer 6. The n-type DBR 3, laminated film 4, and p-type contact layer 6 of this embodiment are provided outside the mesa M, rather than inside it, as shown in FIG.

[0117] The stacked film 4 of this embodiment includes multiple active layers 4a and multiple TJ layers 4c arranged alternately, but does not include an oxide layer 4b or a non-oxide layer 4b'. Thus, the stacked film 4 of this embodiment includes a non-implanted region Q1 and an implanted region Q2, similar to the stacked film 4 of the second embodiment.

[0118] The p-type DBR 5 of this embodiment is included in the mesa M and is made of a dielectric material. The emission diameter D of this embodiment is determined based on the dimensions of the p-type DBR 5. The emission diameter D of this embodiment is 30 μm or more, for example, 50 μm.

[0119] 3 to 6 also apply to this embodiment. In this embodiment, the difference Δλ at room temperature is set to, for example, about −6 nm.

[0120] The light-emitting device of this embodiment, like the light-emitting devices of the first to third embodiments, includes a plurality of active layers 4a and a plurality of TJ layers 4c, has an emission diameter of 30 μm or more, and is configured so that the temperature at which the oscillation wavelength of the light-emitting device coincides with the gain peak wavelength of these active layers 4a is 50° C. or less. Therefore, according to this embodiment, like the first to third embodiments, it is possible to stably generate high output from the light-emitting device.

[0121] Fifth Embodiment FIG. 17 is a cross-sectional view showing the structure of a light emitting device according to a fifth embodiment.

[0122] The light emitting device of this embodiment will be described in detail below with reference to Fig. 17. In this description, Fig. 18 will also be referred to as appropriate. Fig. 18 is a plan view showing the structure of the light emitting device of the fifth embodiment. Fig. 17 shows a vertical cross section taken along line EE' shown in Fig. 18.

[0123] The light emitting device of this embodiment is a back-emitting VCSEL light emitting device and includes a plurality of light emitting elements arranged in a two-dimensional array. Fig. 18 shows nine mesas M constituting nine light emitting elements. Each mesa M of this embodiment has a circular shape in plan view. The diameter of each mesa M in plan view is, for example, 100 µm or more.

[0124] FIG. 17 shows an XZ cross section of one of these light-emitting elements. The components shown in FIG. 17 are generally the same as those shown in FIG. 1. The light-emitting device of this embodiment includes multiple anode electrodes 15, each separated for each light-emitting element, and the multiple light-emitting elements are electrically connected to different anode electrodes 15. Furthermore, the light-emitting device of this embodiment includes multiple cathode electrodes 16, each separated for each light-emitting element, and the multiple light-emitting elements are electrically connected to different cathode electrodes 16. The multiple anode electrodes 15 and multiple cathode electrodes 16 of this embodiment enable these light-emitting elements to emit light by individually driving them. Note that FIG. 18 shows the pillar portion P1 of each anode electrode 15 and the pillar portion P2 of each cathode electrode 16, and does not show other portions of the anode electrodes 15 and cathode electrodes 16.

[0125] Furthermore, the n-type DBR 3 of this embodiment is provided between the substrate 1 and the n-type contact layer 2, rather than between the n-type contact layer 2 and the laminated film 4. This structure is called an intra-cavity structure, which makes it possible to improve the stress resistance of the mesa M. Similarly, the p-type DBR 5 of this embodiment is provided between the p-type contact layer 6 and the p-type electrode 11, rather than between the laminated film 4 and the p-type contact layer 6. As shown in FIG. 17 , the n-type DBR 3 of this embodiment is provided outside the mesa M, rather than inside it.

[0126] The stacked film 4 of this embodiment includes multiple active layers 4a, one oxide layer 4b, one non-oxide layer 4b', and multiple TJ layers 4c. Therefore, the stacked film 4 and p-type contact layer 6 of this embodiment include a non-implanted region Q1 and an implanted region Q2, similar to the stacked film 4 and p-type contact layer 6 of the second embodiment. The shape of the non-oxide layer 4b' is approximately circular in plan view, and the shape of the oxide layer 4b is approximately annular in plan view. The emission diameter D of this embodiment is determined based on the dimensions of the non-oxide film 4b'. The emission diameter D of this embodiment is 30 μm or more, for example, 100 μm.

[0127] 3 to 6 also apply to this embodiment. In this embodiment, the difference Δλ at room temperature is set to, for example, about −6 nm.

[0128] The light-emitting device of this embodiment, like the light-emitting devices of the first to fourth embodiments, includes a plurality of active layers 4a and a plurality of TJ layers 4c, has an emission diameter of 30 μm or more, and is configured so that the temperature at which the oscillation wavelength of the light-emitting device matches the gain peak wavelength of these active layers 4a is 50° C. or less. Therefore, according to this embodiment, like the first to fourth embodiments, it is possible to stably generate high output from the light-emitting device.

[0129] Sixth Embodiment (1) Configuration of Distance Measuring Device 101 Fig. 19 is a block diagram showing an example of the configuration of a distance measuring device 101 according to a sixth embodiment. The distance measuring device 101 according to this embodiment is mounted on, for example, an automobile.

[0130] As shown in the figure, the distance measuring device 101 includes an emitter 102, a driver 103, a power supply circuit 104, an emitter optical system 105, a receiver optical system 106, a receiver 107, a signal processor 108, a controller 109, and a temperature detector 110.

[0131] The light-emitting unit 102 emits light from a plurality of light sources. The light-emitting unit 102 in this example has light-emitting elements 102a that are VCSELs (Vertical Cavity Surface Emitting Lasers) as the light sources, and the light-emitting elements 102a are arranged in a predetermined pattern, such as a matrix. The light-emitting unit 102 is, for example, the light-emitting device according to any one of the first to fifth embodiments.

[0132] The driving unit 103 includes a power supply circuit for driving the light emitting unit 102 .

