阅读说明：本技术 一种InP基垂直腔面发射激光器 (InP-based vertical cavity surface emitting laser ) 是由 杨翠柏 于 2021-08-10 设计创作，主要内容包括：本发明提供了一种InP基垂直腔面发射激光器及其制备方法,其中的一种InP基垂直腔面发射激光器包括以下结构：InP衬底；依次位于所述InP衬底上的缓冲层、第一DBR反射层、长波激光发射单元、第二DBR反射层和电极接触层；所述第一DBR反射层和第二DBR反射层均包括第一折射率材料层和第二折射率材料层交替重叠的多层结构,所述第一折射率材料层晶格常数小于所述InP衬底,所述第二折射率材料层晶格常数大于所述InP衬底。本发明采用应变类型相反的两种材料交替生长制作DBR层,可以通过应变补偿的方式降低因晶格失配产生的应力,减少外延片翘曲的风险。(The invention provides an InP-based vertical cavity surface emitting laser and a preparation method thereof, wherein the InP-based vertical cavity surface emitting laser comprises the following structures: an InP substrate; the buffer layer, the first DBR reflecting layer, the long-wave laser emitting unit, the second DBR reflecting layer and the electrode contact layer are sequentially arranged on the InP substrate; the first DBR reflection layer and the second DBR reflection layer respectively comprise a multilayer structure formed by alternately overlapping a first refractive index material layer and a second refractive index material layer, the lattice constant of the first refractive index material layer is smaller than that of the InP substrate, and the lattice constant of the second refractive index material layer is larger than that of the InP substrate. According to the invention, the DBR layer is prepared by alternately growing two materials with opposite strain types, so that the stress generated by lattice mismatch can be reduced in a strain compensation mode, and the risk of warping of an epitaxial wafer is reduced.)

1. An InP-based vertical cavity surface emitting laser comprising the following structure:

an InP substrate;

the buffer layer, the first DBR reflecting layer, the long-wave laser emitting unit, the second DBR reflecting layer and the electrode contact layer are sequentially arranged on the InP substrate;

wherein the content of the first and second substances,

the first DBR reflection layer and the second DBR reflection layer respectively comprise a multilayer structure formed by alternately overlapping a first refractive index material layer and a second refractive index material layer, the lattice constant of the first refractive index material layer is smaller than that of the InP substrate, and the lattice constant of the second refractive index material layer is larger than that of the InP substrate.

2. The InP based vcsel of claim 1, wherein: the InP substrate is an n-type InP single crystal substrate;

the buffer layer is an n-type InP buffer layer;

the first DBR reflecting layer is an n-type DBR reflecting layer, the second DBR reflecting layer is a p-type DBR reflecting layer, and the number of alternately overlapped growing pairs of the n-type DBR reflecting layer and the p-type DBR reflecting layer is different;

the electrode contact layer is a p-type InP electrode contact layer.

3. The InP based vcsel of claim 2, wherein: the thickness of the n-type InP buffer layer is 200-800 nm; the thickness of the p-type InP electrode contact layer is 100-400 nm, and the doping concentration is more than 3 multiplied by 10¹⁸cm^-3。

4. The InP based vcsel of claim 2, wherein: the number of alternately overlapped growth pairs of the n-type DBR layers is 30-50 pairs, and the number of alternately overlapped growth pairs of the p-type DBR layers is 20-40 pairs.

5. The InP based vcsel of claim 1, wherein: the material of the first refractive index material layer and the second refractive index material layer is binary or ternary III/V compound.

6. The InP based vcsel of claim 5, wherein: the first refractive index material layer is one of AlP, GaP, AlAs, GaAs, AlGaAs and AlGaP; the second refractive index material layer is one of AlSb, GaSb and AlGaSb.

