A multi-step ridge type laser structure and a method for manufacturing the same
By employing a multi-step ridge structure in a gallium nitride-based blue-green semiconductor laser, the carrier distribution is optimized, solving the problems of large divergence angle and poor beam quality, and improving the reliability and output performance of the laser.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SICHUAN BLU RADIUM TECH CO LTD
- Filing Date
- 2025-01-24
- Publication Date
- 2026-05-15
AI Technical Summary
Existing gallium nitride-based blue-green semiconductor lasers have problems with large divergence angles and poor beam quality in their side-emitting laser structures. This is mainly due to the increase in high-order side-mode gain caused by phenomena such as thermal lensing, lateral current spread, and longitudinal spatial hole burning.
A multi-step ridge laser structure is adopted. By setting an N-type electrode layer, a substrate layer, a buffer layer, a first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, an electron blocking layer, a second confinement layer, a P-type GaN layer, a P-type ohmic contact layer, and a P-type electrode layer in the laser, a multi-step ridge structure is formed, which optimizes the carrier distribution and suppresses lateral high-order modes.
It significantly suppresses lateral higher-order modes of the laser, improves the reliability and lifespan of the laser, reduces the effects of thermal lensing and lateral current spread, and enhances the output performance of the laser.
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Figure CN119944436B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of gallium nitride semiconductor laser technology, specifically relating to a multi-step ridge laser structure and its fabrication method. Background Technology
[0002] Gallium nitride (GaN) semiconductor lasers are important semiconductor optoelectronic devices with wide applications in laser displays, laser communications, and laser surgery. Laser displays are considered the ultimate display technology, and chip-level semiconductor red, green, and blue primary color lasers play an indispensable role in laser displays. Relatively speaking, red and blue semiconductor lasers are currently more mature, while green semiconductor lasers are still in the early stages of development.
[0003] Gallium nitride (GaN)-based blue-green semiconductor lasers are promising solutions for achieving monolithic integration of three primary color lasers while maintaining continuously tunable wavelengths. Current applications demand high power and low beam divergence from GaN semiconductor lasers. Currently, GaN-based blue semiconductor lasers can achieve continuous power exceeding 15W per tube, and GaN-based green semiconductor lasers can achieve continuous power exceeding 2.5W per tube. However, traditional edge-emitting laser structures for GaN-based blue-green semiconductor lasers (i.e., edge-emitting laser structures where the emitting region is confined to a small portion on one side; this limited emission region improves coupling efficiency with optical fibers and integrated optical paths) still face problems such as large divergence angles and poor beam quality. Specifically, existing ridge-type edge-emitting lasers, due to thermal lensing, lateral current spread, and longitudinal spatial hole burning, result in higher-order side modes achieving higher gains, increasing the number of lasing side modes and further deteriorating the divergence angle and beam quality. Summary of the Invention
[0004] The purpose of this invention is to provide a multi-step ridge laser structure and its fabrication method to solve the problems of large divergence angle and poor beam quality in existing edge-emitting laser structures used to fabricate gallium nitride-based blue-green semiconductor lasers.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] In a first aspect, a multi-step ridge laser structure is provided, comprising an N-type electrode layer, a substrate layer, a buffer layer, a first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, an electron blocking layer, a second confinement layer, a P-type GaN layer, a P-type ohmic contact layer, and a P-type electrode layer arranged sequentially from bottom to top, wherein the widths of the second waveguide layer, the electron blocking layer, the second confinement layer, the P-type GaN layer, and the P-type ohmic contact layer decrease sequentially to form a multi-step ridge structure.
[0007] Based on the above-described invention, a novel edge-emitting laser scheme suitable for fabricating gallium nitride-based blue-green semiconductor lasers is provided. This scheme comprises, in order from bottom to top, an N-type electrode layer, a substrate layer, a buffer layer, a first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, an electron blocking layer, a second confinement layer, a P-type GaN layer, a P-type ohmic contact layer, and a P-type electrode layer. The widths of the second waveguide layer, electron blocking layer, second confinement layer, P-type GaN layer, and P-type ohmic contact layer decrease sequentially, forming a multi-step ridge structure. This not only significantly suppresses lateral high-order modes of the laser and optimizes carrier distribution but also improves the reliability and lifetime of the laser. Furthermore, it reduces the influence of factors including thermal lensing and lateral current spread effects, suppresses lateral high-order modes of the laser, improves the output performance of the laser, and facilitates practical application and promotion.
