Near ultraviolet laser with component gradient electron blocking layer and preparation method of near ultraviolet laser
By using a component gradient electron barrier layer in AlGaN near-ultraviolet laser, the electron leakage problem is solved, the hole injection rate is improved, the threshold current is reduced, and the output power and photoelectric performance of the laser are improved.
Patent Information
- Application Number
- CN202311841017.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-28
- Publication Date
- 2025-07-01
AI Technical Summary
In AlGaN near-ultraviolet lasers, electron leakage from the active region to the p-type region leads to carrier loss, resulting in an increase in threshold current density and reducing photoelectric performance.
An electron barrier layer with gradient components is used to reduce electron leakage and increase hole injection by the proportion of Al component that changes linearly along the growth direction. An AlxGa1-xN material is used, where x is the proportion of Al component, 0
Effectively reduce electron leakage, improve hole injection, reduce threshold current, and improve the output power and photoelectric performance of the laser.
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Figure CN120237532A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of AlGaN near-ultraviolet lasers, and particularly to a near-ultraviolet laser with a composition-graded electron blocking layer and a preparation method thereof. Background Art
[0002] AlGaN near-ultraviolet lasers have a large adjustable bandgap of 3.4 to 6.2 eV. Due to their good chemical stability, long lifespan, stable operation and other characteristics, they have been widely studied and are mainly applied in the fields of air and water purification, sterilization, disinfection equipment requiring ultraviolet light radiation, and high-density optical information storage, etc.
[0003] Compared with GaN blue lasers and green lasers, the quantum wells of AlGaN near-ultraviolet lasers are shallower, resulting in more electrons leaking into the p-type region. However, when a large number of electrons leak from the active region into the p-type region, the number of holes injected into the active region must be less than that of electrons. The leaked electrons recombine with the holes in the p-type region, leading to carrier loss. In the face of this problem, AlGaN near-ultraviolet lasers often add an electron blocking layer with a fixed composition during the growth process. While the electron blocking layer with a fixed composition blocks electron leakage, it also hinders the injection of holes from the p-type region into the active region. A low hole injection rate will increase the probability of non-radiative recombination, thereby increasing the threshold current density and reducing the optoelectronic performance of AlGaN near-ultraviolet lasers. Summary of the Invention
[0004] In view of at least one of the above technical problems, the present invention provides a near-ultraviolet laser with a composition-graded electron blocking layer and a preparation method thereof.
[0005] One aspect of the present invention provides a near-ultraviolet laser with a composition-graded electron blocking layer, including: a substrate 101, a lower confinement layer 102, a lower waveguide layer 103, a multi-quantum well layer 104, an upper waveguide layer 105, and an electron blocking layer 106 stacked in sequence along a first direction, where the first direction is the material growth direction of the near-ultraviolet laser; and an upper confinement layer 107 and an ohmic contact layer 108 stacked in sequence in a partial region on the surface of the electron blocking layer 106 facing away from the upper waveguide layer 105, wherein the electron blocking layer 106 has a graded composition for improving the output power and optoelectronic performance of the near-ultraviolet laser.
[0006] In some exemplary embodiments of the present invention, the electron blocking layer 106 has a composition that varies linearly along the first direction.
[0007] In some exemplary embodiments of the present invention, the material of the electron blocking layer 106 is selected as Al x Ga 1-x N, where x is the Al component in the Al xGa 1-x The proportion in GaN, where 0 < x < 1.
[0008] In some exemplary embodiments of the present invention, the proportion of the Al component in the electron blocking layer 106 increases linearly along the first direction in the electron blocking layer 106.
[0009] In some exemplary embodiments of the present invention, the upper confinement layer 107 and the lower confinement layer 102 have the same proportion of the Al component, and the proportion of the Al component in the upper confinement layer 107 or the lower confinement layer 102 is equal to the minimum proportion of the Al component in the electron blocking layer 106.
[0010] In some exemplary embodiments of the present invention, the Al component in the electron blocking layer 106 in the Al x Ga 1-x The minimum proportion in N is 0.2, and the maximum proportion is 0.3; and the electron blocking layer 106 is P-type doped with the doping element Mg and the doping concentration is 2×10 19 cm -3 , and the thickness of the electron blocking layer 106 is 20 nm.
