Semiconductor light-emitting device

Abstract

A semiconductor light emitting device is provided that can extract high-power laser light having desired characteristics by optimizing the size of the element. [Solution] The semiconductor light-emitting device 1 has a plurality of unit light-emitting elements 2, each of which has a substrate 3, an active layer 4, a phase modulation layer 5 including a basic region 5a having a first refractive index and a plurality of modified refractive index regions 5b having a second refractive index and distributed two-dimensionally within the basic region 5a, a stacked structure K including a plurality of light emission regions F that emit laser light L generated by mode formation of light incident on the phase modulation layer 5 from the active layer 4 to the outside, and a first electrode 11 and a second electrode 12 having mutually different polarities, and the stacked structures K in the plurality of unit light-emitting elements 2 are independent of each other, and a light-emitting element array 21 is formed by arranging the plurality of unit light-emitting elements 2 two-dimensionally while spaced apart from each other.

Description

[Technical Field]

[0001] The present disclosure relates to semiconductor light emitting devices. [Background technology]

[0002] As a technology related to this type of field, for example, there is a semiconductor light-emitting device described in Non-Patent Document 1. The semiconductor light-emitting device described in Non-Patent Document 1 is a light-emitting device known as a photonic crystal surface-emitting laser (PCSEL). This semiconductor light-emitting device is configured by stacking photonic crystal layers including an active layer and a phase modulation layer on a substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-131320 [Non-patent literature]

[0004] [Non-Patent Document 1] M. Yoshida et al., “High-brightness scalable continuous-wave single-mode photonic crystal laser.” Nature 618,727-732 (2023) Summary of the Invention [Problem to be solved by the invention]

[0005] Increasing the output power of semiconductor light-emitting devices such as those described above is a challenge in terms of expanding their applications. One approach to increasing the output power of semiconductor light-emitting devices is to increase the device area. However, due to factors such as substrate warpage caused by heat generation during operation, it is believed that there is a limit to how much output power can be achieved by increasing the device area. Furthermore, simply increasing the size of the light-emitting region according to the size of the device can lead to problems such as mode competition and beam pattern distortion due to non-uniform temperature distribution within the light-emitting region.

[0006] One method for suppressing mode competition and beam pattern disturbance while increasing the area of ​​the element is to array the light-emitting regions of the element. For example, the semiconductor light-emitting element disclosed in Patent Document 1 is a light-emitting element known as an iPMSEL (integrable phase-modulating surface-emitting laser), which is capable of outputting a two-dimensional beam pattern. In this semiconductor light-emitting element, multiple light-emitting regions spaced apart from one another are arranged on a single substrate. When such an arrangement of multiple light-emitting regions is considered, mode competition and beam pattern disturbance can be suppressed. However, warping of the substrate due to heat generation during operation remains an issue.

[0007] Another approach to increasing the output power of semiconductor light-emitting devices is to array multiple semiconductor light-emitting devices. When considering an array of multiple semiconductor light-emitting devices, it is possible to arrange devices of a size that can resolve issues such as mode competition. However, if the device size is too small, the Fabry-Perot resonance mode between the device end faces becomes dominant over the diffraction effect in the photonic crystal layer, making it difficult to extract laser light in the direction perpendicular to the surface. Furthermore, the manufacturing difficulty and cost associated with aligning multiple semiconductor light-emitting devices and establishing electrical continuity between each semiconductor light-emitting device increases, potentially resulting in a reduced yield.

[0008] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a semiconductor light-emitting device that can extract high-power laser light with desired characteristics by optimizing the size of the element. [Means for solving the problem]

[0009] The gist of the present disclosure is as follows.

[0010] [1] A semiconductor light-emitting device having a plurality of unit light-emitting elements, wherein the unit light-emitting elements have a substrate, an active layer that generates light when a driving current is supplied to the unit light-emitting elements, a phase modulation layer including a basic region having a first refractive index and a plurality of modified refractive index regions that are two-dimensionally distributed within the basic region and have a second refractive index different from the first refractive index, a plurality of light-emitting regions that emit laser light generated by mode formation of the light that has entered the phase modulation layer from the active layer to the outside, and a first electrode on the light-emitting region side and a second electrode on the opposite side of the light-emitting region, the first and second electrodes having different polarities, and the stacked structures in the plurality of unit light-emitting elements are independent of each other, and a light-emitting element array is formed by arranging the plurality of unit light-emitting elements two-dimensionally while being spaced apart from each other.

[0011] In this semiconductor light-emitting device, stacked structures of unit light-emitting elements each having multiple light-emitting regions are separated from one another, and the multiple unit light-emitting elements are arranged two-dimensionally while being isolated from one another to form a light-emitting element array. In this semiconductor light-emitting device, by including multiple light-emitting regions in each unit light-emitting element whose stacked structures are separated from one another, the element size of each unit light-emitting element can be sufficiently ensured, and the influence of Fabry-Perot resonance modes between the element end faces can be reduced. Furthermore, by arranging unit light-emitting elements each having multiple light-emitting regions two-dimensionally, it is possible to extract laser light from each light-emitting region while eliminating the effects of substrate warping due to heat generation during operation and problems with mode competition. Therefore, this semiconductor light-emitting device can extract high-power laser light with desired characteristics.