[0008] In one possible design, the N-type electrode layer adopts the following four-layer metal electrode structure from the inside out: the first layer is a titanium layer with a thickness of 40-60 nanometers, the second layer is an aluminum layer with a thickness of 80-120 nanometers, the third layer is a titanium layer with a thickness of 40-60 nanometers, and the outermost layer is a gold layer with a thickness of 80-120 nanometers.
[0009] And / or, the P-type electrode layer adopts the following three-layer metal electrode structure from the inside out: the first layer is a platinum layer with a thickness of 40-60 nanometers, the second layer is a palladium layer with a thickness of 40-60 nanometers, and the outermost layer is a gold layer with a thickness of 500-700 nanometers.
[0010] In one possible design, the substrate layer is a GaN substrate or a sapphire substrate, wherein the GaN substrate has been doped to a concentration of 2.5 × 10⁻⁶. 18 ~3.5×10 18 cm -3 N-type doping treatment;
[0011] And / or, the buffer layer is a GaN layer with a thickness of 10–300 micrometers, wherein the GaN layer has been doped with a concentration of 1 × 10⁻⁶. 18 ~1×10 19 cm -3 N-type doping treatment.
[0012] In one possible design, the first confinement layer is made of Al with a thickness of 0.5 to 2 micrometers. x Ga 1-x N material layer, wherein the Al x Ga 1-x The Al component content x in the N material layer is 0.01 to 0.15, wherein the Al x Ga1-x The N material layer has been doped to a concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 N-type doping treatment;
[0013] And / or, the second confining layer is made of Al with a thickness of 0.5 to 2 micrometers. y Ga 1-y N material layer, wherein the Al y Ga 1-y The Al component content y in the N material layer is 0.01–0.15, wherein the Al y Ga 1-y The N material layer has been doped to a concentration of 1×10⁻⁶. 19 ~5×10 19 cm -3 P-type doping treatment.
[0014] In one possible design, the first waveguide layer uses In with a thickness of 0.1 to 1 micrometer. x Ga 1-x N material layer, wherein the In x Ga 1-x The In component content x in the N material layer is 0.05~0.15, wherein the In x Ga 1-x The N material layer has been doped to a concentration of 1×10⁻⁶. 17 ~5×10 17 cm -3 N-type doping treatment;
[0015] And / or, the second waveguide layer is made of In with a thickness of 0.1 to 1 micrometer. y Ga 1-y N material layer, wherein the In y Ga 1-y The In content y in the N material layer is 0.02–0.10, wherein the In x Ga 1-x The N material layer has been doped to a concentration of 1×10⁻⁶. 17 ~5×10 17 cm -3 N-type doping treatment.
[0016] In one possible design, the active layer employs a multi-quantum-well structure consisting of n well layers and n+1 barrier layers stacked alternately, where n represents a positive integer greater than or equal to 2, and the well layers are made of In with a thickness of 2–5 nanometers. p Ga 1-p N material layer, the In p Ga 1-pThe In component content (p) in the N material layer is 0.08–0.35, wherein the In... p Ga 1-p The N material layer has been doped to a concentration of 1×10⁻⁶. 16 ~1×10 17 cm -3 The barrier layer is an N-type doped layer with a thickness of 3–20 nanometers. q Ga 1-q N material layer, the In q Ga 1-q The In component content q in the N material layer is 0 to 0.05, wherein the In q Ga 1-q The N material layer has been doped to a concentration of 1×10⁻⁶. 17 ~5×10 17 cm -3 N-type doping treatment.
[0017] In one possible design, the electron blocking layer is made of Al with a thickness of 5–30 nanometers. z Ga 1-a N material layer, wherein the Al z Ga 1-a The Al component content z in the N material layer is 0.1–0.25, wherein the Al z Ga 1-a The N material layer has been overdoped to a concentration of 5 × 10⁻⁶. 19 ~2×10 20 cm -3 P-type doping treatment.
