Multi-step ridge type laser structure and preparation method thereof

Abstract

The invention discloses a multi-step ridge type laser structure and a preparation method thereof, and relates to the technical field of gallium nitride semiconductor lasers. The multi-step ridge-type laser structure comprises an N-type electrode layer, a substrate layer, a buffer layer, a first limiting layer, a first waveguide layer, an active layer, a second waveguide layer, an electron blocking layer, a second limiting layer, a P-type GaN layer, a P-type ohmic contact layer and a P-type electrode layer which are sequentially arranged from bottom to top, the widths of the second waveguide layer, the electron blocking layer, the second limiting layer, the P-type GaN layer and the P-type ohmic contact layer are sequentially reduced and form a multi-step ridge structure, so that the lateral high-order mode of the laser can be remarkably inhibited, the carrier distribution is optimized, the reliability of the laser can be improved, the service life of the laser can be prolonged, and the service life of the laser can be prolonged. Therefore, the influence of factors including a thermal lens effect and a lateral current expansion effect can be reduced, a lateral high-order mode of the laser can be suppressed, and the output performance of the laser can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of gallium nitride semiconductor lasers, and in particular relates to a multi-step ridge laser structure and a preparation method thereof. Background Art

[0002] Gallium nitride semiconductor laser is an important semiconductor optoelectronic device, which is widely used in laser display, laser communication and laser surgery. Among them, laser display is known as the ultimate display technology, and chip-level semiconductor red, green and blue primary color lasers play an indispensable role in laser display. Relatively speaking, red and blue semiconductor lasers are relatively mature at present, while green semiconductor lasers are still in the early stages of development.

[0003] Gallium nitride-based blue-green semiconductor lasers are very promising blue-green laser solutions that can achieve monolithic integration of three primary color lasers while achieving continuous adjustable wavelength. Existing application scenarios have put forward requirements for high power and low beam divergence for gallium nitride semiconductor lasers. At present, gallium nitride-based blue light semiconductor lasers can achieve a single-tube continuous power of more than 15W, and gallium nitride-based green light semiconductor lasers can achieve a single-tube continuous power of more than 2.5W. However, the edge-emitting laser structure (i.e., an edge-emitting light-emitting laser structure, whose light-emitting area is limited to a very small part of one side, and the limited light emission area can improve the coupling efficiency with optical fiber and integrated optical circuits) of traditional gallium nitride-based blue-green semiconductor lasers still faces problems such as large divergence angle and poor beam quality. That is, due to the thermal lens effect, lateral current expansion effect and longitudinal space hole burning, the existing ridge edge-emitting lasers will obtain higher gain in the high-order side modes of the laser, increase the number of lasing side modes, and further deteriorate the divergence angle and beam quality of the laser. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-step ridge laser structure and a preparation method thereof, so as to solve the problems of large divergence angle and poor beam quality existing in the edge-emitting laser structure of the existing gallium nitride-based blue-green semiconductor laser.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[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 in sequence 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 in sequence to form a multi-step ridge structure.

[0007] Based on the above invention content, a new edge-emitting laser scheme suitable for making gallium nitride-based blue-green semiconductor lasers is provided, 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 sequence 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 are successively reduced to form a multi-step ridge structure, which can not only significantly suppress the lateral high-order mode of the laser, optimize the carrier distribution, but also improve the reliability and life of the laser, thereby reducing the influence of factors including thermal lens effect and lateral current expansion effect, suppressing the lateral high-order mode of the laser, improving the output performance of the laser, and facilitating practical application and promotion.

[0008] In a possible design, the N-type electrode layer adopts the following four-layer metal electrode structure from inside to outside: the first layer is a titanium layer with a thickness of 40 to 60 nanometers, the second layer is an aluminum layer with a thickness of 80 to 120 nanometers, the third layer is a titanium layer with a thickness of 40 to 60 nanometers, and the outermost layer is a gold layer with a thickness of 80 to 120 nanometers;

[0009] And / or, the P-type electrode layer adopts the following three-layer metal electrode structure from inside to 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.

[0010] In a 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 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 to 300 microns, wherein the GaN layer has been doped with a concentration of 1×10 18 ~1×10 19 cm -3 N-type doping treatment.

[0012] In a possible design, the first confinement layer is made of Al with a thickness of 0.5 to 2 microns. 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. x Ga1-x The N material layer has been doped to a concentration of 1×10 18 ~1×10 19 cm -3 N-type doping treatment;

[0013] And / or, the second limiting layer is made of Al with a thickness of 0.5 to 2 microns. 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. y Ga 1-y The N material layer has been doped to a concentration of 1×10 19 ~5×10 19 cm -3 P-type doping treatment.