[0012] [2] The semiconductor light-emitting device according to [1], wherein the light-emitting element has a heat-conductive outermost layer thermally coupled to the active layer and the phase modulation layer. In this case, heat generated in the light-emitting element during operation can be efficiently dissipated to the outside via the heat-conductive outermost layer, thereby stabilizing the output of the laser light.

[0013] [3] The semiconductor light-emitting device according to [2] further comprises a cooling section that is thermally coupled in common to the heat-conductive outermost layer of each of the plurality of unit light-emitting elements. This allows each unit light-emitting element to be efficiently cooled even when a large number of unit light-emitting elements are arranged two-dimensionally. Furthermore, by sharing the cooling section among the plurality of unit light-emitting elements, it is possible to avoid the structure of the light-emitting element array becoming complicated.

[0014] [4] The semiconductor light-emitting device according to [3], wherein the cooling section has a positioning section corresponding to each of the plurality of unit light-emitting elements, thereby improving the positional accuracy of each unit light-emitting element when a large number of unit light-emitting elements are arranged two-dimensionally.

[0015] [5] The semiconductor light-emitting device according to [4], wherein the positioning portion is a wall portion extending in the stacking direction of the laminated structure, and an insulating film is provided on the surface of the wall portion facing the laminated structure. In this case, the positioning of the unit light-emitting element can be easily performed by abutting the laminated structure against the wall portion. Furthermore, by providing an insulating film on the surface of the wall portion facing the laminated structure, the occurrence of a short circuit due to the wall portion can be prevented.

[0016] [6] The semiconductor light-emitting device according to any one of [1] to [5], wherein the light-emitting element has a conductive outermost layer electrically connected to the second electrode, in which case the light-emitting elements can be easily electrically connected to each other via the conductive outermost layer.

[0017] [7] The semiconductor light-emitting device according to [6], wherein the conductive outermost layer has a protruding portion that protrudes in a direction intersecting the stacking direction of the laminated structure. By providing the protruding portion on the conductive outermost layer, electrical connection between adjacent unit light-emitting elements can be facilitated.

[0018] [8] The semiconductor light-emitting device according to [7], wherein the adjacent light-emitting elements are electrically connected in series by connecting the protruding portion of one of the light-emitting elements to the first electrode of the other light-emitting element. With this configuration, wiring can be simplified even when a large number of light-emitting elements are arranged two-dimensionally.

[0019] [9] The semiconductor light-emitting device according to [8], wherein a current path having a current supply unit and a fuse element is formed for each of the adjacent unit light-emitting elements. With this configuration, when adjacent unit light-emitting elements are divided into a single segment, providing each segment SG with a current supply unit reduces variations in laser light output between the segments. Furthermore, providing each segment with a fuse element allows laser light output to continue from the other segments SG even if one segment fails. In this case, replacing the failed segment while the remaining segments are still operating allows laser light output to be smoothly restored. Note that "adjacent unit light-emitting elements" is not limited to a pair of adjacent unit light-emitting elements, but may also include three or more adjacent unit light-emitting elements.

[0020]

[10] The semiconductor light-emitting device according to [9], wherein the current paths of adjacent light-emitting elements are electrically connected to a common ground. With this configuration, wiring can be simplified even when a large number of light-emitting elements are arranged two-dimensionally.

[0021]

[11] The semiconductor light-emitting device according to any one of [1] to

[10] , further comprising an illumination optical system for homogenizing the laser light emitted from the light-emitting region. In this case, regardless of which of the plurality of light-emitting regions emits the laser light, the laser light can be irradiated onto the same irradiation region at the designed irradiation position. This allows for even higher output power of the semiconductor light-emitting device and increases the degree of freedom in driving the device. [Effects of the Invention]

[0022] According to the present disclosure, by optimizing the size of the element, it is possible to extract high-power laser light having desired characteristics. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 2 is a schematic cross-sectional view showing the configuration of a unit light-emitting element. [Figure 2] FIG. 2 is an enlarged plan view showing a part of a phase modulation layer. [Figure 3] FIG. 1 is a schematic plan view showing a configuration of a semiconductor light emitting device. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 2 is a schematic diagram illustrating an example of an illumination optical system. [Figure 6] FIG. 10 is a schematic diagram showing another example of an illumination optical system. [Figure 7] 1A and 1B are schematic diagrams illustrating an example of a method for driving a semiconductor light emitting device. [Figure 8] 10A and 10B are schematic diagrams showing another example of a method for driving a semiconductor light emitting device. [Figure 9] FIG. 10 is a plan view showing another example of a phase modulation layer. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, preferred embodiments of a semiconductor light emitting device according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0025] The semiconductor light-emitting device 1 according to this embodiment (see FIGS. 2 and 3) is a device equipped with a light-emitting element known as a photonic crystal surface-emitting laser (PCSEL). In this embodiment, the semiconductor light-emitting device 1 is an integrable phase-modulating surface-emitting laser (iPMSEL) capable of outputting a two-dimensional beam pattern. The semiconductor light-emitting device 1 has a plurality of unit light-emitting elements 2. Each unit light-emitting element 2 outputs a phase-controlled plane wave as laser light L in a direction intersecting the thickness direction of the unit light-emitting element 2, thereby forming an optical image of any shape.