7. The InP based vcsel of claim 1, wherein: the long-wave laser emission unit is composed of multiple quantum well materials, the multiple quantum well materials comprise potential barrier materials and potential well materials, the potential barrier materials are InP, the potential well materials are one of GaInAsP or AlGaInAs of low band gap materials, and the number of quantum wells is 2-5.

8. A preparation method of an InP-based vertical cavity surface emitting laser is characterized by comprising the following steps:

step S1: growing a buffer layer on the InP substrate;

step S2: forming a first DBR reflective layer on the buffer layer, the first DBR reflective layer including a structure in which first and second refractive index material layers alternately overlap in a multilayer structure, the first refractive index material layer having a smaller lattice constant than the InP substrate, the second refractive index material layer having a larger lattice constant than the InP substrate;

step S3: forming a long-wave laser emitting unit on the first DBR reflective layer;

step S4: forming a second DBR reflective layer including a multilayer structure in which first and second refractive index material layers are alternately overlapped on the long wave laser emission unit; the material of the first DBR reflecting layer is the same as that of the second DBR reflecting layer;

step S5: an electrode contact layer is formed on the second DBR reflective layer.

9. The method of manufacturing an InP-based vcsel according to claim 8, wherein: the InP substrate is an n-type InP single crystal substrate;

the buffer layer is an n-type InP buffer layer;

the first DBR reflecting layer is an n-type DBR reflecting layer, and the second DBR reflecting layer is a p-type DBR reflecting layer;

the electrode contact layer is a p-type InP electrode contact layer.

10. The method of manufacturing an InP-based vcsel according to claim 9, wherein: the material of the first refractive index material layer and the second refractive index material layer is binary or ternary III/V group compound, wherein the first refractive index material layer is one of AlP, GaP, AlAs, GaAs, AlGaAs and AlGaP; the second refractive index material layer is one of AlSb, GaSb and AlGaSb.

Technical Field

The invention relates to the technical field of semiconductor lasers, in particular to an InP-based vertical cavity surface emitting laser.

Background

The long-wavelength vertical cavity surface laser (VCSEL) with the lasing wavelength within the range of 1300-1600 nm can be applied to the fields of long-distance optical fiber communication, vehicle-mounted radar and the like, and has wide development prospects. At present, the semiconductor long-wavelength VCSEL is mostly developed by using an InP substrate, an active region can be made of GaInAsP or AlGaInAs, and a Distributed Bragg Reflector (DBR) can be made of a combination of GaInAsP/InP or AlGaInAs/InP. However, because the refractive index difference between GaAs and AlGaAs materials is large, GaAs/AlGaAs is one of the most mature semiconductor DBR material systems, but due to large lattice mismatch with an InP substrate, when InP-based long-wavelength VCSELs are prepared by using GaAs/AlGaAs as a DBR, large stress is generated, which causes warpage of an epitaxial material sheet, affects material quality and increases process difficulty.

Disclosure of Invention

The invention aims to overcome the defects and shortcomings of the prior art and provides an InP-based vertical cavity surface emitting laser, wherein two materials with opposite strain types are alternately grown to manufacture a DBR layer, and the stress generated by lattice mismatch can be reduced in a strain compensation mode. Compared with the traditional InP-based long-wavelength VCSEL, the technology can avoid the adoption of quaternary material DBRs (distributed Bragg reflectors) such as GaInAsP (gallium indium arsenide phosphide) with low thermal conductivity and small refractive index difference on one hand, and can eliminate the warping of an epitaxial wafer caused by the adoption of the GaAs/AlGaAs DBR on the other hand, thereby reducing the stress on an epitaxial material layer.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

an InP-based VCSEL is provided, including the following structure:

an InP substrate;

the buffer layer, the first DBR reflecting layer, the long-wave laser emitting unit, the second DBR reflecting layer and the electrode contact layer are sequentially arranged on the InP substrate;

wherein the content of the first and second substances,

the first DBR reflection layer and the second DBR reflection layer respectively comprise a multilayer structure formed by alternately overlapping a first refractive index material layer and a second refractive index material layer, the lattice constant of the first refractive index material layer is smaller than that of the InP substrate, and the lattice constant of the second refractive index material layer is larger than that of the InP substrate.