[0133] The power supply circuit 104 generates a power supply voltage for the drive unit 103 based on an input voltage from, for example, a battery (not shown) provided in the distance measuring device 101. The drive unit 103 drives the light emitting unit 102 based on the power supply voltage.

[0134] Light emitted from the light-emitting unit 102 is irradiated onto a subject S, which is the object of distance measurement, via a light-emitting side optical system 105. Then, the light thus irradiated is reflected from the subject S and enters the light-receiving surface of a light-receiving unit 107 via a light-receiving side optical system 106.

[0135] The light receiving unit 107 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 106 as described above, converts it into an electrical signal, and outputs it.

[0136] The light receiving unit 107 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 the signal processing unit 108 at the subsequent stage.

[0137] Furthermore, the light receiving unit 107 in this example outputs a frame synchronization signal Fs to the driving unit 103. This enables the driving unit 103 to cause the light emitting element 102a in the light emitting unit 102 to emit light at a timing according to the frame period of the light receiving unit 107.

[0138] The signal processing unit 108 is configured as a signal processor, for example, a DSP (Digital Signal Processor), etc. The signal processing unit 108 performs various signal processes on the digital signal input from the light receiving unit 107.

[0139] The control unit 109 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 103 to control the light emission operation by the light emitting unit 102, and controls the light receiving operation by the light receiving unit 107.

[0140] The control unit 109 has a function as a distance measuring unit 109a. The distance measuring unit 109a measures the distance to the subject S based on a signal input via the signal processing unit 108 (i.e., a signal obtained by receiving reflected light from the subject S). The distance measuring unit 109a 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.

[0141] A specific distance measurement method used by the distance measuring device 101 will be described later.

[0142] The temperature detection unit 110 detects the temperature of the light emitting unit 102. The temperature detection unit 110 may be configured to detect temperature using, for example, a diode.

[0143] In this example, information about the temperature detected by the temperature detection unit 110 is supplied to the drive unit 103, which enables the drive unit 103 to drive the light emitting unit 102 based on the temperature information.

[0144] (2) Distance Measurement Method The distance measurement method used in the distance measuring device 101 may be, for example, a structured light (STL) method or a time of flight (ToF) method.

[0145] 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.

[0146] FIG. 20 is a diagram for explaining the STL system of the sixth embodiment.

[0147] In the STL method, pattern light Lp having a dot pattern such as that shown in Fig. 20A 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 so as not to overlap between blocks BL).

[0148] FIG. 20B is an explanatory diagram of the distance measurement principle of the STL system.

[0149] In this example, a wall W and a box BX placed in front of it are treated as the subject S, and pattern light Lp is irradiated onto the subject S. "G" in the figure schematically represents the angle of view of the light receiving unit 107.

[0150] In addition, in the drawing, "BLn" 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 unit 107.

[0151] 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.

[0152] 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.

[0153] When the STL system is adopted, for example, a global shutter type IR (Infrared) light receiving unit is used as the light receiving unit 107. In the case of the STL system, the distance measuring unit 109a controls the drive unit 103 so that the light emitting unit 102 emits pattern light, detects distortion of the pattern in the image signal obtained via the signal processing unit 108, and calculates the distance based on the distortion of the pattern.

[0154] 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 unit 102, reflected by the object, and reaching the light-receiving unit 107.

[0155] When a so-called direct ToF (dToF) method is adopted as the ToF method, a SPAD (Single Photon Avalanche Diode) is used as the light receiving unit 107, and the light emitting unit 102 is pulse-driven. In this case, the distance measuring unit 109a calculates the time difference between light emission and reception of light emitted from the light emitting unit 102 and received by the light receiving unit 107, based on a signal input via the signal processing unit 108, and calculates the distance to each part of the subject S based on the time difference and the speed of light.

[0156] When a so-called indirect ToF (iToF) method (phase difference method) is adopted as the ToF method, a light receiving unit capable of receiving, for example, IR light is used as the light receiving unit 107 .

[0157] Although the light emitting devices of the first to fifth embodiments are used as light sources for the distance measuring device 101 in the sixth embodiment, they may also be used in other ways. For example, the light emitting devices of these embodiments may be used as light sources for optical devices such as printers, or may be used as lighting devices.

[0158] Seventh Embodiment Fig. 21 is a block diagram showing the configuration of a vehicle 20 according to a seventh embodiment. Fig. 21 shows an example of the configuration of a vehicle control system 20a, which is an example of a mobility device control system.

[0159] The vehicle control system 20 a is provided in the vehicle 20 and performs processing related to driving assistance and automatic driving of the vehicle 20 .

[0160] The vehicle control system 20a includes a vehicle control ECU (Electronic Control Unit) 21, a communication unit 22, a map information storage unit 23, a position information acquisition unit 24, an external recognition sensor 25, an in-vehicle sensor 26, a vehicle sensor 27, a memory unit 31, a driving assistance / autonomous driving control unit 32, a DMS (Driver Monitoring System) 33, an HMI (Human Machine Interface) 34, and a vehicle control unit 35. The external recognition sensor 25 includes, for example, the distance measuring device 101 of the sixth embodiment.

[0161] The vehicle control ECU 21, communication unit 22, map information storage unit 23, position information acquisition unit 24, external recognition sensor 25, in-vehicle sensor 26, vehicle sensor 27, memory unit 31, cruise assist / autonomous driving control unit 32, driver monitoring system (DMS) 33, human-machine interface (HMI) 34, and vehicle control unit 35 are interconnected via a communication network 41 for mutual communication. The communication network 41 is configured, for example, by an in-vehicle communication network or bus conforming to a digital bidirectional communication standard such as a Controller Area Network (CAN), a Local Interconnect Network (LIN), a Local Area Network (LAN), FlexRay (registered trademark), or Ethernet (registered trademark). Different communication networks 41 may be used depending on the type of data being transmitted. For example, a CAN may be used for data related to vehicle control, and an Ethernet may be used for large-volume data. In addition, each part of the vehicle control system 20a may be directly connected without going through the communication network 41, using wireless communication intended for communication over relatively short distances, such as near field communication (NFC) or Bluetooth (registered trademark).

