CN109728502B

CN109728502B - Vertical cavity surface emitting laser epitaxial structure and preparation method thereof

Info

Publication number: CN109728502B
Application number: CN201910015307.1A
Authority: CN
Inventors: 田宇; 韩效亚; 吴真龙; 杜石磊
Original assignee: Xiamen Changelight Co Ltd
Current assignee: Xiamen Changelight Co Ltd
Priority date: 2019-01-08
Filing date: 2019-01-08
Publication date: 2020-07-31
Anticipated expiration: 2039-01-08
Also published as: CN109728502A

Abstract

The invention discloses a vertical cavity surface light emitting deviceAn epitaxial structure of laser and its preparation method are provided, wherein the N-type DBR layer is composed of Al with different Al component contents_YGa_1‑YAs composition, different from Al_YGa_1‑YBarrier junction reduction between As layers and utilization of adjacent Al_YGa_1‑YThe tensile potential barrier height of stress variation between the As layer for the whole degree of depth of potential barrier junction of N type DBR layer becomes shallow, reduces the series resistance of N type DBR layer, reduces the voltage at N type DBR layer both ends, reduces the threshold current of DBR layer, makes the electric current consume less in N type DBR layer, and then reduces epitaxial structure's heat loss, improves epitaxial structure's power conversion efficiency and slope efficiency. In addition, Al of different Al compositions_YGa_1‑YAs forms a step between As, the potential barrier difference is reduced, so that electrons can jump more easily, the number of pairs of electrons and holes combined is increased, the number of particle inversions is increased, and the gain is improved.

Description

Vertical cavity surface emitting laser epitaxial structure and preparation method thereof

Technical Field

The invention relates to the technical field of lasers, in particular to a vertical cavity surface emitting laser epitaxial structure and a preparation method thereof.

Background

A Vertical Cavity Surface Emitting laser (Vertical Cavity Surface Emitting L laser, referred to as VCSE L for short) is a semiconductor laser Emitting laser light from a Surface perpendicular to a substrate, has the characteristics of small volume, long service life, high efficiency, output of a circular spot, single longitudinal mode and the like, and is widely applied to the fields of optical fiber communication, optical storage, laser printing and the like.

At present, the epitaxial structure of the VCSE L mainly obtains high reflectivity in the modes of an abrupt DBR, a stacked DBR, a linear DBR and the like, but the threshold current of the conventional VCSE L is large.

Disclosure of Invention

The invention aims to provide a vertical cavity surface emitting laser epitaxial structure and a preparation method thereof, so as to reduce the threshold current of VCSE L.

In order to solve the technical problems, the invention provides the following technical scheme:

a vertical cavity surface emitting laser epitaxial structure, comprising:

a substrate;

the buffer layer is positioned on the first side surface of the substrate;

the N-type distributed Bragg reflection layer is positioned on one side, away from the substrate, of the buffer layer and comprises a plurality of first stacked units which are stacked;

the first limiting layer is positioned on one side, away from the buffer layer, of the N-type distributed Bragg reflection layer;

a first waveguide layer located on a side of the first confinement layer facing away from the distributed Bragg reflector layer;

the quantum hydrazine light-emitting layer is positioned on one side, away from the first limiting layer, of the first waveguide layer;

the second waveguide layer is positioned on one side, away from the first waveguide layer, of the quantum hydrazine light-emitting layer;

the second limiting layer is positioned on one side, away from the quantum hydrazine light-emitting layer, of the second waveguide layer;

the oxide layer is positioned on one side, away from the second waveguide layer, of the second limiting layer;

the P-type distributed Bragg reflection layer is positioned on one side, away from the second limiting layer, of the oxidation layer, and the P-type distributed Bragg reflection layer comprises a plurality of stacked second stacking units;

the first stacking unit comprises a first N-type transition layer, a second N-type transition layer, a third N-type transition layer, a first N-type reflection layer, a fourth N-type transition layer, a fifth N-type transition layer, a sixth N-type transition layer and a second N-type reflection layer which are stacked, wherein the composition of aluminum in the first N-type transition layer is gradually changed from Y1 to Y2, the composition of aluminum in the second N-type transition layer is gradually changed from Y2 to Y3, the composition of aluminum in the third N-type transition layer is gradually changed from Y3 to Y4, the composition of aluminum in the first N-type reflection layer is Y4, the composition of aluminum in the fourth N-type transition layer is gradually changed from Y4 to Y3, the composition of aluminum in the fifth N-type transition layer is gradually changed from Y3 to Y2, the composition of aluminum in the sixth N-type transition layer is gradually changed from Y2 to Y1, the composition of aluminum in the second N-type reflection layer is gradually changed from Y4 to Y59648, and Y5838 is smaller than Y1;

the second stacking unit comprises a first P-type reflecting layer and a second P-type reflecting layer which are stacked, wherein the composition of aluminum in the first P-type reflecting layer is larger than that of aluminum in the second P-type reflecting layer.

Optionally, the gradual change curves of the aluminum components in the first N-type transition layer, the third N-type transition layer, and the fifth N-type transition layer satisfy a sinusoidal curve with 1/4 cycles.

The gradual change curves of the aluminum components in the second N-type transition layer, the fourth N-type transition layer and the sixth N-type transition layer meet the cosine curve of 1/4 periods.

Alternatively, Y1 is 0.1, Y2 is 0.6, Y3 is 0.4, and Y4 is 0.9.

Optionally, the second stacking unit further includes:

the first P-type transition layer, the second P-type transition layer and the third P-type transition layer are positioned between the first P-type reflection layer and the oxidation layer and are arranged in a stacked mode, the component of aluminum in the first P-type transition layer is gradually changed from Y1 to Y2, the component of aluminum in the second P-type transition layer is gradually changed from Y2 to Y3, the component of aluminum in the third P-type transition layer is gradually changed from Y3 to Y4, and the component of aluminum in the first P-type reflection layer is Y4;

the fourth P type transition layer, the fifth P type transition layer and the sixth P type transition layer are stacked and arranged between the first P type reflection layer and the second P type reflection layer, the component of aluminum is gradually changed from Y4 to Y3 in the fourth P type transition, the component of aluminum is gradually changed from Y3 to Y2 in the fifth P type transition, the component of aluminum is gradually changed from Y2 to Y1 in the sixth P type transition, and the component of aluminum is Y1 in the second P type reflection layer.

Optionally, the thicknesses of the first N-type transition layer, the second N-type transition layer, the third N-type transition layer, the fourth N-type transition layer, the fifth N-type transition layer, and the sixth N-type transition layer are the same;

the first P-type transition layer, the second P-type transition layer, the third P-type transition layer, the fourth P-type transition layer, the fifth P-type transition layer and the sixth P-type transition layer have the same thickness.

Optionally, the thickness of the first N-type transition layer ranges from 1 nm to 10nm, inclusive;

the thickness of the first P-type transition layer ranges from 1 nm to 10nm, inclusive.

