A gallium nitride laser and a method for improving its lateral mode based on a counter waveguide

Abstract

This application discloses a gallium nitride (GaN) laser and a method for improving its lateral modes based on an anti-waveguide. The method includes: processing the epitaxial structure of the GaN laser to remove a contact layer, a second optical confinement layer, and a portion of the second waveguide layer, thereby forming a ridge structure; and depositing a high-refractive-index thin film on at least a portion of the surface of the second waveguide layer surrounding the ridge structure to form an anti-waveguide structure. By forming the anti-waveguide structure in the GaN laser, this application enables modulation of the effective refractive index in regions other than the ridge structure, providing an effective means of modulating the effective refractive index difference between the ridge structure and the regions outside it. Furthermore, by adjusting the magnitude of this effective refractive index difference, the generation of more higher-order modes can be suppressed, reducing beam quality M. 2 This factor significantly improves the spot quality of gallium nitride lasers.

Description

Technical Field

[0001] This application relates to a gallium nitride (GaN) laser, specifically to a method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide, thereby improving its beam quality, belonging to the field of semiconductor technology. Background Technology

[0002] Semiconductor lasers based on gallium nitride (GaN) and other group III nitrides have important applications in laser display, laser lighting, laser communication, materials processing and laser medicine, and have therefore attracted widespread attention from well-known domestic and foreign companies and top global research institutions.

[0003] Since Nichia Corporation of Japan developed the world's first gallium nitride laser in 1996, the output power, electro-optical conversion efficiency and other performance aspects of gallium nitride lasers have been greatly improved. However, beam quality, one of the important performance characteristics of gallium nitride lasers, has not been significantly improved.

[0004] Generally, the beam quality of a laser is determined by its beam quality factor (also known as M). 2 The diffraction limit factor (DPP) is evaluated by dividing the product of the actual beam waist width and the far-field divergence angle by the product of the beam waist width and the far-field divergence angle of the fundamental mode Gaussian beam. Ideally, M... 2 The factor equals 1. However, the beam quality M of narrow-ridge lasers currently only possessing the fundamental mode is... 2 The factor can reach 1.

[0005] For a laser with a side-emitting ridge structure, a relatively ideal M-wave structure can be achieved by adjusting the epitaxial layer structure of the laser in the vertical direction. 2 While the output power of gallium nitride lasers can be increased by increasing the ridge width, this is limited by the narrow ridge width and catastrophic optical damage in the lateral direction, preventing the injection of sufficiently large current and thus hindering the achievement of high-power fundamental transverse mode output. Currently, although the output power of gallium nitride lasers can be increased by increasing the ridge width, this leads to the generation of more higher-order transverse modes in the lateral direction and multilobes in the far field. 2 As the factor increases, the beam quality deteriorates. Summary of the Invention

[0006] The main objective of this application is to provide a gallium nitride laser and a method for improving its lateral mode based on an anti-waveguide, so as to overcome the aforementioned problems existing in the prior art.

[0007] In order to achieve the aforementioned objectives, this application adopts the following approach:

[0008] One aspect of this application provides a method for improving the lateral mode of a gallium nitride laser based on an anti-waveguide, comprising:

[0009] An epitaxial structure for a gallium nitride laser is provided, the epitaxial structure comprising a first optical confinement layer, a first waveguide layer, a light-emitting active layer, a second waveguide layer, a second optical confinement layer, and a contact layer stacked sequentially along a specified direction;

[0010] The epitaxial structure is processed to partially remove the contact layer, the second optical confinement layer, and the second waveguide layer, thereby forming the ridge structure of the gallium nitride laser. The height of the ridge structure is less than the sum of the thicknesses of the contact layer, the second optical confinement layer, and the second waveguide layer.

[0011] A high-refractive-index thin film is disposed on at least a portion of the surface of the second waveguide layer surrounding the ridge structure to form an anti-waveguide structure.

[0012] Another aspect of this application provides a gallium nitride laser, including an epitaxial structure and a first electrode and a second electrode cooperating with the epitaxial structure. The epitaxial structure includes a first optical confinement layer, a first waveguide layer, a light-emitting active layer, a second waveguide layer, a second optical confinement layer, and a contact layer sequentially disposed along a specified direction. The contact layer, the second optical confinement layer, and a portion of the second waveguide layer cooperate to form a ridge structure, and the height of the ridge structure is less than the sum of the thicknesses of the contact layer, the second optical confinement layer, and the second waveguide layer. The laser further includes an anti-waveguide structure comprising a high-refractive-index thin film, which is deposited on at least a portion of the surface of the second waveguide layer surrounding the ridge structure.