[0011] In some exemplary embodiments of the present invention, the upper confinement layer 107 is a P-type doped Al 0.2 Ga 0.8 N layer with the doping element Mg and the doping concentration is 5×10 18 cm -3 , the thickness of the upper confinement layer 107 is 0.5 μm; the lower confinement layer 102 is an N-type doped Al 0.2 Ga 0.8 N layer with the doping element Si and the doping concentration is 5×10 18 cm -3 , and the thickness of the lower confinement layer 102 is 0.6 μm.
[0012] In some exemplary embodiments of the present invention, the multiple quantum well layer 104 includes a plurality of quantum barrier layers and a plurality of quantum well layers arranged alternately, where the number of the quantum barrier layers is 3, the number of the quantum well layers is 2, any one of the quantum barrier layers is Al 0.07 Ga 0.93 N with a thickness of 10 nm, any one of the quantum well layers is GaN with a thickness of 6 nm; the substrate 101 is GaN and the thickness of the substrate 101 is 1 μm; the lower waveguide layer 103 is an unintentionally doped Al 0.08 Ga 0.92 N layer, and the thickness of the lower waveguide layer 103 is 80 nm; the upper waveguide layer 105 is an unintentionally doped Al 0.08 Ga 0.92N layers, the thickness of the upper waveguide layer 105 is 80 nm; the ohmic contact layer 108 is a heavily P-doped GaN layer, the doping element is Mg, and the doping concentration is 1×10 20 cm -3 , and the thickness of the ohmic contact layer 108 is 20 nm.
[0013] In some exemplary embodiments of the present invention, the near-ultraviolet laser further includes: a P-type electrode 109 disposed on the surface of the ohmic contact layer 108 facing away from the upper confinement layer 107, and the material of the P-type electrode 109 is Pd / Pt / Au; and an N-type electrode 110 disposed on the surface of the substrate 101 facing away from the lower confinement layer 102, and the material of the N-type electrode 110 is Ti / Al / Ti / Au.
[0014] Another aspect of the present invention provides a method for manufacturing a near-ultraviolet laser with a composition-graded electron blocking layer, including: S1, preprocessing the substrate 101; S2, epitaxially growing a lower confinement layer 102, a lower waveguide layer 103, a multi-quantum well layer 104, and an upper waveguide layer 105 on the substrate 101 in sequence along a first direction, where the first direction is the material growth direction of the near-ultraviolet laser; S3, on the surface of the upper waveguide layer 105 facing away from the multi-quantum well layer 104, epitaxially grow an electron blocking layer 106 with a graded composition by adjusting the flow rate of the carrier gas, where the carrier gas includes hydrogen; S4, sequentially grow an upper confinement layer 107 and an ohmic contact layer 108 on a partial area of the surface of the electron blocking layer 106 facing away from the upper waveguide layer 105; S5, evaporate an N-type electrode 110 on the surface of the substrate 101 facing away from the lower confinement layer 102; S6, evaporate a P-type electrode 109 on the surface of the ohmic contact layer 108 facing away from the upper confinement layer 107.
[0015] The near-ultraviolet laser with a composition-graded electron blocking layer provided by the present invention uses an Al-composition-graded electron blocking layer to replace the traditional fixed-composition electron blocking layer, and has the following beneficial effects:
[0016] 1. The near-ultraviolet laser with a composition-graded electron blocking layer can more effectively reduce electron leakage, and can also improve hole injection, increase the output power of the laser, and obtain a lower threshold current, thereby achieving the improvement of the electrical performance of the laser;
[0017] 2. The composition grading causes the refractive index to change, the optical confinement factor becomes larger, and the optical field is closer to the active region, thereby achieving the improvement of the optical performance of the laser. Description of the Drawings
[0018] Figure 1Cross-sectional view of a near-ultraviolet laser with a compositionally graded electron blocking layer according to some illustrative embodiments of the present invention;
[0019] Figure 2 Comparison graph of the power-current relationship between a near-ultraviolet laser with a compositionally graded electron blocking layer and a near-ultraviolet laser with a conventional electron blocking layer according to some illustrative embodiments of the present invention;
[0020] Figure 3 Fabrication method of a near-ultraviolet laser with a compositionally graded electron blocking layer according to some illustrative embodiments of the present invention.