Optionally, the value range of the number of the first stacking units in the N-type distributed bragg reflector is 1 to 100, including an end point value;

the value range of the number of the second stacking units in the P-type distributed Bragg reflection layer is 1-100, including an end point value;

a preparation method of a vertical cavity surface emitting laser epitaxial structure comprises the following steps:

forming a buffer layer on the first side surface of the substrate;

forming an N-type distributed Bragg reflection layer on one side, away from the substrate, of the buffer layer, wherein the N-type distributed Bragg reflection layer comprises a plurality of stacked first stacked units;

forming a first limiting layer on one side, away from the buffer layer, of the N-type distributed Bragg reflection layer;

forming a first waveguide layer on one side of the first limiting layer, which faces away from the distributed Bragg reflection layer;

forming a quantum hydrazine light-emitting layer on one side of the first waveguide layer, which is far away from the first limiting layer;

forming a second waveguide layer on one side of the quantum hydrazine light-emitting layer, which is far away from the first waveguide layer;

forming a second limiting layer on one side of the second waveguide layer, which is far away from the quantum hydrazine light-emitting layer;

forming an oxide layer on one side of the second limiting layer, which is far away from the second waveguide layer;

forming a P-type distributed Bragg reflection layer on one side, away from the second limiting layer, of the oxidation layer, wherein the P-type distributed Bragg reflection layer comprises a plurality of stacked second stacking units;

wherein the first stacking unit comprises a first N-type transition layer, a second N-type transition layer, a third N-type transition layer, a first N-type reflection layer, a fourth N-type transition layer, a fifth N-type transition layer, a sixth N-type transition layer and a second N-type reflection layer which are stacked, the composition of aluminum in the first N-type transition layer is gradually changed from Y1 to Y2, the composition of aluminum in the second N-type transition layer is gradually changed from Y2 to Y3, the composition of aluminum in the third N-type transition layer is gradually changed from Y3 to Y4, the composition of aluminum in the first N-type reflection layer is Y4, the composition of aluminum in the fourth N-type transition layer is gradually changed from Y4 to Y3, the composition of aluminum in the fifth N-type transition layer is gradually changed from Y3 to Y2, the composition of aluminum in the sixth N-type transition layer is gradually changed from Y2 to Y1, the second N-type transition layer is gradually changed from Y3959638 to Y5848, and the second N-type reflection layer is smaller than Y1;

Optionally, the second stacking unit further includes:

be located first P type reflection stratum with between the second P type reflection stratum, range upon range of fourth P type transition layer, fifth P type transition layer and the sixth P type transition layer that sets up, aluminium's component is by Y4 gradual change to Y3 in the fourth P type transition layer, aluminium's component is by Y3 gradual change to Y2 in the fifth P type transition layer, aluminium's component is by Y2 gradual change to Y1 in the sixth P type transition layer, aluminium's component is Y1 in the second P type reflection stratum.

Optionally, the growth environment of the N-type bragg reflector and the growth environment of the P-type bragg reflector include at least one of a nitrogen environment and a hydrogen environment.

The scheme has the following advantages:

in the epitaxial structure of the vertical cavity surface emitting laser provided by the invention, the N-type DBR layer is made of Al with different Al component contents_YGa_1-YAs composition, different from Al_YGa_1-YBarrier junction reduction between As layers and utilization of adjacent Al_YGa_1-YAnd the stress between the As layers changes and stretches the barrier height, so that the integral depth of the barrier junction of the N-type DBR layer becomes shallow, the series resistance of the N-type DBR layer is reduced, the voltages at two ends of the N-type DBR layer are reduced, the threshold current of the DBR layer is reduced, the current is less consumed in the N-type DBR layer, the heat loss of the epitaxial structure is reduced, and the power conversion efficiency and the slope efficiency of the epitaxial structure are improved. And Al of different Al composition_YGa_1-YAs forms a step, the potential barrier difference is reduced, so that electrons are easier to jump, the number of the electron and hole recombination logarithm is increased, the particle inversion number is increased, the gain is improved, and the generation of heat is reduced.

Drawings

In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of an epitaxial structure of a VCSEL provided in an embodiment of the invention;

FIG. 2 is a schematic structural diagram of a first stacked unit in an VCSEL epitaxial structure according to an embodiment of the invention;

fig. 3 is a graph of the energy band of a first stacked unit in a first epitaxial structure, a second epitaxial structure, and a third epitaxial structure as a function of its growth thickness, in accordance with an embodiment of the present invention; the curve a is a curve graph of the variation of the energy band of the first stacking unit in the first epitaxial structure along with the growth thickness of the first stacking unit, the curve b is a curve graph of the variation of the energy band of the first stacking unit in the second epitaxial structure along with the growth thickness of the first stacking unit, and the curve c is a curve graph of the variation of the energy band of the first stacking unit in the third epitaxial structure along with the growth thickness of the first stacking unit;

FIG. 4 is a schematic structural diagram of a second stacked unit in an epitaxial structure of a VCSEL according to an embodiment of the invention;

fig. 5 is a flowchart of a method for fabricating an epitaxial structure of a vertical cavity surface emitting laser according to an embodiment of the 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. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.

As described in the background section, the threshold current of the prior art VCSE L is large.

The inventor researches and finds that the existing VCSE L generally includes a high-reflection AlGaAs layer and a low-reflection AlGaAs layer stacked in an N-type DBR, wherein the composition of Al in the high-reflection AlGaAs layer is 0.1, and the composition of Al in the low-reflection AlGaAs layer is 0.9, so that a large barrier junction is formed between the high-reflection AlGaAs layer and the low-reflection AlGaAs layer, which results in a high resistance value of the VCSE L, a high voltage of the VCSE L, excessive current consumption in the DBR, a large threshold current of the VCSE L, and the power conversion rate and slope efficiency of the VCSE L.

In view of this, an embodiment of the present invention provides an epitaxial structure of a vertical cavity surface emitting laser, as shown in fig. 1, the epitaxial structure includes:

a substrate 10;

a buffer layer 20 on a first side surface of the substrate 10;

an N-type distributed bragg reflector layer 30 located on a side of the buffer layer 20 facing away from the substrate 10, the N-type distributed bragg reflector layer 30 including a plurality of first stacked units stacked;

a first confinement layer 40 located on a side of the N-type distributed bragg reflector layer 30 facing away from the buffer layer 20;

a first waveguide layer 50 on a side of the first confinement layer 40 facing away from the distributed bragg reflector layer 30;

a quantum well light-emitting layer 60 on a side of the first waveguide layer 50 facing away from the first confinement layer 40;

a second waveguide layer 70 on a side of the quantum well light-emitting layer 60 facing away from the first waveguide layer 50;

a second confinement layer 80 on a side of the second waveguide layer 70 facing away from the quantum well light-emitting layer 60;

an oxide layer 90 on a side of the second confinement layer 80 facing away from the second waveguide layer 70;

the P-type distributed Bragg reflection layer 100 is positioned on one side, away from the second limiting layer 80, of the oxidation layer 90, and the P-type distributed Bragg reflection layer 100 comprises a plurality of stacked second stacked units;

Optionally, in an embodiment of the present invention, the N-type transition layer is an N-type AlGaAs layer.