[0013] Compared with existing technologies, this application achieves modulation of the effective refractive index of the region outside the ridge structure of a gallium nitride laser by inserting a high refractive index layer to form an anti-waveguide structure. This provides an effective means of modulating the effective refractive index difference between the ridge structure and the region outside it. Furthermore, by adjusting the magnitude of this effective refractive index difference, the generation of more higher-order modes can be suppressed, and the beam quality M can be reduced. 2 This factor significantly improves the spot quality of gallium nitride lasers. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the epitaxial structure of a gallium nitride laser in Example 1;

[0016] Figure 2 Based on Figure 1 A schematic diagram of the ridge structure of the laser formed by epitaxial structure processing is shown.

[0017] Figure 3 Is Figure 2 A schematic diagram showing the formation of a high-refractive-index thin film on the device structure shown;

[0018] Figure 4 Is Figure 3 A schematic diagram showing the formation of an insulating dielectric film and a first electrode on the device structure shown;

[0019] Figure 5 Is Figure 4 The diagram shows a second electrode disposed on the device structure. Detailed Implementation

[0020] Given the lack of effective solutions in the existing technology to improve the beam quality of gallium nitride lasers, the applicant has conducted extensive research and practice to propose the technical solution of this application, which will be explained in detail below.

[0021] Some embodiments of this application provide a method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide, including:

[0022] An epitaxial structure for a gallium nitride laser is provided, the epitaxial structure comprising a first optical confinement layer, a first waveguide layer, a light-emitting active layer, a second waveguide layer, a second optical confinement layer, and a contact layer stacked sequentially along a specified direction;

[0023] The epitaxial structure is processed to partially remove the contact layer, the second optical confinement layer, and the second waveguide layer, thereby forming the ridge structure of the gallium nitride laser. The height of the ridge structure is less than the sum of the thicknesses of the contact layer, the second optical confinement layer, and the second waveguide layer.

[0024] A high-refractive-index thin film is disposed on at least a portion of the surface of the second waveguide layer surrounding the ridge structure to form an anti-waveguide structure, wherein the refractive index of the high-refractive-index thin film is at least greater than the refractive index of the ridge structure.

[0025] In this application, the "specified direction" is determined by the orientation of the extension structure in space. It can be a direction from top to bottom or from bottom to top, or from left to right or from right to left, from front to back or from back to front, etc., and is not limited to these.

[0026] In one embodiment, the material of the high refractive index film includes, but is not limited to, any one of polycrystalline silicon or amorphous silicon, polycrystalline germanium or amorphous germanium, polycrystalline gallium arsenide or amorphous gallium arsenide.

[0027] In one embodiment, the thickness of the high refractive index film is 0.005 μm to 0.2 μm, preferably 0.02 μm to 0.1 μm, and more preferably 0.05 μm to 0.1 μm.

[0028] In one embodiment, the area of ​​the second waveguide layer surface surrounding the ridge structure is covered by a high-refractive-index thin film.

[0029] In one embodiment, the method further includes: covering at least the surface of the second waveguide layer and the sidewalls of the ridge structure with a continuous insulating dielectric film, and exposing at least a portion of the top surface of the ridge structure.

[0030] In one embodiment, the thickness of the insulating dielectric film is 0.05 μm to 0.5 μm, preferably 0.1 μm to 0.25 μm, and more preferably 0.15 μm to 0.25 μm.

[0031] In one embodiment, the insulating dielectric film is made of any one or more combinations of SiO2, silicon nitride, aluminum oxide, zirconium oxide, and aluminum nitride, and is not limited thereto.

[0032] In one embodiment, the method further includes: disposing a first electrode on the epitaxial structure, and at least a local area of ​​the first electrode covering the top surface of the ridge structure, and forming an ohmic contact with the contact layer.

[0033] In one embodiment, the first electrode is continuously deposited on the second semiconductor layer and the ridge structure.

[0034] In one embodiment, the material of the epitaxial structure is selected from GaN-based semiconductor materials, including GaN, AlGaN, InGaN, InN, or AlInGaN, etc.