[0026] [Configuration of unit light-emitting element] First, the light emitting element 2 constituting the semiconductor light emitting device 1 will be described. FIG. 1 is a schematic cross-sectional view showing the configuration of the light emitting element 2. As shown in FIG. 1, the light emitting element 2 has a laminated structure K including a substrate 3, an active layer 4, and a phase modulation layer 5. The substrate 3 is, for example, a semiconductor substrate. The substrate 3 is made of a compound semiconductor such as a GaAs-based semiconductor, an InP-based semiconductor, or a nitride-based semiconductor. The substrate 3 has a first surface 3a and a second surface 3b facing each other. The opposing direction of the first surface 3a and the second surface 3b is along the stacking direction of the layers in the laminated structure K.

[0027] In this embodiment, a cladding layer 6A, an active layer 4, a phase modulation layer 5, and a cladding layer 6B are stacked in this order on the first surface 3a of the substrate 3. Furthermore, a contact layer 7, an insulating layer 8, and an outermost layer 9 are stacked on the cladding layer 6B. In the example of FIG. 1, the cladding layer 6A is a cladding layer with an n-type conductivity, and the cladding layer 6B is a cladding layer with a p-type conductivity. The active layer 4 and the phase modulation layer 5 are sandwiched between the cladding layer 6A and the cladding layer 6B.

[0028] 1, the phase modulation layer 5 is disposed between the active layer 4 and the cladding layer 6B, but the phase modulation layer 5 may also be disposed between the cladding layer 6A and the active layer 4. An optical guide layer may be disposed, if necessary, between the active layer 4 and the cladding layer 6A or between the active layer 4 and the cladding layer 6B. The optical guide layer may include a carrier barrier layer for efficiently confining carriers in the active layer 4.

[0029] The cladding layer 6A, the active layer 4, the cladding layer 6B, and the contact layer 7 are made of compound semiconductors such as GaAs-based semiconductors, InP-based semiconductors, and nitride-based semiconductors. The active layer 4 has, for example, a multiple quantum well structure. The energy band gaps of the cladding layer 6A and the cladding layer 6B are larger than the energy band gap of the active layer 4. The thickness directions of the cladding layer 6A, the active layer 4, the cladding layer 6B, and the contact layer 7 are aligned with the stacking direction of each layer in the stacked structure K.

[0030] The phase modulation layer 5 is, for example, a photonic crystal layer whose refractive index changes periodically, and is optically coupled to the active layer 4. The thickness direction of the phase modulation layer 5 is aligned with the stacking direction of each layer in the stacked structure K. In the example of FIG. 1, the phase modulation layer 5 has a plurality of phase modulation regions 5A and a connection region 5B. The connection region 5B has, for example, a lattice shape in plan view. The plurality of phase modulation regions 5A are each arranged in an opening portion of the lattice-shaped connection region 5B. The planar shape of the phase modulation region 5A is, for example, a rectangular shape. The phase modulation regions 5A are arranged two-dimensionally in the in-plane direction of the phase modulation layer 5 and are optically coupled to each other.

[0031] The phase modulation region 5A and the connection region 5B are configured to include a basic region 5a having a first refractive index and a plurality of modified refractive index regions 5b having a second refractive index different from the first refractive index and distributed two-dimensionally within the basic region 5a. The basic region 5a is configured from a compound semiconductor such as a GaAs-based semiconductor, an InP-based semiconductor, or a nitride-based semiconductor. The modified refractive index regions 5b are configured from, for example, voids. The modified refractive index regions 5b may be covered by a cap layer provided on the basic region 5a. The cap layer may be, for example, a layer that constitutes part of the phase modulation layer 5 and is made of the same material as the basic region 5a.

[0032] The multiple modified refractive index regions 5b are distributed two-dimensionally in each phase modulation region 5A. Here, the multiple modified refractive index regions 5b form a lattice-like, approximately periodic structure. For example, in the case of M-point oscillation, if the equivalent refractive index of the mode is n and the lattice spacing is a, the wavelength λ selected by each phase modulation region 5A is expressed as λ = (√2) × a × n. The wavelength λ is included in the emission wavelength range of the active layer 4. Each phase modulation region 5A selects a band edge wavelength near the wavelength λ from the emission wavelengths of the active layer 4 and outputs it to the outside. Light incident on each phase modulation region 5A from the active layer 4 forms a mode according to the arrangement of the modified refractive index regions 5b in each phase modulation region 5A and is output as laser light L from the light emission region F of the second surface 3b of the substrate 3 to the outside of the unit light emitting element 2.

[0033] Fig. 2 is an enlarged plan view showing a portion of the phase modulation region 5A. Although Fig. 2 shows only one phase modulation region 5A, the other phase modulation regions 5A have the same configuration. In Fig. 2, a virtual square lattice is set for the phase modulation region 5A. Square unit constituent regions R, each centered on a lattice point O of the square lattice, are arranged two-dimensionally. The center of gravity of each unit constituent region R coincides with the lattice point O of the virtual square lattice.