[0018] In one possible design, the p-type GaN layer is a first GaN material layer with a thickness of 50–70 nanometers, wherein the first GaN material layer has been doped with a concentration of 1 × 10⁻⁶. 17 ~1×10 18 cm -3 P-type doping treatment;
[0019] And / or, the P-type ohmic contact layer employs a second GaN material layer with a thickness of 20–100 nanometers, wherein the second GaN material layer has been doped with a concentration of 1 × 10⁻⁶. 20 ~5×10 20 cm -3 P-type doping treatment.
[0020] In one possible design, the width of the P-type ohmic contact layer is 1–10 micrometers, the width of the P-type GaN layer is 10–20 micrometers, the second confinement layer includes an upper sublayer and a lower sublayer for forming a single-step ridge structure, the upper sublayer has a width of 20–50 micrometers and a thickness between one-third and two-thirds of the thickness of the second confinement layer, the lower sublayer has a width of 50–100 micrometers and a thickness equal to the remaining thickness of the second confinement layer, and the width of the electron blocking layer is the same as the width of the lower sublayer.
[0021] In a second aspect, a method for fabricating the multi-step ridge laser structure as described in the first aspect or any possible design within the first aspect is provided, comprising:
[0022] A buffer layer, a first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, an electron blocking layer, a second confinement layer, a P-type GaN layer, and a P-type ohmic contact layer are epitaxially grown sequentially from the top surface of the substrate.
[0023] In a top-to-bottom order, the P-type ohmic contact layer, the P-type GaN layer, the second confinement layer, and the electron blocking layer are sequentially subjected to material removal processes through photolithography and / or etching processes, so that the widths of the second waveguide layer, the electron blocking layer, the second confinement layer, the P-type GaN layer, and the P-type ohmic contact layer are sequentially reduced and a multi-step ridge structure is formed.
[0024] A P-type electrode layer is epitaxially grown upward on the stepped surface of the multi-step ridge structure;
[0025] An N-type electrode layer is epitaxially grown downwards on the bottom surface of the substrate.
[0026] The beneficial effects of the above scheme are:
[0027] (1) This invention provides a novel edge-emitting laser scheme suitable for fabricating gallium nitride-based blue-green semiconductor lasers, which includes an N-type electrode layer, a substrate layer, a buffer layer, a first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, an electron blocking layer, a second confinement layer, a P-type GaN layer, a P-type ohmic contact layer, and a P-type electrode layer arranged in order from bottom to top. The widths of the second waveguide layer, the electron blocking layer, the second confinement layer, the P-type GaN layer, and the P-type ohmic contact layer decrease sequentially and form a multi-step ridge structure. This not only significantly suppresses the lateral high-order modes of the laser and optimizes the carrier distribution, but also improves the reliability and lifetime of the laser. In addition, it can reduce the influence of factors including thermal lensing effect and lateral current spread effect, suppress the lateral high-order modes of the laser, improve the output performance of the laser, and facilitate practical application and promotion.
[0028] (2) The new structure does not require new process methods. It only uses multiple photolithography and etching processes. The related processes are very mature and suitable for large-scale promotion and use. Attached Figure Description
[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0030] Figure 1 This is a schematic diagram of the layer structure of a multi-step ridge laser structure provided in an embodiment of this application.
[0031] Figure 2 A schematic flowchart illustrating the fabrication method of the multi-step ridge laser structure provided in this application embodiment.
[0032] In the above figures: 1-N-type electrode layer; 2-substrate layer; 3-buffer layer; 4-first confinement layer; 5-first waveguide layer; 6-active layer; 61-well layer; 62-barrier layer; 7-second waveguide layer; 8-electron blocking layer; 9-second confinement layer; 91-upper sublayer; 92-lower sublayer; 10-P-type GaN layer; 11-P-type ohmic contact layer; 12-P-type electrode layer. Detailed Implementation
[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in conjunction with the accompanying drawings and descriptions of the embodiments or the prior art. Obviously, the following description of the structure of the accompanying drawings is only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these embodiments without creative effort. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.