[0035] In one embodiment, the first optical confinement layer and the first waveguide layer are N-type, and the second waveguide layer, the second optical confinement layer, and the contact layer are P-type.

[0036] In one embodiment, the insulating dielectric layer is continuously deposited on the second waveguide layer and the ridge structure, and the first electrode is continuously deposited on the insulating dielectric layer.

[0037] Some embodiments of this application provide a gallium nitride laser including an epitaxial structure, a first electrode and a second electrode cooperating with the epitaxial structure, and an anti-waveguide structure. The epitaxial structure includes a first optical confinement layer, a first waveguide layer, a light-emitting active layer, a second waveguide layer, a second optical confinement layer, and a contact layer sequentially disposed along a specified direction. The contact layer, the second optical confinement layer, and a portion of the second waveguide layer cooperate to form a ridge structure, and the height of the ridge structure is less than the sum of the thicknesses of the contact layer, the second optical confinement layer, and the second waveguide layer. The anti-waveguide structure includes a high-refractive-index thin film, which is deposited on at least a portion of the surface of the second waveguide layer surrounding the ridge structure. For light emitted by the light-emitting active layer, the refractive index of the high-refractive-index thin film is at least greater than the refractive index of the ridge structure.

[0038] In one embodiment, the material of the high refractive index film includes, but is not limited to, any one of polycrystalline silicon or amorphous silicon, polycrystalline germanium or amorphous germanium, polycrystalline gallium arsenide or amorphous gallium arsenide.

[0039] In one embodiment, the thickness of the high refractive index film is 0.005 μm to 0.2 μm, preferably 0.02 μm to 0.1 μm, and more preferably 0.05 μm to 0.1 μm.

[0040] In one embodiment, the gallium nitride laser further includes an insulating dielectric film, which is continuously deposited on the surface of the second waveguide layer and the sidewall of the ridge structure. The first electrode has at least a local area disposed on the top surface of the ridge structure and forms an ohmic contact with the contact layer. The top surface of the ridge structure is the top surface of the epitaxial structure, and the second electrode is disposed in conjunction with the bottom surface of the epitaxial structure.

[0041] The thickness and material of the high refractive index thin film, insulating dielectric film, etc., can be as described above.

[0042] The material and structure of the epitaxial structure can also be as described above.

[0043] In one embodiment, the gallium nitride laser further includes a conductive substrate, and the epitaxial structure includes a buffer layer, a first optical confinement layer, a first waveguide layer, a light-emitting active layer, a second waveguide layer, a second optical confinement layer, and a contact layer sequentially disposed on a first surface of the substrate, and the second electrode is disposed on a second surface of the substrate, with the first surface and the second surface facing away from each other.

[0044] The conductive substrate includes, but is not limited to, gallium nitride, silicon carbide, silicon, or gallium arsenide substrates.

[0045] The applicant has discovered that the number of lateral higher-order transverse modes in a gallium nitride laser is related to the effective refractive index n of the ridge waveguide region.in The effective refractive index n outside the ridge waveguide region out The difference Δn = n in -n out Closely related, the number of lateral higher-order modes can be modulated by adjusting the value of Δn. Without affecting the photoelectric properties of the laser, appropriately reducing Δn can suppress the generation of more higher-order transverse modes and reduce the beam quality M. 2 The beam quality factor (Δn) is used to improve the beam quality of a laser, particularly its lateral beam quality. To effectively modulate Δn, high-refractive-index layers such as polycrystalline (amorphous) silicon, polycrystalline (amorphous) germanium, or polycrystalline (amorphous) gallium arsenide are inserted outside the ridge structure to form an anti-waveguide structure. These high-refractive-index layers modulate the effective refractive index outside the ridge structure. The effective refractive index varies with the thickness of the inserted layer, providing an effective means of modulating the effective refractive index difference (Δn) between the inside and outside of the ridge area. By adjusting the magnitude of Δn, the generation of higher-order modes is suppressed, and the beam quality (M) is reduced. 2 Factors that improve the beam quality of lasers.

[0046] Some embodiments of this application provide a method for manufacturing the laser, including:

[0047] A buffer layer, a first optical confinement layer, a first waveguide layer, a light-emitting active layer, a second waveguide layer, a second optical confinement layer, and a contact layer are sequentially grown on the first surface of a substrate to form the epitaxial structure of a laser.

[0048] Local areas of the contact layer, the second optical confinement layer, and the second waveguide layer are etched away to form the ridge structure of the laser.

