Vertical resonator type light emitting element

Abstract

A vertical cavity type light emitting element capable of stably emitting light of a specific polarization direction is provided. The vertical cavity type light emitting element according to the present invention is characterized by having: a gallium nitride-based semiconductor substrate; a first multilayer film mirror formed on the substrate; a semiconductor structure layer including one semiconductor layer having a first conductivity type formed on the first multilayer film mirror, an active layer formed on the first semiconductor layer, and a second semiconductor layer having a second conductivity type opposite to the first conductivity type formed on the active layer; a second multilayer film mirror formed on the semiconductor structure layer and forming a resonator together with the first multilayer film mirror; and a current confinement structure formed between the first multilayer film mirror and the second multilayer film mirror and converging a current to one region of the active layer. The vertical cavity type light emitting element is further characterized in that a diffraction grating including a plurality of slit structures parallel to each other is formed in a region overlapping with the one region when viewed from a direction normal to a top surface of the bulk substrate.

Description

Technical Field

[0001] This invention relates to vertical resonator type light-emitting elements, such as vertical resonator type surface-emitting lasers (VCSELs). Background Technology

[0002] Traditionally, as a type of semiconductor laser, a vertical resonator type semiconductor surface-emitting laser (hereinafter also simply referred to as a surface-emitting laser) is known, which includes a semiconductor layer that emits light by applying a voltage and multilayer film mirrors facing each other, with the semiconductor layer inserted therebetween. For example, Patent Document 1 discloses a vertical resonator type semiconductor laser having an n-electrode and a p-electrode respectively connected to an n-type semiconductor layer and a p-type semiconductor layer.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-98328 Summary of the Invention

[0006] The problem to be solved by the present invention

[0007] For example, in a vertical resonator type light-emitting element such as a surface-emitting laser, an optical resonator is formed using opposing mirrors. For example, in a surface-emitting laser, light emitted from the semiconductor layer resonates in the optical resonator to generate laser light by applying a voltage to the semiconductor layer via electrodes.

[0008] However, as an example of the problem, the luminous efficiency of a vertical resonator type semiconductor laser element is lower than that of a horizontal resonator type semiconductor laser having a resonator in the in-plane direction of a semiconductor layer including an active layer.

[0009] Light emitted from vertical resonator semiconductor laser elements using GaN-based substrates is typically elliptically polarized or linearly polarized with different polarization directions. The polarization direction is difficult to stabilize during operation; for example, it varies depending on changes in drive current and operating temperature.

[0010] The present invention was made in view of the above-mentioned problems, and its object is to provide a vertical resonator type light-emitting element with high luminous efficiency and capable of stably emitting light in a specific polarization direction.

[0011] Solution to the problem

[0012] The vertical resonator-type light-emitting element according to the present invention includes: a gallium nitride-based semiconductor substrate; a first multilayer mirror made of a nitride semiconductor formed on the substrate; a semiconductor structure layer including a first semiconductor layer, an active layer, and a second semiconductor layer, wherein the first semiconductor layer is made of a nitride semiconductor having a first conductivity type formed on the first multilayer mirror, the active layer is made of a nitride semiconductor formed on the first semiconductor layer, and the second semiconductor layer is formed on the active layer and is made of a nitride semiconductor having a second conductivity type opposite to the first conductivity type; a second multilayer mirror formed on the semiconductor structure layer, the second multilayer mirror and the first multilayer mirror constituting a resonator; and a current limiting structure formed between the first multilayer mirror and the second multilayer mirror to concentrate current in a region of the active layer, wherein when viewed from the normal direction of the upper surface of the gallium nitride-based semiconductor substrate, a diffraction grating made of a plurality of parallel slit structures is formed in a region overlapping with said region. Attached Figure Description

[0013] Figure 1 This is a perspective view of a surface-emitting laser according to the first embodiment.

[0014] Figure 2 This is a top view of a surface-emitting laser according to the first embodiment.

[0015] Figure 3 This is a cross-sectional view of a surface-emitting laser according to the first embodiment.

[0016] Figure 4 This is a cross-sectional view of a surface-emitting laser according to the second embodiment.

[0017] Figure 5 This is a cross-sectional view of a surface-emitting laser according to the third embodiment.

[0018] Figure 6 This is a cross-sectional view of a surface-emitting laser according to the fourth embodiment.

[0019] Figure 7 This is a cross-sectional view of a surface-emitting laser according to the fifth embodiment.

[0020] Figure 8 This is a cross-sectional view of a surface-emitting laser based on a modified example. Detailed Implementation

[0021] Embodiments of the present invention will be described below. Although a semiconductor surface-emitting laser element will be used as an example in the following description, the present invention is applicable not only to surface-emitting lasers, but also to various vertical resonator type light-emitting elements, such as vertical resonator type light-emitting diodes.

[0022] Implementation Method 1

[0023] Figure 1 This is a perspective view of a vertical resonator type surface-emitting laser (VCSEL, hereinafter also simply referred to as surface-emitting laser) 10 according to Embodiment 1.

[0024] Substrate 11 is a gallium nitride-based semiconductor substrate, such as a GaN substrate. Substrate 11 is, for example, a substrate having a rectangular upper surface shape. Substrate 11 is a coreless substrate, which is manufactured such that dislocations are uniformly distributed thereon and no core is formed as an aggregate of dislocation defects.

[0025] The upper surface of substrate 11 is offset from surface C by 0.5° in the M-plane direction. The upper surface of substrate 11 is almost not offset from surface C in the A-plane direction, and the angle of offset from surface C in the A-plane direction is 0 ± 0.01°.

[0026] In the region including the central portion of the upper surface of the substrate 11, a slit groove GV1 is formed. The slit groove GV1 is a plurality of slit structures, each of which extends in the direction along the m-axis and is arranged in a grid shape.

[0027] The first multilayer reflector 13 is a semiconductor multilayer reflector made of semiconductor layers already grown on the substrate 11. The first multilayer reflector 13 is formed by alternately stacking low-refractive-index semiconductor films with AlInN composition and high-refractive-index semiconductor films with GaN composition and a refractive index higher than that of the low-refractive-index semiconductor films. In other words, the first multilayer reflector 13 is a distributed Bragg reflector (DBR) made of semiconductor material.

[0028] The first multilayer reflector 13 is formed, for example, by providing a buffer layer with GaN composition on the upper surface of the substrate 11 and alternately forming the aforementioned high refractive index semiconductor film and low refractive index semiconductor film on the buffer layer.

[0029] The semiconductor structure layer 15 is a stacked structure composed of multiple semiconductor layers formed on the first multilayer film reflector 13. The semiconductor structure layer 15 has an n-type semiconductor layer (first semiconductor layer) 17 formed on the first multilayer film reflector 13, a light-emitting layer (or active layer) 19 formed on the n-type semiconductor layer 17, and a p-type semiconductor layer (second semiconductor layer) 21 formed on the active layer 19.