[0034] One modified refractive index area 5b is provided in each unit constituent region R. The planar shape of the modified refractive index area 5b is, for example, circular. The lattice point O may be located inside or outside the modified refractive index area 5b. Each modified refractive index area 5b has a center of gravity G. In the example of FIG. 2, the center of gravity G of the modified refractive index area 5b is located on a line D set for each lattice point O. The line D passes through the lattice point O corresponding to each unit constituent region R and is inclined with respect to each side of the square lattice. With such an arrangement of the modified refractive index areas 5b, two of the four wave vectors (e.g., in-plane wave vectors ±π / a, ±a) that form the standing wave at point M are phase-modulated, while the remaining two are not, thereby forming a stable standing wave. Note that the center of gravity G of the modified refractive index area 5b in the connection region 5B coincides with the lattice point O. For example, when a virtual lattice point corresponding to M-point oscillation is set, by placing the center of gravity G of the modified refractive index area 5b at a position that coincides with the lattice point O, it is possible to create an area in which a standing wave is formed in the in-plane direction and no diffraction occurs in the direction perpendicular to the plane.

[0035] Returning to FIG. 1 , the stacked structure K of the unit light-emitting element 2 has a first electrode 11 and a second electrode 12 with opposite polarities. The first electrode 11 is, for example, an n-side electrode located on the light-emitting region F side, and is provided on the second surface 3b of the substrate 3. The first electrode 11 is ohmically connected to the substrate 3. The first electrode 11 has a plurality of openings 11a. The openings 11a are arranged so as to correspond one-to-one to the phase modulation regions 5A. When viewed from the stacking direction of the layers in the stacked structure K, the openings 11a overlap with the corresponding phase modulation regions. The planar shape of the openings 11a is, for example, rectangular. Each of the plurality of openings 11a constitutes a light-emitting region F. In this embodiment, 2 × 2 light-emitting regions F are arranged in a lattice pattern on the second surface 3b side of the substrate 3.

[0036] An anti-reflection film 13 is provided on a portion of the second surface 3b of the substrate 3 that is exposed through the opening 11a. The anti-reflection film 13 is composed of a single layer or a multilayer of a dielectric material such as silicon nitride or silicon oxide. The dielectric multilayer film can be a film formed by laminating two or more dielectric layers selected from a group of dielectric layers consisting of titanium oxide, silicon dioxide, silicon monoxide, niobium oxide, tantalum pentoxide, magnesium fluoride, titanium oxide, aluminum oxide, cerium oxide, indium oxide, and zirconium oxide. The dielectric multilayer film is formed by laminating multiple films, each having an optical film thickness of λ / 4 for light with a wavelength λ, for example.

[0037] The second electrode 12 is, for example, a p-side electrode located on the opposite side to the light emission region F, and is provided on the contact layer 7. The second electrode 12 is ohmically connected to the contact layer 7. When viewed from the stacking direction of the layers in the stacked structure K, the second electrode 12 overlaps the corresponding phase modulation region. The planar shape of the opening 11a is, for example, rectangular. The second electrodes 12 are spaced apart from each other. The second electrodes 12 are arranged so as to correspond one-to-one to the phase modulation region 5A and the light emission region F. That is, in this embodiment, 2 × 2 second electrodes 12 are arranged in a lattice pattern on the second surface 3b side of the substrate 3.

[0038] In order to narrow the current range, the contact layer 7 described above is removed by etching or the like, except for the portion where the second electrode 12 is to be provided. As a result, the contact layer 7 is divided into multiple portions corresponding to the second electrodes 12. An insulating layer 8 is provided on the surface of the cladding layer 6B in the portion where the contact layer 7 has been removed. The insulating layer 8 is made of an inorganic insulating material such as silicon nitride or silicon oxide. Note that it is not necessary to remove the contact layer 7 from the portion where the second electrode 12 is not provided. In this case, the insulating layer 8 is provided on the contact layer 7 between the second electrodes 12.

[0039] The outermost layer 9 is a heat-conductive outermost layer thermally coupled to the active layer 4 and the phase modulation layer 5. The outermost layer 9 constitutes the outermost portion of the laminated structure K on the side opposite the light-emitting region F. The outermost layer 9 is a conductive outermost layer electrically connected to the second electrode 12. The outermost layer 9 is formed, for example, by vapor deposition, so as to fill in the irregularities on the surfaces of the insulating layer 8 and the second electrode 12. In this embodiment, the outermost layer 9 is made of a material with high thermal conductivity and high electrical conductivity, such as gold, and functions as both a heat-conductive outermost layer and an electrically conductive outermost layer. The outermost layer 9 is provided on the cladding layer 6B so as to cover the contact layer 7, the insulating layer 8, and the second electrode 12. The outermost layer 9 has a protruding portion 9a protruding in a direction intersecting the stacking direction of the laminated structure K and a main portion 9b located on the cladding layer 6B.