[0049] A high-refractive-index thin film is disposed on at least a portion of the surface of the second waveguide layer surrounding the ridge structure to form an anti-waveguide structure;

[0050] An insulating dielectric layer is formed on the epitaxial structure, and the insulating dielectric layer at least continuously covers the high refractive index film and the sidewalls of the ridge structure.

[0051] A first electrode is disposed on the insulating dielectric layer, the first electrode extending to cover the top surface of the ridge structure and forming an ohmic contact with the contact layer;

[0052] A second electrode is disposed on a second surface of the substrate, the second surface being opposite to the first surface.

[0053] The substrate is a conductive substrate, and its material is as described above. In some cases, the substrate can also be an insulating substrate such as a sapphire substrate, but after the epitaxial structure is grown and before the second electrode is fabricated, the substrate needs to be peeled off and the second electrode fabricated on the bottom surface of the epitaxial structure.

[0054] In one embodiment, the epitaxial structure can be etched from the surface of the contact layer using methods such as dry etching or wet etching until a predetermined depth is reached within the second waveguide layer. This removes a portion of the contact layer and the second optical confinement layer, as well as a portion of the second waveguide layer above the predetermined depth, thereby forming a ridge structure. The height and width of the ridge structure can be determined according to the specifications of the gallium nitride laser.

[0055] In one embodiment, a continuous insulating dielectric layer can be first formed on the epitaxial structure, and the insulating dielectric layer can continuously cover the surface of the epitaxial structure, the high refractive index film and the surface of the ridge structure. Then, windows can be opened on the insulating dielectric layer by means of mask etching, so that the top surface of the ridge structure is partially or completely exposed.

[0056] In this application, each semiconductor material layer in the epitaxial structure can be grown and formed using methods such as HVPE (hydride vapor phase epitaxy), MOCVD (metal-organic chemical vapor deposition), and MBE (molecular beam epitaxy), but is not limited to these methods.

[0057] In this application, the first electrode and the second electrode can be formed by metal evaporation, magnetron sputtering, or other methods, and their materials can be Ti, Al, Au, Ag, Cu, Ni, Pt, Pd, Cr, ITO, etc., and are not limited to these.

[0058] In a typical implementation, a method for improving the beam quality of a gallium nitride laser based on a lateral non-uniform waveguide structure includes the following steps:

[0059] 1) An epitaxial structure of a gallium nitride laser is formed by sequentially growing an N-type GaN buffer layer, an N-type AlGaN optical confinement layer, an N-type AlInGaN waveguide layer, an active light-emitting layer, a P-type AlInGaN waveguide layer, a P-type AlGaN optical confinement layer, and a P-type GaN electrode contact layer on the front side of a conductive substrate such as gallium nitride, silicon carbide, silicon, or gallium arsenide substrate.

[0060] 2) Based on the structure of the gallium nitride laser die and the design dimensions of the corresponding die segmentation channel, the epitaxial structure is etched to the P-type AlGaN light confinement layer using photoresist or dielectric film as a mask, and part of the P-type AlInGaN waveguide layer is etched away to form the ridge structure of the laser.

[0061] 3) Deposit high-refractive-index thin films such as polycrystalline (amorphous) silicon, polycrystalline (amorphous) germanium, and polycrystalline (amorphous) gallium arsenide on the surface of the device structure formed in step 2), excluding the area covered by the ridge structure, to form an anti-waveguide structure.

[0062] 4) Deposit an insulating dielectric film on the surface of the device structure formed in step 3), and make the insulating dielectric film continuously cover the high refractive index film and the sidewalls of the ridge structure, so that the top surface of the ridge structure is exposed.

[0063] 5) The first electrode, which serves as a P-type ohmic contact electrode, is deposited on the device structure formed in step 3) and then annealed to form an ohmic contact between the first electrode and the top surface of the ridge structure.

[0064] 6) A second electrode, serving as an N-type ohmic contact electrode, is deposited on the back side of the substrate. In this step, the substrate may be thinned before depositing the second electrode, for example, by thinning it from the back side to 70–100 μm, but is not limited thereto.

[0065] 7) Divide the laser die along the designed die dividing line to form the die of a single laser.

[0066] In this embodiment, by inserting a high-refractive-index layer in the region outside the ridge structure of the gallium nitride laser to form an anti-waveguide structure, and by using the high-refractive-index layer to modulate the effective refractive index in the region outside the ridge structure, the generation of more higher-order modes can be suppressed, and the beam quality of the laser can be significantly improved.