It can be seen that in the vertical cavity surface emitting laser epitaxial structure provided in the embodiments of the present invention, the N-type distributed bragg reflector layer includes not only the first N-type reflector layer and the second N-type reflector layer, but also the first N-type transition layer, the second N-type transition layer, and the third N-type transition layer located between the first N-type reflector layer and the second N-type reflector layer, and the fourth N-type transition layer, the fifth N-type transition layer, and the sixth N-type transition layer located between the first N-type reflector layer and the second N-type reflector layer, where the composition of aluminum in the first N-type transition layer is gradually changed from Y1 to Y2, the composition of aluminum in the second N-type transition layer is gradually changed from Y2 387 to Y3, the composition of aluminum in the third N-type transition layer is gradually changed from Y3 to Y4, the composition of aluminum in the first N-type reflector layer is Y4, and the composition of aluminum in the fourth N-type transition layer is gradually changed from Y39 4 to Y8678, the composition of aluminum in the fifth N-type transition layer is gradually changed from Y3 to Y2, the composition of aluminum in the sixth N-type transition layer is gradually changed from Y2 to Y1, the composition of aluminum in the second N-type reflection layer is Y1, Y1 is smaller than Y3 and smaller than Y3, so that the composition of Al in the N-type distributed Bragg reflection layer is increased from Y3 to Y3 and then decreased from Y3 to Y3, stepped composition change is adopted, the change from Y3 to Y3 is firstly changed, the change from Y3 to Y3 is gradually changed from Y3 to Y3, the change from Y3 to Y3 is finally changed from Y3, a small barrier junction is generated between Al (Y3) and Al (Y3), the change between Al (Y3) and Al (Y3) is generated, the adjacent tensile barrier layer is generated between the Y3 and the adjacent N-type transition layer, and the adjacent tensile barrier change between Al (Y3) is generated, and the adjacent N-type transition layer is reduced by using the adjacent tensile stress of the adjacent N-type transition layer, the whole depth of the barrier junction of the N-type Bragg reflection layer is reduced, so that the series resistance of the N-type Bragg reflection layer is reduced, the voltage at two ends of the N-type Bragg reflection layer is reduced, the threshold current of the N-type Bragg reflection layer is reduced, the current is less consumed in the N-type Bragg reflection layer, the heat loss of the epitaxial structure is reduced, and the power conversion efficiency and the slope efficiency of the epitaxial structure are improved.

It should be noted that, because the factors affecting the overall resistance of the first stacking unit include the series resistance of the first stacking unit and the doping concentration of the first stacking unit, in the embodiment of the present invention, the series resistance of the first stacking unit is reduced, so that on the premise of the same overall resistance, the doping concentration in the first stacking unit may be smaller, thereby reducing the background of the first stacking unit, reducing the loss of the first stacking unit, and improving the gain.

In addition, because the AlGaAs layer with the composition of 0.1 of Al and the AlGaAs layer with the composition of 0.9 of Al have a high barrier difference, electrons are difficult to transition, so that electrons are limited in a barrier junction, and a large amount of heat is generated, in the epitaxial structure provided by the embodiment of the invention, the first N-type reflecting layer in the N-type bragg reflecting layer is away from the second N-type emitting layer, and a plurality of N-type transition layers are arranged between the first N-type reflecting layer and the second N-type reflecting layer, so that a plurality of steps are formed between the first N-type reflecting layer and the second N-type reflecting layer by using the N-type transition layers, so that the electrons in the N-type bragg reflecting layer are more easily transitioned, and further, the recombination pairs of electrons and holes in the epitaxial structure are increased, so that the number of particles in the epitaxial structure is increased, and the gain is improved.

On the basis of any of the above embodiments, in an embodiment of the present invention, the gradual change curves of the aluminum components in the first N-type transition layer, the third N-type transition layer, and the fifth N-type transition layer satisfy a sine curve with 1/4 cycles, and the gradual change curves of the aluminum components in the second N-type transition layer, the fourth N-type transition layer, and the sixth N-type transition layer satisfy a cosine curve with 1/4 cycles, so that the change of the aluminum components in each transition layer in the N-type bragg reflection layer is smoother, the series resistance of the N-type bragg reflection layer is further reduced, the voltage at two ends of the N-type bragg reflection layer is reduced, the threshold current of the N-type bragg reflection layer is reduced, the current is less dissipated in the N-type bragg reflection layer, the heat dissipation of the epitaxial structure is further reduced, and the power conversion efficiency and the slope efficiency of the epitaxial structure are improved, meanwhile, the number of electron and hole recombination pairs in the epitaxial structure is increased, the number of particle inversion in the epitaxial structure is increased, and the gain is improved.

Specifically, in an embodiment of the present invention, Y1 is 0.1, Y4 is 0.9, and in a specific implementation manner of this embodiment, Y2 is 0.6, and Y3 is 0.4, but the present invention is not limited thereto, as long as Y1 is less than Y3 and less than Y2 and less than Y4 are ensured.

As shown in fig. 3, fig. 3 shows a graph of the energy band of the first stack unit in the first epitaxial structure, the second epitaxial structure, and the third epitaxial structure as a function of the growth thickness thereof; the curve a is a graph of the variation of the energy band of the first stacking unit in the first epitaxial structure along with the growth thickness of the first stacking unit, the curve b is a graph of the variation of the energy band of the first stacking unit in the second epitaxial structure along with the growth thickness of the first stacking unit in the second epitaxial structure, and the curve c is a graph of the variation of the energy band of the first stacking unit in the third epitaxial structure along with the growth thickness of the first stacking unit in the third epitaxial structure.

Specifically, the first epitaxial structure, the second epitaxial structure and the third epitaxial structure are the same except that the first stacking unit is different, wherein,

the first stacking unit in the first epitaxial structure comprises a first N-type reflecting layer and a second N-type reflecting layer which are stacked, wherein the composition of aluminum in the first N-type reflecting layer is 0.9, and the composition of aluminum in the second N-type reflecting layer is 0.1;

the first stacking unit in the second epitaxial structure is an aluminum composition gradient structure, including: the first N-type transition layer, the second N-type transition layer, the third N-type transition layer, the first N-type reflection layer, the fourth N-type transition layer, the fifth N-type transition layer, the sixth N-type transition layer and the second N-type reflection layer, wherein the aluminum component in the first N-type transition layer is gradually changed from 0.1 to 0.3, the aluminum component in the second N-type transition layer is gradually changed from 0.3 to 0.6, the aluminum component in the third N-type transition layer is gradually changed from 0.6 to 0.9, the aluminum component in the first N-type reflection layer is 0.9, the aluminum component in the fourth N-type transition layer is gradually changed from 0.9 to 0.6, the aluminum component in the fifth N-type transition layer is gradually changed from 0.6 to 0.3, the aluminum component in the sixth N-type transition layer is gradually changed from 0.3 to 0.1, and the aluminum component in the second N-type reflection layer is 0.1;

the first stacking unit in the third epitaxial structure is an aluminum component pull-up structure, and comprises: the light-emitting diode comprises a first N-type transition layer, a second N-type transition layer, a third N-type transition layer, a first N-type reflection layer, a fourth N-type transition layer, a fifth N-type transition layer, a sixth N-type transition layer and a second N-type reflection layer, wherein the aluminum component in the first N-type transition layer is gradually changed from 0.1 to 0.6, the aluminum component in the second N-type transition layer is gradually changed from 0.6 to 0.4, the aluminum component in the third N-type transition layer is gradually changed from 0.4 to 0.9, the aluminum component in the first N-type reflection layer is 0.9, the aluminum component in the fourth N-type transition layer is gradually changed from 0.9 to 0.4, the aluminum component in the fifth N-type transition layer is gradually changed from 0.4 to 0.6, the aluminum component in the sixth N-type transition layer is gradually changed from 0.6 to 0.1, and the aluminum component in the second N-type reflection layer is 0.1.

As can be seen from fig. 3, compared to the first epitaxial structure and the second epitaxial structure, the difference between the maximum value and the minimum value of the energy band of the first stacked unit in the third epitaxial structure is the smallest, that is, the barrier junction of the first stacked unit in the third epitaxial structure is the smallest.

In addition to any of the above embodiments, in an embodiment of the present invention, the thicknesses of the first N-type transition layer, the second N-type transition layer, the third N-type transition layer, the fourth N-type transition layer, the fifth N-type transition layer, and the sixth N-type transition layer are the same. Optionally, in an embodiment of the present invention, a thickness of the first N-type transition layer ranges from 1 nm to 10nm, inclusive; however, the present invention is not limited thereto, as the case may be.