[0162] In the following description, when each unit of the vehicle control system 20a communicates via the communication network 41, the description of the communication network 41 will be omitted. For example, when the vehicle control ECU 21 and the communication unit 22 communicate via the communication network 41, it will simply be described that the vehicle control ECU 21 and the communication unit 22 communicate with each other.

[0163] [Vehicle Control ECU 21] The vehicle control ECU 21 is configured by various processors such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), etc. The vehicle control ECU 21 controls all or part of the functions of the vehicle control system 20a.

[0164] [Communication Unit 22] The communication unit 22 communicates with various devices inside and outside the vehicle, other vehicles, servers, base stations, etc., and transmits and receives various data. At this time, the communication unit 22 can communicate using multiple communication methods.

[0165] The following provides an overview of communication with the outside of the vehicle that can be performed by the communication unit 22. The communication unit 22 communicates with a server (hereinafter referred to as an external server) or the like on an external network via a base station or an access point using a wireless communication method such as 5G (fifth generation mobile communication system), LTE (Long Term Evolution), or DSRC (Dedicated Short Range Communications). The external network with which the communication unit 22 communicates is, for example, the Internet, a cloud network, or a network specific to a carrier. The communication method used by the communication unit 22 with the external network is not particularly limited as long as it is a wireless communication method that enables digital two-way communication at a communication speed equal to or higher than a predetermined distance.

[0166] Furthermore, for example, the communication unit 22 can communicate with a terminal located near the vehicle using P2P (Peer to Peer) technology. The terminal located near the vehicle can be, for example, a terminal worn by a mobile object moving at a relatively slow speed, such as a pedestrian or a bicycle, a terminal installed at a fixed location in a store, or an MTC (Machine Type Communication) terminal. Furthermore, the communication unit 22 can also perform V2X communication. V2X communication refers to communication between the vehicle and others, such as vehicle-to-vehicle communication with another vehicle, vehicle-to-infrastructure communication with a roadside unit, vehicle-to-home communication, and vehicle-to-pedestrian communication with a terminal carried by a pedestrian.

[0167] The communication unit 22 can receive, for example, a program for updating software that controls the operation of the vehicle control system 20a from the outside (over the air). The communication unit 22 can also receive map information, traffic information, information about the surroundings of the vehicle 20, and the like from the outside. For example, the communication unit 22 can also transmit information about the vehicle 20 and the surroundings of the vehicle 20 to the outside. Information about the vehicle 20 that the communication unit 22 transmits to the outside includes, for example, data indicating the status of the vehicle 20 and the recognition result by the recognition unit 73. Furthermore, for example, the communication unit 22 performs communication corresponding to a vehicle emergency notification system such as e-call.

[0168] For example, the communication unit 22 receives electromagnetic waves transmitted by a road traffic information and communication system (VICS (Vehicle Information and Communication System) (registered trademark)) such as a radio beacon, an optical beacon, or FM multiplex broadcasting.

[0169] The following provides an overview of communication with the vehicle interior that can be performed by the communication unit 22. The communication unit 22 can communicate with each device in the vehicle using, for example, wireless communication. The communication unit 22 can communicate with each device in the vehicle using a communication method that enables bidirectional digital communication at a predetermined communication speed or higher via wireless communication, such as wireless LAN, Bluetooth, NFC, or Wireless USB (WUSB). The communication unit 22 can also communicate with each device in the vehicle using wired communication. For example, the communication unit 22 can communicate with each device in the vehicle using wired communication via a cable connected to a connection terminal (not shown). The communication unit 22 can communicate with each device in the vehicle using a communication method that enables bidirectional digital communication at a predetermined communication speed or higher via wired communication, such as Universal Serial Bus (USB), High-Definition Multimedia Interface (HDMI) (registered trademark), or Mobile High-Definition Link (MHL).

[0170] Here, the in-vehicle device refers to, for example, a device in the vehicle that is not connected to the communication network 41. Possible in-vehicle devices include, for example, a mobile device or wearable device carried by a passenger such as a driver, and an information device brought into the vehicle and temporarily installed therein.

[0171] [Map Information Storage Unit 23] The map information storage unit 23 stores one or both of a map acquired from an external source and a map created by the vehicle 20. For example, the map information storage unit 23 stores a three-dimensional high-precision map, a global map that is less accurate than a high-precision map and covers a wide area, and the like.

[0172] Examples of high-precision maps include dynamic maps, point cloud maps, and vector maps. A dynamic map is a map consisting of four layers of dynamic information, quasi-dynamic information, quasi-static information, and static information, and is provided to the vehicle 20 from an external server or the like. A point cloud map is a map made up of a point cloud (point group data). A vector map is a map that corresponds traffic information such as the positions of lanes and traffic lights to the point cloud map and is adapted to an advanced driver assistance system (ADAS) or autonomous driving (AD).

[0173] The point cloud map and the vector map may be provided, for example, from an external server or the like, or may be created in the vehicle 20 based on sensing results from the camera 51, radar 52, LiDAR 53, etc. as a map for matching with a local map described later, and stored in the map information storage unit 23. Furthermore, when a high-precision map is provided from an external server or the like, map data of, for example, an area of ​​several hundred square meters relating to the planned route along which the vehicle 20 will travel is acquired from the external server or the like in order to reduce communication capacity.

[0174] [Location Information Acquisition Unit 24] The location information acquisition unit 24 receives GNSS (Global Navigation Satellite System) signals from satellites and acquires location information of the vehicle 20. The acquired location information is supplied to the driving assistance / autonomous driving control unit 32. Note that the location information acquisition unit 24 is not limited to a method using GNSS signals, and may acquire location information using a beacon, for example.