[0030] The n-type semiconductor layer 17, serving as the first conductivity type semiconductor layer, is a semiconductor layer formed on the first multilayer mirror 13. The n-type semiconductor layer 17 is a semiconductor layer having GaN composition and doped with Si as an n-type impurity. The n-type semiconductor layer 17 has a prism-shaped lower portion 17A and a cylindrical upper portion 17B disposed on the lower portion 17A. Specifically, for example, the n-type semiconductor layer 17 has a cylindrical upper portion 17B protruding from the upper surface 17S of the prism-shaped lower portion 17A. In other words, the n-type semiconductor layer 17 has a frustum structure including the upper portion 17B.

[0031] The active layer 19 is formed on the upper portion 17B of the n-type semiconductor layer 17 and has a quantum well structure, which includes a well layer with InGaN composition and a blocking layer with GaN composition. In the surface-emitting laser 10, light is generated in the active layer 19.

[0032] The p-type semiconductor layer 21, which is the second conductivity type semiconductor layer, is a semiconductor layer having GaN composition formed on the active layer 19. The p-type semiconductor layer 21 is doped with Mg as a p-type impurity.

[0033] The n-electrode 23 is a metal electrode disposed on the upper surface 17S of the lower portion 17A of the n-type semiconductor layer 17 and electrically connected to the n-type semiconductor layer 17. The n-electrode 23 is formed in a ring shape to surround the upper portion 17B of the n-type semiconductor layer 17. The n-electrode 23 forms a first electrode layer that is electrically in contact with the n-type semiconductor layer 17 and provides external current to the semiconductor structure layer 15.

[0034] The insulating layer 25 is a layer made of an insulator formed on the p-type semiconductor layer 21. The insulating layer 25 is formed of a substance such as SiO2, for example, with a refractive index lower than that of the material forming the p-type semiconductor layer 21. The insulating layer 25 is formed in a ring shape on the p-type semiconductor layer 21 and has an opening (not shown) in the center portion that exposes the p-type semiconductor layer 21.

[0035] The transparent electrode 27 is a semi-transparent metal oxide film formed on the upper surface of the insulating layer 25. The transparent electrode 27 covers the entire upper surface of the insulating layer 25 and the entire upper surface of the p-type semiconductor layer 21 exposed through an opening formed in the central portion of the insulating layer 25. As the metal oxide film forming the transparent electrode 27, ITO or IZO, which is semi-transparent to light emitted from the active layer 19, can be used, for example.

[0036] The p-electrode 29 is a metal electrode formed on the transparent electrode 27. The p-electrode 29 is electrically connected via the transparent electrode 27 to the upper surface of the p-type semiconductor layer 21 exposed through an opening in the insulating layer 25. The transparent electrode 27 and the p-electrode 29 form a second electrode layer that is in electrical contact with the p-type semiconductor layer 21 and provides external current to the semiconductor structure layer 15. In this embodiment, the p-electrode 29 is formed in a ring shape along the outer edge of the upper surface of the transparent electrode 27.

[0037] The second multilayer mirror 31 is a cylindrical multilayer mirror formed on the upper surface of the transparent electrode 27 in the region surrounded by the p electrode 29. The second multilayer mirror 31 is a dielectric multilayer mirror, wherein a low-refractive-index dielectric film made of Al₂O₃ and a high-refractive-index dielectric film made of Ta₂O₅ with a refractive index higher than that of the low-refractive-index dielectric film are alternately stacked. In other words, the second multilayer mirror 31 is a distributed Bragg mirror (DBR) made of dielectric material.

[0038] Figure 2 This is a top view of the surface-emitting laser 10. As described above, the surface-emitting laser 10 has a semiconductor structure layer 15, which includes an n-type semiconductor layer 17, an active layer 19 with a circular upper surface, and a p-type semiconductor layer 21 (see above) formed on a substrate 11 having a rectangular upper surface shape. Figure 1 An insulating layer 25 and a transparent electrode 27 are formed on a p-type semiconductor layer 21. A p-electrode 29 and a second multilayer reflector 31 are formed on the transparent electrode 27.

[0039] exist Figure 2 In the middle, the axis that passes through the center of the surface-emitting laser 10 and extends along the m-axis direction of the substrate 11, that is, the direction in which the slit groove GV1 formed on the upper surface of the substrate 11 extends is axis AX1.

[0040] The insulating layer 25 has an opening 25H, which is a circular opening, exposing the p-type semiconductor layer 21 of the insulating layer 25. For example... Figure 2 As shown, when viewed from above the surface-emitting laser 10, the opening 25H is formed in the central portion of the insulating layer 25, and when viewed from above the surface-emitting laser 10, the opening 25H is covered by the second multilayer mirror 31. In other words, the opening 25H is formed in the region of the insulating layer 25 opposite to the lower surface of the second multilayer mirror 31.

[0041] The opening 25H has a circular shape with its center on the axis AX1. Therefore, the p-type semiconductor layer 21 is electrically connected to the transparent electrode 27 via the electrical contact surface 21S in the circular region exposed through the opening 25H on the upper surface of the p-type semiconductor layer 21.

[0042] like Figure 2As shown, the slits GV1 extend parallel to each other and are formed on the region opposite the electrical contact surface 21S, separated by the semiconductor structure layer 15 and the first multilayer reflector 13. In other words, the slits GV1 are formed to overlap with the electrical contact surface 21S in the normal direction of the upper surface of the substrate 11 in the top view.

[0043] Figure 3 It is along Figure 2 The image shows a cross-sectional view of the surface-emitting laser 10 taken from line 3-3. As described above, the surface-emitting laser 10 has a substrate 11 serving as a GaN substrate, and a first multilayer mirror 13 is formed on the substrate 11. Note that the lower surface of the substrate 11 may be coated with an AR coating.

[0044] The slits GV1 formed on the upper surface of the substrate 11 together with the lower surface of the first multilayer mirror 13 form a gap. In other words, the first multilayer mirror 13 is formed to cover the slits GV1, and the semiconductor material forming the first multilayer mirror 13 is not filled in the slits GV1. That is, a gap is formed between the first multilayer mirror 13 and the substrate 11 in the direction perpendicular to the axis AX1. Figure 3 A diffraction grating structure consisting of multiple gaps extending along the direction of the paper.

[0045] A semiconductor structure layer 15 is formed on the first multilayer mirror 13. The semiconductor structure layer 15 is a stack formed by sequentially forming an n-type semiconductor layer 17, an active layer 19, and a p-type semiconductor layer 21. A protrusion 21P protruding upward is formed at the center of the upper surface of the p-type semiconductor layer 21.