On the basis of any one of the above embodiments, in an embodiment of the present invention, the value range of the number of the first stacking units in the N-type distributed bragg reflector is 1 to 100, including an endpoint value; however, the present invention is not limited thereto, as the case may be.

If the P-type DBR of the VCSE L includes only the stacked high-reflective AlGaAs layer and low-reflective AlGaAs layer, where the composition of Al in the high-reflective AlGaAs layer is 0.1 and the composition of Al in the low-reflective AlGaAs layer is 0.9, a large barrier junction between the high-reflective AlGaAs layer and the low-reflective AlGaAs layer will be formed, which results in a high resistance value of the VCSE L, a high voltage of the VCSE L, and excessive current consumption in the DBR, resulting in a large threshold current of the VCSE L, and affecting the power conversion rate and slope efficiency of the VCSE L.

On the basis of any of the above embodiments, in an embodiment of the present invention, as shown in fig. 4, the second stacking unit further includes:

a first P-type transition layer 1001, a second P-type transition layer 1002 and a third P-type transition layer 1003 which are positioned between the first P-type reflection layer 1004 and the oxidation layer 90 and are arranged in a stacked manner, wherein the composition of aluminum in the first P-type transition layer 1001 is gradually changed from Y1 to Y2, the composition of aluminum in the second P-type transition layer 1002 is gradually changed from Y2 to Y3, the composition of aluminum in the third P-type transition layer 1003 is gradually changed from Y3 to Y4, and the composition of aluminum in the first P-type reflection layer 1004 is Y4;

and a fourth P-type transition layer 1005, a fifth P-type transition layer 1006 and a sixth P-type transition layer 1007 are stacked between the first P-type reflection layer 1004 and the second P-type reflection layer 1008, wherein the composition of aluminum in the fourth P-type transition layer 1005 is gradually changed from Y4 to Y3, the composition of aluminum in the fifth P-type transition layer 1006 is gradually changed from Y3 to Y2, the composition of aluminum in the sixth P-type transition layer 1007 is gradually changed from Y2 to Y1, and the composition of aluminum in the second P-type reflection layer is Y1.

Optionally, in an embodiment of the present invention, the P-type transition layer is a P-type AlGaAs layer.

In the embodiment of the present invention, the P-type distributed bragg reflector layer includes not only a first P-type reflector layer and a second P-type reflector layer, but also a first P-type transition layer, a second P-type transition layer and a third P-type transition layer between the first P-type reflector layer and the second P-type reflector layer facing away from the second P-type reflector layer, and a fourth P-type transition layer, a fifth P-type transition layer and a sixth P-type transition layer between the first P-type reflector layer and the second P-type reflector layer, wherein the composition of aluminum in the first P-type transition layer is gradually changed from Y1 to Y2, the composition of aluminum in the second P-type transition layer is gradually changed from Y2 to Y3, the composition of aluminum in the third P-type transition layer is gradually changed from Y3 to Y4, the composition of aluminum in the first P-type reflector layer is Y4, the composition of aluminum in the fourth P-type transition layer is gradually changed from Y4 to Y8292, the composition of aluminum in the fifth P-type transition layer is gradually changed from Y3523 to Y4934, the composition of aluminum in the sixth P-type transition layer is gradually changed from Y2 to Y1, the composition of aluminum in the second P-type reflection layer is Y1, Y1 is smaller than Y3 and smaller than Y2 and smaller than Y4, so that in the process that the composition of the Al in the P-type distributed Bragg reflection layer is increased from Y1 to Y4 and then is decreased from Y4 to Y1, the composition changes in a step mode are adopted, the composition changes are gradually changed from Y1 to Y2, from Y2 to Y3, from Y3 to Y4, from Y4 to Y3, from Y3 to Y2, and finally from Y2 to Y1, a small barrier junction is generated between the Al (Y1) and the Al (Y2), a small barrier junction is generated between the Al (Y2) and the Al (Y3), a small barrier junction is generated between the Al (Y3) and the Al (Y4), and the adjacent transition layers are reduced in the transition layers, and the adjacent P-type reflection layers and the P-type barrier layers are changed by utilizing the tensile stress of the adjacent P-type transition layers, the whole depth of the barrier junction of the P-type Bragg reflection layer is reduced, so that the series resistance of the P-type Bragg reflection layer is reduced, the voltage at two ends of the P-type Bragg reflection layer is reduced, the threshold current of the P-type Bragg reflection layer is reduced, the current is less consumed in the P-type Bragg reflection layer, the heat loss of the epitaxial structure is further reduced, and the power conversion efficiency and the slope efficiency of the epitaxial structure are improved.

In the epitaxial structure provided in the embodiment of the present invention, the first P-type reflective layer in the P-type bragg reflective layer is away from the second P-type reflective layer, and a plurality of P-type transition layers are disposed between the first P-type reflective layer and the second P-type reflective layer, so that a plurality of steps are formed between the first P-type reflective layer and the second P-type reflective layer by using each P-type transition layer, so that a hole in the P-type bragg reflective layer is more easily transited, and further a recombination pair of an electron and a hole in the epitaxial structure is increased, and further a number of particles in the epitaxial structure is increased and a gain is improved.

On the basis of any of the above embodiments, in an embodiment of the present invention, the gradual change curve of the aluminum component in the first P-type transition layer, the third P-type transition layer, and the fifth P-type transition layer satisfies a sine curve with 1/4 cycles, and the gradual change curve of the aluminum component in the second P-type transition layer, the fourth P-type transition layer, and the sixth P-type transition layer satisfies a cosine curve with 1/4 cycles, so that the change of the aluminum component in each transition layer in the P-type bragg reflection layer is smoother, the series resistance of the P-type bragg reflection layer is further reduced, the voltage at two ends of the P-type bragg reflection layer is reduced, the threshold current of the P-type bragg reflection layer is reduced, the current is less dissipated in the P-type bragg reflection layer, the heat dissipation of the epitaxial structure is further reduced, and the power conversion efficiency and the slope efficiency of the epitaxial structure are improved, meanwhile, the number of electron and hole recombination pairs in the epitaxial structure is increased, the number of particle inversion in the epitaxial structure is increased, and the gain is improved.

In an embodiment of the invention, on the basis of any of the above embodiments, the thicknesses of the first P-type transition layer, the second P-type transition layer, the third P-type transition layer, the fourth P-type transition layer, the fifth P-type transition layer and the sixth P-type transition layer are the same. Optionally, in an embodiment of the present invention, a thickness of the first P-type transition layer ranges from 1 nm to 10nm, inclusive; however, the present invention is not limited thereto, as the case may be.

On the basis of any one of the above embodiments, in an embodiment of the present invention, the number of the second stacked units in the P-type distributed bragg reflector ranges from 1 to 100, inclusive; however, the present invention is not limited thereto, as the case may be.

On the basis of any one of the above embodiments, in an embodiment of the present invention, the epitaxial structure further includes: and a P-type cap layer (i.e., a P-cap layer) located on a side of the P-type bragg reflector layer facing away from the oxide layer, but the present invention is not limited thereto, as the case may be.

Correspondingly, the embodiment of the invention also provides a preparation method of the epitaxial structure of the vertical cavity surface emitting laser, and the preparation method is used for preparing the epitaxial structure provided by any embodiment. As shown in fig. 5, the preparation method includes:

s1: a buffer layer is formed on the first side surface of the substrate. Optionally, in an embodiment of the present invention, the substrate is a GaAs substrate, and the buffer layer is a GaAs buffer layer.

On the basis of the above embodiment, in an embodiment of the present invention, forming a buffer layer on a first side surface of a substrate includes:

and forming a buffer layer with a first thickness on the surface of the substrate in a first temperature and first pressure environment.