[0040] The protruding portion 9a is used for electrically connecting the unit light emitting elements 2 to each other (details will be described later). The protruding portion 9a is made of, for example, indium solder. The main body portion 9b is made of, for example, gold. The outermost layer 9 does not necessarily have to function as both a heat-conductive outermost layer and an electrically conductive outermost layer. For example, a layer with excellent heat conductivity and electrical conductivity may be provided on the cladding layer 6B so as to cover the contact layer 7, the insulating layer 8, and the second electrode 12, and an outermost layer having only heat conductivity may be provided on this layer. In this case, the outermost part of the laminated structure K may be formed by the layer with excellent heat conductivity and electrical conductivity and the heat-conductive outermost layer.

[0041] In the light-emitting element 2 having the above configuration, when a driving current is supplied between the first electrode 11 and the second electrode 12, electrons and holes recombine in the portion of the active layer 4 directly below the second electrode 12, and light is emitted from that portion. The electrons and holes that contribute to light emission and the light output from the active layer 4 are efficiently confined between the cladding layers 6A and 6B.

[0042] Light output from the active layer 4 is incident on the phase modulation layer 5. In the phase modulation layer 5, the incident light resonates in the in-plane direction in the phase modulation region 5A, forming a mode according to the arrangement of the multiple modified refractive index regions 5b, and becomes laser light L. A portion of the laser light L passes through the substrate 3 and is output to the outside from the opening 11a, which is the light output region F. The remaining portion of the laser light L is reflected by the second electrode 12, passes through the substrate 3, and is output to the outside from the opening 11a, which is the light output region F.

[0043] In this embodiment, the second electrode 12 is electrically connected to a current path Q (see FIGS. 3 and 4) via wiring, which will be described later. Each of the current paths Q electrically connected to each segment SG can freely change the magnitude of the drive current supplied to the segment SG. Therefore, the on / off state and intensity of the laser light L emitted from each light emission region F can be set independently for each light emission region F.

[0044] [Configuration of semiconductor light-emitting device] FIG. 3 is a schematic plan view showing the configuration of a semiconductor light-emitting device. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. As shown in FIGS. 3 and 4, in the semiconductor light-emitting device 1, a light-emitting element array 21 is formed by two-dimensionally arranging a plurality of unit light-emitting elements 2 spaced apart from one another. In this embodiment, one light-emitting element array 21 is formed by arranging 2×2 unit light-emitting elements 2 in a lattice pattern. In the semiconductor light-emitting device 1, the light-emitting element array 21 is further arranged two-dimensionally. In the examples of FIGS. 3 and 4, the light-emitting element array 21 is arranged in one direction, but in an actual semiconductor light-emitting device, n×m (n and m are integers) light-emitting element arrays 21 may be arranged in a lattice pattern.

[0045] The unit light-emitting elements 2 arranged in the light-emitting element array 21 are not limited to a 2×2 arrangement, but may be arranged in an i×j arrangement (i and j are integers). The number of unit light-emitting elements arranged in the light-emitting element array 21 may differ for each light-emitting element array 21. In the semiconductor light-emitting device 1, n×m light-emitting element arrays 21 do not have to be arranged, and a single light-emitting element array 21 may be used as the semiconductor light-emitting device 1.

[0046] The stacked structures K in the plurality of unit light emitting elements 2 constituting the light emitting element array 21 are independent of each other. That is, the substrate 3, cladding layer 6A, active layer 4, phase modulation layer 5, cladding layer 6B, contact layer 7, insulating layer 8, outermost layer 9, first electrode 11, second electrode 12, antireflection film 13, and light emitting region F in the plurality of unit light emitting elements 2 are spaced apart at predetermined intervals in the arrangement direction.

[0047] The light-emitting element array 21 includes a cooling section 22 that is thermally coupled in common to the outermost layer 9 of each of the plurality of unit light-emitting elements 2. The cooling section 22 is formed, for example, by a Peltier element. The cooling section 22 may be formed, for example, by a plate-like member having pipes therein for circulating a cooling medium. In this embodiment, the cooling section 22 has positioning sections P corresponding to each of the plurality of unit light-emitting elements 2 included in the light-emitting element array 21.

[0048] The positioning portion P is formed, for example, by a wall portion Pa extending in the stacking direction of the laminated structure K of the unit light emitting element 2. In the example of FIGS. 3 and 4, the wall portion Pa is formed in a lattice shape so as to separate 2×2 unit light emitting elements 2 from each other in a plan view of the light emitting element array 21. The wall portion Pa is perpendicular to the main body portion of the cooling portion 22 (the portion bonded to the outermost layer 9) and extends in the stacking direction of the laminated structure K at a height reaching the substrate 3. The wall portion Pa is formed, for example, by providing a recess in the main body portion of the cooling portion 22. In this case, the wall portion Pa is formed by the main body portion of the cooling portion 22.

[0049] An insulating film 23 is provided on the surface of the wall portion Pa facing the stacked structure K. The insulating film 23 is made of an inorganic insulating material such as silicon nitride or silicon oxide. In this embodiment, the insulating film 23 is provided on the entire surface of the wall portion Pa facing the stacked structure K. The unit light emitting element 2 included in the light emitting element array 21 is positioned on the cooling portion 22 by abutting one side surface of the stacked structure K (here, the side surface opposite to the protruding direction of the protruding portion 9a of the outermost layer 9) against the wall portion Pa via the insulating film 23.