[0046] An insulating layer 25 is formed to cover the area except for the protrusion 21P on the upper surface of the p-type semiconductor layer 21. As described above, the insulating layer 25 is made of a material with a refractive index lower than that of the p-type semiconductor layer 21. The insulating layer 25 has an opening 25H exposing the protrusion 21P. For example, the opening 25H and the protrusion 21P have similar shapes, and the inner surface of the opening 25H and the outer surface of the protrusion 21P are in contact with each other.

[0047] The transparent electrode 27 is formed as the upper surface of the protrusion 21P exposed through the opening 25H of the insulating layer 25, covering the insulating layer 25. That is, the transparent electrode 27 is in electrical contact with the p-type semiconductor layer 21 in the area exposed through the opening 25H on the upper surface of the p-type semiconductor layer 21. In other words, the area exposed through the opening 25H on the upper surface of the p-type semiconductor layer 21 is the electrical contact surface 21S that provides electrical contact between the p-type semiconductor layer 21 and the transparent electrode 27.

[0048] As described above, the p-electrode 29 is a metal electrode and is formed along the outer edge of the upper surface of the transparent electrode 27. That is, the p-electrode 29 is in electrical contact with the transparent electrode 27. Therefore, the p-electrode 29 is in electrical contact or connected to the p-type semiconductor layer 21 via the transparent electrode 27 on the electrical contact surface 21S exposed through the opening 25H on the upper surface of the p-type semiconductor layer 21.

[0049] The second multilayer reflector 31 is formed in the region on the upper surface of the transparent electrode 27 on the opening 25H of the insulating layer 25, in other words, in the region on the electrical contact surface 21S, i.e., the central portion of the upper surface of the transparent electrode 27. The lower surface of the second multilayer reflector 31 is opposite to the upper surface of the first multilayer reflector 13, separated by the transparent electrode 27 and the semiconductor structure layer 15. Due to the arrangement of the first multilayer reflector 13 and the second multilayer reflector 31, the first multilayer reflector 13 and the second multilayer reflector 31 form a resonator OC that causes the light emitted from the active layer 19 to resonate.

[0050] In the surface-emitting laser 10, the reflectivity of the first multilayer mirror 13 is slightly lower than that of the second multilayer mirror 31. Therefore, a portion of the light resonating between the first multilayer mirror 13 and the second multilayer mirror 31 is extracted to the outside through the first multilayer mirror 13 and the substrate 11.

[0051] The operation of the surface-emitting laser 10 will be described here. In the surface-emitting laser 10, when a voltage is applied between the n-electrode 23 and the p-electrode 29, current flows in the semiconductor structure layer 15, as shown by the dashed line in the figure, and light is emitted from the active layer 19. The light emitted from the active layer 19 is repeatedly reflected between the first multilayer mirror 13 and the second multilayer mirror 31, which have slit slots GV1, to achieve a resonant state (i.e., laser oscillation).

[0052] In the surface-emitting laser 10, current is injected into the p-type semiconductor layer 21 only from the portion exposed through the opening 25H, i.e., the electrical contact surface 21S. Since the p-type semiconductor layer 21 is quite thin, the current does not diffuse in the in-plane direction of the p-type semiconductor layer 21, i.e., it does not diffuse along the in-plane direction of the semiconductor structure layer 15.

[0053] Therefore, in the surface-emitting laser 10, current is supplied only to the region directly below the electrical contact surface 21S defined by the opening 25H in the active layer 19, and light is emitted only from this region. That is, in the surface-emitting laser 10, the opening 25H has a current-limiting structure that restricts the range of current supply in the active layer 19.

[0054] In other words, in the surface-emitting laser 10, a current-limiting structure is formed between the first multilayer mirror 13 and the second multilayer mirror 31. The current-limiting structure restricts the current so that it flows only in the central region CA of the active layer 19. The central region CA is a cylindrical region with the electrical contact surface 21S as its bottom surface; that is, the current is concentrated in one region of the active layer by the current-limiting structure. The central region CA, which includes the area where the current flows in the active layer 19, is defined by the electrical contact surface 21S.

[0055] As described above, in this embodiment, the reflectivity of the first multilayer mirror 13 is lower than that of the second multilayer mirror 31. Therefore, a portion of the light resonating between the first multilayer mirror 13 and the second multilayer mirror 31 is transmitted to the slit slot GV1, and also resonates between the second multilayer mirror 31 and the slit slot GV1. A portion of the resonant light is transmitted through the first multilayer mirror 13, the slit slot GV1, and the substrate 11 to be extracted to the outside. Therefore, the surface-emitting laser 10 emits light from the lower surface of the substrate 11 in a direction perpendicular to the lower surface of the substrate 11 and the in-plane direction of each layer of the semiconductor structure layer 15. In other words, the lower surface of the substrate 11 is the light-emitting surface of the surface-emitting laser 10.

[0056] The electrical contact surface 21S of the p-type semiconductor layer 21 of the semiconductor structure layer 15 and the opening 25H of the insulating layer 25 define a light-emitting center, which serves as the center of the light-emitting region in the active layer 19, thereby defining the central axis (light-emitting center axis) AX2 of the resonator OC. The central axis AX2 of the resonator OC passes through the center of the electrical contact surface 21S of the p-type semiconductor layer 21 and extends in a direction perpendicular to the in-plane direction of the semiconductor structure layer 15.

[0057] The light-emitting region of the active layer 19 is, for example, a region with a predetermined width from which light with a predetermined intensity or greater is emitted within the active layer 19, and its center is the light-emitting center. Alternatively, the light-emitting region of the active layer 19 may be a region in which a current with a predetermined density or greater is injected, and its center is the light-emitting center. A straight line passing through the light-emitting center and perpendicular to the in-plane direction of the upper surface of the substrate 11 or each layer of the semiconductor structure layer 15 is the central axis AX2.

[0058] The light-emitting central axis AX2 is a straight line extending along the resonator length direction of the resonator OC, which is composed of the first multilayer film reflector 13 and the second multilayer film reflector 31. The central axis AX2 corresponds to the optical axis of the laser emitted from the surface-emitting laser 10.

[0059] Here, exemplary structures of the first multilayer mirror 13, the semiconductor structure layer 15, and the second multilayer mirror 31 in the surface-emitting laser 10 will be described. In this embodiment, the first multilayer mirror 13 is composed of a 1 μm GaN base layer and 42 pairs of n-GaN layers and AlInN layers formed on the upper surface of the substrate 11.

[0060] The n-type semiconductor layer 17 is an n-GaN layer with a thickness of 1580 nm. The active layer 19 is made of an active layer with a multiple quantum well structure, wherein four pairs of 4 nm GaInN layers and 5 nm GaN layers are stacked. On the active layer 19, a Mg-doped AlGaN electron blocking layer is formed, and on it, a p-type semiconductor layer 21 made of a 50 nm p-GaN layer is formed. The second multilayer mirror 31 is made by stacking 10.5 pairs of Nb₂O₅ and SiO₂. The resonant wavelength in this case is 440 nm.