Specifically, in one embodiment of the present invention, the first temperature ranges from 600 ℃ to 700 ℃, inclusive; the first pressure is 50 mbr; the first thickness is in a range of 10-25nm, inclusive, but the invention is not limited thereto, as the case may be.

S2: and forming an N-type Distributed Bragg Reflector (DBR) layer on the side, facing away from the substrate, of the buffer layer, wherein the N-type Distributed Bragg Reflector (DBR) layer comprises a plurality of stacked first stacked units. The first stacking unit comprises a first N-type transition layer, a second N-type transition layer, a third N-type transition layer, a first N-type reflection layer, a fourth N-type transition layer, a fifth N-type transition layer, a sixth N-type transition layer and a second N-type reflection layer which are stacked, wherein the composition of aluminum in the first N-type transition layer is gradually changed from Y1 to Y2, the composition of aluminum in the second N-type transition layer is gradually changed from Y2 to Y3, the composition of aluminum in the third N-type transition layer is gradually changed from Y3 to Y4, the composition of aluminum in the first N-type reflection layer is Y4, the composition of aluminum in the fourth N-type transition layer is gradually changed from Y4 to Y3, the composition of aluminum in the fifth N-type transition layer is gradually changed from Y3 to Y2, the composition of aluminum in the sixth N-type transition layer is gradually changed from Y2 to Y1, the second N-type transition layer is gradually changed from Y3959648 to Y1, and the second N-type reflection layer is smaller than Y3.

Optionally, the growth temperature of the N-type bragg reflection layer ranges from 660 ℃ to 780 ℃, inclusive.

In one embodiment of the present invention, the method of forming the first stacking unit includes:

s21: and forming a first N-type transition layer on one side of the buffer layer, which is far away from the substrate. Optionally, the doping concentration range of the first N-type transition layer is 5E17-5E18, but the present invention is not limited thereto, as the case may be.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the first N-type transition layer is gradually changed from Y1 to Y2, the growth pressure of the first N-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 2.5E18, that is, 2.5 × 1018.

S22: and forming a second N-type transition layer on one side of the first N-type transition layer, which is far away from the buffer layer. Optionally, the doping concentration range of the second N-type transition layer is 3E17-4E18, but the present invention is not limited thereto, as the case may be.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the second N-type transition layer is gradually changed from Y2 to Y3, the growth pressure of the second N-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 2E 18. However, the present invention is not limited thereto, as the case may be.

S23: and forming a third N-type transition layer on one side of the second N-type transition layer, which is far away from the first N-type transition layer. Optionally, the doping concentration of the third N-type transition layer ranges from 3E17 to 1.5E18, but the present invention is not limited thereto, and is specifically determined according to the circumstances.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the third N-type transition layer is gradually changed from Y3 to Y4, the growth pressure of the third N-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 1.5E 18. However, the present invention is not limited thereto, as the case may be.

S24: and forming a first N-type reflecting layer on one side of the third N-type transition layer, which is far away from the second N-type transition layer. Optionally, the doping concentration of the first N-type reflective layer ranges from 5E17 to 5E18, but the present invention is not limited thereto, and is specifically determined according to the circumstances.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the first N-type reflective layer is Y4, the growth pressure of the first N-type reflective layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 63nm, and the doping concentration is 1E 18. However, the present invention is not limited thereto, as the case may be.

S25: and forming a fourth N-type transition layer on one side of the first N-type reflection layer, which is far away from the third N-type transition layer. Optionally, the doping concentration of the fourth N-type transition layer ranges from 3E17 to 1.5E18, but the present invention is not limited thereto, and is specifically determined according to the circumstances.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the fourth N-type transition layer is gradually changed from Y4 to Y3, the growth pressure of the fourth N-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 1.5E 18. However, the present invention is not limited thereto, as the case may be.

S26: and forming a fifth N-type transition layer on one side of the fourth N-type transition layer, which is far away from the first N-type reflection layer. Optionally, the doping concentration of the fifth N-type transition layer ranges from 3E17 to 4E18, but the present invention is not limited thereto, and is specifically determined according to the circumstances.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the fifth N-type transition layer is gradually changed from Y3 to Y2, the growth pressure of the fifth N-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 2E 18. However, the present invention is not limited thereto, as the case may be.

S27: and forming a sixth N-type transition layer on one side of the fifth N-type transition layer, which is far away from the fourth N-type transition layer. Optionally, the doping concentration of the sixth N-type transition layer ranges from 5E17 to 5E18, but the invention is not limited thereto, and is specifically determined as the case may be.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the sixth N-type transition layer is gradually changed from Y2 to Y1, the growth pressure of the sixth N-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 2.5E 18. However, the present invention is not limited thereto, as the case may be.

S28: and forming a second N-type reflecting layer on one side of the sixth N-type transition layer, which is far away from the fifth N-type transition layer. Optionally, the doping concentration of the second N-type reflective layer ranges from 5E17 to 5E18, but the invention is not limited thereto, and is specifically determined according to the circumstances.

Specifically, in a specific embodiment of the present invention, the aluminum composition in the second N-type reflective layer is Y1, the growth pressure of the second N-type reflective layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 63nm, and the doping concentration is 3E 18. However, the present invention is not limited thereto, as the case may be.

On the basis of any of the above embodiments, in an embodiment of the present invention, a growth cycle of the first stacking unit in the N-type bragg-type reflective layer ranges from 1 to 100 inclusive, but the present invention is not limited thereto, as the case may be.

In an embodiment of the present invention, on the basis of any of the above embodiments, the thickness of the N-type bragg reflector layer is 4 micrometers, but the present invention is not limited thereto, as the case may be.

On the basis of any of the above embodiments, in an embodiment of the present invention, Y1 is 0.1, Y4 is 0.9, and in a specific implementation manner of this embodiment, Y2 is 0.6, and Y3 is 0.4, but the present invention is not limited to this, as long as Y1 is less than Y3 and less than Y2 and less than Y4 are ensured.

On the basis of any of the above embodiments, in an embodiment of the present invention, the gradient curves of the aluminum composition in the first N-type transition layer, the third N-type transition layer, and the fifth N-type transition layer satisfy a sine curve with a period of 1/4, and the gradient curves of the aluminum composition in the second N-type transition layer, the fourth N-type transition layer, and the sixth N-type transition layer satisfy a cosine curve with a period of 1/4, so that the change of the aluminum composition in each transition layer in the N-type bragg reflection layer is smoother.

Specifically, on the basis of the above-mentioned embodiment, in an embodiment of the present invention, the flow rate of introducing the aluminum source during the preparation of the first stacking unit satisfies: y ═ a + bcosX to effect a change in the Al composition in the first N-type transition layer, the second N-type transition layer, the third N-type transition layer, the fourth N-type transition layer, the fifth N-type transition layer, and the sixth N-type transition layer. Y is the aluminum source flow required in the growth process of the first N-type transition layer, the second N-type transition layer, the third N-type transition layer, the fourth N-type transition layer, the fifth N-type transition layer or the sixth N-type transition layer; a is a fixed numerical value, and can be selected as an initial flow value of the aluminum source flow required in the growth of the first N-type transition layer, the second N-type transition layer, the third N-type transition layer, the fourth N-type transition layer, the fifth N-type transition layer or the sixth N-type transition layer; cosX is a cosine coefficient; b is a cosine multiple. Wherein in the growth process of the first N-type transition layer, the third N-type transition layer and the fifth N-type transition layer, the value range of X is [ pi/2-0 ]; and in the growth process of the second N-type transition layer, the fourth N-type transition layer and the sixth N-type transition layer, the value range of X is (0 to (-pi/2)).