[0175] [External Recognition Sensor 25] The external recognition sensor 25 includes various sensors used to recognize the situation outside the vehicle 20, and supplies sensor data from each sensor to each part of the vehicle control system 20a. The type and number of sensors included in the external recognition sensor 25 are arbitrary.

[0176] For example, the external recognition sensor 25 includes a camera 51, a radar 52, a LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) 53, and an ultrasonic sensor 54. Without being limited to this, the external recognition sensor 25 may be configured to include one or more types of sensors selected from the camera 51, the radar 52, the LiDAR 53, and the ultrasonic sensor 54. The number of cameras 51, radars 52, LiDARs 53, and ultrasonic sensors 54 is not particularly limited as long as the number is a number that can be realistically installed on the vehicle 20. Furthermore, the types of sensors included in the external recognition sensor 25 are not limited to this example, and the external recognition sensor 25 may include other types of sensors. Examples of sensing areas of each sensor included in the external recognition sensor 25 will be described later.

[0177] The imaging method of the camera 51 is not particularly limited. For example, cameras of various imaging methods capable of distance measurement, such as a time-of-flight (ToF) camera, a stereo camera, a monocular camera, and an infrared camera, can be applied to the camera 51 as needed. However, the camera 51 may simply acquire an image without distance measurement.

[0178] Furthermore, for example, the external recognition sensor 25 may include an environmental sensor for detecting the environment of the vehicle 20. The environmental sensor is a sensor for detecting the environment such as weather, climate, brightness, etc., and may include various sensors such as a raindrop sensor, a fog sensor, a sunlight sensor, a snow sensor, and an illuminance sensor.

[0179] Furthermore, for example, the external recognition sensor 25 includes a microphone used to detect sounds around the vehicle 20 and the location of sound sources.

[0180] [In-vehicle sensor 26] The in-vehicle sensor 26 includes various sensors for detecting information inside the vehicle, and supplies sensor data from each sensor to each component of the vehicle control system 20 a. The types and number of the various sensors included in the in-vehicle sensor 26 are not particularly limited as long as they are of types and numbers that can be realistically installed in the vehicle 20.

[0181] For example, the interior sensor 26 may include one or more types of sensors selected from the group consisting of a camera, radar, a seating sensor, a steering wheel sensor, a microphone, and a biometric sensor. The camera included in the interior sensor 26 may be a camera using any of various imaging methods capable of measuring distances, such as a Time of Flight (ToF) camera, a stereo camera, a monocular camera, or an infrared camera. The camera included in the interior sensor 26 may also be a camera simply for acquiring captured images, regardless of distance measurement. The biometric sensor included in the interior sensor 26 may be provided, for example, on a seat, a steering wheel, or the like, and detect various types of biometric information of a passenger, such as a driver.

[0182] [Vehicle Sensor 27] The vehicle sensor 27 includes various sensors for detecting the state of the vehicle 20, and supplies sensor data from each sensor to each unit of the vehicle control system 20a. The types and number of the various sensors included in the vehicle sensor 27 are not particularly limited as long as they are of types and numbers that can be realistically installed on the vehicle 20.

[0183] For example, the vehicle sensor 27 includes a speed sensor, an acceleration sensor, an angular velocity sensor (gyro sensor), and an inertial measurement unit (IMU) that integrates these sensors. For example, the vehicle sensor 27 includes a steering angle sensor that detects the steering angle of the steering wheel, a yaw rate sensor, an accelerator sensor that detects the amount of accelerator pedal operation, and a brake sensor that detects the amount of brake pedal operation. For example, the vehicle sensor 27 includes a rotation sensor that detects the number of rotations of the engine or motor, an air pressure sensor that detects tire air pressure, a slip ratio sensor that detects tire slip ratio, and a wheel speed sensor that detects the rotation speed of the wheels. For example, the vehicle sensor 27 includes a battery sensor that detects the remaining battery charge and temperature, and an impact sensor that detects external impacts.

[0184] [Storage Unit 31] The storage unit 31 includes at least one of a non-volatile storage medium and a volatile storage medium, and stores data and programs. The storage unit 31 is used, for example, as an electrically erasable programmable read-only memory (EEPROM) and a random access memory (RAM). Examples of storage media that can be used include magnetic storage devices such as hard disk drives (HDDs), semiconductor storage devices, optical storage devices, and magneto-optical storage devices. The storage unit 31 stores various programs and data used by each component of the vehicle control system 20a. For example, the storage unit 31 includes an event data recorder (EDR) and a data storage system for automated driving (DSSAD), and stores information about the vehicle 20 before and after an event such as an accident, as well as information acquired by the in-vehicle sensors 26.

[0185] [Driving assistance / automatic driving control unit 32] The driving assistance / automatic driving control unit 32 controls driving assistance and automatic driving of the vehicle 20. For example, the driving assistance / automatic driving control unit 32 includes an analysis unit 61, an action planning unit 62, and an operation control unit 63.

[0186] The analysis unit 61 performs an analysis process of the vehicle 20 and the surrounding situation. The analysis unit 61 includes a self-position estimation unit 71, a sensor fusion unit 72, and a recognition unit 73.

[0187] The self-position estimation unit 71 estimates the self-position of the vehicle 20 based on the sensor data from the external recognition sensor 25 and the high-precision map stored in the map information storage unit 23. For example, the self-position estimation unit 71 generates a local map based on the sensor data from the external recognition sensor 25 and matches the local map with the high-precision map to estimate the self-position of the vehicle 20. The position of the vehicle 20 is based on, for example, the center of the rear wheel pair axle.