[0034] It should be understood that although the terms "first" and "second", etc., may be used herein to describe various objects, these objects should not be limited by these terms. These terms are only used to distinguish one object from another. For example, the first object may be referred to as the second object, and similarly, the second object may be referred to as the first object, without departing from the scope of the exemplary embodiments of the invention.
[0035] It should be understood that the term "and / or" that may appear in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, or A and B exist simultaneously. Another example is A, B and / or C, which can mean that any one of A, B, and C or any combination thereof exists. The term " / and" that may appear in this document describes another relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone or A and B exist simultaneously. In addition, the character " / " that may appear in this document generally indicates that the related objects before and after it are in an "or" relationship.
[0036] Example 1
[0037] like Figure 1 As shown, the multi-step ridge laser structure provided in this embodiment includes, but is not limited to, the following layers arranged in order from bottom to top: an N-type electrode layer 1, a substrate layer 2, a buffer layer 3, a first confinement layer 4, a first waveguide layer 5, an active layer 6, a second waveguide layer 7, an electron blocking layer 8, a second confinement layer 9, a P-type GaN layer 10, a P-type ohmic contact layer 11, and a P-type electrode layer 12. The widths of the second waveguide layer 7, the electron blocking layer 8, the second confinement layer 9, the P-type GaN layer 10, and the P-type ohmic contact layer 11 decrease sequentially to form a multi-step ridge structure.
[0038] like Figure 1 As shown, in the specific structure of the multi-step ridge laser, the N-type electrode layer 1 is responsible for electron injection and diffusion. Specifically, but not limited to, it employs a four-layer metal electrode structure from the inside out: the first layer is a titanium layer with a thickness of 40–60 nanometers (e.g., 50 nanometers); the second layer is an aluminum layer with a thickness of 80–120 nanometers (e.g., 100 nanometers); the third layer is a titanium layer with a thickness of 40–60 nanometers (e.g., 50 nanometers); and the outermost layer is a gold layer with a thickness of 80–120 nanometers (e.g., 100 nanometers). The substrate layer 2 provides physical support for the entire device, ensuring its structural stability and mechanical strength. Specifically, but not limited to, it uses a GaN substrate or a sapphire substrate, wherein the GaN substrate has been doped to a concentration of 2.5 × 10⁻⁶. 18 ~3.5×10 18 cm -3 (For example, 3×10) 18 cm -3 The buffer layer 3 is an N-type doped layer. It is used to improve electrical performance and stability, and may specifically, but is not limited to, a GaN layer with a thickness of 10–300 micrometers, wherein the GaN layer has been doped with a concentration of 1 × 10⁻⁶. 18 ~1×1019 cm -3 (For example, 3×10) 18 cm -3 The buffer layer 3 is N-type doped. Furthermore, the buffer layer 3 can be grown on the substrate layer 2 using a conventional two-step method, specifically having a combined thickness of 150 micrometers for the substrate layer 2 and the buffer layer 3.
[0039] The first confinement layer 4 plays a crucial role in the laser by confining hole injection and light propagation. Specifically, but not limited to, it uses an Al layer with a thickness of 0.5 to 2 micrometers (for example, 1 micrometer). x Ga 1-x N material layer, wherein the Al x Ga 1-x The Al component content x in the N material layer is 0.01 to 0.15 (for example, 0.08), wherein the Al x Ga 1-x The N material layer has been doped to a concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 (For example, 3×10) 18 cm -3 The first waveguide layer 5 is used to guide the propagation of optical signals, and specifically, but not limited to, using In with a thickness of 0.1 to 1 micrometer (for example, 0.2 micrometers). x Ga 1- x N material layer, wherein the In x Ga 1-x The In content x in the N material layer is 0.05 to 0.15 (for example, 0.08), wherein the In x Ga 1-x The N material layer has been doped to a concentration of 1×10⁻⁶. 17 ~5×10 17 cm -3 (For example, 1×10) 17 cm -3 N-type doping treatment of ).