[0014] In a possible design, the first waveguide layer is made of In with a thickness of 0.1 to 1 micron. 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 to 0.15. x Ga 1-x The N material layer has been doped to a concentration of 1×10 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 micron. y Ga 1-y N material layer, wherein the In y Ga 1-y The In component content y in the N material layer is 0.02 to 0.10. x Ga 1-x The N material layer has been doped to a concentration of 1×10 17 ~5×10 17 cm -3 N-type doping treatment.

[0016] In a possible design, the active layer adopts a multi-quantum well structure formed by alternating n well layers and n+1 barrier layers, wherein n represents a positive integer greater than or equal to 2, and the well layer adopts In with a thickness of 2 to 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 to 0.35. p Ga 1-p The N material layer has been doped to a concentration of 1×10 16 ~1×10 17 cm -3 The barrier layer is made of In with a thickness of 3 to 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. q Ga 1-q The N material layer has been doped to a concentration of 1×10 17 ~5×10 17 cm -3 N-type doping treatment.

[0017] In a possible design, the electron blocking layer is made of Al with a thickness of 5 to 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. z Ga 1-a The N material layer has been doped to a concentration of 5×10 19 ~2×10 20 cm -3 P-type doping treatment.

[0018] In a possible design, the P-type GaN layer uses a first GaN material layer with a thickness of 50 to 70 nanometers, wherein the first GaN material layer has been doped with a concentration of 1×10 17 ~1×10 18 cm -3 P-type doping treatment;

[0019] And / or, the P-type ohmic contact layer is a second GaN material layer with a thickness of 20 to 100 nanometers, wherein the second GaN material layer has been doped with a concentration of 1×10 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 to 10 microns, the width of the P-type GaN layer is 10 to 20 microns, the second confinement layer includes an upper sublayer and a lower sublayer for forming a single-step ridge structure, the width of the upper sublayer is 20 to 50 microns and the thickness is between one third and two thirds of the thickness of the second confinement layer, the width of the lower sublayer is 50 to 100 microns and the thickness is the remaining thickness of the second confinement layer, and the width of the electron blocking layer is consistent with the width of the lower sublayer.

[0021] In a second aspect, a method for preparing the multi-step ridge laser structure according to the first aspect or any possible design of the first aspect is provided, comprising:

[0022] Epitaxially growing upward in sequence on the top surface of the substrate layer to obtain 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;

[0023] In order from top to bottom, 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 processing by a photolithography process and / or an etching process, 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 to form a multi-step ridge structure;

[0024] Epitaxially growing upward on the step surface of the multi-step ridge structure to obtain a P-type electrode layer;

[0025] An N-type electrode layer is obtained by downward epitaxial growth on the bottom surface of the substrate layer.

[0026] Beneficial effects of the above scheme:

[0027] (1) The present invention provides a novel edge-emitting laser solution suitable for manufacturing gallium nitride-based blue-green semiconductor lasers, namely, 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 are sequentially arranged 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 are successively reduced to form a multi-step ridge structure, which can not only significantly suppress the lateral high-order mode of the laser, optimize the carrier distribution, but also improve the reliability and life of the laser, thereby reducing the influence of factors including thermal lens effect and lateral current expansion effect, suppressing the lateral high-order mode of the laser, improving the output performance of the laser, and facilitating practical application and promotion;

[0028] (2) The new structure does not require the use of new process methods, only multiple additional photolithography and etching processes are used. The relevant processes are very mature and suitable for large-scale promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 Schematic diagram of the layer structure of the multi-step ridge laser structure provided in an embodiment of the present application.

[0031] Figure 2 A schematic flow chart of a method for preparing a multi-step ridge laser structure provided in an embodiment of the present application.

[0032] In the above drawings: 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 DESCRIPTION

[0033] In order 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 combination with the drawings and the description of the embodiments or the prior art. Obviously, the following description of the structures of the drawings is only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these embodiments without creative work. It should be noted that the description of these embodiments is used to help 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 object. For example, a first object can be referred to as a second object, and similarly, a second object can be referred to as a first object without departing from the scope of the exemplary embodiments of the present invention.