[0061] The insulating layer 25 is a 20 nm thick layer made of SiO2. In other words, the protrusion 21P on the upper surface of the p-type semiconductor layer 21 protrudes 20 nm from the periphery. That is, the p-type semiconductor layer 21 has a layer thickness of 50 nm in the protrusion 21P and a layer thickness of 30 nm in other regions. The upper surface of the insulating layer 25 is configured to be positioned at the same height as the upper surface of the protrusion 21P of the p-type semiconductor layer 21. These configurations are merely examples.

[0062] The optical characteristics inside the surface-emitting laser 10 are described below. As mentioned above, in the surface-emitting laser 10, the refractive index of the insulating layer 25 is lower than that of the p-type semiconductor layer 21. Between the first multilayer mirror 13 and the second multilayer mirror 31, the layer thicknesses of the active layer 19 and the n-type semiconductor layer 17 are the same at any location in the plane of the same layer.

[0063] Accordingly, due to the difference in refractive index between the p-type semiconductor layer 21 and the insulating layer 25, the equivalent refractive index (optical distance between the first multilayer mirror 13 and the second multilayer mirror 31, and corresponding to the resonant wavelength) in the resonator OC formed between the first multilayer mirror 13 and the second multilayer mirror 31 of the surface-emitting laser 10 is different in the cylindrical central region CA with the electrical contact surface 21S as the bottom surface and the tubular peripheral region PA surrounding the central region CA.

[0064] Specifically, between the first multilayer mirror 13 and the second multilayer mirror 31, the equivalent refractive index in the peripheral region PA is lower than that in the central region CA; that is, the equivalent resonant wavelength in the central region CA is smaller than that in the peripheral region PA. Note that the position of light emission in the active layer 19 is the region directly below the opening 25H and the electrical contact surface 21S. That is, the light-emitting region in the active layer 19 is the part that overlaps with the central region CA in the active layer 19, in other words, the region that overlaps with the electrical contact surface 21S in the top view.

[0065] Therefore, in the surface-emitting laser 10, a central region CA comprising a light-emitting region including an active layer 19 and a peripheral region PA surrounding the central region CA and having a refractive index lower than that of the central region CA are formed. This reduces optical loss caused by the diffusion (radiation) of standing waves within the central region CA into the peripheral region PA. That is, a large amount of light remains in the central region CA, and the laser is extracted to the outside in this state. Thus, a large amount of light is concentrated in the central region CA around the emission center axis AX2 of the resonator OC, ensuring the generation and emission of lasers with high output and high density.

[0066] As described above, in the surface-emitting laser 10 of this embodiment, the upper surface of the substrate 11 is a surface offset from the C surface by 0.5° in the M-plane direction. When a semiconductor layer is grown on a growth surface offset towards the M-plane of the substrate 11, as in the surface-emitting laser 10 of this embodiment, the optical gain of light with a polarization direction in the m-axis direction becomes greater than that of light with polarization directions in other directions. Therefore, laser light with a polarization direction in the m-axis direction is prone to oscillation. Consequently, in the light emitted from the central region CA of the surface-emitting laser 10, a large amount of light has a polarization direction in the m-axis direction.

[0067] In the surface-emitting laser 10, a diffraction grating is formed in a region including the central portion of the upper surface of the substrate 11. The diffraction grating is composed of a hollow space formed by a plurality of grooves GV1, each groove GV1 extending in the direction along the m-axis and arranged in a grid shape.

[0068] The diffraction grating formed by the slit groove GV1 imparts high reflectivity to light with a polarization direction that extends along the m-axis of the slit groove GV1 forming the diffraction grating in the central region CA of the reflective structure formed by the first multilayer film mirror 13.

[0069] That is, due to the formation of the slit groove GV1, the reflectivity of light with polarization in the m-axis direction is higher than that of light with polarization in other polarization directions, and light with polarization in the m-axis direction may preferentially oscillate. In other words, the slit groove GV1 reduces the loss of light with polarization in the m-axis direction along the surface-emitting laser 10.

[0070] Therefore, in the surface-emitting laser 10, the semiconductor structure layer 15 is grown on the upper surface of the substrate 11 as a surface offset from the C-plane to the M-plane, and a diffraction grating structure composed of slit grooves GV1 extending along the m-axis is formed on the upper surface of the substrate 11. With this configuration, the surface-emitting laser 10 allows for the stable generation of emitted light, wherein light with a polarization direction (specifically, the polarization direction along the m-axis) is dominant.

[0071] Considering the fact that the diffraction grating structure formed by the aforementioned slit groove GV1 has high reflectivity for light with a polarization direction in the m-axis direction, the slit groove GV1 preferably has a width approximately the same as the wavelength of the light emitted from the active layer 19. Preferably, the slit grooves GV1 are arranged at intervals approximately the same as the wavelength of the light emitted from the active layer 19.

[0072] The slit groove GV1 can extend further outward from the region opposite to the opening 25H, i.e., the central region CA. The slit groove GV1 can even be located outside the central region CA.

[0073] When the surface-emitting laser 10 of Embodiment 1 was actually driven to confirm the polarization direction of the emitted light, it was confirmed that when driven by a driving current of 3mA to 13mA, under the condition of device temperature of 20°C to 80°C, emitted light in which the polarization direction in the m-axis direction is dominant can be stably obtained.

[0074] As described above, the surface-emitting laser of the present invention can achieve high luminous efficiency and stably obtain emitted light with a specific polarization direction. This is particularly effective when the emitted light from the surface-emitting laser is used in devices with optical systems employing liquid crystals or polarizers.

[0075] (Manufacturing method)

[0076] The following describes an example of a method for manufacturing a surface-emitting laser 10. First, an n-GaN substrate having an upper surface is prepared as substrate 11, which is a crystal plane inclined from the C-plane to the M-plane as described above, and a slotted groove GV1 is formed on the upper surface by exposure patterning and dry etching. Subsequently, an n-GaN layer (1 μm thick) is formed on the upper surface of substrate 11 as a base layer by metal-organic vapor phase epitaxy (MOVPE). Subsequently, an n-GaN / AlInN layer is deposited on the base layer 42 to form a first multilayer reflector 13.

[0077] Next, an n-type semiconductor layer 17 is formed by forming Si-doped n-GaN (1580 nm thick) on the first multilayer mirror 13, and then an active layer 19 is formed by stacking four pairs of layers consisting of GaInN (4 nm thick) and GaN (5 nm thick) on the n-type semiconductor layer 17.

[0078] Next, an electron blocking layer (not shown) made of Mg-doped AlGaN is formed on the active layer 19, and then a p-GaN layer (with a thickness of 50 nm) is deposited on the electron blocking layer to form a p-type semiconductor layer 21.