[0040] The active layer 6 is used to convert electrical energy into light energy to generate laser light. Specifically, but not limited to, it employs a multi-quantum-well structure consisting of n well layers 61 and n+1 barrier layers 62 stacked alternately, where n represents a positive integer greater than or equal to 2 (e.g., ...). Figure 1 As shown, n is 2 for example), the well layer 61 uses In with a thickness of 2 to 5 nanometers (2.5 nanometers for example). p Ga 1-p N material layer, the In p Ga 1-pThe In content p in the N material layer is 0.08–0.35 (for example, 0.12), wherein the In p Ga 1-p The N material layer has been doped to a concentration of 1×10⁻⁶. 16 ~1×10 17 cm -3 (For example, 5×10) 16 cm -3 The barrier layer 62 is an N-type doped layer with a thickness of 3–20 nanometers (for example, the thickness of the bottom barrier layer is 5 nanometers, and the thickness of the other two barrier layers is 10 nanometers). q Ga 1-q N material layer, the In q Ga 1-q The In component content q in the N material layer is 0 to 0.05 (for example, 0.02), wherein the In q Ga 1-q The N material layer has been doped to a concentration of 1×10⁻⁶. 17 ~5×10 17 cm -3 (For example, 1×10) 17 cm -3 N-type doping treatment of ).
[0041] The second waveguide layer 7 is also used to guide the propagation of optical signals, specifically, but not limited to, using In with a thickness of 0.1 to 1 micrometer (for example, 0.1 micrometer). y Ga 1-y N material layer, wherein the In y Ga 1-y The In content y in the N material layer is 0.02 to 0.10 (for example, 0.04), wherein the In x Ga 1-x The N material layer has been doped to a concentration of 1×10⁻⁶. 17 ~5×10 17 cm -3 (For example, 1×10) 17 cm -3 The laser undergoes N-type doping treatment. The electron blocking layer 8 is used to form an energy barrier to confine electron movement, thereby improving laser performance and protecting the quantum well structure. Specifically, but not limited to, it employs an Al layer with a thickness of 5–30 nanometers (e.g., 20 nanometers). z Ga 1-a N material layer, wherein the Al z Ga 1-a The Al component content z in the N material layer is 0.1–0.25 (for example, 0.15), wherein the Al z Ga 1-a The N material layer has been overdoped to a concentration of 5 × 10⁻⁶.19 ~2×10 20 cm -3 (For example, 5×10) 19 cm -3 The second confinement layer 9 plays a crucial role in the laser by confining electron injection and light propagation. Specifically, but not limited to, it employs an Al layer with a thickness of 0.5–2 micrometers (e.g., 0.6 micrometers). y Ga 1-y N material layer, wherein the Al y Ga 1-y The Al component content y in the N material layer is 0.01 to 0.15 (for example, 0.08), wherein the Al y Ga 1-y The N material layer has been doped to a concentration of 1×10⁻⁶. 19 ~5×10 19 cm -3 (For example, 3×10) 19 cm -3 P-type doping treatment of ).
[0042] The p-type GaN layer 10 is used to generate a certain excitation light, and specifically, but not limited to, a first GaN material layer with a thickness of 50-70 nanometers (e.g., 60 nanometers), wherein the first GaN material layer has been doped with a concentration of 1×10⁻⁶. 17 ~1×10 18 cm -3 (For example, 2×10) 19 cm -3 The p-type ohmic contact layer 11 is used to improve crystallinity and extend lifetime, regulate carrier concentration, and improve luminescence efficiency and spectral purity. Specifically, but not limited to, it employs a second GaN material layer with a thickness of 20–100 nanometers (e.g., 100 nanometers), wherein the second GaN material layer has been doped with a concentration of 1 × 10⁻⁶. 20 ~5×10 20 cm -3 (For example, 1×10) 20 cm -3 The laser is p-type doped. The p-type electrode layer 12 is used to inject holes and forms a PN junction together with the n-type electrode layer 1 to start the operation of the laser. Specifically, but not limited to, it adopts the following three-layer metal electrode structure from the inside to the outside: the first layer is a platinum layer with a thickness of 40-60 nanometers (for example, 50 nanometers), the second layer is a palladium layer with a thickness of 40-60 nanometers (for example, 50 nanometers), and the outermost layer is a gold layer with a thickness of 500-700 nanometers (for example, 600 nanometers).