[0188] The local map is, for example, a three-dimensional high-precision map or an occupancy grid map created using a technology such as SLAM (Simultaneous Localization and Mapping). The three-dimensional high-precision map is, for example, the point cloud map described above. The occupancy grid map is a map in which the three-dimensional or two-dimensional space around the vehicle 20 is divided into grids of a predetermined size and the occupancy status of objects is indicated on a grid-by-grid basis. The occupancy status of objects is indicated, for example, by the presence or absence of an object and its probability of existence. The local map is also used, for example, in the detection process and recognition process of the situation outside the vehicle 20 by the recognition unit 73.

[0189] The self-position estimation unit 71 may estimate the self-position of the vehicle 20 based on the position information acquired by the position information acquisition unit 24 and the sensor data from the vehicle sensor 27 .

[0190] The sensor fusion unit 72 performs sensor fusion processing to obtain new information by combining multiple different types of sensor data (for example, image data supplied from the camera 51 and sensor data supplied from the radar 52). Methods for combining different types of sensor data include integration, fusion, and association.

[0191] The recognition unit 73 executes a detection process for detecting the situation outside the vehicle 20 and a recognition process for recognizing the situation outside the vehicle 20 .

[0192] For example, the recognition unit 73 performs detection processing and recognition processing of the situation outside the vehicle 20 based on information from the external recognition sensor 25, information from the self-position estimation unit 71, information from the sensor fusion unit 72, and the like.

[0193] Specifically, for example, the recognition unit 73 performs detection processing and recognition processing of objects around the vehicle 20. The object detection processing is, for example, processing to detect the presence or absence, size, shape, position, movement, etc. of an object. The object recognition processing is, for example, processing to recognize attributes such as the type of object, or to identify a specific object. However, the detection processing and the recognition processing are not necessarily clearly separated, and may overlap.

[0194] For example, the recognition unit 73 detects objects around the vehicle 20 by performing clustering to classify a point cloud based on sensor data from the radar 52, the LiDAR 53, or the like into clusters of points. This allows the presence, size, shape, and position of objects around the vehicle 20 to be detected.

[0195] For example, the recognition unit 73 performs tracking to follow the movement of clusters of point clouds classified by clustering, thereby detecting the movement of objects around the vehicle 20. As a result, the speed and traveling direction (movement vector) of the objects around the vehicle 20 are detected.

[0196] For example, the recognition unit 73 detects or recognizes vehicles, people, bicycles, obstacles, structures, roads, traffic lights, traffic signs, road markings, etc. based on image data supplied from the camera 51. The recognition unit 73 may also recognize the types of objects around the vehicle 20 by performing recognition processing such as semantic segmentation.

[0197] For example, the recognition unit 73 can perform recognition processing of traffic rules around the vehicle 20 based on the map stored in the map information storage unit 23, the estimation result of the self-position by the self-position estimation unit 71, and the recognition result of the objects around the vehicle 20 by the recognition unit 73. Through this processing, the recognition unit 73 can recognize the positions and states of traffic lights, the contents of traffic signs and road markings, the contents of traffic regulations, and lanes that can be traveled, etc.

[0198] For example, the recognition unit 73 can perform a recognition process of the environment around the vehicle 20. The surrounding environment that the recognition unit 73 recognizes may include the weather, temperature, humidity, brightness, and road surface conditions.

[0199] The behavior planning unit 62 creates a behavior plan for the vehicle 20. For example, the behavior planning unit 62 creates the behavior plan by performing route planning and route tracking processing.

[0200] Global path planning is a process for planning a rough route from the start to the goal. This route planning also includes a process for generating a trajectory (local path planning) that takes into account the motion characteristics of the vehicle 20 on the planned route and enables safe and smooth travel in the vicinity of the vehicle 20.

[0201] Path following is a process of planning an operation for safely and accurately traveling along a route planned by a route plan within a planned time. The behavior planning unit 62 can, for example, calculate a target speed and a target angular velocity of the vehicle 20 based on the results of this path following process.

[0202] The operation control unit 63 controls the operation of the vehicle 20 in order to realize the action plan created by the action planning unit 62 .

[0203] For example, the operation control unit 63 controls the steering control unit 81, the brake control unit 82, and the drive control unit 83 included in the vehicle control unit 35 described later to perform acceleration / deceleration control and direction control so that the vehicle 20 travels along the trajectory calculated by the trajectory plan. For example, the operation control unit 63 performs cooperative control with the aim of realizing ADAS functions such as collision avoidance or impact mitigation, following driving, vehicle speed maintenance driving, collision warning for the host vehicle, and lane departure warning for the host vehicle. For example, the operation control unit 63 performs cooperative control with the aim of automatic driving, which drives autonomously without driver operation.

[0204] [DMS 33] The DMS 33 performs processes such as authenticating the driver and recognizing the driver's state based on sensor data from the in-vehicle sensors 26 and input data input to the HMI 34 (described later). Examples of the driver's state to be recognized include physical condition, alertness, concentration, fatigue, line of sight, level of intoxication, driving operation, and posture.

[0205] The DMS 33 may be configured to perform authentication processing for passengers other than the driver and recognition processing for the conditions of the passengers. Furthermore, for example, the DMS 33 may be configured to perform recognition processing for the conditions inside the vehicle based on sensor data from the in-vehicle sensor 26. Possible conditions inside the vehicle to be recognized include, for example, temperature, humidity, brightness, and odor.

[0206] [HMI 34] The HMI 34 receives input of various data and instructions, and presents various data to the driver and the like.

[0207] The following provides an overview of data input via the HMI 34. The HMI 34 includes input devices for a person to input data. The HMI 34 generates input signals based on data, instructions, and the like input via the input devices and supplies the signals to each component of the vehicle control system 20a. The HMI 34 includes input devices such as a touch panel, buttons, switches, and levers. The HMI 34 may also include input devices that allow information to be input by voice, gestures, or other means other than manual operation. Furthermore, the HMI 34 may use, as input devices, externally connected devices such as a remote control device using infrared or radio waves, or a mobile or wearable device compatible with the operation of the vehicle control system 20a.