Further, the InP substrate is an n-type InP single crystal substrate;

the buffer layer is an n-type InP buffer layer;

the first DBR reflecting layer is an n-type DBR reflecting layer, the second DBR reflecting layer is a p-type DBR reflecting layer, the materials of the n-type DBR reflecting layer and the p-type DBR reflecting layer can be the same or different, but the doping types are opposite, and the number of pairs of alternately overlapped growth of the n-type DBR reflecting layer and the p-type DBR reflecting layer is different;

the electrode contact layer is a p-type InP electrode contact layer.

Further, the thickness of the n-type InP buffer layer is 200-800 nm; the thickness of the p-type InP electrode contact layer is 100-400 nm, and the doping concentration is larger than 3 x 1018 cm-3.

Furthermore, the number of alternately overlapped growth pairs of the n-type DBR layers is 30-50 pairs, and the number of alternately overlapped growth pairs of the p-type DBR layers is 20-40 pairs.

Further, the material of the first refractive index material layer and the material of the second refractive index material layer are binary or ternary III/V group compounds.

Further, the first refractive index material layer is one of AlP, GaP, AlAs, GaAs, AlGaAs and AlGaP; the second refractive index material layer is one of AlSb, GaSb and AlGaSb.

Further, the long-wave laser emission unit is composed of multiple quantum well materials, the multiple quantum well materials comprise potential barrier materials and potential well materials, the potential barrier materials are InP, the potential well materials are one of GaInAsP or AlGaInAs of low band gap materials, and the number of quantum wells is 2-5.

The invention also relates to a preparation method of the InP-based vertical cavity surface emitting laser, which comprises the following steps:

step S1: growing a buffer layer on the InP substrate;

step S2: forming a first DBR reflective layer on the buffer layer, the first DBR reflective layer including a structure in which first and second refractive index material layers alternately overlap in a multilayer structure, the first refractive index material layer having a smaller lattice constant than the InP substrate, the second refractive index material layer having a larger lattice constant than the InP substrate;

step S3: forming a long-wave laser emitting unit on the first DBR reflective layer;

step S4: forming a second DBR reflective layer including a multilayer structure in which first and second refractive index material layers are alternately overlapped on the long wave laser emission unit; the material of the first DBR reflecting layer is the same as that of the second DBR reflecting layer;

step S5: an electrode contact layer is formed on the second DBR reflective layer.

Further, the InP substrate is an n-type InP single crystal substrate;

the buffer layer is an n-type InP buffer layer;

the first DBR reflecting layer is an n-type DBR reflecting layer, and the second DBR reflecting layer is a p-type DBR reflecting layer;

the electrode contact layer is a p-type InP electrode contact layer.

Further, the material of the first refractive index material layer and the second refractive index material layer is binary or ternary III/V compound, wherein the first refractive index material layer is one of AlP, GaP, AlAs, GaAs, AlGaAs and AlGaP; the second refractive index material layer is one of AlSb, GaSb and AlGaSb.

In the technical scheme of the invention, the InP-based vertical-cavity surface-emitting laser forms an InP buffer layer on an InP single-crystal substrate, can buffer part of stress, and utilizes two materials with opposite strain types and larger refractive index difference to combine to form a DBR reflection layer, and reduces the stress of the DBR layer caused by lattice mismatch in a strain compensation mode, thereby reducing the warping degree of an epitaxial wafer, improving the material quality and improving the working performance of the InP-based long-wavelength VCSEL.

