CN116207612A - VCSEL epitaxial structure, manufacturing method thereof and VCSEL chip - Google Patents

Abstract

The invention provides a VCSEL epitaxial structure, a manufacturing method thereof and a VCSEL chip, wherein the VCSEL epitaxial structure comprises the following components: an N-type DBR reflection layer, a resonant cavity layer and a P-type DBR reflection layer laminated on a substrate, wherein the resonant cavity layer comprises an active region, the P-type DBR reflection layer comprises a first DBR stack structure and a first AlGaAs transition layer, and the first DBR stack structure comprises Al alternately laminated _x GaAs layer and Al _y A GaAs layer, a first AlGaAs transition layer arranged on Al _x GaAs layer and Al _y Between the GaAs layers, the doping concentration of the P-type DBR reflecting layer is sequentially increased along the first direction, and the thickness of the first AlGaAs transition layer is reduced along with the increase of the doping concentration of the P-type DBR reflecting layer, so that the series resistance is reduced, and the absolute reflectivity is improved.

Description

VCSEL epitaxial structure, manufacturing method thereof and VCSEL chip

Technical Field

The invention relates to the technical field of light emitting diodes, in particular to a VCSEL epitaxial structure, a manufacturing method thereof and a VCSEL chip.

Background

VCSEL (Vertical-Cavity Surface Emitting Laser) chip is widely used in the fields of optical communication, optical interconnection, optical storage and the like because of the advantages of small volume, circular output light spots, single longitudinal mode output, small threshold current, low price, easy integration into a large-area array and the like.

DBR (distributed Bragg reflective, distributed bragg reflection) is a mirror structure that comprises a tunable multilayer structure of two optical materials. Most commonly a quarter mirror, wherein each layer has a thickness corresponding to a quarter wavelength. In the field of vertical cavity surface emitting lasers, the resonant cavity does not depend on a cleavage surface, but forms a semiconductor Bragg reflector through single-chip growth of a multi-layer dielectric film, the reflectivity can exceed 99%, and the degradation of the laser performance caused by mechanical damage, surface oxidation, contamination and the like of the cleavage cavity in the edge emitting laser can be avoided. In the field of avalanche photodetectors, the use of front side illuminated chip structures in combination with bragg reflectors can replace conventional back side illuminated chip structures.

To achieve high reflectivity, the two materials that make up the DBR need to have a large refractive index difference, resulting in a large bandgap difference, resulting in a DBR with high series resistance, resulting in excessive power loss. The interface barrier peak prevents carriers from flowing to generate large series resistance, the effective mass of holes is large, the mobility of P-type doped carriers is low, and particularly the P-type DBR has high series resistance, so that the performance of a semiconductor device is affected. To reduce the series resistance, a graded DBR structure is designed with a transition layer that reduces the barrier spike and improves the barrier shape by a graded junction to reduce the series resistance.

However, in the conventional VCSEL chip, the series resistance of the graded DBR structure with the transition layer is improved compared with the abrupt DBR structure without the transition layer under the same logarithmic condition, but the absolute reflectivity is lower than that of the abrupt DBR structure without the transition layer.

Disclosure of Invention

In view of this, the present invention provides a VCSEL epitaxial structure, a method for fabricating the same, and a VCSEL chip, so as to solve the problems that in the existing VCSEL chip, the series resistance of the graded DBR structure with a transition layer is improved compared with the abrupt DBR structure without a transition layer, but the absolute reflectivity is lower than that of the abrupt DBR structure without a transition layer.

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

a VCSEL epitaxial structure comprising:

a substrate;

an N-type DBR reflective layer, a resonant cavity layer, and a P-type DBR reflective layer sequentially stacked on the substrate along a first direction, the resonant cavity layer comprising an active region, the first direction being perpendicular to the substrate and directed from the substrate to the P-type DBR reflective layer;

wherein the P-type DBR reflection layer comprises a first DBR stack structure and a first AlGaAs-based layerA transition layer, the first DBR stack structure including Al alternately laminated _x GaAs layer and Al _y A GaAs layer, the first AlGaAs transition layer is arranged on the Al _x GaAs layer and Al _y Between GaAs layers, where x<y；

The doping concentration of the P-type DBR reflection layer is sequentially increased along the first direction, and the thickness of the first AlGaAs transition layer is reduced along with the increase of the doping concentration of the P-type DBR reflection layer.