[0208] The presentation of data by the HMI 34 will be briefly described. The HMI 34 generates visual information, auditory information, and tactile information for the occupant or the outside of the vehicle. The HMI 34 also performs output control, controlling the output, output content, output timing, output method, etc. of each piece of generated information. The HMI 34 generates and outputs, as visual information, information indicated by images or lights, such as an operation screen, a status display of the vehicle 20, a warning display, and a monitor image showing the situation around the vehicle 20. The HMI 34 also generates and outputs, as auditory information, information indicated by sounds, such as voice guidance, warning sounds, and warning messages. The HMI 34 also generates and outputs, as tactile information, information imparted to the occupant's sense of touch by, for example, force, vibration, movement, etc.

[0209] Examples of output devices that the HMI 34 uses to output visual information include a display device that displays an image on its own to present visual information and a projector device that projects an image to present visual information. The display device may be a device that displays visual information within the occupant's field of view, such as a head-up display, a transmissive display, or a wearable device with an augmented reality (AR) function, in addition to a display device having a normal display. The HMI 34 may also use display devices included in a navigation system, an instrument panel, a camera monitoring system (CMS), an electronic mirror, a lamp, or the like provided in the vehicle 20 as output devices that output visual information.

[0210] As an output device for the HMI 34 to output auditory information, for example, an audio speaker, a headphone, or an earphone can be applied.

[0211] For example, a haptic element using haptic technology can be applied as an output device for outputting tactile information from the HMI 34. The haptic element is provided on a part of the vehicle 20 that an occupant comes into contact with, such as a steering wheel or a seat.

[0212] [Vehicle Control Unit 35] The vehicle control unit 35 controls each unit of the vehicle 20. The vehicle control unit 35 includes a steering control unit 81, a brake control unit 82, a drive control unit 83, a body system control unit 84, a light control unit 85, and a horn control unit 86.

[0213] The steering control unit 81 detects and controls the state of the steering system of the vehicle 20. The steering system includes, for example, a steering mechanism including a steering wheel, an electric power steering, etc. The steering control unit 81 includes, for example, a steering ECU that controls the steering system, an actuator that drives the steering system, etc.

[0214] The brake control unit 82 detects and controls the state of the brake system of the vehicle 20. The brake system includes, for example, a brake mechanism including a brake pedal, an antilock brake system (ABS), a regenerative brake mechanism, etc. The brake control unit 82 includes, for example, a brake ECU that controls the brake system, an actuator that drives the brake system, etc.

[0215] The drive control unit 83 detects and controls the state of the drive system of the vehicle 20. The drive system includes, for example, an accelerator pedal, a drive force generating device for generating drive force such as an internal combustion engine or a drive motor, and a drive force transmission mechanism for transmitting the drive force to the wheels. The drive control unit 83 includes, for example, a drive ECU for controlling the drive system, and an actuator for driving the drive system.

[0216] The body system control unit 84 detects and controls the states of the body system systems of the vehicle 20. The body system systems include, for example, a keyless entry system, a smart key system, a power window device, a power seat, an air conditioning system, an airbag, a seat belt, a shift lever, etc. The body system control unit 84 includes, for example, a body system ECU that controls the body system systems, an actuator that drives the body system systems, etc.

[0217] The light control unit 85 detects and controls the states of various lights of the vehicle 20. Examples of lights to be controlled include headlights, backlights, fog lights, turn signals, brake lights, projections, and bumper displays. The light control unit 85 includes a light ECU that controls the lights, an actuator that drives the lights, and the like.

[0218] The horn control unit 86 detects and controls the state of the car horn of the vehicle 20. The horn control unit 86 includes, for example, a horn ECU that controls the car horn, an actuator that drives the car horn, and the like.

[0219] Fig. 22 is a plan view showing a sensing area of ​​the vehicle 20 according to the seventh embodiment. Fig. 22 shows an example of a sensing area of ​​the camera 51, radar 52, LiDAR 53, ultrasonic sensor 54, etc. of the external recognition sensor 25 shown in Fig. 21. Note that Fig. 22 schematically shows the vehicle 20 as viewed from above, with the left end side being the front end (front) side of the vehicle 20 and the right end side being the rear end (rear) side of the vehicle 20.

[0220] [Sensing Areas 1-1F, 1-1B] Sensing area 1-1F and sensing area 1-1B are examples of sensing areas of the ultrasonic sensors 54. Sensing area 1-1F covers the periphery of the front end of the vehicle 20 with multiple ultrasonic sensors 54. Sensing area 1-1B covers the periphery of the rear end of the vehicle 20 with multiple ultrasonic sensors 54.

[0221] The sensing results in the sensing area 1-1F and the sensing area 1-1B are used, for example, for parking assistance for the vehicle 20.

[0222] [Sensing Areas 1-2F, B, L, R] Sensing area 1-2F to sensing area 1-2B show examples of sensing areas of a short-range or medium-range radar 52. Sensing area 1-2F covers a position farther in front of the vehicle 20 than sensing area 1-1F. Sensing area 1-2B covers a position farther behind the vehicle 20 than sensing area 1-1B. Sensing area 1-2L covers the periphery behind the left side of the vehicle 20. Sensing area 1-2R covers the periphery behind the right side of the vehicle 20.

[0223] The sensing results in sensing area 1-2F are used, for example, to detect vehicles, pedestrians, and the like that are present in front of the vehicle 20. The sensing results in sensing area 1-2B are used, for example, for collision prevention functions behind the vehicle 20. The sensing results in sensing area 1-2L and sensing area 1-2R are used, for example, to detect objects in blind spots on the sides of the vehicle 20.