[0043] Specifically, the width of the P-type ohmic contact layer 11 is 1 to 10 micrometers (for example, 10 micrometers), the width of the P-type GaN layer 10 is 10 to 20 micrometers (for example, 20 micrometers), the second confinement layer 9 includes an upper sublayer 91 and a lower sublayer 92 for forming a single-step ridge structure, the width of the upper sublayer 91 is 20 to 50 micrometers (for example, 50 micrometers) and the thickness is between one-third and two-thirds of the thickness of the second confinement layer 9, the width of the lower sublayer 92 is 50 to 100 micrometers (for example, 100 micrometers) and the thickness is the remaining thickness of the second confinement layer 9, and the width of the electron blocking layer 8 (for example, 100 micrometers) is the same as the width of the lower sublayer 92. Furthermore, since the average width of the second confinement layer 9 is necessarily smaller than the width of the lower sub-layer 92, the premise that "the widths of the second waveguide layer 7, the electron blocking layer 8, the second confinement layer 9, the P-type GaN layer 10 and the P-type ohmic contact layer 11 decrease sequentially" is satisfied.
[0044] Based on the above-mentioned multi-step ridge laser structure, the following technical objectives can be achieved: (1) By using the stepped ridge waveguide, the accumulation of charge carriers near the mesa can be reduced, the thermal distribution of the laser can be optimized, thereby reducing the thermal lensing effect of the laser, suppressing higher-order modes, and improving beam quality; (2) By optimizing the longitudinal charge carrier injection channel, the lateral current spread effect of the laser can be reduced, thereby controlling the lateral modes of the laser; (3) The gain of the active region can be increased, and the cavity surface catastrophe caused by charge carrier accumulation can be reduced simultaneously, thereby improving the reliability of the laser. In summary, based on the innovative multi-step ridge laser structure, the lateral higher-order modes of the laser can be significantly suppressed, the charge carrier distribution can be optimized, and the reliability and lifetime of the laser can also be improved.
[0045] In summary, the multi-step ridge laser structure provided in this embodiment has the following technical advantages:
[0046] (1) This embodiment provides a novel edge-emitting laser scheme suitable for fabricating gallium nitride-based blue-green semiconductor lasers, which includes an N-type electrode layer, a substrate layer, a buffer layer, a first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, an electron blocking layer, a second confinement layer, a P-type GaN layer, a P-type ohmic contact layer, and a P-type electrode layer arranged in a bottom-to-top order. The widths of the second waveguide layer, the electron blocking layer, the second confinement layer, the P-type GaN layer, and the P-type ohmic contact layer decrease sequentially and form a multi-step ridge structure. This not only significantly suppresses the lateral high-order modes of the laser and optimizes the carrier distribution, but also improves the reliability and lifetime of the laser. In addition, it can reduce the influence of factors including thermal lensing effect and lateral current spread effect, suppress the lateral high-order modes of the laser, improve the output performance of the laser, and facilitate practical application and promotion.
[0047] Example 2
[0048] Based on the technical solution of Embodiment 1, this embodiment also provides a method for fabricating a multi-step ridge laser structure as described in Embodiment 1. Figure 2 As shown, it includes, but is not limited to, the following steps S1 to S4.
[0049] S1. A buffer layer 3, a first confinement layer 4, a first waveguide layer 5, an active layer 6, a second waveguide layer 7, an electron blocking layer 8, a second confinement layer 9, a P-type GaN layer 10, and a P-type ohmic contact layer 11 are epitaxially grown sequentially on the top surface of the substrate layer 2.
[0050] In step S1, the specific epitaxial growth process required is an existing process, which will not be described in detail here.
[0051] S2. In order from top to bottom, the P-type ohmic contact layer 11, the P-type GaN layer 10, the second confinement layer 9 and the electron blocking layer 8 are sequentially subjected to material removal processes through photolithography and / or etching processes, so that the widths of the second waveguide layer 7, the electron blocking layer 8, the second confinement layer 9, the P-type GaN layer 10 and the P-type ohmic contact layer 11 are sequentially reduced and a multi-step ridge structure is formed.