Preferably, the thickness of the first AlGaAs transition layer decreases linearly with increasing doping concentration of the P-type DBR reflective layer;

or, the thickness of the first AlGaAs transition layer is reduced stepwise along with the increase of the doping concentration of the P-type DBR reflection layer;

or, the thickness of the first AlGaAs transition layer decreases in a parabolic shape as the doping concentration of the P-type DBR reflection layer increases.

Preferably, the Al _x GaAs layer, the Al _y The GaAs layer and the first AlGaAs transition layer are doped in a P type, and the doping concentration of the first AlGaAs transition layer is larger than that of the Al adjacent to the first AlGaAs transition layer _x GaAs layer and Al _y Doping concentration of GaAs layer.

Preferably, the thickness of the first AlGaAs transition layer ranges from 5nm to 25nm, inclusive.

Preferably, the N-type DBR reflection layer includes a second DBR stack structure including Al alternately laminated and arranged _a GaAs layer and Al _b A GaAs layer, the second AlGaAs transition layer is arranged on the Al _a GaAs layer and Al _b Between GaAs layers, wherein a<b。

Preferably, the doping concentration of the N-type DBR reflective layer increases gradually along the opposite direction of the first direction, and the thickness of the second AlGaAs transition layer decreases as the doping concentration of the N-type DBR reflective layer increases.

Preferably, the Al _a GaAs layer, the Al _b The GaAs layer and the second AlGaAs transition layer are doped with N type, and the second AlGaThe doping concentration of the As transition layer is larger than that of the Al adjacent to the As transition layer _a GaAs layer and Al _b Doping concentration of GaAs layer.

Preferably, in the first direction, the resonant cavity layer includes an N-type confinement layer, the active region, a P-type confinement layer, and an oxide layer stacked in this order.

Preferably, the VCSEL epitaxial structure further comprises:

a buffer layer between the substrate and the N-type DBR reflective layer;

and the ohmic contact layer is positioned on one side of the P-type DBR reflection layer away from the resonant cavity layer.

The invention also provides a preparation method of the VCSEL epitaxial structure, which comprises the following steps:

providing a substrate;

an N-type DBR reflecting layer, a resonant cavity layer and a P-type DBR reflecting layer are sequentially grown on the substrate by adopting MOCVD equipment through a metal organic chemical vapor deposition method, and the resonant cavity layer comprises an active region;

wherein the P-type DBR reflection layer comprises a first DBR stack structure and a first AlGaAs transition layer, the first DBR stack structure comprises alternately laminated Al _x GaAs layer and Al _y A GaAs layer, the first AlGaAs transition layer is arranged on the Al _x GaAs layer and Al _y Between GaAs layers, where x<y；

The doping concentration of the P-type DBR reflection layer is sequentially increased along the first direction, and the thickness of the first AlGaAs transition layer is reduced along with the increase of the doping concentration of the P-type DBR reflection layer.

A VCSEL chip comprising a VCSEL epitaxial structure according to any of the preceding claims.

By the technical scheme, the following effects are achieved:

1. the VCSEL epitaxial structure provided by the invention comprises a P-type DBR reflection layer, a first AlGaAs transition layer and a first DBR stack structure, wherein the first DBR stack structure comprises Al alternately laminated _x GaAs layer and Al _y GaAs layer, first AlGaAThe s transition layer is arranged on Al _x GaAs layer and Al _y Between the GaAs layers, the doping concentration of the P-type DBR reflection layer increases in order along the first direction, and the thickness of the first AlGaAs transition layer tends to decrease as the doping concentration of the P-type DBR reflection layer increases, i.e., in the P-type DBR reflection layer, al is disposed closer to the active region _x GaAs layer and Al _y The lower the doping concentration of the GaAs layer is, the absorption loss is reduced, and the barrier is reduced by adopting the first AlGaAs transition layer with thicker thickness, so that the series resistance can be effectively reduced; the farther away from the active region Al _x GaAs layer and Al _y The doping concentration of the GaAs layer is set higher to reduce the series resistance, and the absolute reflectivity is improved by adopting the first AlGaAs transition layer with relatively smaller thickness, so that the series resistance is reduced and the absolute reflectivity is improved by the arrangement.