[0224] [Sensing Areas 1-3F, B, L, R] Sensing area 1-3F to sensing area 1-3B show examples of sensing areas sensed by camera 51. Sensing area 1-3F covers a position farther in front of vehicle 20 than sensing area 1-2F. Sensing area 1-3B covers a position farther in rear of vehicle 20 than sensing area 1-2B. Sensing area 1-3L covers the periphery of the left side of vehicle 20. Sensing area 1-3R covers the periphery of the right side of vehicle 20.

[0225] The sensing results in sensing area 1-3F can be used, for example, for recognizing traffic lights and traffic signs, lane departure prevention assistance systems, and automatic headlight control systems. The sensing results in sensing area 1-3B can be used, for example, for parking assistance and surround view systems. The sensing results in sensing area 1-3L and sensing area 1-3R can be used, for example, for surround view systems.

[0226] [Sensing area 1-4] Sensing area 1-4 shows an example of the sensing area of ​​the LiDAR 53. Sensing area 1-4 covers a position farther ahead of the vehicle 20 than sensing area 1-3F. On the other hand, sensing area 1-4 has a narrower range in the left-right direction than sensing area 1-3F.

[0227] The sensing results in the sensing areas 1-4 are used to detect objects such as surrounding vehicles, for example.

[0228] [Sensing area 1-5] Sensing area 1-5 shows an example of the sensing area of ​​the long-range radar 52. Sensing area 1-5 covers a position further ahead of the vehicle 20 than sensing area 1-4. On the other hand, sensing area 1-5 has a narrower range in the left-right direction than sensing area 1-4.

[0229] The sensing results in the sensing areas 1-5 are used for, for example, adaptive cruise control (ACC), emergency braking, collision avoidance, and the like.

[0230] The sensing areas of the cameras 51, radar 52, LiDAR 53, and ultrasonic sensors 54 included in the external recognition sensor 25 may have various configurations other than those shown in FIG. 22 . Specifically, the ultrasonic sensors 54 may also sense the sides of the vehicle 20, and the LiDAR 53 may sense the rear of the vehicle 20. The installation positions of the sensors are not limited to the above-described examples. The number of each sensor may be one or more.

[0231] Although the embodiments of the present disclosure have been described above, these embodiments may be implemented with various modifications within the scope of the gist of the present disclosure. For example, two or more embodiments may be implemented in combination.

[0232] The present disclosure may also be configured as follows.

[0233] (1) A light-emitting device comprising: a plurality of active layers and a plurality of tunnel junction layers included in a light-emitting element; an anode electrode electrically connected to the light-emitting element; and a cathode electrode electrically connected to the light-emitting element, wherein the light-emitting element has an emission diameter of 30 μm or more, and the temperature at which the oscillation wavelength of the light-emitting element and the gain peak wavelength of the plurality of active layers coincide is 50° C. or less.

[0234] (2) The light-emitting device according to (1), further comprising a plurality of oxide layers and a plurality of non-oxide layers included in the light-emitting element, each non-oxide layer being provided within a corresponding oxide layer.

[0235] (3) The light-emitting device according to (2), wherein the number of the oxide layers is equal to or greater than the number of the active layers.

[0236] (4) The light-emitting device according to (2), wherein the diameter of each of the non-oxidized layers is different.

[0237] (5) The light-emitting device according to (1), wherein each active layer includes a non-insulating region and an insulating region provided around the non-insulating region.

[0238] (6) The light-emitting device according to (5), wherein the insulating region is provided near an end face of each active layer and contains impurity atoms.

[0239] (7) The light emitting device according to (5), wherein the distance between the end face of each active layer and the boundary between the insulating region and the non-insulating region is 1 μm or more.

[0240] (8) The light emitting device according to (5), wherein the light emitting element emits light such that the light intensity at the boundary between the insulating region and the non-insulating region is less than 10% of the peak light intensity.

[0241] (9) The light emitting device according to (1), wherein the light emitting element has an intra-cavity structure.

[0242] (10) The light emitting device according to (1), wherein the shape of the light emitting region of the light emitting element is circular or polygonal in plan view.

[0243] (11) The light-emitting device according to (1), wherein the half-width of the gain spectrum observed when the plurality of active layers are simultaneously excited is greater than 25 nm.

[0244] (12) The output of the light-emitting element is represented by Po [W], the number of the active layers is represented by Na [pieces], and the light-emitting area of ​​the light-emitting element is represented by Se [cm ２ ], Na≧0.0144×Po ０．４９１ ×Se －０．４８８ The light emitting device according to (1), wherein the following holds true.

[0245] (13) The output of the light-emitting element is expressed as Po [W], the number of the active layers is expressed as Na [pieces], and the light-emitting area of ​​the light-emitting element is expressed as Se [cm ２ ], Na≧0.0171×Po ０．４９１ ×Se －０．４８８ The light emitting device according to (1), wherein the following holds true.

[0246] (14) The output of the light-emitting element is represented by Po [W], the number of the active layers is represented by Na [pieces], and the light-emitting area of ​​the light-emitting element is represented by Se [cm ２ ], Na≧0.0203×Po ０．４９１ ×Se －０．４８８ The light emitting device according to (1), wherein the following holds true.

[0247] (15) The light emitting device according to (1), wherein the temperature at which the oscillation wavelength and the gain peak wavelength coincide is 30° C. or lower.

[0248] (16) The light emitting device according to (1), wherein the temperature at which the oscillation wavelength and the gain peak wavelength coincide is 10° C. or less.

[0249] (17) The light emitting device according to (1), further comprising a plurality of light emitting elements including the light emitting element.

[0250] (18) The light emitting device according to (17), wherein the plurality of light emitting elements are arranged in a one-dimensional array or a two-dimensional array.

[0251] (19) The light-emitting device according to (17), wherein the anode electrode and the cathode electrode function as an anode electrode and a cathode electrode common to the plurality of light-emitting elements.