[0052] In step S2, the photolithography process and the etching process are existing processes, and will not be described in detail here.
[0053] S3. A P-type electrode layer 12 is obtained by epitaxial growth on the stepped surface of the multi-step ridge structure.
[0054] S4. An N-type electrode layer 1 is epitaxially grown downward on the bottom surface of the substrate layer 2.
[0055] The above step S4 is not limited to being performed after step S3, but can also be performed before steps S1, S2 or S3.
[0056] In summary, based on the technical effects of Embodiment 1, this embodiment also has the following technical effects: (1) The new structure does not require the use of new process methods, but only uses multiple photolithography and etching processes. The related processes are very mature and suitable for large-scale promotion and use.
[0057] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A multi-step ridge laser structure, characterized in that, It includes an N-type electrode layer (1), a substrate layer (2), a buffer layer (3), a first confinement layer (4), a first waveguide layer (5), an active layer (6), a second waveguide layer (7), an electron blocking layer (8), a second confinement layer (9), a P-type GaN layer (10), a P-type ohmic contact layer (11), and a P-type electrode layer (12) arranged in order from bottom to top. The widths of the second waveguide layer (7), the electron blocking layer (8), the second confinement layer (9), the P-type GaN layer (10), and the P-type ohmic contact layer (11) decrease sequentially and form a multi-step ridge structure. The second confinement layer (9) is used to confine electron injection and light propagation in the laser, and includes an upper sublayer (91) and a lower sublayer (92) for forming a single-step ridge structure, wherein the thickness of the upper sublayer (91) is between one-third and two-thirds of the thickness of the second confinement layer (9), and the thickness of the lower sublayer (92) is the remaining thickness of the second confinement layer (9); The width of the P-type ohmic contact layer (11) is 1 to 10 micrometers, the width of the P-type GaN layer (10) is 10 to 20 micrometers, the width of the upper sublayer (91) is 20 to 50 micrometers, the width of the lower sublayer (92) is 50 to 100 micrometers, and the width of the electron blocking layer (8) is the same as the width of the lower sublayer (92). The P-type electrode layer (12) is obtained by growing upwards on the stepped surface of the multi-step ridge structure.
2. The multi-step ridge laser structure as described in claim 1, characterized in that, The N-type electrode layer (1) adopts the following four-layer metal electrode structure from the inside to the outside: the first layer is a titanium layer with a thickness of 40-60 nanometers, the second layer is an aluminum layer with a thickness of 80-120 nanometers, the third layer is a titanium layer with a thickness of 40-60 nanometers, and the outermost layer is a gold layer with a thickness of 80-120 nanometers. And / or, the P-type electrode layer (12) adopts the following three-layer metal electrode structure from the inside to the outside: the first layer is a platinum layer with a thickness of 40 to 60 nanometers, the second layer is a palladium layer with a thickness of 40 to 60 nanometers, and the outermost layer is a gold layer with a thickness of 500 to 700 nanometers.
3. The multi-step ridge laser structure as described in claim 1, characterized in that, The substrate layer (2) is a GaN substrate or a sapphire substrate, wherein the GaN substrate has been doped to a concentration of 2.5 × 10⁻⁶. 18 ~3.5×10 18 cm -3 N-type doping treatment; And / or, the buffer layer (3) is a GaN layer with a thickness of 10 to 300 micrometers, wherein the GaN layer has been doped with a concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 N-type doping treatment.
4. The multi-step ridge laser structure as described in claim 1, characterized in that, The first confinement layer (4) is made of Al with a thickness of 0.5 to 2 micrometers. x Ga 1-x N material layer, wherein the Al x Ga 1-x The Al component content x in the N material layer is 0.01 to 0.15, wherein the Al x Ga 1-x The N material layer has been doped to a concentration of 1×10⁻⁶. 18 ~1×10 19 cm -3 N-type doping treatment; And / or, the second confinement layer (9) is made of Al with a thickness of 0.5 to 2 micrometers. y Ga 1-y N material layer, wherein the Al y Ga 1-y The Al component content y in the N material layer is 0.01–0.15, wherein the Al y Ga 1-y The N material layer has been doped to a concentration of 1×10⁻⁶. 19 ~5×10 19 cm -3 P-type doping treatment.