2. According to the manufacturing method of the VCSEL epitaxial structure, the VCSEL epitaxial structure formed by simple and convenient manufacturing process can effectively solve the problems that under the condition of the same logarithm of DBR in the existing VCSEL chip, the series resistance of the graded DBR structure with the transition layer is improved compared with that of the abrupt DBR structure without the transition layer, but the absolute reflectivity is lower than that of the abrupt DBR structure without the transition layer.

3. The VCSEL chip provided by the invention can effectively solve the problem that the series resistance of the graded DBR structure with the transition layer is improved compared with that of the abrupt DBR structure without the transition layer in the same logarithmic condition in the conventional VCSEL chip by using the VCSEL epitaxial structure, but the absolute reflectivity is lower than that of the abrupt DBR structure without the transition layer, so that the luminous efficiency of the VCSEL chip is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic view of a VCSEL epitaxial structure according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of the reflective layer of the P-type DBR of FIG. 1;

fig. 3.1 to 3.3 are schematic diagrams showing thickness of a VCSEL epitaxial structure according to another embodiment of the present invention as a function of doping concentration;

FIG. 4 is a schematic diagram of an N-type DBR reflective layer of a VCSEL epitaxial structure according to another embodiment of the present invention;

the symbols in the drawings illustrate:

1. a substrate; 2. a buffer layer; 3. an N-type DBR reflection layer; 31. a second DBR stack structure; 311. al (Al) _a A GaAs layer; 312. al (Al) _b A GaAs layer; 32. a second AlGaAs transition layer; 4. a resonant cavity layer; 41. an N-type limiting layer; 42. an active region; 43. a P-type limiting layer; 44. an oxide layer; 5. a P-type DBR reflective layer; 51. a first DBR stack structure; 511. al (Al) _x A GaAs layer; 512. al (Al) _y A GaAs layer; 52. a first AlGaAs transition layer; 6. an ohmic contact layer.

Detailed Description

For the sake of clarity of the disclosure, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present application is not limited to the specific embodiments disclosed below.

Next, the present application will be described in detail with reference to the schematic drawings, wherein the cross-sectional views of the device structure are not to scale for the sake of illustration, and the schematic drawings are merely examples, which should not limit the scope of protection of the present application. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.

The embodiment of the invention provides a VCSEL epitaxial structure, as shown in fig. 1 to 2, including:

a substrate 1;

an N-type DBR reflective layer 3, a resonant cavity layer 4, and a P-type DBR reflective layer 5 sequentially stacked on the substrate 1 in a first direction, the resonant cavity layer 4 including an active region 42, the first direction being perpendicular to the substrate 1 and directed from the substrate 1 to the P-type DBR reflective layer 5;

wherein the P-type DBR reflection layer 5 comprises a first DBR stack structure 51 and a first AlGaAs transition layer 52, the first DBR stack structure 51 comprises Al alternately laminated _x GaAs layer 511 and Al _y A GaAs layer 512, a first AlGaAs transition layer 52 disposed on Al _x GaAs layer 511 and Al _y Between GaAs layers 512, where x<y；

The doping concentration of the P-type DBR reflective layer 5 increases in order along the first direction, and the thickness of the first AlGaAs transition layer 52 tends to decrease as the doping concentration of the P-type DBR reflective layer 5 increases.

Specifically, in the VCSEL epitaxial structure, the material of the substrate 1 may be GaAs material; in the first DBR stack structure 51, the optical thickness of each sub-layer is one quarter of the optical wavelength; the sequentially increasing doping concentration of the P-type DBR reflective layer 5 can be linear, stepped, parabolic, or any other form known in the art.

Alternatively, in the present embodiment, the Al composition of the first AlGaAs transition layer 52 gradually increases from x to y or gradually decreases from y to x.

Alternatively, in this embodiment, the thickness of the first AlGaAs transition layer 52 ranges from 5nm to 25nm, inclusive.

Alternatively, in the present embodiment, al _x GaAs layer 511, al _y The GaAs layer 512 and the first AlGaAs transition layer 52 are P-doped, and the first AlGaAs transition layer 52 has a doping concentration greater than that of Al adjacent thereto _x GaAs layer 511 and Al _y Doping concentration of GaAs layer 512.