[0021] Reference numerals:
[0022] 100: Near-ultraviolet laser with a compositionally graded electron blocking layer
[0023] 101: Substrate
[0024] 102: Lower confinement layer
[0025] 103: Lower waveguide layer
[0026] 104: Multiple quantum well layer
[0027] 105: Upper waveguide layer
[0028] 106: Electron blocking layer
[0029] 107: Upper confinement layer
[0030] 108: Ohmic contact layer
[0031] 109: P-type electrode
[0032] 110: N-type electrode Detailed description of the invention
[0033] To make the objectives, technical solutions, and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to specific embodiments and the accompanying drawings.
[0034] Figure 1 Cross-sectional view of a near-ultraviolet laser with a compositionally graded electron blocking layer according to some illustrative embodiments of the present invention.
[0035] As Figure 1As shown, in some embodiments, a near-ultraviolet laser 100 with a compositionally graded electron blocking layer includes: a substrate 101, a lower confinement layer 102, a lower waveguide layer 103, a multiple quantum well layer 104, an upper waveguide layer 105, an electron blocking layer 106 stacked in sequence along a first direction, and an upper confinement layer 107 and an ohmic contact layer 108 stacked in sequence in a partial region on the surface of the electron blocking layer 106 facing away from the upper waveguide layer 105. The first direction is the material growth direction of the near-ultraviolet laser 100.
[0036] In this embodiment, the electron blocking layer 106 has a graded composition, which is used to improve the output power and optoelectronic performance of the near-ultraviolet laser 100.
[0037] Compared with traditional near-ultraviolet lasers, the near-ultraviolet laser with a compositionally graded electron blocking layer in this embodiment can reduce electron leakage and improve hole injection, thereby increasing the output power of the laser and obtaining a lower threshold current. In addition, the compositional grading causes a change in the refractive index, the optical confinement factor becomes larger, and the optical field is closer to the active region, enabling the improvement of the optoelectronic performance of the laser.
[0038] Please continue to refer to Figure 1 , in some embodiments, the electron blocking layer 106 has a composition that varies linearly along the first direction.
[0039] In some embodiments, the material of the electron blocking layer 106 is selected as Al x Ga 1-x N, where x is the proportion of the Al component in Al x Ga 1-x N, and 0 < x < 1. 1 - x is the proportion of the Ga component in Al x Ga 1-x N, that is, the sum of the proportions of the Ga component and the Al component in Al x Ga 1-x N is 1. For example, when x is 0.2, Al x Ga 1-x N is Al 0.2 Ga 0.8 N, the proportion of the Al component in Al x Ga 1-x N is 0.2, and the proportion of the Ga component in Al x Ga 1-x N is 0.8.
[0040] In some embodiments, the proportion of the Al component in the electron blocking layer 106 increases linearly along the first direction. It can be understood that since x is the proportion of the Al component in the electron blocking layer 106 in Al x Ga 1-xThe proportion of Al in N increases linearly along the first direction. The proportion of Al component in the electron blocking layer 106 increases linearly along the first direction. Correspondingly, the proportion of Ga component in the electron blocking layer 106 decreases linearly along the first direction.
[0041] Please continue to refer to Figure 1 , in some embodiments, the upper confinement layer 107 and the lower confinement layer 102 have the same proportion of Al component, and the proportion of Al component in the upper confinement layer 107 or the lower confinement layer 102 is equal to the minimum proportion of Al component in the electron blocking layer 106.
[0042] In some embodiments, the proportion of Al component in the electron blocking layer 106 in Al x Ga 1-x The minimum proportion of N is 0.2, and the maximum proportion is 0.3. Understandably, the variation range of x in Al x Ga 1-x N increases linearly from 0.2 to 0.3 along the material growth direction. The electron blocking layer 106 is P-type doped, the doping element is Mg, and the doping concentration is 2×10 19 cm -3 , and the thickness of the electron blocking layer 106 is 20 nm.
[0043] In some embodiments, the upper confinement layer 107 is a P-type doped Al 0.2 Ga 0.8 N layer, the doping element is Mg, and the doping concentration is 5×10 18 cm -3 , and the thickness of the upper confinement layer 107 is 0.5 μm.
[0044] The lower confinement layer 102 is an N-type doped Al 0.2 Ga 0.8 N layer, the doping element is Si, and the doping concentration is 5×10 18 cm -3 , and the thickness of the lower confinement layer 102 is 0.6 μm.