In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a schematic diagram of an InP-based VCSEL structure according to the present invention;

FIG. 2 is a flow chart of a method for fabricating an InP-based VCSEL according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. Meanwhile, in the description of the present invention, the terms "first", "second", and the like are used only for distinguishing the description, and are not to be construed as indicating or implying relative importance.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an InP-based vcsel according to an embodiment of the present disclosure, including:

an n-type InP substrate 1, an n-type InP buffer layer 2, an n-type DBR reflecting layer 3, a long-wave laser emitting unit 4, a p-type DBR reflecting layer 5 and a p-type InP electrode contact layer 6 are sequentially laminated from bottom to top. Wherein the n-type InP substrate 1 is an n-type single crystal InP substrate.

The n-type DBR reflective layer (first DBR reflective layer) and the p-type DBR reflective layer (second DBR reflective layer) each include a multilayer structure in which a first refractive index material layer having a smaller lattice constant than the InP substrate and a second refractive index material layer having a larger lattice constant than the InP substrate are alternately overlapped. Therefore, the DBR reflecting layer can be formed by combining two materials with opposite strain types and larger refractive index difference, and the stress of the DBR layer caused by lattice mismatch is reduced in a strain compensation mode.

In the InP-based vertical-cavity surface-emitting laser, the thickness of the n-type InP buffer layer is 200-800 nm; the thickness of the p-type InP electrode contact layer is 100-400 nm, and the doping concentration is more than 3 multiplied by 10¹⁸cm^-3。

The number of alternately overlapped growth pairs of the first refractive index material layer and the second refractive index material layer in the n-type DBR layer is 30-50 pairs, and the number of alternately overlapped growth pairs of the first refractive index material layer and the second refractive index material layer in the p-type DBR layer is 20-40 pairs.

And the material of the first refractive index material layer and the second refractive index material layer is binary or ternary III/V compound; the first refractive index material layer is one of AlP, GaP, AlAs, GaAs, AlGaAs and AlGaP; the second refractive index material layer is one of AlSb, GaSb and AlGaSb.

The long-wave laser emission unit is composed of multiple quantum well materials, the multiple quantum well materials comprise potential barrier materials and potential well materials, the potential barrier materials are InP, the potential well materials are one of GaInAsP or AlGaInAs of low band gap materials, and the number of quantum wells is 2-5.

The invention also relates to a preparation method of the InP-based vertical cavity surface emitting laser, which is characterized by comprising the following steps of:

step S1: growing a buffer layer on the InP substrate;

step S2: forming a first DBR reflective layer on the buffer layer, the first DBR reflective layer including a structure in which first and second refractive index material layers alternately overlap in a multilayer structure, the first refractive index material layer having a smaller lattice constant than the InP substrate, the second refractive index material layer having a larger lattice constant than the InP substrate;

step S3: forming a long-wave laser emitting unit on the first DBR reflective layer;

step S4: forming a second DBR reflective layer including a multilayer structure in which first and second refractive index material layers are alternately overlapped on the long wave laser emission unit; the material of the first DBR reflecting layer is the same as that of the second DBR reflecting layer, the doping types are different, and the number of pairs of alternately overlapped growth of the n-type DBR reflecting layer and the p-type DBR reflecting layer is different; or the material of the first DBR reflective layer and the material of the second DBR reflective layer may be different as long as the DBR reflecting effect is achieved.

Step S5: an electrode contact layer is formed on the second DBR reflective layer.

The InP substrate is an n-type InP single crystal substrate;

the buffer layer is an n-type InP buffer layer;

the first DBR reflecting layer is an n-type DBR reflecting layer, and the second DBR reflecting layer is a p-type DBR reflecting layer;

the electrode contact layer is a p-type InP electrode contact layer.

The material of the first refractive index material layer and the material of the second refractive index material layer are binary or ternary III/V group compounds, wherein the first refractive index material layer is one of AlP, GaP, AlAs, GaAs, AlGaAs and AlGaP; the second refractive index material layer is one of AlSb, GaSb and AlGaSb.