[0079] Next, the peripheral portions of the p-type semiconductor layer 21, the active layer 19, and the n-type semiconductor layer 17 are etched to form a mesa shape, exposing the upper surface 17S of the n-type semiconductor layer 17 in the peripheral portions. In other words, in this process, the following steps are completed: Figure 1 The semiconductor structure layer 15 includes a cylindrical portion made of an n-type semiconductor layer 17, an active layer 19, and a p-type semiconductor layer 21.

[0080] Next, the periphery of the central portion of the upper surface of the p-type semiconductor layer 21 is etched to form a protrusion 21P. Subsequently, an insulating layer 25 is formed by forming a SiO2 film on the semiconductor structure layer 15 and removing a portion of the film to form an opening 25H. In other words, SiO2 is embedded in the etched and removed portion of the upper surface of the p-type semiconductor layer 21.

[0081] Next, a transparent electrode 27 is formed by forming a 20 nm ITO film on the insulating layer 25. Then, a p electrode 29 and an n electrode 23 are formed by forming Au films on the upper surface of the transparent electrode 27 and the upper surface 17S of the n-type semiconductor layer 17, respectively.

[0082] Next, a 40 nm Nb2O5 film is formed as a spacer layer (not shown) on the transparent electrode 27, and then a second multilayer reflector 31 is formed by forming a 10.5-pair film of Nb2O5 / SiO2 as a pair on the spacer layer.

[0083] When the AR coating is applied to the back side of the substrate 11, the back side of the substrate 11 is finally polished, and then an AR coating made of Nb2O5 / SiO2 is formed on the polished surface to complete the surface emitting laser 10.

[0084] Implementation Method 2

[0085] The surface-emitting laser 40, which is embodiment 2 of the present invention, is described below. The surface-emitting laser 40 differs from the surface-emitting laser 10 in that, instead of the slit groove GV1, the slit groove GV2 is formed on the lower surface of the substrate 11, that is, on the light-emitting surface of the surface-emitting laser 40.

[0086] Figure 4 It shows along a path similar to Figure 2 The cross-sectional view of the surface-emitting laser 40, shown by the cross-sectional line, is that, corresponding to... Figure 3 The cross section.

[0087] like Figure 4 As shown, in the surface-emitting laser 40, a plurality of slits GV2 are formed in the central region CA on the lower surface of the substrate 11. In other words, the plurality of slits GV2 are formed in the region on the lower surface of the substrate 11 opposite to the opening 25H and the electrical contact surface 21S, that is, in the region where light is emitted.

[0088] In other words, in the surface-emitting laser 40, a plurality of slit grooves GV2 are formed on the lower surface of the substrate 11, and the area where they are formed overlaps with the area where the slit grooves GV1 are formed in the surface-emitting laser 10 of Embodiment 1 in the top view.

[0089] The slit grooves GV2 of the surface-emitting laser 40 are grooves that extend parallel to the axis AX1 on the lower surface of the substrate 11 and are arranged in a direction perpendicular to the axis AX1, i.e., slit-shaped recesses. That is, the slit grooves GV2 are grooves that extend parallel to each other along the m-axis direction on the lower surface of the substrate 11.

[0090] The slit groove GV2 provides similar effects to the slit groove GV1 in Embodiment 1 described above. That is, the diffraction grating formed by the slit groove GV2 provides high reflectivity for light with polarization direction in the extension direction of each slit groove GV2 forming the diffraction grating in the central region CA of the reflective structure formed by the first multilayer film mirror 13 and the substrate 11.

[0091] In other words, the diffraction grating formed by the slit groove GV2 provides a high reflectivity for light with polarization direction in the m-axis direction for the reflective structure formed by the first multilayer film mirror 13 and the substrate 11.

[0092] Therefore, due to the formation of the slit groove GV2, the reflectivity of light with polarization in the m-axis direction is higher than that of light with polarization in other polarization directions, and light with polarization in the m-axis direction may preferentially oscillate in the surface-emitting laser 40.

[0093] Therefore, by using a surface-emitting laser 40, a diffraction grating structure consisting of slit grooves GV2 is formed on the lower surface of the substrate 11 to perform further polarization control of the emitted light. Thus, similar to the surface-emitting laser 10 of Embodiment 1, emitted light in which the polarization direction is dominant can be stably obtained.

[0094] After polishing the lower surface of the substrate 11 in the final step of the manufacturing method of the surface-emitting laser 10 in Embodiment 1 described above, the slot groove GV2 can be formed by performing an etching process such as dry etching on the lower surface of the substrate 11, for example.

[0095] The slit groove GV2 can extend further outward from the region opposite to the opening 25H, i.e., the central region CA. The slit groove GV2 can even be located outside the central region CA.

[0096] Implementation Method 3

[0097] The surface-emitting laser 50, which is embodiment 3 of the present invention, is described below. The surface-emitting laser 50 differs from the surface-emitting laser 40 in that a protrusion is formed on the lower surface of the substrate 11, that is, the light-emitting surface of the surface-emitting laser 50 described in embodiment 2 and the slit groove GV2 are formed on the surface of the protrusion.

[0098] Figure 5 It shows along a path similar to Figure 2 The cross-sectional view of the surface-emitting laser 50, shown by the cross-sectional line, is that, corresponding to... Figure 3 The cross-section. For example... Figure 5 As shown, in the surface-emitting laser 50, a downwardly convex lens-shaped protrusion 51 is formed in the region of the lower surface of the substrate 11, including the region opposite to the opening 25H and the electrical contact surface 21S (i.e., the central region CA).

[0099] The protrusion 51 is in the shape of a convex lens with the central axis AX2 as shown in Embodiment 1. A plurality of slits GV2 are formed on the surface of the protrusion 51, and each slit GV2 extends along the m-axis in the same manner as the surface-emitting laser 40 in Embodiment 2.

[0100] By providing the protrusion 51, the amount of light reflected from the reflective structure formed by the first multilayer mirror 13 and the substrate 11 toward the central region CA can be increased using the surface-emitting laser 50 of Embodiment 3. Therefore, the optical oscillation efficiency in the central region CA, which is the main part of the emitted light, can be further improved using the surface-emitting laser 50.

[0101] For example, the shape of the resist can be transferred to the back side of the substrate 11 by depositing a resist with the same shape as the protrusion 51 on the back side of the substrate 11 and dry etching the entire back side of the substrate 11.

[0102] Although the protrusion 51 is described above as having a convex lens shape, the shape of the protrusion 51 can be any other shape, as long as the light reflected by the reflective structure formed by the first multilayer film reflector 13 and the substrate 11 can be collected in the central region CA. For example, the protrusion 51 can have a downwardly convex parabolic shape.

[0103] The slit groove GV2 can extend further outward from the region opposite to the opening 25H, i.e., the central region CA. The slit groove GV2 can even be located outside the central region CA. The slit groove GV2 can even extend to the outside of the protrusion 51. The slit groove GV2 can even be located outside the protrusion 51.