[0045] Please continue to refer to Figure 1 , in some embodiments, the multiple quantum well layer 104 includes a plurality of quantum barrier layers and a plurality of quantum well layers arranged alternately. Among them, the number of quantum barrier layers is 3, the number of quantum well layers is 2, and any quantum barrier layer is Al 0.07 Ga 0.93 N, with a thickness of 10 nm, and any quantum well layer is GaN, with a thickness of 6 nm. Understandably, along the first direction, in the multiple quantum well layer 104, one quantum well layer is arranged between two quantum barrier layers. The total thickness of the multiple quantum well layer 104 is 42 nm.
[0046] The substrate 101 is GaN, and the thickness of the substrate 101 is 1 μm.
[0047] The lower waveguide layer 103 is an unintentionally doped Al 0.08 Ga 0.92 N layer, and the thickness of the lower waveguide layer 103 is 80 nm.
[0048] The upper waveguide layer 105 is an unintentionally doped Al 0.08 Ga 0.92 N layer, and the thickness of the upper waveguide layer 105 is 80 nm.
[0049] The ohmic contact layer 108 is a heavily P-doped GaN layer, the doping element is Mg, and the doping concentration is 1×10 20 cm -3 , and the thickness of the ohmic contact layer 108 is 20 nm.
[0050] Please continue to refer to Figure 1 , in some embodiments, the near-ultraviolet laser 100 further includes: a P-type electrode 109 and an N-type electrode 110.
[0051] The P-type electrode 109 is disposed on the surface of the ohmic contact layer 108 facing away from the upper confinement layer 107, and the material of the P-type electrode 109 is Pd / Pt / Au.
[0052] The N-type electrode 110 is disposed on the surface of the substrate 101 facing away from the lower confinement layer 102, and the material of the N-type electrode 110 is Ti / Al / Ti / Au.
[0053] Figure 2 is a comparison diagram of the power-current relationship between a near-ultraviolet laser with a compositionally graded electron blocking layer and a near-ultraviolet laser with a conventional electron blocking layer according to some exemplary embodiments of the present invention.
[0054] As Figure 2 shown, the abscissa is the current mA of the near-ultraviolet laser, and the ordinate is the output power mW of the near-ultraviolet laser. When the composition of the electron blocking layer is fixed, i.e., the Al 0.3 Ga 0.7 N electron blocking layer, the threshold current of the near-ultraviolet laser is about 52 mA, and the output power at 120 mA current is about 101 mW. When the composition of the electron blocking layer is graded, i.e., the Al 0.2→0.3 Ga 0.8→0.7 N electron blocking layer, the threshold current of the near-ultraviolet laser is about 47 mA, and the output power at 120 mA current is about 139 mW. It can be seen that, compared with the near-ultraviolet laser with a conventional electron blocking layer, the near-ultraviolet laser provided by the present invention with a compositionally graded electron blocking layer can improve the output power of the near-ultraviolet laser and obtain a lower threshold current.
[0055] The above has described the near-ultraviolet laser with a compositionally graded electron blocking layer. Next, the preparation method of the near-ultraviolet laser with a compositionally graded electron blocking layer will be further described.
[0056] Figure 3 It is a preparation method of a near-ultraviolet laser with a compositionally graded electron blocking layer according to some exemplary embodiments of the present invention.
[0057] As Figure 3 shown, the preparation method of the near-ultraviolet laser with a compositionally graded electron blocking layer includes S1 to S6.
[0058] S1, pre-treat the substrate 101.
[0059] For example, the substrate 101 can be pre-treated in a hydrogen atmosphere.
[0060] S2, epitaxially grow a lower confinement layer 102, a lower waveguide layer 103, a multi-quantum well layer 104, and an upper waveguide layer 105 on the substrate 101 in sequence along a first direction, where the first direction is the material growth direction of the near-ultraviolet laser.
[0061] For example, using trimethylgallium, trimethylaluminum, and ammonia as precursors to provide Ga, Al, and N sources respectively, epitaxially grow an AlGaN lower confinement layer 102 on the GaN substrate 101 with hydrogen as the carrier gas, and the growth temperature is 700 - 1100 °C.