[0067] To make the objectives, technical solutions, and advantages of this application clearer, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of this application shown in and described with reference to the drawings are merely exemplary, and this application is not limited to these embodiments.

[0068] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the structures and / or processing steps closely related to the scheme according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0069] Example 1: A method for improving the lateral mode of a gallium nitride laser based on an anti-waveguide includes the following steps:

[0070] (1) Using MOCVD, Si doping concentration of approximately 2 × 10⁻⁶ was sequentially grown on a GaN substrate 10. 18 cm -3 The N-type GaN buffer layer 11 has a thickness of approximately 1.2 μm and a Si doping concentration of approximately 1.5 × 10⁻⁶. 18 cm -312. An N-type AlGaN light confinement layer; 13. An unintentionally doped N-type GaN waveguide layer with a thickness of approximately 0.2 μm; 14. A GaN / InGaN quantum well light-emitting active layer capable of emitting 450 nm blue light; 15. An unintentionally doped P-type GaN waveguide layer with a thickness of approximately 0.15 μm; 16. A Mg doping concentration of approximately 1 × 10⁻⁶ μm. 19 cm -3 A p-type AlGaN light confinement layer of approximately 16 nm thickness and Mg doping concentration of approximately 1 × 10⁻⁶. 20 cm -3 The P-type GaN electrode contact layer 17 forms the epitaxial structure of the laser, such as... Figure 1 As shown.

[0071] (2) Using photoresist as a mask, the epitaxial structure is etched using ion beam technology until the P-type AlGaN light confinement layer is reached, and part of the P-type AlInGaN waveguide layer is removed, thereby forming the ridge structure 20 of the laser. The width of this ridge structure is approximately 45 μm. Figure 2 As shown.

[0072] (3) Polycrystalline silicon layers 30 of different thicknesses are prepared on the region outside the ridge structure of the device structure prepared in multiple steps (2) using magnetron sputtering, such as Figure 3 As shown.

[0073] (4) A continuous SiO2 insulating dielectric film 40 with a thickness of about 200 nm is formed in the region outside the ridge structure and on the sidewall of the ridge structure of the device structure prepared in multiple steps (3) using plasma enhanced chemical vapor deposition (PECVD). Then, Ni / Au is deposited on the insulating dielectric film 40 and the top surface of the ridge structure. The electrode is then alloyed at 500°C for 5 minutes in a nitrogen atmosphere to form a good ohmic contact electrode 50, i.e., the first electrode, on the surface of the ridge structure. Figure 4 As shown.

[0074] (5) The GaN substrate is thinned to 80 μm from the back side using methods such as grinding, and Ti (0.1 μm) / Al (0.4 μm) / Ti (0.1 μm) / Au (0.5 μm) is deposited on the back side of the substrate to form an N-type contact electrode 60, i.e., the second electrode. Figure 5 As shown.

[0075] (6) Finally, the laser die on the epitaxial wafer can be divided into individual laser dies with cavity surfaces and a certain cavity length by using die dicing and other die dicing techniques along the designed die dicing path.

[0076] The multiple lasers fabricated in this embodiment have an output power of 5W. 2 The factors can be found in Table 1 below.

[0077] Comparative Example 1 The method for preparing a gallium nitride laser provided in this comparative example is basically the same as that in Example 1, except that step (3) is omitted.

[0078] Table 1. M values ​​of gallium nitride lasers with polycrystalline silicon layers of different thicknesses prepared in Example 1 and Comparative Example 1. 2 factor

[0079]

[0080] Example 2: A method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide includes the following steps:

[0081] (1)~(2): are basically the same as steps (1)~(2) in Example 1.

[0082] (3) An amorphous silicon layer 30 with a thickness of about 100 nm is prepared on the region outside the ridge structure of the device structure prepared in step (2) by magnetron sputtering.

[0083] (4): The steps are basically the same as those in Example 1, except that the thickness of the SiO2 insulating dielectric film is about 150 nm.

[0084] (5)~(6): Same as steps (5)~(6) of Example 1.

[0085] The laser's M at an output power of 5W 2 The factor is approximately 6.2.

[0086] Example 3: A method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide includes the following steps:

[0087] (1)~(2): are basically the same as steps (1)~(2) in Example 1.