5. The multi-step ridge laser structure as described in claim 1, characterized in that, The first waveguide layer (5) is made of In with a thickness of 0.1 to 1 micrometer. x Ga 1-x N material layer, wherein the In x Ga 1-x The In component content x in the N material layer is 0.05~0.15, wherein the In x Ga 1-x The N material layer has been doped to a concentration of 1×10⁻⁶. 17 ~5×10 17 cm -3 N-type doping treatment; And / or, the second waveguide layer (7) is made of In with a thickness of 0.1 to 1 micrometer. y Ga 1-y N material layer, wherein the In y Ga 1-y The In content y in the N material layer is 0.02–0.10, wherein the In x Ga 1-x The N material layer has been doped to a concentration of 1×10⁻⁶. 17 ~5×10 17 cm -3 N-type doping treatment.
6. The multi-step ridge laser structure as described in claim 1, characterized in that, The active layer (6) adopts a multi-quantum well structure consisting of n well layers (61) and n+1 barrier layers (62) stacked alternately, where n represents a positive integer greater than or equal to 2, and the well layers (61) are made of In with a thickness of 2 to 5 nanometers. p Ga 1-p N material layer, the In p Ga 1-p The In component content (p) in the N material layer is 0.08–0.35, wherein the In... p Ga 1-p The N material layer has been doped to a concentration of 1×10⁻⁶. 16 ~1×10 17 cm -3 The barrier layer (62) is an N-type doped layer with a thickness of 3–20 nanometers. q Ga 1-q N material layer, the In q Ga 1-q The In component content q in the N material layer is 0 to 0.05, wherein the In q Ga 1-q The N material layer has been doped to a concentration of 1×10⁻⁶. 17 ~5×10 17 cm -3 N-type doping treatment.
7. The multi-step ridge laser structure as described in claim 1, characterized in that, The electron blocking layer (8) is made of Al with a thickness of 5-30 nanometers. z Ga 1-a N material layer, wherein the Al z Ga 1-a The Al component content z in the N material layer is 0.1–0.25, wherein the Al z Ga 1-a The N material layer has been overdoped to a concentration of 5 × 10⁻⁶. 19 ~2×10 20 cm -3 P-type doping treatment.
8. The multi-step ridge laser structure as described in claim 1, characterized in that, The p-type GaN layer (10) is a first GaN material layer with a thickness of 50-70 nanometers, wherein the first GaN material layer has been doped with a concentration of 1×10⁻⁶. 17 ~1×10 18 cm -3 P-type doping treatment; And / or, the P-type ohmic contact layer (11) is a second GaN material layer with a thickness of 20-100 nanometers, wherein the second GaN material layer has been doped with a concentration of 1×10⁻⁶. 20 ~5×10 20 cm -3 P-type doping treatment.
9. A method for fabricating a multi-step ridge laser structure as described in any one of claims 1 to 8, comprising: A buffer layer (3), a first confinement layer (4), a first waveguide layer (5), an active layer (6), a second waveguide layer (7), an electron blocking layer (8), a second confinement layer (9), a P-type GaN layer (10), and a P-type ohmic contact layer (11) are epitaxially grown sequentially on the top surface of the substrate layer (2). In order from top to bottom, the P-type ohmic contact layer (11), the P-type GaN layer (10), the second confinement layer (9) and the electron blocking layer (8) are sequentially subjected to material removal processes through photolithography and / or etching processes, so that the widths of the second waveguide layer (7), the electron blocking layer (8), the second confinement layer (9), the P-type GaN layer (10) and the P-type ohmic contact layer (11) are sequentially reduced and a multi-step ridge structure is formed; A P-type electrode layer (12) is epitaxially grown upward on the stepped surface of the multi-step ridge structure; An N-type electrode layer (1) is epitaxially grown downward on the bottom surface of the substrate layer (2).