[0062] Epitaxially grow an AlGaN lower waveguide layer 103 on the AlGaN lower confinement layer 102 with hydrogen as the carrier gas, and its growth temperature is 700 - 1100 °C.
[0063] Epitaxially grow a GaN / AlGaN multi-quantum well layer 104 on the AlGaN lower waveguide layer 103. Among them, epitaxially grow an AlGaN quantum barrier layer with hydrogen as the carrier gas; epitaxially grow a GaN quantum well layer with hydrogen as the carrier gas, and its growth temperature is 700 - 900 °C.
[0064] Epitaxially grow an upper waveguide layer 105 on the GaN / AlGaN multi-quantum well layer 104 with hydrogen as the carrier gas, and its growth temperature is 700 - 1100 °C.
[0065] S3, on the surface of the upper waveguide layer 105 facing away from the multi-quantum well layer 104, epitaxially grow an electron blocking layer 106 with a graded composition by adjusting the flow rate of the carrier gas. Among them, the carrier gas includes hydrogen.
[0066] For example, using hydrogen as the carrier gas, epitaxially grow an electron blocking layer 106 with a graded composition by automatically adjusting different flow rates. The epitaxial growth thickness is 20 nm, and its growth temperature is 700 - 1100 °C.
[0067] It should be noted that the flow rate of the carrier gas can be controlled by programming. For example, the starting and ending flow rates of the TMA1 and TMGa carrier gases are defined in the program, and during growth, the system will cause the flow rate of the carrier gas to change linearly with time, preparing an electron blocking layer with a gradually changing composition.
[0068] S4. On a partial area of the surface of the electron blocking layer 106 facing away from the upper waveguide layer 105, an upper confinement layer 107 and an ohmic contact layer 108 are sequentially grown.
[0069] In step S2, for example, with hydrogen as the carrier gas, the AlGaN upper confinement layer 107 is grown at a high temperature. On the AlGaN upper confinement layer 107, with hydrogen as the carrier gas, the GaN ohmic contact layer 108 is grown at a high temperature.
[0070] S5. An N-type electrode 110 is evaporated on the surface of the substrate 101 facing away from the lower confinement layer 102.
[0071] In step S2, for example, under the N-type GaN substrate 101, the N-type electrode 110 is evaporated by using a magnetron sputtering technique, and the N-type electrode material is Ti / Al / Ti / Au.
[0072] S6. A P-type electrode 109 is evaporated on the surface of the ohmic contact layer 108 facing away from the upper confinement layer 107.
[0073] In step S2, for example, on the P-type ohmic contact layer 108, the P-type electrode 109 is also evaporated by using a magnetron sputtering technique, and the P-type electrode material is Pd / Pt / Au.
[0074] So far, the preparation of a near-ultraviolet laser with a compositionally graded electron blocking layer is completed.
[0075] In summary, for the near-ultraviolet laser with a compositionally graded electron blocking layer and its preparation method provided by the present invention, by using an electron blocking layer with a gradually changing Al composition to replace the traditional electron blocking layer with a fixed composition, it can more effectively reduce electron leakage, improve hole injection, thereby increasing the output power of the laser and obtaining a lower threshold current, thus realizing the improvement of the electrical performance of the laser. At the same time, the compositional gradient causes a change in the refractive index, the optical confinement factor becomes larger, and the optical field is closer to the active region, thus realizing the improvement of the optical performance of the laser.
[0076] In the above specific embodiments, the purpose, technical solution, and beneficial effects of the present invention are further described in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A near-ultraviolet laser with a compositionally graded electron blocking layer, characterized in that, Comprising: A substrate (101), a lower confinement layer (102), a lower waveguide layer (103), a multi-quantum well layer (104), an upper waveguide layer (105), and an electron blocking layer (106) stacked in sequence along a first direction, where the first direction is the material growth direction of the near-ultraviolet laser; and an upper confinement layer (107) and an ohmic contact layer (108) stacked in sequence in a partial region on the surface of the electron blocking layer (106) facing away from the upper waveguide layer (105). Among them, the electron blocking layer (106) has a gradually changing composition, which is used to improve the output power and optoelectronic performance of the near-ultraviolet laser.
2. The near-ultraviolet laser according to claim 1, wherein The electron blocking layer (106) has a composition that varies linearly along the first direction.