[0104] Implementation Method 4

[0105] The surface-emitting laser 60, which is embodiment 4 of the present invention, is described below. The surface-emitting laser 60 differs from the surface-emitting laser 10 in that a slit groove GV3 is formed on the upper surface of the first multilayer mirror 13 instead of a slit groove GV1. That is, in the surface-emitting laser 60, a hollow slit groove GV3 is formed along the interface between the first multilayer mirror 13 and the semiconductor structure layer 15.

[0106] In other words, in the surface-emitting laser 60, a hollow diffraction grating structure composed of slit grooves GV3 is formed along the interface between the first multilayer film reflector 13 and the semiconductor structure layer 15.

[0107] Figure 6 It shows along a path similar to Figure 2 The cross-sectional view of the surface-emitting laser 60, shown by the cross-sectional line, is that, corresponding to... Figure 3 The cross-section. For example... Figure 6As shown, in the surface-emitting laser 60, a plurality of slit grooves GV3 are formed in the region (i.e., the central region CA) on the lower surface of the n-type semiconductor layer 17 opposite to the opening 25H and the electrical contact surface 21S. In other words, in the surface-emitting laser 60, a plurality of slit grooves GV3 are formed on the lower surface of the n-type semiconductor layer 17, and their formation region overlaps with the region where the slit grooves GV1 of the surface-emitting laser 10 of Embodiment 1 are formed in the top view.

[0108] The slits GV3 of the surface-emitting laser 60 are as follows: each slit is parallel to axis AX1 on the upper surface of the first multilayer mirror 13 (see...). Figure 2 The groove extends and is arranged in a direction perpendicular to the axis AX1, i.e., a slit-shaped recess. That is, the slit groove GV3 is a groove that extends parallel to each other along the m-axis at the interface between the first multilayer film mirror 13 and the semiconductor structure layer 15, and forms a diffraction grating structure composed of slits extending along the m-axis.

[0109] The slit groove GV3 provides similar effects to the slit groove GV1 in Embodiment 1 described above. That is, in the central region CA of the reflective structure formed by the first multilayer mirror 13 and the substrate 11, the diffraction grating formed by the slit groove GV3 provides high reflectivity for light having a polarization direction in the extension direction of each slit groove GV3, i.e., in the m-axis direction. Therefore, due to the formation of the slit groove GV3, the reflectivity of light having a polarization direction in the m-axis direction is higher than that of light having a polarization direction in other polarization directions, and light having a polarization direction in the m-axis direction may preferentially oscillate.

[0110] Therefore, by using a surface-emitting laser 60, a diffraction grating structure composed of slit grooves GV3 is formed at the interface between the first multilayer film reflector 13 and the semiconductor structure layer 15 to perform polarization control of the emitted light. Thus, similar to the surface-emitting laser 10 of Embodiment 1, emitted light with a dominant polarization direction can be stably obtained.

[0111] In the surface-emitting laser 60, a diffraction grating structure composed of a slit groove GV3 is formed in the region between the first multilayer mirror 13 and the second multilayer mirror 31. That is, compared with the surface-emitting lasers 10, 40 and 50 of embodiments 1 to 3 described above, in the surface-emitting laser 60, the slit groove GV3 forming the diffraction grating structure is located closer to the active layer 19.

[0112] Therefore, in the surface-emitting laser 60, the intensity of light emitted from the active layer 19 in the region where the slit groove GV3 is formed is greater than the intensity in surface-emitting lasers 10, 40, and 50 of other embodiments. Consequently, more light can be reflected by the diffraction grating structure formed by the slit groove GV3, and the polarization control effect is superior to that of surface-emitting lasers of other embodiments. Therefore, in the surface-emitting laser 60, the emitted light can be stably obtained, wherein light with a single polarization direction is more dominant compared to surface-emitting lasers of other embodiments described above.

[0113] The slot GV3 can be formed as follows: A GaN layer is used as the uppermost layer of the first multilayer mirror 13, and the uppermost GaN layer is etched to form the slot GV3. Subsequently, a GaN layer is grown and planarized to cover the portion where GaN has been removed, i.e., to leave the slot GV3 unfilled. Subsequently, an n-GaN layer is grown on the planarized surface to form an n-type semiconductor layer 17.

[0114] The slit groove GV3 can extend further outward from the region opposite to the opening 25H, i.e., the central region CA. The slit groove GV3 can even be located outside the central region CA.

[0115] The diffraction grating structure formed by the slit groove GV3 does not need to have a hollow structure. That is, an embedded type (embedded structure) diffraction grating structure in which the slit groove GV3 is filled with semiconductor material can be provided.

[0116] When an embedded diffraction grating structure is provided, in the fabrication of the surface-emitting laser 60, an AlInN layer is used as the uppermost layer of the first multilayer mirror 13, and after forming a slit groove GV3 on the AlInN layer as the uppermost layer by etching, a GaN layer is grown and planarized to fill the slit groove GV3, and then an n-GaN layer is grown on the planarized surface to form an n-type semiconductor layer 17.

[0117] The slit groove GV3 can be filled with GaN or remain hollow, depending on the growth conditions used to grow the GaN layer on the slit groove GV3. Therefore, the diffraction grating structure formed by the slit groove GV3 can have an embedded structure or a hollow structure.

[0118] Of course, when the diffraction grating structure formed by the slit groove GV3 has an embedded structure, a polarization control effect similar to that of a hollow diffraction grating structure can be achieved.

[0119] Implementation Method 5

[0120] The surface-emitting laser 70, as embodiment 5 of the present invention, is described below. The surface-emitting laser 70 differs from the surface-emitting laser 10 of embodiment 1 in that, instead of the insulating layer 25, a tunnel junction structure is formed in the semiconductor structure layer 15 to form the aforementioned current-limiting structure. Specifically, the surface-emitting laser 70 differs from the surface-emitting laser 10 in the structure above the p-type semiconductor layer 21.

[0121] The surface-emitting laser 70 differs from the surface-emitting laser 10 in that it uses a slit groove GV4 formed along the interface between the semiconductor structure layer 15 and the second multilayer film reflector 75 instead of a slit groove GV1 to form a diffraction grating structure.

[0122] Figure 7 It shows along a path similar to Figure 2 The cross-sectional view of the surface-emitting laser 70, shown by the cross-sectional line, is that, corresponding to... Figure 3 The cross-section. For example... Figure 7 As shown, in the surface-emitting laser 70, a tunnel bonding layer 71 is formed on the protrusion 21P of the p-type semiconductor layer 21. That is, in the surface-emitting laser 70, the tunnel bonding layer 71 is formed in the central region CA of the semiconductor structure layer 15.