Alternatively, in another embodiment of the present application, as shown in fig. 3.1, the thickness of the first AlGaAs transition layer 52 decreases linearly with increasing doping concentration of the P-type DBR reflective layer 5;

or, as shown in fig. 3.2, the thickness of the first AlGaAs transition layer 52 decreases stepwise with an increase in the doping concentration of the P-type DBR reflective layer 5;

alternatively, as shown in fig. 3.3, the thickness of the first AlGaAs transition layer 52 decreases in a parabolic shape as the doping concentration of the P-type DBR reflective layer 5 increases.

Alternatively, in another embodiment of the present application, as shown in fig. 4, the N-type DBR reflective layer 3 includes a second DBR stack structure 31 and a second AlGaAs transition layer 32, the second DBR stack structure 31 including Al alternately stacked _a GaAs layer 311 and Al _b A GaAs layer 312, a second AlGaAs transition layer 32 disposed on Al _a GaAs layer 311 and Al _b Between GaAs layers 312, where a<b。

Specifically, in the second DBR stack structure 31, the optical thickness of each sub-layer is one quarter of the optical wavelength.

Alternatively, in the present embodiment, the Al composition of the second AlGaAs transition layer 32 gradually increases from a to b or gradually decreases from b to a.

Alternatively, in the present embodiment, al _a GaAs layer 311, al _b The GaAs layer 312 and the second AlGaAs transition layer 32 are N-doped, and the second AlGaAs transition layer 32 has a doping concentration greater than that of Al adjacent thereto _a GaAs layer 311 and Al _b Doping concentration of GaAs layer 312.

Alternatively, in this embodiment, the doping concentration of the N-type DBR reflective layer 3 is sequentially increased in the opposite direction to the first direction, and the thickness of the second AlGaAs transition layer 32 is constant.

In particular, the form of sequentially increasing doping concentration of the N-type DBR reflective layer 3 may be linear, stepped, parabolic, or any other form known in the art.

Alternatively, in another embodiment of the present application, the doping concentration of the N-type DBR reflective layer 3 sequentially increases in the opposite direction to the first direction, and the thickness of the second AlGaAs transition layer 32 tends to decrease as the doping concentration of the N-type DBR reflective layer 3 increases.

In the present embodiment, al is provided in the N-type DBR reflective layer closer to the active region _a GaAs layer and Al _b The lower the doping concentration of the GaAs layer is, the absorption loss is reduced, and the barrier is reduced by adopting the second AlGaAs transition layer with thicker thickness, so that the series resistance can be effectively reduced; the farther away from the active region Al _a GaAs layer and Al _b The GaAs layer has a higher doping concentration for reducing the series resistance, and the absolute reflectivity is improved by adopting the second AlGaAs transition layer with a relatively thinner thickness, so that the series resistance is reduced and the absolute reflectivity is improved.

Alternatively, in this embodiment, the thickness of the second AlGaAs transition layer 32 ranges from 5nm to 25nm, inclusive.

Alternatively, in another embodiment of the present application, referring to fig. 3.1, the thickness of the second AlGaAs transition layer 32 decreases linearly with increasing doping concentration of the N-type DBR reflective layer 3;

alternatively, referring to fig. 3.2, the thickness of the second AlGaAs transition layer 32 decreases stepwise with an increase in the doping concentration of the N-type DBR reflective layer 3;

alternatively, as shown with reference to fig. 3.3, the thickness of the second AlGaAs transition layer 32 decreases in a parabolic shape as the doping concentration of the N-type DBR reflective layer 3 increases.

Alternatively, in another embodiment of the present application, referring to fig. 1, the resonator layer 4 includes an N-type confinement layer 41, an active region 42, a P-type confinement layer 43, and an oxide layer 44, which are sequentially stacked in the first direction.

Optionally, in another embodiment of the present application, referring to fig. 1, the VCSEL epitaxial structure further includes:

a buffer layer 2 located between the substrate 1 and the N-type DBR reflective layer 3.

Specifically, in the VCSEL epitaxial structure, the material of the buffer layer 2 may be GaAs material.

An ohmic contact layer 6 on the side of the P-type DBR reflective layer 5 facing away from the resonator layer 4.