3. The near-ultraviolet laser according to claim 1 or 2, characterized in that, The material of the electron blocking layer (106) is selected as Al x Ga 1-x N, where x is the proportion of the Al component in the Al x Ga 1-x N, and 0 < x < 1.
4. The near-ultraviolet laser according to claim 3, wherein The proportion of the Al component in the electron blocking layer (106) increases linearly along the first direction in the electron blocking layer (106).
5. The near-ultraviolet laser according to claim 4, characterized in that, The upper confinement layer (107) and the lower confinement layer (102) have the same proportion of the Al component, and the proportion of the Al component in the upper confinement layer (107) or the lower confinement layer (102) is equal to the minimum proportion of the Al component in the electron blocking layer (106).
6. The near-ultraviolet laser according to claim 5, characterized in that, The minimum proportion of the Al component in the electron blocking layer (106) in the Al x Ga 1-x N is 0.2, and the maximum proportion is 0.3; And The electron blocking layer (106) is P-type doped with Mg as the doping element and has a doping concentration of 2×10 19 cm -3 , and the thickness of the electron blocking layer (106) is 20 nm.
7. The near-ultraviolet laser according to claim 6, characterized in that, The upper confinement layer (107) is a P-type doped Al 0.2 Ga 0.8 N layer, the doping element is Mg, and the doping concentration is 5×10 18 cm -3 , and the thickness of the upper confinement layer (107) is 0.5 μm; The lower confinement layer (102) is an N-type doped Al 0.2 Ga 0.8 N layer, the doping element is Si, and the doping concentration is 5×10 18 cm -3 . The thickness of the lower confinement layer (102) is 0.6 μm.
8. The near-ultraviolet laser according to claim 7, characterized in that, The multi - quantum well layer (104) includes a plurality of quantum barrier layers and a plurality of quantum well layers arranged alternately, wherein the number of the quantum barrier layers is 3, the number of the quantum well layers is 2, and any one of the quantum barrier layers is Al 0.07 Ga 0.93 N with a thickness of 10 nm, and any one of the quantum well layers is GaN with a thickness of 6 nm; The substrate (101) is GaN, and the thickness of the substrate (101) is 1 μm; The lower waveguide layer (103) is an unintentionally doped Al 0.08 Ga 0.92 N layer, and the thickness of the lower waveguide layer (103) is 80 nm; The upper waveguide layer (105) is an unintentionally doped Al 0.08 Ga 0.92 N layer, and the thickness of the upper waveguide layer (105) is 80 nm; The ohmic contact layer (108) is a heavily P-doped GaN layer, doped with Mg at a doping concentration of 1×10 20 cm -3 , and the thickness of the ohmic contact layer (108) is 20 nm.
9. The near-ultraviolet laser according to claim 8, characterized in that, The near-ultraviolet laser further comprises: A P-type electrode (109) disposed on the surface of the ohmic contact layer (108) facing away from the upper confinement layer (107), and the material of the P-type electrode (109) is Pd / Pt / Au; and An N-type electrode (110) disposed on the surface of the substrate (101) facing away from the lower confinement layer (102), and the material of the N-type electrode (110) is Ti / Al / Ti / Au.
10. A method for preparing a near-ultraviolet laser having a compositionally graded electron blocking layer as described in any one of claims 1 to 9, characterized in that, Comprising: S1, performing pretreatment on the substrate (101); S2, epitaxially growing a lower confinement layer (102), a lower waveguide layer (103), a multi-quantum well layer (104), and an upper waveguide layer (105) in sequence on the substrate (101) along a first direction, where the first direction is the material growth direction of the near-ultraviolet laser; S3, on the surface of the upper waveguide layer (105) facing away from the multi-quantum well layer (104), epitaxially growing an electron blocking layer (106) with a gradually changing composition by adjusting the flow rate of the carrier gas, where the carrier gas includes hydrogen; S4, growing an upper confinement layer (107) and an ohmic contact layer (108) in sequence on a partial region of the surface of the electron blocking layer (106) facing away from the upper waveguide layer (105); S5, evaporating an N-type electrode (110) on the surface of the substrate (101) facing away from the lower confinement layer (102); S6, evaporating a P-type electrode (109) on the surface of the ohmic contact layer (108) facing away from the upper confinement layer (107).