[0123] The tunnel junction layer 71 includes: a highly doped p-type semiconductor layer 71A, which is a p-type semiconductor layer formed on the p-type semiconductor layer 21 and has a higher doping concentration than the p-type semiconductor layer 21; and a highly doped n-type semiconductor layer 71B, which is an n-type semiconductor layer formed on the highly doped p-type semiconductor layer 71A and has a higher doping concentration than the n-type semiconductor layer 17.

[0124] An n-type semiconductor layer 73 is formed on the p-type semiconductor layer 21 and the tunnel bonding layer 71. The n-type semiconductor layer 73 is formed to embed the tunnel bonding layer 71 on the upper surface of the p-type semiconductor layer 21. In other words, the n-type semiconductor layer 73 is formed to cover the side surface of the protrusion 21P and the side and upper surfaces of the tunnel bonding layer 71.

[0125] The second multilayer reflector 75 is an n-type semiconductor layer formed on the upper surface of the n-type semiconductor layer 73 and having a doping concentration similar to that of the n-type semiconductor layer 17. That is, the doping concentration of the n-type semiconductor layer 73 is lower than that of the highly doped n-type semiconductor layer 71B.

[0126] The stacked structure consisting of a p-type semiconductor layer 21, a tunnel junction layer 71, and an n-type semiconductor layer 73 generates a tunneling effect in the tunnel junction layer 71 portion. As a result, in the surface-emitting laser 70, a current-limiting structure is formed between the p-type semiconductor layer 21 and the n-type semiconductor layer 73, in which current flows only in the portion of the tunnel junction layer 71 and is confined to the central region CA.

[0127] The second multilayer mirror 75 is a semiconductor multilayer mirror made of semiconductor layers formed on an n-type semiconductor layer 73. The second multilayer mirror 75 is formed by alternately stacking low-refractive-index semiconductor films with AlInN composition and high-refractive-index semiconductor films with GaN composition and a higher refractive index than the low-refractive-index semiconductor films, and thus exhibits n-type semiconductor characteristics. In other words, the second multilayer mirror 75 is a distributed Bragg reflector (DBR) made of semiconductor material.

[0128] The second n-electrode 77 is a metal electrode formed along the peripheral edge portion of the upper surface of the second multilayer mirror 75. In the surface-emitting laser 70, due to the conductive properties of the second multilayer mirror 75, current flows from the second n-electrode 77 through the second multilayer mirror 75, the n-type semiconductor layer 73, the tunnel bonding layer 71, the p-type semiconductor layer 21, the active layer 19, and the n-type semiconductor layer 17 to the n-electrode 23.

[0129] In the surface-emitting laser 70, the slit groove GV4 is a groove formed in the region directly above the tunnel bonding layer 71 on the upper surface of the n-type semiconductor layer 73 and extending in the m-axis direction. A second multilayer mirror 75 is stacked on the slit groove GV4 to cover it. That is, the interior of the slit groove GV4 is hollow, and a diffraction grating structure consisting of the hollow space is formed by the slit groove GV4.

[0130] The slit groove GV4 provides similar effects to the slit groove GV1 in Embodiment 1 described above. That is, in the central region CA of the reflective structure formed by the second multilayer mirror 75, the diffraction grating formed by the slit groove GV4 provides high reflectivity for light having a polarization direction along the m-axis direction, which is the extension direction of each slit groove GV4 forming the diffraction grating. Therefore, due to the formation of the slit groove GV4, the reflectivity of light with a polarization direction in the m-axis direction is higher than that of light with polarization directions in other polarization directions, and light with a polarization direction in the m-axis direction may preferentially oscillate.

[0131] Therefore, by using a surface-emitting laser 70, a diffraction grating structure composed of slit grooves GV4 is formed on the upper surface of the n-type semiconductor layer 73 to perform polarization control of the emitted light. Thus, similar to the surface-emitting laser 10 of Embodiment 1, emitted light with a dominant polarization direction can be stably obtained.

[0132] In the surface-emitting laser 70, a slit groove GV4 is formed along the interface between the semiconductor structure layer 15 and the second multilayer film reflector 75. That is, compared with the surface-emitting lasers 10, 40 and 50 of embodiments 1 to 3 described above, in the surface-emitting laser 70, the slit groove GV4 forming the diffraction grating structure is located closer to the active layer 19.

[0133] Therefore, in the surface-emitting laser 70, the intensity of light emitted from the active layer 19 in the region where the slit groove GV4 is formed is greater than the intensity in the surface-emitting lasers 10, 40, and 50 of embodiments 1 to 3. Therefore, the diffraction grating structure formed by the slit groove GV4 can reflect more light, and the polarization control effect described above is superior to the polarization control effect of the surface-emitting lasers in other embodiments. Therefore, in the surface-emitting laser 70, the emitted light can be stably obtained, wherein light with a single polarization direction is more dominant compared to the surface-emitting lasers of embodiments 1 to 3 described above.

[0134] The slot GV4 can be formed as follows: The slot GV4 is formed on the upper surface of the n-type semiconductor layer 73 by etching. Subsequently, an n-GaN layer, also part of the n-type semiconductor layer 73, is formed to cover the slot GV4 and planarize it. Subsequently, a second multilayer reflector 75 is formed.

[0135] The slit groove GV4 can extend not only within the central region CA, but also further outwards. The slit groove GV4 can even be located outside the central region CA.

[0136] like Figure 8 As shown, the slit groove GV4 can be formed on the lower surface of the second multilayer mirror 75. In this case, it can be formed by etching the n-AlInN layer, which is the first layer of the second multilayer mirror 75, to form the groove constituting the slit groove, then forming an n-GaN layer to cover the groove from above and planarizing the n-GaN layer, and then forming the thin film layer of the second multilayer mirror 75.

[0137] In embodiments 1 to 4 described above, an insulating layer 25 is provided to form an electrical contact surface 21S and an insulating region around the electrical contact surface 21S on the upper surface of the p-type semiconductor layer 21 to create current limitation and form a region with a low refractive index. However, instead of providing the insulating layer 25, other methods can be used to create current limitation and generate a region with a low refractive index.

[0138] For example, in the above embodiment, an insulating region, a region with a low refractive index, and an electrical contact surface 21S can be formed by etching the upper surface of the p-type semiconductor layer 21 on which the insulating layer 25 is disposed. By performing ion implantation on the upper surface of the p-type semiconductor layer 21 on which the insulating layer 25 is disposed, an insulating region, a region with a low refractive index, and an electrical contact surface 21S can be formed to produce a current-limiting effect similar to that achieved by forming the insulating layer 25 in the above embodiment. When ion implantation is performed, for example, B ions, Al ions, or oxygen ions are implanted into the p-type semiconductor layer 21.