[0050] Regarding the positioning of the plurality of unit light emitting elements 2 included in the light emitting element array 21, the stacked structure K of the plurality of unit light emitting elements 2 may be fabricated collectively by a semiconductor film formation process. In this case, the outermost layer 9 may be stacked on each unit light emitting element 2, a common cooling section 22 may be bonded to the outermost layer 9 of each unit light emitting element 2, and then the stacked structure K of each unit light emitting element 2 may be separated by dry etching or wet etching. According to this method, sufficient positional accuracy of the plurality of unit light emitting elements 2 included in the light emitting element array 21 can be ensured even without providing a wall section Pa to the cooling section 22.

[0051] The protruding portions 9a of the outermost layer 9 are used to electrically connect the plurality of unit light emitting elements 2 included in the light emitting element array 21. In this embodiment, a current path Q is formed for each pair of adjacent unit light emitting elements 2 among the 2×2 unit light emitting elements 2. The pair of adjacent unit light emitting elements 2 are electrically connected in series by connecting the protruding portion 9a of one unit light emitting element 2 to the first electrode 11 of the other unit light emitting element 2.

[0052] In this embodiment, a current path Q is formed for each pair of adjacent unit light emitting elements 2. The current paths Q for each pair of adjacent unit light emitting elements 2 are electrically connected to a common ground GD (see FIG. 4). Each current path Q has a current supply unit 24 and a fuse element 25. In each current path Q, the current supply unit 24 and the fuse element 25 are electrically connected in series between the first electrode 11 of one unit light emitting element 2 and the protruding portion 9a of the other unit light emitting element 2. Note that the "adjacent unit light emitting elements 2" that form the current path Q are not limited to a pair of unit light emitting elements 2 adjacent to each other, and may include a case where three or more unit light emitting elements are adjacent to each other.

[0053] The current supply unit 24 is a circuit including, for example, a power supply, a voltage converter, etc., and supplies a drive current to a pair of adjacent unit light emitting elements 2 via the first electrode 11 and the second electrode 12. The fuse element 25 is a component that stops the flow of current to the unit light emitting elements 2 when an overcurrent occurs in the current path Q due to a leak or the like. The fuse element 25 may be, for example, a bonding wire configured to break when a predetermined overcurrent flows. By providing the fuse element 25 in each current path Q of each pair of adjacent unit light emitting elements 2, it is possible to continue emitting laser light L for pairs of unit light emitting elements 2 that are not malfunctioning. A segment SG including a malfunctioning unit light emitting element 2 can be replaced while the segment SG that does not include the malfunctioning unit light emitting element 2 is still being driven.

[0054] In this embodiment, the semiconductor light-emitting device 1 further includes an illumination optical system 31 that homogenizes the laser light L emitted from the light emission region F. FIG. 5 is a schematic diagram showing an example of the illumination optical system. In the example of FIG. 5, the illumination optical system 31 is configured with a pair of fly-eye lenses 32A, 32B and a fly-eye integrator 34 that includes an illumination lens 33. The fly-eye integrator 34 is arranged, for example, in one-to-one correspondence with each of the plurality of unit light-emitting elements 2 included in the light-emitting element array 21. The laser light L emitted from the plurality of light emission regions F of the unit light-emitting element 2 is spatially spread by the fly-eye integrator 34 and forms an optical image at the designed irradiation position S with a uniform illuminance distribution.

[0055] Fig. 6 is a schematic diagram showing an example of an illumination optical system. In the example of Fig. 6, illumination optical system 31 is composed of rod lens 35 and rod integrator 36 including illumination lens 33. Rod integrator 36 is arranged so as to correspond one-to-one with each of the plurality of unit light emitting elements 2 included in light emitting element array 21, for example. Laser light L emitted from the plurality of light emission regions F of unit light emitting element 2 is spatially spread by rod integrator 36 and forms a light image with a uniform illuminance distribution in the same irradiation region at designed irradiation position S.

[0056] In the semiconductor light-emitting device 1 equipped with the illumination optical system 31, it is preferable to sequentially light up the segments SG from the viewpoint of improving the effective duty ratio when using the laser light L as the signal light. In this case, for example, as shown in FIG. 7, the segments SG may be sequentially lighted one by one. When lighting up the segments SG, it is preferable to light up a segment SG that is not adjacent to the segment SG that was previously lighted. This makes it possible to prevent the heat generated by lighting up a segment SG from affecting the next segment SG that is to be lighted.

[0057] 8, multiple (here, two) segments SG may be sequentially lit. In this case, too, in order to prevent the heat generated by lighting a light-emitting region F from affecting the next light-emitting region F to be lit, it is preferable to light a pair of light-emitting regions F that is not adjacent to the pair of light-emitting regions F that was lit immediately before.