The following specific examples will be used to illustrate the specific fabrication of an InP-based VCSEL, including the following steps:

step S1: growing a buffer layer on the InP substrate;

selecting a 4-inch n-type InP single crystal wafer as a substrate, and growing an n-type InP buffer layer on the upper surface of the InP substrate by using a metal organic chemical vapor deposition technology or a molecular beam epitaxy technology, wherein the thickness of the n-type InP buffer layer is 300nm in the embodiment;

step S2: forming a first DBR reflection layer on the buffer layer, wherein the first DBR reflection layer is of a structure of alternately overlapping multiple layers of first refractive index materials and second refractive index materials, the lattice constant of the first refractive index material layer is smaller than that of the InP substrate, and the lattice constant of the second refractive index material layer is larger than that of the InP substrate;

wherein the first DBR reflective layer is an n-type DBR reflective layer. An n-type DBR reflecting layer is grown on the n-type InP buffer layer by adopting a metal organic chemical vapor deposition technology or a molecular beam epitaxy technology, in the embodiment, the n-type DBR reflecting layer is composed of n-type doped AlAs/AlSb, wherein the lattice constant of the AlAs with the first refractive index is smaller than that of the InP, and the lattice constant of the AlSb with the second refractive index is larger than that of the InP, so that due to the difference of the lattice constants, the DBR reflecting layer can be formed by combining two materials with opposite strain types and larger refractive index difference, and the stress of the DBR layer caused by lattice mismatch is reduced in a strain compensation mode. In this example, the AlAs/AlSb logarithm is 40 pairs;

step S3: forming a long-wave laser emitting unit on the first DBR reflective layer;

growing a long-wave laser emission unit of a multi-quantum well structure on an n-type DBR (distributed Bragg reflector) layer (a first DBR layer) by adopting a metal organic chemical vapor deposition technology or a molecular beam epitaxy technology, wherein the multi-quantum well structure comprises a potential barrier material and a potential well material, the potential barrier material is InP, the potential well material is a low band gap material GaInAsP, the optical band gap of the GaInAsP is 0.8-1.0 eV, and the number of quantum wells is 3;

step S4: forming a second DBR reflective layer on the long-wave laser emission unit, wherein the second DBR reflective layer is of a multilayer structure formed by alternately overlapping a first refractive index material and a second refractive index material;

the second DBR reflecting layer is a p-type DBR reflecting layer, the p-type DBR reflecting layer grows on the long-wave laser emission unit by adopting a metal organic chemical vapor deposition technology or a molecular beam epitaxy technology, the p-type DBR reflecting layer is composed of p-type doped AlAs/AlSb, the lattice constant of the AlAs with the first refractive index is smaller than that of InP, and the lattice constant of the AlSb with the second refractive index is larger than that of InP, so that due to the difference of the lattice constants, the DBR reflecting layer can be formed by combining two materials with opposite strain types and larger refractive index difference, and the stress of the DBR layer caused by lattice mismatch is reduced in a strain compensation mode. The AlAs/AlSb logarithm was 30 pairs.

Step S5: an electrode contact layer is formed on the second DBR reflective layer.

Growing a p-type InP electrode contact layer on the p-type DBR reflecting layer (second DBR reflecting layer) by metal organic chemical vapor deposition or molecular beam epitaxy with a thickness of 300nm and a doping concentration of 5 × 10¹⁸cm^-3。

In this InP base vertical cavity surface emitting laser, the substrate, the buffer layer, barrier layer and electrode contact layer all adopt the InP material, use the same material can reduce the stress that mismatch and produce between the layer structure, and the DBR material layer all adopts the different binary of double-deck lattice constant or ternary III V clan material layer repeated stack structure, the refractive index difference of the different material layer of double-deck lattice constant is great, and can cushion the stress that produces with InP substrate lattice mismatch, thereby reduce the epitaxial wafer warpage, improve the material quality, promote the working property of InP base long wave VCSEL.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.