[0035] It should be understood that the term "and / or" that may appear in this document is merely a description of the association relationship between associated objects, indicating that there may be three relationships. For example, A and / or B can indicate three situations: A exists alone, B exists alone, or A and B exist at the same time. For another example, A, B and / or C can indicate the existence of any one of A, B and C or any combination of them. The term " / and" that may appear in this document describes another type of association object relationship, indicating that there may be two relationships. For example, A / and B can indicate two situations: A exists alone or A and B exist at the same time. In addition, the character " / " that may appear in this document generally indicates that the previous and next associated objects are in an "or" relationship.

[0036] Embodiment 1

[0037] like Figure 1 As shown, the multi-step ridge laser structure provided in this embodiment includes but is not limited to 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, which are arranged in sequence from bottom to top, wherein 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 successively reduced to form a multi-step ridge structure.

[0038] like Figure 1 As shown, in the specific structure of the multi-step ridge laser structure, the N-type electrode layer 1 is responsible for the injection and diffusion of electrons, which specifically but not limited to adopt the following four-layer metal electrode structure from inside to outside: the first layer is a titanium layer with a thickness of 40 to 60 nanometers (for example, 50 nanometers), the second layer is an aluminum layer with a thickness of 80 to 120 nanometers (for example, 100 nanometers), the third layer is a titanium layer with a thickness of 40 to 60 nanometers (for example, 50 nanometers), and the outermost layer is a gold layer with a thickness of 80 to 120 nanometers (for example, 100 nanometers). The substrate layer 2 is used to provide physical support for the entire device to ensure the structural stability and mechanical strength of the entire device. It specifically but not limited to adopting a GaN substrate or a sapphire substrate, wherein the GaN substrate has been doped with a concentration of 2.5×10 18 ~3.5×10 18 cm -3 (For example, 3×10 18 cm -3 The buffer layer 3 is used to improve the electrical performance and stability, and can be, but is not limited to, a GaN layer with a thickness of 10 to 300 microns, wherein the GaN layer has been doped with a concentration of 1×10 18 ~1×1019 cm -3 (For example, 3×10 18 cm -3 ) is subjected to N-type doping treatment. In addition, the buffer layer 3 can be grown on the substrate layer 2 by a conventional two-step method, and specifically, the sum of the thickness of the substrate layer 2 and the buffer layer 3 is 150 microns.

[0039] The first limiting layer 4 plays a key role in limiting hole injection and light propagation in the laser. Specifically, but not limited to, the first limiting layer 4 is made of Al with a thickness of 0.5 to 2 microns (for example, 1 micron). 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). x Ga 1-x The N material layer has been doped to a concentration of 1×10 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 the optical signal, and specifically but not limited to, In with a thickness of 0.1 to 1 micron (for example, 0.2 micron) 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 to 0.15 (for example, 0.08). x Ga 1-x The N material layer has been doped to a concentration of 1×10 17 ~5×10 17 cm -3 (For example, 1×10 17 cm -3 ) is subjected to N-type doping treatment.

[0040] The active layer 6 is used to convert electrical energy into light energy to generate laser light, and specifically but not limited to, a multi-quantum well structure formed by alternately stacking n well layers 61 and n+1 barrier layers 62, wherein n represents a positive integer greater than or equal to 2 (e.g. Figure 1 As shown, n is 2 for example, and the well layer 61 is made of In with a thickness of 2 to 5 nanometers (for example, 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 to 0.35 (for example, 0.12). p Ga 1-p The N material layer has been doped to a concentration of 1×10 16 ~1×10 17 cm -3 (For example, 5×10 16 cm -3 ) is N-type doped, and the barrier layer 62 is made of In with a thickness of 3 to 20 nanometers (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). q Ga 1-q The N material layer has been doped to a concentration of 1×10 17 ~5×10 17 cm -3 (For example, 1×10 17 cm -3 ) is subjected to N-type doping treatment.

[0041] The second waveguide layer 7 is also used to guide the propagation of the optical signal, and specifically but not limited to, an In waveguide layer with a thickness of 0.1 to 1 micron (for example, 0.1 micron) is used. y Ga 1-y N material layer, wherein the In y Ga 1-y The In component content y in the N material layer is 0.02 to 0.10 (for example, 0.04). x Ga 1-x The N material layer has been doped to a concentration of 1×10 17 ~5×10 17 cm -3 (For example, 1×10 17 cm -3 The electron blocking layer 8 is used to form an energy barrier to limit the movement of electrons, thereby improving the laser performance and protecting the quantum well structure. Specifically, but not limited to, Al2O3 with a thickness of 5 to 30 nanometers (for example, 20 nanometers) is used. 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 to 0.25 (for example, 0.15). z Ga 1-a The N material layer has been doped to a concentration of 5×1019 ~2×10 20 cm -3 (For example, 5×10 19 cm -3 The second limiting layer 9 plays a key role in limiting electron injection and light propagation in the laser. Specifically but not limited to, the second limiting layer 9 is made of Al with a thickness of 0.5 to 2 microns (for example, 0.6 microns). 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). y Ga 1-y The N material layer has been doped to a concentration of 1×10 19 ~5×10 19 cm -3 (For example, 3×10 19 cm -3 ) is subjected to P-type doping treatment.