The present embodiment provides a method for manufacturing a VCSEL epitaxial structure, for manufacturing the VCSEL epitaxial structure, as shown in fig. 1 to 2, the method comprising the steps of:

providing a substrate 1;

an N-type DBR reflection layer 3, a resonant cavity layer 4 and a P-type DBR reflection layer 5 are sequentially grown on a substrate 1 by adopting MOCVD equipment through a metal organic chemical vapor deposition method, and the resonant cavity layer 4 comprises an active region 42;

wherein the P-type DBR reflection layer 5 comprises a first DBR stack structure 51 and a first AlGaAs transition layer 52, the first DBR stack structure 51 comprises Al alternately laminated _x GaAs layer 511 and Al _y A GaAs layer 512, a first AlGaAs transition layer 52 disposed on Al _x GaAs layer 511 and Al _y Between GaAs layers 512, where x<y；

The doping concentration of the P-type DBR reflective layer 5 increases in order along the first direction, and the thickness of the first AlGaAs transition layer 52 tends to decrease as the doping concentration of the P-type DBR reflective layer 5 increases.

Specifically, in the VCSEL epitaxial structure, the material of the substrate 1 may be GaAs material; in the first DBR stack structure 51, the optical thickness of each sub-layer is one quarter of the optical wavelength; the sequentially increasing doping concentration of the P-type DBR reflective layer 5 can be linear, stepped, parabolic, or any other form known in the art.

Alternatively, in the present embodiment, the Al composition of the first AlGaAs transition layer 52 gradually increases from x to y or gradually decreases from y to x.

Alternatively, in this embodiment, the thickness of the first AlGaAs transition layer 52 ranges from 5nm to 25nm, inclusive.

Alternatively, in the present embodiment, al _x GaAs layer 511, al _y The GaAs layer 512 and the first AlGaAs transition layer 52 are P-doped, and the first AlGaAs transition layer 52 has a doping concentration greater than that of Al adjacent thereto _x GaAs layer 511 and Al _y Doping concentration of GaAs layer 512.

Alternatively, in another embodiment of the present application, referring to fig. 3.1, the thickness of the first AlGaAs transition layer 52 decreases linearly with increasing doping concentration of the P-type DBR reflective layer 5;

alternatively, referring to fig. 3.2, the thickness of the first AlGaAs transition layer 52 decreases stepwise with increasing doping concentration of the P-type DBR reflective layer 5;

alternatively, referring to fig. 3.3, the thickness of the first AlGaAs transition layer 52 decreases in a parabolic shape as the doping concentration of the P-type DBR reflective layer 5 increases.

Alternatively, in another embodiment of the present application, referring to fig. 4, the N-type DBR reflective layer 3 includes a second DBR stack structure 31 and a second AlGaAs transition layer 32, the second DBR stack structure 31 including Al alternately stacked _a GaAs layer 311 and Al _b A GaAs layer 312, a second AlGaAs transition layer 32 disposed on Al _a GaAs layer 311 and Al _b Between GaAs layers 312, where a<b。

Specifically, in the second DBR stack structure 31, the optical thickness of each sub-layer is one quarter of the optical wavelength.

Alternatively, in the present embodiment, the Al composition of the second AlGaAs transition layer 32 gradually increases from a to b or gradually decreases from b to a.

Alternatively, in the present embodiment, al _a GaAs layer 311, al _b The GaAs layer 312 and the second AlGaAs transition layer 32 are N-doped, and the second AlGaAs transition layer 32 has a doping concentration greater than that of Al adjacent thereto _a GaAs layer 311 and Al _b Doping concentration of GaAs layer 312.

Alternatively, in this embodiment, the doping concentration of the N-type DBR reflective layer 3 is sequentially increased in the opposite direction to the first direction, and the thickness of the second AlGaAs transition layer 32 is constant.

In particular, the form of sequentially increasing doping concentration of the N-type DBR reflective layer 3 may be linear, stepped, parabolic, or any other form known in the art.

Alternatively, in another embodiment of the present application, the doping concentration of the N-type DBR reflective layer 3 is sequentially increased in the opposite direction to the first direction, and the thickness of the second AlGaAs transition layer 32 is decreased as the doping concentration of the N-type DBR reflective layer 3 is increased.