[0252] (20) The light-emitting device according to (17), wherein the plurality of light-emitting elements are electrically connected to a plurality of anode electrodes different from one another and / or to a plurality of cathode electrodes different from one another.

[0253] (21) The light emitting device according to (17), wherein the pitch between the light emitting elements is 0.6 or more of the width of the light emitting region of each light emitting element.

[0254] (22) The light emitting device according to (17), wherein the pitch between the light emitting elements is 0.7 or more of the width of the light emitting region of each light emitting element.

[0255] 1: Substrate, 2: n-type contact layer, 3: n-type DBR, 4: Stacked film, 4a: Active layer, 4b: Oxidized layer, 4b': Non-oxidized layer, 4c: Tunnel junction layer, 5: p-type DBR, 6: p-type contact layer, 11: p-type electrode, 12: n-type electrode, 13: Passivation film, 13a: Part, 13b: Part, 13c: Part, 14: AR coating film, 15: Anode electrode, 15a: Part, 15b: Part, 15c: Part, 16: Cathode electrode, 20: Vehicle, 20a: Vehicle control system, 21: Vehicle control ECU, 22: Communication unit, 23: Map information storage unit, 24: Position information acquisition unit, 25: External recognition sensor, 26: In-vehicle sensor, 27: Vehicle sensor, 31: Memory unit, 32: Cruise assistance / autonomous driving control unit, 33: DMS, 34: HMI, 35: Vehicle control unit, 41: Communication network, 51: Camera, 52: Radar, 53: LiDAR, 54: Ultrasonic sensor, 61: Analysis unit, 62: Action planning unit, 63: Operation control unit, 71: Self-position estimation unit, 72: Sensor fusion unit, 73: Recognition unit, 81: Steering control unit, 82: Brake control unit, 83: Drive control unit, 84: Body system control unit, 85: Light control unit, 86: Horn control unit, 101: Distance measuring device, 102: Light emitting unit, 102a: Light emitting element, 103: Drive unit, 104: Power supply circuit, 105: Light emitting side optical system, 106: Light receiving side optical system, 107: Light receiving unit, 108: Signal processing unit, 109: Control unit, 109a: Distance measuring unit, 110: Temperature detection unit

Claims

1. A light-emitting device comprising a plurality of active layers and a plurality of tunnel junction layers included in a light-emitting element, an anode electrode electrically connected to the light-emitting element, and a cathode electrode electrically connected to the light-emitting element, wherein a light-emitting diameter of the light-emitting element is 30 μm or more, and a temperature at which an oscillation wavelength of the light-emitting element coincides with a gain peak wavelength of the plurality of active layers is 50° C. or less.

2. The light-emitting device according to claim 1, further comprising a plurality of oxide layers and a plurality of non-oxide layers included in the light-emitting element, wherein each non-oxide layer is provided in a corresponding oxide layer.

3. The light-emitting device according to claim 2, wherein a number of the oxide layers is equal to or greater than a number of the active layers.

4. The light-emitting device according to claim 2, wherein a diameter of each non-oxide layer is different for each non-oxide layer.

5. The light-emitting device according to claim 1, wherein each active layer includes a non-insulating region and an insulating region provided around the non-insulating region.

6. The light-emitting device according to claim 5, wherein the insulating region is provided near an end face of each active layer and contains impurity atoms.

7. The light-emitting device according to claim 5, wherein a distance between an end face of each active layer and a boundary between the insulating region and the non-insulating region is 1 μm or more.

8. The light-emitting device according to claim 5, wherein the light-emitting element emits light such that a light intensity at a boundary between the insulating region and the non-insulating region is less than 10% of a peak of the light intensity.

9. The light-emitting device according to claim 1, wherein the light-emitting element has an intracavity structure.

10. The light-emitting device according to claim 1, wherein a shape of a light-emitting region of the light-emitting element is circular or polygonal in plan view.

11. The light-emitting device according to claim 1, wherein a full width at half maximum of a gain spectrum observed when the plurality of active layers are simultaneously excited is greater than 25 nm.

12. When the output of the light-emitting element is represented by Po [W], the number of the active layers is represented by Na [pieces], and the light-emitting area of the light-emitting element is represented by Se [cm ２ , the light-emitting device according to claim 1, wherein Na ≧ 0.0144 × Po ０．４９１ × Se －０．４８８ holds true.

13. When the output of the light-emitting element is represented by Po [W], the number of the active layers is represented by Na [pieces], and the light-emitting area of the light-emitting element is represented by Se [cm ２ , Na ≧ 0.0171 × Po ０．４９１ × Se －０．４８８ is satisfied, the light-emitting device according to claim 1.

14. When the output of the light-emitting element is represented by Po [W], the number of the active layers is represented by Na [pieces], and the light-emitting area of the light-emitting element is represented by Se [cm ２ , the light-emitting device according to claim 1, wherein Na ≧ 0.0203 × Po ０．４９１ × Se －０．４８８ is satisfied.

15. The light-emitting device according to claim 1, wherein a temperature at which the oscillation wavelength coincides with the gain peak wavelength is 30° C. or less.

16. The light-emitting device according to claim 1, further comprising a plurality of light-emitting elements including the light-emitting element.

17. The light-emitting device according to claim 16, wherein the plurality of light-emitting elements are arranged in a one-dimensional array or a two-dimensional array.

18. The light-emitting device according to claim 16, wherein the anode electrode and the cathode electrode function as a common anode electrode and a common cathode electrode for the plurality of light-emitting elements.

19. The light-emitting device according to claim 16, wherein the plurality of light-emitting elements are electrically connected to a plurality of anode electrodes different from each other and / or are electrically connected to a plurality of cathode electrodes different from each other.

20. The light-emitting device according to claim 16, wherein the pitch between the light-emitting elements is 0.6 or more times the width of the light-emitting region of each light-emitting element.

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