[0058] [Action and effect] As described above, in the semiconductor light-emitting device 1, the stacked structures K of the unit light-emitting elements 2, each having a plurality of light-emitting regions F, are separated from one another, and the plurality of unit light-emitting elements 2 are arranged two-dimensionally while being isolated from one another to form the light-emitting element array 21. In the semiconductor light-emitting device 1, the stacked structures K include multiple light-emitting regions F in each of the unit light-emitting elements 2, which are separated from one another. This ensures a sufficient element size for each unit light-emitting element 2, and reduces the effects of Fabry-Perot resonance modes between the element end faces. Furthermore, by arranging the unit light-emitting elements 2, each having multiple light-emitting regions F, in a two-dimensional array, it is possible to extract laser light L from each light-emitting region F while eliminating the effects of warping of the substrate 3 due to heat generation during operation and problems with mode competition. Therefore, the semiconductor light-emitting device 1 can extract high-power laser light L with desired characteristics.

[0059] Specifically, when the element size of the unit light-emitting element 2 is approximately 500 μm×500 μm or more, the influence of the Fabry-Perot resonance mode can be effectively reduced. Also, when the element size of the unit light-emitting element 2 is approximately 20 mm×20 mm or less, warpage of the substrate can be effectively suppressed. In this case, the size of the light-emitting region F is preferably approximately 50 μm×50 μm or more and approximately 500 μm×500 μm or less.

[0060] In this embodiment, the light emitting element 2 has a heat-conductive outermost layer thermally coupled to the active layer 4 and the phase modulation layer 5. In this case, heat generated in the light emitting element 2 during operation can be efficiently released to the outside via the heat-conductive outermost layer, thereby stabilizing the output of the laser light L.

[0061] In this embodiment, the semiconductor light-emitting device 1 includes a cooling section 22 that is thermally coupled in common to the heat-conductive outermost layer of each of the plurality of unit light-emitting elements 2. This allows each unit light-emitting element 2 to be efficiently cooled even when a large number of unit light-emitting elements 2 are arranged two-dimensionally. Furthermore, by sharing the cooling section 22 with the plurality of unit light-emitting elements 2, it is possible to avoid the structure of the light-emitting element array 21 becoming complicated.

[0062] In this embodiment, the cooling section 22 has a positioning section P corresponding to each of the plurality of unit light emitting elements 2. This improves the positioning accuracy of each unit light emitting element 2 when arranging a large number of unit light emitting elements 2 two-dimensionally. In this embodiment, the positioning section P is a wall section Pa extending in the stacking direction of the stacked structure K, and an insulating film 23 is provided on the surface of the wall section Pa facing the stacked structure K. With this configuration, the unit light emitting element 2 can be easily positioned by abutting the stacked structure K against the wall section Pa. Furthermore, by providing the insulating film 23 on the surface of the wall section Pa facing the stacked structure K, it is possible to prevent short circuits caused by the wall section Pa.

[0063] In this embodiment, the light emitting element 2 has a conductive outermost layer electrically connected to the second electrode 12. In this case, the light emitting elements 2 can be easily electrically connected to each other via the conductive outermost layer. In this embodiment, the conductive outermost layer has a protruding portion 9a that protrudes in a direction intersecting the stacking direction in the stacked structure K. Providing the protruding portion 9a on the conductive outermost layer facilitates electrical connection between adjacent light emitting elements 2.

[0064] In this embodiment, adjacent unit light emitting elements 2 are electrically connected in series by connecting the protruding portion 9a of one unit light emitting element 2 to the first electrode 11 of the other unit light emitting element 2. With this configuration, wiring can be simplified even when a large number of unit light emitting elements 2 are arranged two-dimensionally.

[0065] In this embodiment, a current path Q having a current supply section 24 and a fuse element 25 is formed for each adjacent unit light emitting element 2. According to this configuration, when adjacent unit light emitting elements 2 are divided into one segment SG, by providing each segment SG with a current supply section 24, variations in the output of laser light L between the segments SG can be suppressed. Furthermore, by providing each segment SG with a fuse element 25, even if a failure occurs in one segment SG, it is possible to continue outputting laser light L from the other segments SG.

[0066] In this embodiment, the current paths Q of adjacent unit light emitting elements 2 are electrically connected to a common ground GD. With this configuration, even when a large number of unit light emitting elements 2 are arranged two-dimensionally, the wiring can be simplified.

[0067] In this embodiment, the semiconductor light emitting device 1 further includes an illumination optical system 31 that homogenizes the laser light L emitted from the segments SG. This allows the laser light L to be irradiated onto the same irradiation area at the designed irradiation position S, regardless of which of the multiple segments SG the laser light L is emitted from. This allows for even higher output from the semiconductor light emitting device 1 and increases the degree of freedom in driving the device.

[0068] [Variations] The present disclosure is not limited to the above-described embodiments. For example, in the above-described embodiments, an iPMSEL is used as an example of a PCSEL, but the present disclosure can also be applied to a normal PCSEL that does not control the phase distribution of light in the in-plane direction. In the case of a normal PCSEL, as shown in FIG. 9, in the phase modulation region 5A, the center of gravity G of the modified refractive index region 5b is positioned so as to overlap with a virtual lattice point O corresponding to, for example, Γ-point oscillation.