[0139] In the above embodiment, it has been described that the upper surface of the substrate 11 is offset from the C surface by 0.5° in the M-plane direction, that is, the angle of offset from the C surface in the M-plane direction is 0.5°. However, the offset angle is not limited to this angle. When the offset angle is, for example, about 0.3° to 0.8°, the above-mentioned polarization control effect can be sufficiently obtained. When the offset angle of the upper surface of the substrate 11 is 0.8° or less, the semiconductor multilayer constituting the first multilayer reflector 13 can be formed to stably have a satisfactory reflectivity.

[0140] In the above embodiment, although a coreless substrate is used as substrate 11, a strip-core substrate can also be used. In this case, in the top view of substrate 11, the stripe direction of the core of substrate 11 and the tilt direction of the crystal plane of the upper surface of substrate 11 are parallel or perpendicular to each other. That is, in the above embodiment, the m-axis direction of substrate 11 and the stripe direction of the core of substrate 11 are parallel or perpendicular to each other.

[0141] In the above embodiment, the case where the upper surface of the substrate 11 is offset from the C surface in the M-plane direction has been described. However, the upper surface of the substrate 11 may be offset from the C surface in the A-plane direction, but hardly offset in the M-plane direction.

[0142] In this case, in order to obtain the aforementioned polarization control effect, for the same reasons as described above regarding the range of offset angles of the C-plane, the offset angle from the C-plane in the A-plane direction is preferably about 0.3° to 0.8°, and the offset angle from the C-plane to the M-plane is preferably 0 ± 0.1°. When the upper surface of the substrate 11 is offset from the C-plane to the A-plane, it should be understood that AX1 corresponds to the a-axis in the description of the shape of the electrical contact surface 21S in the above embodiment.

[0143] When the upper surface of the substrate 11 is offset from the C surface in the A-plane direction, a large amount of light with a polarization direction along the a-axis can be extracted, and the emission of light with a polarization direction other than the a-axis can be suppressed. Therefore, by using the surface-emitting laser 10, the change in the polarization direction of the light extracted from the emitting surface in the in-plane direction of the emitting surface can be suppressed.

[0144] In the above embodiments, although the case where the upper surface of the substrate 11 is offset from the C surface in the M-plane direction or the A-plane direction has been described, the upper surface of the substrate 11 does not necessarily have to be offset from the C surface. Even in this case, the diffraction grating structure formed by the above-described slit slots GV1, GV2, GV3 and GV4 causes light with a polarization direction parallel to the slit slot to oscillate preferentially, and emitted light in which light with a polarization direction parallel to the slit slot is dominant can be obtained.

[0145] In Embodiment 3, the case where a protrusion 51 is formed and a slit groove GV2 is formed on the lower surface of the protrusion 51 is described. However, in other embodiments different from Embodiment 3, the protrusion 51 may be formed on the lower surface of the substrate of the surface-emitting laser. When the protrusion 51 is formed in the surface-emitting laser of other embodiments, the protrusion 51 still produces the effect of increasing the amount of light reflected to the central region CA. That is, when the protrusion 51 is formed in the surface-emitting laser of other embodiments, the effect of further improving the optical oscillation efficiency in the central region CA, which is the main part of generating emitted light, can also be obtained.

[0146] The various values, dimensions, materials, etc. in the above embodiments are merely examples and can be appropriately selected according to the application and the surface-emitting laser to be manufactured.

[0147] Explanation of reference numerals in the attached figures

[0148] 10, 40, 50, 60, 70 surface-emitting lasers

[0149] 11 base plate

[0150] 13 First Multilayer Film Reflector

[0151] 15 Semiconductor structural layers

[0152] 17 n-type semiconductor layers

[0153] 19. Active layer

[0154] 21 p-type semiconductor layer

[0155] 23 n electrode

[0156] 25 Insulation layer

[0157] 27 Transparent Electrode

[0158] 29 p electrode

[0159] 31 Second Multilayer Film Reflector

[0160] 71 Tunnel Joint Layer

[0161] 73 n-type semiconductor layer

[0162] 75 Second Multilayer Reflector

[0163] 77 Second n-electrode

Claims

1. A vertical resonator type light-emitting element, the vertical resonator type light-emitting element comprising: Gallium nitride-based semiconductor substrates; A first multilayer reflector made of a nitride semiconductor formed on the gallium nitride-based semiconductor substrate; A semiconductor structure layer, comprising a first semiconductor layer, an active layer, and a second semiconductor layer, wherein the first semiconductor layer is made of a nitride semiconductor having a first conductivity type formed on the first multilayer film reflector, the active layer is made of a nitride semiconductor formed on the first semiconductor layer, and the second semiconductor layer is formed on the active layer and is made of a nitride semiconductor having a second conductivity type opposite to the first conductivity type; The second multilayer film reflector is formed on the semiconductor structure layer, and the second multilayer film reflector and the first multilayer film reflector constitute a resonator. as well as A current-limiting structure is formed between the first multilayer mirror and the second multilayer mirror to concentrate the current in a region of the active layer, wherein... When viewed from the normal direction of the upper surface of the gallium nitride-based semiconductor substrate, a diffraction grating is formed in the region overlapping with the aforementioned region. This diffraction grating is made of a plurality of parallel slit structures. Each of the plurality of slit structures is a recessed portion formed on the back side of the gallium nitride-based semiconductor substrate.

2. The vertical resonator type light-emitting element according to claim 1, wherein, The plurality of slit structures are formed between the first multilayer film mirror and the second multilayer film mirror.

3. The vertical resonator type light-emitting element according to claim 1, wherein, The upper surface of the gallium nitride-based semiconductor substrate is a surface offset from the C-plane to the M-plane or the A-plane. When the upper surface is offset toward the M-plane, each slit structure in the plurality of slit structures extends in the m-axis direction, and when the upper surface is offset toward the A-plane, each slit structure in the plurality of slit structures extends in the a-axis direction.

4. The vertical resonator type light-emitting element according to claim 3, wherein, When the upper surface is offset toward the M-plane, the upper surface of the gallium nitride-based semiconductor substrate is a surface offset from the C-plane to the M-plane by an angle of 0.8° or less; and when the upper surface is offset toward the A-plane, the upper surface of the gallium nitride-based semiconductor substrate is a surface offset from the C-plane to the A-plane by an angle of 0.8° or less.

5. The vertical resonator type light-emitting element according to claim 3, wherein, The gallium nitride-based semiconductor substrate is a strip-shaped core substrate, and when the upper surface is offset towards the M-plane, the core of the gallium nitride-based semiconductor substrate extends in the direction along the m-axis, and when the upper surface is offset towards the M-plane, the core of the gallium nitride-based semiconductor substrate extends in the direction along the a-axis.

6. The vertical resonator type light-emitting element according to claim 1, wherein, When viewed from the normal direction of the upper surface of the gallium nitride-based semiconductor substrate, the region of the lower surface of the gallium nitride-based semiconductor substrate that overlaps with the region has a downwardly convex lens shape.

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