Taking the growth process of the first N-type transition layer as an example, Y is the flow rate of an aluminum source required in the growth process of the first N-type transition layer; a is a fixed numerical value, and can be selected as an initial flow value of the aluminum source flow required in the growth of the first N-type transition layer, namely the aluminum source flow value required when the aluminum component is 0.1, and the value range of X is [ pi/2-0 ];

taking the growth process of the second N-type transition layer as an example, Y is the flow rate of the aluminum source required in the growth process of the second N-type transition layer; a is a fixed numerical value and can be selected as an initial flow value of the aluminum source flow required in the growth of the second N-type transition layer, namely the aluminum source flow value required when the aluminum component is 0.6, and the value range of X is between 0 and minus pi/2.

On the basis of any one of the above embodiments, in an embodiment of the present invention, the growth environment of the N-type bragg reflector includes a nitrogen environment, that is, the N-type bragg reflector is grown in the nitrogen environment; in another embodiment of the present invention, the growth environment of the N-type bragg reflector includes a hydrogen environment, i.e., the N-type bragg reflector is grown in the hydrogen environment; in yet another embodiment of the present invention, the growth environment of the N-type bragg reflector layer includes nitrogen and hydrogen, i.e., the N-type bragg reflector layer is grown in an environment in which nitrogen and hydrogen are mixed. The present invention is not limited in this regard as long as the growth environment of the N-type bragg reflector layer includes at least one of a nitrogen environment and a hydrogen environment.

S3: and forming a first limiting layer on one side of the N-type distributed Bragg reflection layer, which is far away from the buffer layer.

Optionally, in an embodiment of the present invention, a growth temperature of the first confinement layer ranges from 650 ℃ to 800 ℃, a growth pressure is 50mbar, and a growth thickness is 60 nm; however, the present invention is not limited thereto, as the case may be.

S4: and forming a first waveguide layer on the side of the first limiting layer, which faces away from the distributed Bragg reflection layer.

Optionally, in an embodiment of the present invention, the growth temperature of the first waveguide layer ranges from 650 ℃ to 800 ℃, the growth pressure is 50mbar, and the growth thickness is 50 nm; however, the present invention is not limited thereto, as the case may be.

S5: and forming a quantum hydrazine light-emitting layer on one side of the first waveguide layer, which is far away from the first limiting layer.

Optionally, in an embodiment of the present invention, the growth temperature of the quantum hydrazine light emitting layer is 650 ℃ to 800 ℃, the growth pressure is 50mbar, and the growth thickness is 45 nm; however, the present invention is not limited thereto, as the case may be.

S6: and forming a second waveguide layer on one side of the quantum hydrazine light-emitting layer, which is far away from the first waveguide layer.

Optionally, in an embodiment of the present invention, the growth temperature of the second waveguide layer ranges from 650 ℃ to 800 ℃, the growth pressure is 50mbar, and the growth thickness is 50 nm; however, the present invention is not limited thereto, as the case may be.

S7: and forming a second limiting layer on one side of the second waveguide layer, which is far away from the quantum hydrazine light-emitting layer.

Optionally, in an embodiment of the present invention, a growth temperature of the second confinement layer ranges from 650 ℃ to 800 ℃, a growth pressure is 50mbar, and a growth thickness is 60 nm; however, the present invention is not limited thereto, as the case may be.

S8: forming an oxide layer on the second confinement layer at a side away from the second waveguide layer

Optionally, in an embodiment of the present invention, a growth temperature of the oxide layer ranges from 650 ℃ to 800 ℃, a growth pressure is 50mbar, and a growth thickness is 100 nm; however, the present invention is not limited thereto, as the case may be.

S9: and forming a P-type Distributed Bragg Reflector (DBR) layer on the side, away from the second limiting layer, of the oxide layer, wherein the P-type Distributed Bragg Reflector (DBR) layer comprises a plurality of stacked second stacked units. The second stacking unit comprises a first P-type reflecting layer and a second P-type reflecting layer which are stacked, wherein the composition of aluminum in the first P-type reflecting layer is larger than that of aluminum in the second P-type reflecting layer. Optionally, the growth temperature of the P-type bragg reflection layer ranges from 660 ℃ to 780 ℃, inclusive.

Specifically, in another embodiment of the present invention, a method for forming the second stacked unit includes: forming a first P-type reflecting layer on one side of the oxide layer, which is far away from the second limiting layer; and forming a second P-type reflecting layer on one side of the first P-type reflecting layer, which is far away from the oxide layer.

On the basis of the above embodiment, in an embodiment of the present invention, the second stacking unit further includes:

In an embodiment of the present invention, a method for preparing the second stacking unit includes:

s91: and forming a first P-type transition layer on one side of the oxide layer, which is far away from the second limiting layer. Optionally, the doping concentration of the first P-type transition layer ranges from 5E17 to 5E18, but the invention is not limited thereto, and is specifically determined as the case may be.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the first P-type transition layer is gradually changed from Y1 to Y2, the growth pressure of the first P-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 5.5E 18. However, the present invention is not limited thereto, as the case may be.

S92: and forming a second P-type transition layer on the side of the first P-type transition layer, which is far away from the oxide layer. Optionally, the doping concentration of the second P-type transition layer is 3E17-4E18, but the invention is not limited thereto, as the case may be.

Specifically, in one embodiment of the present invention, the composition of aluminum in the second P-type transition layer is gradually changed from Y2 to Y3, the growth pressure of the second P-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 5E 18. However, the present invention is not limited thereto, as the case may be.

S93: and forming a third P-type transition layer on one side of the second P-type transition layer, which is far away from the first P-type transition layer. Optionally, the doping concentration of the third P-type transition layer ranges from 3E17 to 1.5E18, but the invention is not limited thereto, and is specifically determined according to the circumstances.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the third P-type transition layer is gradually changed from Y3 to Y4, the growth pressure of the third P-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 4.5E 18. However, the present invention is not limited thereto, as the case may be.

S94: and forming a first P-type reflecting layer on one side of the third P-type transition layer, which is far away from the second P-type transition layer. Optionally, the doping concentration of the first P-type reflective layer ranges from 5E17 to 5E18, but the invention is not limited thereto, and is specifically determined according to the circumstances.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the first P-type reflective layer is Y4, the growth pressure of the first P-type reflective layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 63nm, and the doping concentration is 4E 18. However, the present invention is not limited thereto, as the case may be.

S95: and forming a fourth P-type transition layer on one side of the first P-type reflection layer, which is far away from the third P-type transition layer. Optionally, the doping concentration of the fourth P-type transition layer ranges from 3E17 to 1.5E18, but the invention is not limited thereto, and is specifically determined according to the circumstances.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the fourth P-type transition layer is gradually changed from Y4 to Y3, the growth pressure of the fourth P-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 4.5E 18. However, the present invention is not limited thereto, as the case may be.

S96: and forming a fifth P-type transition layer on one side of the fourth P-type transition layer, which is far away from the first P-type reflection layer. Optionally, the doping concentration of the fifth P-type transition layer ranges from 3E17 to 4E18, but the invention is not limited thereto, and is specifically determined as the case may be.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the fifth P-type transition layer is gradually changed from Y3 to Y2, the growth pressure of the fifth P-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 5E 18. However, the present invention is not limited thereto, as the case may be.

S97: and forming a sixth P-type transition layer on one side of the fifth P-type transition layer, which is far away from the fourth P-type transition layer. Optionally, the doping concentration of the sixth P-type transition layer ranges from 5E17 to 5E18, but the invention is not limited thereto, and is specifically determined as the case may be.