[0042] The P-type GaN layer 10 is used to generate a certain amount of excitation light, which specifically but not limited to a first GaN material layer with a thickness of 50 to 70 nanometers (for example, 60 nanometers), wherein the first GaN material layer has been doped with a concentration of 1×10 17 ~1×10 18 cm -3 (For example, 2×10 19 cm -3 ) is subjected to P-type doping treatment. The P-type ohmic contact layer 11 is used to improve crystallinity and prolong life, regulate carrier concentration, and improve luminous efficiency and spectral purity. Specifically but not limited to, a second GaN material layer with a thickness of 20 to 100 nanometers (for example, 100 nanometers) is used, wherein the second GaN material layer has been doped with a concentration of 1×10 20 ~5×10 20 cm -3 (For example, 1×10 20 cm -3 ) is subjected to P-type doping treatment. The P-type electrode layer 12 is used to inject holes and form a PN junction with the N-type electrode layer 1, thereby starting the operation of the laser. Specifically but not limited to, the following three-layer metal electrode structure is adopted from the inside to the outside: the first layer is a platinum layer with a thickness of 40 to 60 nanometers (for example, 50 nanometers), the second layer is a palladium layer with a thickness of 40 to 60 nanometers (for example, 50 nanometers), and the outermost layer is a gold layer with a thickness of 500 to 700 nanometers (for example, 600 nanometers).

[0043] Specifically, the width of the P-type ohmic contact layer 11 is 1 to 10 microns (for example, 10 microns), the width of the P-type GaN layer 10 is 10 to 20 microns (for example, 20 microns), and 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 microns (for example, 50 microns) 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 microns (for example, 100 microns) 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 microns) is consistent with the width of the lower sublayer 92. In addition, since the average width of the second confinement layer 9 must be smaller than the width of the lower sublayer 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 in sequence" is satisfied.

[0044] Based on the above multi-step ridge laser structure, the following technical objectives can be achieved: (1) Through the step-type ridge waveguide, the aggregation of carriers near the table can be reduced, the thermal distribution of the laser can be optimized, thereby reducing the thermal lens effect of the laser, suppressing high-order modes, and improving the beam quality; (2) By optimizing the longitudinal carrier injection channel, the lateral current expansion effect of the laser can be reduced, thereby controlling the lateral mode of the laser; (3) The gain of the active region can be increased, and the cavity surface catastrophe caused by carrier aggregation can be simultaneously reduced, thereby improving the reliability of the laser. In summary, based on the innovative multi-step ridge laser structure, the lateral high-order modes of the laser can be significantly suppressed, the carrier distribution can be optimized, and the reliability and life of the laser can also be improved.

[0045] In summary, the multi-step ridge laser structure provided in this embodiment has the following technical effects:

[0046] (1) This embodiment provides a novel edge-emitting laser solution suitable for manufacturing a gallium nitride-based blue-green semiconductor laser, namely, 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 in sequence 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 are successively reduced to form a multi-step ridge structure, which can not only significantly suppress the lateral high-order mode of the laser and optimize the carrier distribution, but also improve the reliability and life of the laser, thereby reducing the influence of factors including the thermal lens effect and the lateral current spreading effect, suppressing the lateral high-order mode of the laser, and improving the output performance of the laser, which is convenient for practical application and promotion.

[0047] Embodiment 2

[0048] Based on the technical solution of Example 1, this embodiment further provides a method for preparing the multi-step ridge laser structure as described in Example 1. Figure 2 As shown, the process 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 sequentially epitaxially grown upward on the top surface of the substrate layer 2.

[0050] In the step S1 , the specific epitaxial growth process required is an existing process and will not be described in detail herein.

[0051] S2. 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 processing by means of a photolithography process and / or an etching process, 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 to form a multi-step ridge structure.

[0052] In the step S2, the photolithography process and the etching process are also existing processes, which will not be described in detail here.