[0069] 8, the planar shape of the modified refractive index area 5b is a right-angled isosceles triangle. The planar shape of the modified refractive index area 5b, including in the case of an iPMSEL, can take various forms, such as a perfect circle, an ellipse, a rectangle, or a polygon. The shape of the virtual lattice, including in the case of an iPMSEL, is also not limited to a square lattice, and can take various forms, such as a rectangular lattice, a triangular lattice, a face-centered rectangular lattice, or a honeycomb lattice.

[0070] The lattice constant of the photonic crystal layer (phase modulation layer 5) may be different for each unit light emitting element 2. In this case, it is possible to reduce the influence of variations in the wavelength of light generated in the active layer 4, which is fabricated by epitaxial growth or the like, among the unit light emitting elements 2. Each of the plurality of light emitting element arrays 21 included in the semiconductor light emitting device 1 may be provided with an electrode pad for probe testing. In this case, an electrical test can be easily performed on each of the light emitting element arrays 21. In addition, a mechanism for blowing dry nitrogen toward the plurality of light emitting element arrays 21 included in the semiconductor light emitting device 1 may be provided.

[0071] The semiconductor light-emitting device 1 may include a holding substrate that holds a plurality of light-emitting element arrays 21 arranged two-dimensionally. In this case, an airtight package may be formed with the holding substrate as part of the wall. In the airtight package, a gap between the holding substrate and the semiconductor light-emitting device may be sealed with resin. A cooling means may be provided inside the airtight package in close contact with the holding substrate. Examples of the cooling means in this case include a Peltier element and a cooling pipe through which a cooling medium such as water flows.

[0072] In the above embodiment, the current path Q is formed for each pair of adjacent unit light emitting elements 2 among the 2×2 unit light emitting elements 2, but the manner in which the current path Q is formed in the light emitting element array 21 is not limited to this. For example, the current path Q may be formed for each of the plurality of unit light emitting elements 2 included in the light emitting element array 21, or the current path Q may be formed by electrically connecting all of the plurality of unit light emitting elements 2 included in the light emitting element array 21 in series. [Explanation of symbols]

[0073] 1...semiconductor light-emitting device, 2...unit light-emitting element, 3...substrate, 4...active layer, 5...phase modulation layer, 5a...basic region, 5b...modified refractive index region, 9...outermost layer (heat-conductive outermost layer, conductive outermost layer), 9a...extending portion, 9b...main body portion, 11...first electrode, 12...second electrode, 21...light-emitting element array, 22...cooling portion, 23...insulating film, 24...current supply portion, 25...fuse element, 31...illumination optical system, F...light emission region, K...laminated structure, L...laser light, P...positioning portion, Pa...wall portion, Q...current path, S...irradiation position, SG...segment, G...center of gravity, GD...ground.

Claims

1. A semiconductor light emitting device having a plurality of unit light emitting elements, The unit light emitting element is A substrate; an active layer that generates light when a driving current is applied; a phase modulation layer including a basic region having a first refractive index and a plurality of modified refractive index regions having a second refractive index different from the first refractive index and two-dimensionally distributed within the basic region; a plurality of light emitting regions for emitting laser light generated by mode formation of the light incident from the active layer to the phase modulation layer to the outside; a laminated structure including a first electrode on the light emitting region side and a second electrode on the opposite side to the light emitting region, the first electrode having polarities different from each other; the stacked structures in the plurality of unit light emitting elements are independent of each other, The semiconductor light emitting device has a light emitting element array configured by arranging the plurality of unit light emitting elements spaced apart from one another in a two-dimensional manner.

2. 2. The semiconductor light emitting device according to claim 1, wherein the unit light emitting element has a heat conductive outermost layer thermally coupled to the active layer and the phase modulation layer.

3. 3. The semiconductor light emitting device according to claim 2, further comprising a cooling portion thermally coupled in common to the heat conductive outermost layer of each of the plurality of unit light emitting elements.

4. 4. The semiconductor light emitting device according to claim 3, wherein said cooling section has positioning portions corresponding to each of said plurality of unit light emitting elements.

5. the positioning portion is a wall portion extending in the stacking direction of the stacked structure, The semiconductor light emitting device according to claim 4 , wherein an insulating film is provided on a surface of said wall portion facing said laminated structure.

6. 2. The semiconductor light emitting device according to claim 1, wherein said unit light emitting element has a conductive outermost layer electrically connected to said second electrode.

7. 7. The semiconductor light emitting device according to claim 6, wherein the outermost conductive layer has a protruding portion that protrudes in a direction intersecting the stacking direction of the stacked structure.

8. 8. The semiconductor light emitting device according to claim 7, wherein adjacent light emitting elements are electrically connected in series by connecting the protruding portion of one light emitting element to the first electrode of the other light emitting element.

9. 9. The semiconductor light emitting device according to claim 8, wherein a current path having a current supply portion and a fuse element is formed for each of the adjacent unit light emitting elements.

10. 10. The semiconductor light emitting device according to claim 9, wherein the current paths of adjacent light emitting elements are electrically connected to a common ground.

11. 11. The semiconductor light emitting device according to claim 1, further comprising an illumination optical system that homogenizes the laser light emitted from the light emitting region.

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