Specifically, in a specific embodiment of the present invention, the composition of aluminum in the sixth P-type transition layer is gradually changed from Y2 to Y1, the growth pressure of the sixth P-type transition layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 5nm, and the doping concentration is 5.5E 18. However, the present invention is not limited thereto, as the case may be.

S98: a second P-type reflective layer is optionally formed on a side of the sixth P-type transition layer away from the fifth P-type transition layer, and a doping concentration of the second P-type reflective layer ranges from 5E17 to 5E18, but the invention is not limited thereto, as the case may be.

Specifically, in a specific embodiment of the present invention, the aluminum composition in the second P-type reflective layer is Y1, the growth pressure of the first P-type reflective layer is 50mbr, the growth temperature is 730 ℃, the growth thickness is 63nm, and the doping concentration is 6E 18. However, the present invention is not limited thereto, as the case may be.

On the basis of any of the above embodiments, in an embodiment of the present invention, a growth cycle of the second stacking unit in the P-type bragg-type reflective layer ranges from 1 to 100 inclusive, but the present invention is not limited thereto, as the case may be.

In an embodiment of the present invention, on the basis of any of the above embodiments, the thickness of the P-type bragg reflector layer is 4 microns, but the present invention does not limit this to any specific case.

On the basis of any of the above embodiments, in an embodiment of the present invention, the gradient curves of the aluminum composition in the first P-type transition layer, the third P-type transition layer, and the fifth P-type transition layer satisfy a sine curve with 1/4 cycles, and the gradient curves of the aluminum composition in the second P-type transition layer, the fourth P-type transition layer, and the sixth P-type transition layer satisfy a cosine curve with 1/4 cycles, so that the change of the aluminum composition in each transition layer in the P-type bragg reflection layer is smoother.

Specifically, on the basis of the above embodiment, in an embodiment of the present invention, the flow rate of introducing the aluminum source during the preparation of the second stacking unit satisfies: y ═ a + bcosX to effect a change in the Al composition in the first, second, third, fourth, fifth, and sixth P-type transition layers. In this embodiment, Y is an aluminum source flow rate required during the growth process of the first P-type transition layer, the second P-type transition layer, the third P-type transition layer, the fourth P-type transition layer, the fifth P-type transition layer, or the sixth P-type transition layer; a is a fixed numerical value, and can be selected as an initial flow value of the aluminum source flow required in the growth of the first P-type transition layer, the second P-type transition layer, the third P-type transition layer, the fourth P-type transition layer, the fifth P-type transition layer or the sixth P-type transition layer; cosX is a cosine coefficient; b is a cosine multiple.

In the growth process of the first P-type transition layer, the third P-type transition layer and the fifth P-type transition layer, the value range of X is [ pi/2-0 ]; and in the growth process of the second P-type transition layer, the fourth P-type transition layer and the sixth P-type transition layer, the value range of X is between 0 and minus pi/2.

Taking the growth process of the first P-type transition layer as an example, Y is the flow rate of the aluminum source required in the growth process of the first P-type transition layer; a is a fixed numerical value, and can be selected as an initial flow value of the aluminum source flow required in the growth of the first P-type transition layer, namely the aluminum source flow value required when the aluminum component is 0.1, wherein the value range of X is [ pi/2-0 ];

taking the growth process of the second P-type transition layer as an example, Y is the flow rate of the aluminum source required in the growth process of the second P-type transition layer; a is a fixed numerical value, and can be selected as an initial flow value of the aluminum source flow required in the growth of the second P-type transition layer, namely the aluminum source flow value required when the aluminum component is 0.6, and the value range of X is between 0 and minus pi/2.

On the basis of any one of the above embodiments, in an embodiment of the present invention, the growth environment of the P-type bragg reflector includes a nitrogen environment, that is, the P-type bragg reflector grows in the nitrogen environment; in another embodiment of the present invention, the growth environment of the P-type bragg reflector includes a hydrogen environment, i.e., the P-type bragg reflector is grown in the hydrogen environment; in yet another embodiment of the present invention, the growth environment of the P-type bragg reflector layer includes nitrogen and hydrogen, i.e., the P-type bragg reflector layer is grown in an environment in which nitrogen and hydrogen are mixed. The present invention is not limited in this regard as long as the growth environment of the P-type bragg reflector layer includes at least one of a nitrogen environment and a hydrogen environment.

On the basis of any of the above embodiments, the method further comprises: s10: and forming a P-type cap layer (namely a P-cap layer) on one side of the P-type Bragg reflection layer, which is far away from the oxide layer.

Specifically, in an embodiment of the invention, the growth of the P-type cap layer is only 650-.

As can be seen from the above, in the vcsel epitaxial structure and the vcsel epitaxial method provided in the embodiments of the present invention, the N-type distributed bragg reflector includes not only the first N-type reflector and the second N-type reflector, but also the first N-type transition layer, the second N-type transition layer, and the third N-type transition layer located between the first N-type reflector and the second N-type reflector, and the fourth N-type transition layer, the fifth N-type transition layer, and the sixth N-type transition layer located between the first N-type reflector and the second N-type reflector, where the composition of aluminum in the first N-type transition layer is gradually changed from Y1 to Y2, the composition of aluminum in the second N-type transition layer is gradually changed from Y2 to Y3, the composition of aluminum in the third N-type transition layer is gradually changed from Y3 to Y4, the composition of aluminum in the first N-type reflector is Y4, and the composition of aluminum in the fourth N-type transition layer is gradually changed from Y4 to Y35 3, the composition of aluminum in the fifth N-type transition layer is gradually changed from Y3 to Y2, the composition of aluminum in the sixth N-type transition layer is gradually changed from Y2 to Y1, the composition of aluminum in the second N-type reflection layer is Y1, Y1 is smaller than Y3 and Y2 is smaller than Y4, so that the composition of Al in the N-type distributed Bragg reflection layer is increased from Y1 to Y4 and then decreased from Y4 to Y1, stepped composition changes are adopted, Y1 is gradually changed to Y2, Y2 is gradually changed to Y3, Y3 is gradually changed to Y4, Y4 is gradually changed to Y3, Y3 is gradually changed to Y2, Y2 is gradually changed to Y1, so that barrier junctions between adjacent transition layers are reduced, and the tensile stress between the adjacent N-type transition layer or the N-type transition layer and the adjacent N-type reflection layer is utilized, so that the depth of the N-type transition layer is changed to reduce the total series connection of the Bragg reflection resistance value of the N-type reflection layer, the voltage at two ends of the N-type Bragg reflection layer is reduced, the threshold current of the N-type Bragg reflection layer is reduced, the current is less consumed in the N-type Bragg reflection layer, the heat loss of the epitaxial structure is further reduced, the power conversion efficiency and the slope efficiency of the epitaxial structure are improved, a plurality of steps are formed between the first N-type reflection layer and the second N-type reflection layer by utilizing the N-type transition layers, the electrons in the N-type Bragg reflection layer are more easily transited, the number of the electron and hole recombination pairs in the epitaxial structure is increased, the number of the particles in the epitaxial structure is increased, and the gain is improved.