[0053] S3. Epitaxially grow upward on the step surfaces of the multi-step ridge structure to obtain a P-type electrode layer 12.

[0054] S4. An N-type electrode layer 1 is obtained by epitaxially growing 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 may also be performed before step S1, S2 or S3.

[0056] In summary, based on the technical effects of the first embodiment, this embodiment also has the following technical effects: (1) The new structure does not require the use of new process means, but only uses multiple additional photolithography and etching processes. The relevant processes are very mature and suitable for large-scale promotion and use.

[0057] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-step ridge laser structure, characterized in that: The invention comprises 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) which are arranged in sequence from bottom to top, wherein 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 in sequence and form a multi-step ridge structure.

2. The multi-step ridge laser structure according to claim 1, characterized in that: The N-type electrode layer (1) adopts the following four-layer metal electrode structure from inside to outside: the first layer is a titanium layer with a thickness of 40 to 60 nanometers, the second layer is an aluminum layer with a thickness of 80 to 120 nanometers, the third layer is a titanium layer with a thickness of 40 to 60 nanometers, and the outermost layer is a gold layer with a thickness of 80 to 120 nanometers; And / or, the P-type electrode layer (12) adopts the following three-layer metal electrode structure from inside to 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 according to 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 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 18 ~1×10 19 cm -3 N-type doping treatment.

4. The multi-step ridge laser structure according to claim 1, characterized in that: The first limiting layer (4) is made of Al with a thickness of 0.5 to 2 microns. 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. x Ga 1-x The N material layer has been doped to a concentration of 1×10 18 ~1×10 19 cm -3 N-type doping treatment; And / or, the second limiting layer (9) is made of Al with a thickness of 0.5 to 2 microns. 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. y Ga 1-y The N material layer has been doped to a concentration of 1×10 19 ~5×10 19 cm -3 P-type doping treatment.

5. The multi-step ridge laser structure according to claim 1, characterized in that: The first waveguide layer (5) is made of In with a thickness of 0.1 to 1 micron. 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 to 0.

15. x Ga 1-x The N material layer has been doped to a concentration of 1×10 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 micron. y Ga 1-y N material layer, wherein the In y Ga 1-y The In component content y in the N material layer is 0.02 to 0.

10. x Ga 1-x The N material layer has been doped to a concentration of 1×10 17 ~5×10 17 cm -3 N-type doping treatment.

6. The multi-step ridge laser structure according to claim 1, characterized in that: The active layer (6) adopts a multi-quantum well structure formed by alternately stacking n well layers (61) and n+1 barrier layers (62), wherein n represents a positive integer greater than or equal to 2, and the well layer (61) adopts 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 to 0.

35. p Ga 1-p The N material layer has been doped to a concentration of 1×10 16 ~1×10 17 cm -3 The barrier layer (62) is made of In with a thickness of 3 to 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. q Ga 1-q The N material layer has been doped to a concentration of 1×10 17 ~5×10 17 cm -3 N-type doping treatment.

7. The multi-step ridge laser structure according to claim 1, characterized in that: The electron blocking layer (8) is made of Al with a thickness of 5 to 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. z Ga 1-a The N material layer has been doped to a concentration of 5×10 19 ~2×10 20 cm -3 P-type doping treatment.

8. The multi-step ridge laser structure according to claim 1, characterized in that: The P-type GaN layer (10) is a first GaN material layer with a thickness of 50 to 70 nanometers, wherein the first GaN material layer has been doped with a concentration of 1×10 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 to 100 nanometers, wherein the second GaN material layer has been doped with a concentration of 1×10 20 ~5×10 20 cm -3 P-type doping treatment.

9. The multi-step ridge laser structure according to claim 1, characterized in that: The width of the P-type ohmic contact layer (11) is 1 to 10 microns, the width of the P-type GaN layer (10) is 10 to 20 microns, the second confinement layer (9) comprises 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 microns 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 microns and the thickness is the remaining thickness of the second confinement layer (9), and the width of the electron blocking layer (8) is consistent with the width of the lower sublayer (92).

10. A method for preparing a multi-step ridge laser structure according to any one of claims 1 to 9, 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 sequentially epitaxially grown upward 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 processing by means of a photolithography process and / or an etching process, 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 to form a multi-step ridge structure; Epitaxially growing upward on the step surface of the multi-step ridge structure to obtain a P-type electrode layer (12); An N-type electrode layer (1) is obtained by downward epitaxial growth on the bottom surface of the substrate layer (2).

Images