[0088] (3) A polycrystalline germanium layer 30 with a thickness of about 50 nm is prepared on the region outside the ridge structure of the device structure prepared in step (2) by magnetron sputtering.

[0089] (4): The steps are basically the same as those in Example 1, except that the thickness of the alumina insulating dielectric film is about 50 nm.

[0090] (5)~(6): Same as steps (5)~(6) of Example 1.

[0091] The laser's M at an output power of 5W 2 The factor is approximately 6.7.

[0092] Example 4: A method for improving the lateral mode of a gallium nitride laser based on an anti-waveguide includes the following steps:

[0093] (1)~(2): are basically the same as steps (1)~(2) in Example 1.

[0094] (3) A polycrystalline gallium arsenide layer 30 with a thickness of about 100 nm is prepared on the area outside the ridge structure of the device structure prepared in step (2) by magnetron sputtering.

[0095] (4): The steps are basically the same as those in Example 1, except that the thickness of the alumina insulating dielectric film is about 100 nm.

[0096] (5)~(6): Same as steps (5)~(6) of Example 1.

[0097] The laser's M at an output power of 5W 2 The factor is approximately 6.9.

[0098] Example 5: A method for improving the lateral mode of a gallium nitride laser based on an anti-waveguide includes the following steps:

[0099] (1)~(2): are basically the same as steps (1)~(2) in Example 1.

[0100] (3) An amorphous gallium arsenide layer 30 with a thickness of about 80 nm is prepared on the area outside the ridge structure of the device structure prepared in step (2) by magnetron sputtering.

[0101] (4): The steps are basically the same as those in Example 1, except that the thickness of the silicon nitride insulating dielectric film is about 250 nm.

[0102] (5)~(6): Same as steps (5)~(6) of Example 1.

[0103] The laser's M at an output power of 5W 2 The factor is approximately 7.2.

[0104] Example 6: A method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide includes the following steps:

[0105] (1)~(2): are basically the same as steps (1)~(2) in Example 1.

[0106] (3) An amorphous germanium layer 30 with a thickness of about 80 nm is prepared on the region outside the ridge structure of the device structure prepared in step (2) by magnetron sputtering.

[0107] (4): The steps are basically the same as those in Example 1, except that the thickness of the zirconium oxide insulating dielectric film is about 500 nm.

[0108] (5)~(6): Same as steps (5)~(6) of Example 1.

[0109] The laser's M at an output power of 5W 2 The factor is approximately 6.8.

[0110] Furthermore, referring to the above embodiments, the applicant has also fabricated GaN-based red lasers and GaN-based green lasers of various specifications, and has disposed high-refractive-index thin films of different materials and thicknesses in each laser, and has respectively assessed their M... 2 Factors were tested and it was found that the beam quality emitted by these lasers was significantly improved.

[0111] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide, characterized in that, include: An epitaxial structure for a gallium nitride laser is provided, the epitaxial structure comprising a first optical confinement layer, a first waveguide layer, a light-emitting active layer, a second waveguide layer, a second optical confinement layer, and a contact layer stacked sequentially along a specified direction; The epitaxial structure is processed to partially remove the contact layer, the second optical confinement layer, and the second waveguide layer, thereby forming the ridge structure of the gallium nitride laser. The height of the ridge structure is less than the sum of the thicknesses of the contact layer, the second optical confinement layer, and the second waveguide layer. A high-refractive-index thin film is disposed on at least a portion of the surface of the second waveguide layer surrounding the ridge structure, the high-refractive-index thin film having a higher refractive index than the ridge structure, to form an anti-waveguide structure.

2. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 1, characterized in that: The material of the high refractive index film includes any one of polycrystalline silicon or amorphous silicon, polycrystalline germanium or amorphous germanium, polycrystalline gallium arsenide or amorphous gallium arsenide.

3. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 1, characterized in that: The thickness of the high refractive index film is 0.005 mm to 0.2 mm.

4. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 3, characterized in that: The thickness of the high refractive index film is 0.02 mm to 0.1 mm.

5. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 4, characterized in that: The thickness of the high refractive index film is 0.05 mm to 0.1 mm.

6. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 1, characterized in that, Also includes: A continuous insulating dielectric film is applied to at least the surface of the second waveguide layer and the sidewalls of the ridge structure, and at least a portion of the top surface of the ridge structure is exposed.

7. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 6, characterized in that: The thickness of the insulating dielectric film is 0.05mm to 0.5mm.

8. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 7, characterized in that: The thickness of the insulating dielectric film is 0.1mm to 0.25mm.

9. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 8, characterized in that: The thickness of the insulating dielectric film is 0.15mm to 0.25mm.

10. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 6, characterized in that: The insulating dielectric film is made of any one or more of the following materials: SiO2, silicon nitride, aluminum oxide, zirconium oxide, and aluminum nitride.

11. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 1, characterized in that, Also includes: A first electrode is disposed on the epitaxial structure, and at least a local area of ​​the first electrode is covered on the top surface of the ridge structure and forms an ohmic contact with the contact layer.

12. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 1, characterized in that: The material of the epitaxial structure is selected from GaN-based semiconductor materials.

13. The method for improving the transverse mode of a gallium nitride laser based on an anti-waveguide according to claim 1, characterized in that: The first optical confinement layer and the first waveguide layer are N-type, and the second waveguide layer, the second optical confinement layer, and the contact layer are P-type.

14. A gallium nitride laser, comprising an epitaxial structure and a first electrode and a second electrode cooperating with the epitaxial structure, wherein the epitaxial structure comprises a first optical confinement layer, a first waveguide layer, a light-emitting active layer, a second waveguide layer, a second optical confinement layer, and a contact layer sequentially disposed along a specified direction, wherein the contact layer, the second optical confinement layer, and a portion of the second waveguide layer cooperate to form a ridge structure, and the height of the ridge structure is less than the sum of the thicknesses of the contact layer, the second optical confinement layer, and the second waveguide layer; characterized in that: The laser also includes an anti-waveguide structure comprising a high-refractive-index thin film, the high-refractive-index thin film being deposited on at least a portion of the surface of the second waveguide layer surrounding the ridge structure, and the refractive index of the high-refractive-index thin film being greater than the refractive index of the ridge structure.

15. The gallium nitride laser according to claim 14, characterized in that: The material of the high refractive index film includes any one of polycrystalline silicon or amorphous silicon, polycrystalline germanium or amorphous germanium, polycrystalline gallium arsenide or amorphous gallium arsenide.

16. The gallium nitride laser according to claim 14, characterized in that: The thickness of the high refractive index film is 0.005 mm to 0.2 mm.

17. The gallium nitride laser according to claim 16, characterized in that: The thickness of the high refractive index film is 0.02 mm to 0.1 mm.

18. The gallium nitride laser according to claim 17, characterized in that: The thickness of the high refractive index film is 0.05 mm to 0.1 mm.

19. The gallium nitride laser according to claim 14, characterized in that, It also includes an insulating dielectric film, which is continuously coated on the surface of the second waveguide layer and the sidewall of the ridge structure. The first electrode is partially disposed on the top surface of the ridge structure and forms an ohmic contact with the contact layer. The top surface of the ridge structure is the top surface of the epitaxial structure. The second electrode is disposed in conjunction with the bottom surface of the epitaxial structure.

20. The gallium nitride laser according to claim 19, characterized in that: The thickness of the insulating dielectric film is 0.05mm to 0.5mm.

21. The gallium nitride laser according to claim 20, characterized in that: The thickness of the insulating dielectric film is 0.1mm to 0.25mm.

22. The gallium nitride laser according to claim 21, characterized in that: The thickness of the insulating dielectric film is 0.15mm to 0.25mm.

23. The gallium nitride laser according to claim 19, characterized in that: The insulating dielectric film is made of any one or more of the following materials: SiO2, silicon nitride, aluminum oxide, zirconium oxide, and aluminum nitride.

24. The gallium nitride laser according to claim 14, characterized in that: The material of the epitaxial structure is selected from GaN-based semiconductor materials.

25. The gallium nitride laser according to claim 14, characterized in that: The first optical confinement layer and the first waveguide layer are N-type, and the second waveguide layer, the second optical confinement layer, and the contact layer are P-type.

26. The gallium nitride laser according to claim 14, characterized in that: The gallium nitride laser further includes a conductive substrate, and the epitaxial structure includes a buffer layer, a first optical confinement layer, a first waveguide layer, a light-emitting active layer, a second waveguide layer, a second optical confinement layer, and a contact layer sequentially disposed on a first surface of the substrate. The second electrode is disposed on a second surface of the substrate, and the first surface and the second surface are opposite to each other.

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