Similarly, the P-type distributed bragg reflector comprises a first P-type reflector layer and a second P-type reflector layer, and further comprises a first P-type transition layer, a second P-type transition layer and a third P-type transition layer which are positioned between the first P-type reflector layer and the second P-type reflector layer and are away from the second P-type reflector layer, and a fourth P-type transition layer, a fifth P-type transition layer and a sixth P-type transition layer which are positioned between the first P-type reflector layer and the second P-type reflector layer, wherein the composition of aluminum in the first P-type transition layer is gradually changed from Y1 to Y2, the composition of aluminum in the second P-type transition layer is gradually changed from Y2 to Y3, the composition of aluminum in the third P-type transition layer is gradually changed from Y3 to Y4, the composition of aluminum in the first P-type reflector layer is Y4, the composition of aluminum in the fourth P-type transition layer is gradually changed from Y4 to Y8292, and the composition of aluminum in the fifth P-type transition layer is gradually changed from Y3 to Y4934, the composition of aluminum in the sixth P-type transition layer is gradually changed from Y2 to Y1, the composition of aluminum in the second P-type reflection layer is Y1, Y1 is smaller than Y3 and smaller than Y2 and smaller than Y4, so that in the process that the composition of Al in the P-type distributed Bragg reflection layer is increased from Y1 to Y4 and then is decreased from Y4 to Y1, stepped composition changes are adopted, the change is gradually changed from Y1 to Y2, from Y2 to Y3, from Y3 to Y4, from Y4 to Y3, from Y3 to Y2 and finally from Y2 to Y1, so that barrier junctions between adjacent transition layers are reduced, and the barrier junctions are stretched by utilizing the stress change between the adjacent P-type transition layers or the P-type transition layers and the adjacent P-type reflection layers, so that the overall depth of the barriers of the P-type transition layers is reduced, and the series connection resistance of the P-type Bragg reflection layers is reduced. The threshold current of the P-type Bragg reflection layer is reduced, so that the current is less consumed in the P-type Bragg reflection layer, the heat loss of the epitaxial structure is further reduced, the power conversion efficiency and the slope efficiency of the epitaxial structure are improved, a plurality of steps are formed between the first P-type reflection layer and the second P-type reflection layer by utilizing the P-type transition layers, holes in the P-type Bragg reflection layer are more easily transited, the number of electron and hole recombination pairs in the epitaxial structure is further increased, the number of inverse particles in the epitaxial structure is increased, and the gain is improved.

In summary, the vertical cavity surface emitting laser epitaxial structure and the method for fabricating the same according to the embodiments of the present inventionIn the method, the N-type DBR layer and the P-type DBR layer are respectively made of Al with different Al component contents_YGa_1-YAs composition, different from Al_YGa_1-YBarrier junction reduction between As layers and utilization of adjacent Al_YGa_1-YTensile barrier height of stress variation between the As layer makes N type DBR layer with the whole degree of depth of barrier junction of P type DBR layer becomes shallow, thereby reduces N type DBR layer with the series resistance of P type DBR layer reduces N type DBR layer with the voltage at P type DBR layer both ends reduces N type DBR layer with the threshold current of P type DBR layer for the electric current is in N type DBR layer with P type DBR layer consumes less, and then reduces epitaxial structure's heat loss, improves epitaxial structure's power conversion efficiency and slope efficiency. And Al of different Al composition_YGa_1-YAs forms a step between As, the potential barrier difference is reduced, so that electrons and holes can be more easily transited, the recombination logarithm of the electrons and the holes is increased, the inversion number of particles is increased, the gain is improved, and the generation of heat is reduced.

The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims

1. A vertical cavity surface emitting laser epitaxial structure, comprising:

a substrate;

the buffer layer is positioned on the first side surface of the substrate;

wherein the first stacking unit comprises a first N-type transition layer, a second N-type transition layer, a third N-type transition layer, a first N-type reflection layer, a fourth N-type transition layer, a fifth N-type transition layer, a sixth N-type transition layer and a second N-type reflection layer which are stacked, the composition of aluminum in the first N-type transition layer is gradually changed from Y1 to Y2, the composition of aluminum in the second N-type transition layer is gradually changed from Y2 to Y3, the composition of aluminum in the third N-type transition layer is gradually changed from Y3 to Y4, the composition of aluminum in the first N-type reflection layer is Y4, the composition of aluminum in the fourth N-type transition layer is gradually changed from Y4 to Y3, the composition of aluminum in the fifth N-type transition layer is gradually changed from Y3 to Y2, the composition of aluminum in the sixth N-type transition layer is gradually changed from Y2 to Y1, the composition of aluminum in the second N-type reflection layer is gradually changed from Y4 to Y2, and the Y5838 is smaller than the step distributed Bragg reflection layer with a gradual change of Y1, therefore, barrier junctions between adjacent N-type transition layers or between the N-type transition layers and the adjacent N-type reflecting layers are reduced, and the overall depth of the barrier junctions of the N-type Bragg reflecting layers is reduced by utilizing the stress change between the adjacent N-type transition layers or between the adjacent N-type transition layers and the adjacent N-type reflecting layers to stretch the barrier height, so that the series resistance of the N-type Bragg reflecting layers is reduced;

2. The epitaxial structure of claim 1 wherein the gradual change profile of the aluminum composition in the first N-type transition layer, the third N-type transition layer, the fifth N-type transition layer satisfies a sinusoidal curve with 1/4 cycles;

3. Epitaxial structure according to claim 1, characterized in that Y1 is 0.1, Y2 is 0.6, Y3 is 0.4 and Y4 is 0.9.

4. The epitaxial structure of claim 1, wherein the second stacking unit further comprises:

5. The epitaxial structure of claim 4, wherein the first N-type transition layer, the second N-type transition layer, the third N-type transition layer, the fourth N-type transition layer, the fifth N-type transition layer, and the sixth N-type transition layer are the same thickness;

6. The epitaxial structure of claim 5, wherein the thickness of the first N-type transition layer ranges from 1 nm to 10nm, inclusive;

7. The epitaxial structure of claim 1, wherein the number of the first stacked units in the N-type distributed bragg reflector layer ranges from 1 to 100 inclusive;

the number of the second stacking units in the P-type distributed Bragg reflection layer ranges from 1 to 100 inclusive.

8. A preparation method of a vertical cavity surface emitting laser epitaxial structure is characterized by comprising the following steps:

forming a buffer layer on the first side surface of the substrate;

wherein the first stacking unit comprises a first N-type transition layer, a second N-type transition layer, a third N-type transition layer, a first N-type reflection layer, a fourth N-type transition layer, a fifth N-type transition layer, a sixth N-type transition layer and a second N-type reflection layer which are stacked, the composition of aluminum in the first N-type transition layer is gradually changed from Y1 to Y2, the composition of aluminum in the second N-type transition layer is gradually changed from Y2 to Y3, the composition of aluminum in the third N-type transition layer is gradually changed from Y3 to Y4, the composition of aluminum in the first N-type reflection layer is Y4, the composition of aluminum in the fourth N-type transition layer is gradually changed from Y4 to Y3, the composition of aluminum in the fifth N-type transition layer is gradually changed from Y3 to Y2, the composition of aluminum in the sixth N-type transition layer is gradually changed from Y2 to Y1, the composition of aluminum in the second N-type transition layer is gradually changed from Y4 to Y2, and the second N-type reflection layer is distributed and the distributed Bragg reflection layer is distributed with the gradient of less than Y1, therefore, barrier junctions between adjacent N-type transition layers or between the N-type transition layers and the adjacent N-type reflecting layers are reduced, and the overall depth of the barrier junctions of the N-type Bragg reflecting layers is reduced by utilizing the stress change between the adjacent N-type transition layers or between the adjacent N-type transition layers and the adjacent N-type reflecting layers to stretch the barrier height, so that the series resistance of the N-type Bragg reflecting layers is reduced;

9. The method of manufacturing according to claim 8, wherein the second stacking unit further comprises:

10. The method according to claim 8, wherein the growth environment of the N-type bragg reflector and the P-type bragg reflector includes at least one of a nitrogen environment and a hydrogen environment.