In the present embodiment, al is provided in the N-type DBR reflective layer closer to the active region _a GaAs layer and Al _b The lower the doping concentration of the GaAs layer is to be reducedThe second AlGaAs transition layer with thicker thickness is adopted to reduce potential barrier, so that series resistance can be effectively reduced; the farther away from the active region Al _a GaAs layer and Al _b The GaAs layer has a higher doping concentration for reducing the series resistance, and the absolute reflectivity is improved by adopting the second AlGaAs transition layer with a relatively thinner thickness, so that the series resistance is reduced and the absolute reflectivity is improved.

Alternatively, in this embodiment, the thickness of the second AlGaAs transition layer 32 ranges from 5nm to 25nm, inclusive.

Alternatively, in another embodiment of the present application, referring to fig. 3.1, the thickness of the second AlGaAs transition layer 32 decreases linearly with increasing doping concentration of the N-type DBR reflective layer 3;

alternatively, referring to fig. 3.2, the thickness of the second AlGaAs transition layer 32 decreases stepwise with an increase in the doping concentration of the N-type DBR reflective layer 3;

alternatively, as shown with reference to fig. 3.3, the thickness of the second AlGaAs transition layer 32 decreases in a parabolic shape as the doping concentration of the N-type DBR reflective layer 3 increases.

Alternatively, in another embodiment of the present application, referring to fig. 1, the resonator layer 4 includes an N-type confinement layer 41, an active region 42, a P-type confinement layer 43, and an oxide layer 44 that are sequentially grown in the growth direction.

Optionally, in another embodiment of the present application, referring to fig. 1, the VCSEL epitaxial structure further includes:

before growing the N-type DBR reflection layer 3, a buffer layer 2 is grown, and the buffer layer 2 is positioned between the substrate 1 and the N-type DBR reflection layer 3.

Specifically, in the VCSEL epitaxial structure, the material of the buffer layer 2 may be GaAs material.

After the growth of the P-type DBR reflective layer 5 is completed, an ohmic contact layer 6 is grown on the P-type DBR reflective layer 5.

The embodiment provides a VCSEL chip, where the VCSEL chip includes any of the VCSEL epitaxial structures described above.

In summary, the following effects are achieved through the above technical scheme:

1. the VCSEL epitaxial structure provided by the embodiment comprises a P-type DBR reflection layer comprising a first DBR stack structure and a first AlGaAs transition layer, wherein the first DBR stack structure comprises alternately laminated Al _x GaAs layer and Al _y A GaAs layer, a first AlGaAs transition layer arranged on Al _x GaAs layer and Al _y Between the GaAs layers, the doping concentration of the P-type DBR reflection layer increases in order along the first direction, and the thickness of the first AlGaAs transition layer tends to decrease as the doping concentration of the P-type DBR reflection layer increases, i.e., in the P-type DBR reflection layer, al is disposed closer to the active region _x GaAs layer and Al _y The lower the doping concentration of the GaAs layer is, the absorption loss is reduced, and the barrier is reduced by adopting the first AlGaAs transition layer with thicker thickness, so that the series resistance can be effectively reduced; the farther away from the active region Al _x GaAs layer and Al _y The doping concentration of the GaAs layer is set higher to reduce the series resistance, and the absolute reflectivity is improved by adopting the first AlGaAs transition layer with relatively smaller thickness, so that the series resistance is reduced and the absolute reflectivity is improved by the arrangement.

2. According to the manufacturing method of the VCSEL epitaxial structure, the problem that the series resistance of the graded DBR structure with the transition layer is improved compared with that of the abrupt DBR structure without the transition layer under the condition of the same logarithm in the conventional VCSEL chip, but the absolute reflectivity is lower than that of the abrupt DBR structure without the transition layer can be effectively solved through manufacturing the formed VCSEL epitaxial structure by a simple and convenient process.

3. The VCSEL chip provided by the embodiment can effectively solve the problem that the series resistance of the graded DBR structure with the transition layer is improved compared with the abrupt DBR structure without the transition layer in the same logarithmic condition in the conventional VCSEL chip by using the aforementioned VCSEL epitaxial structure, but the absolute reflectivity is lower than that of the abrupt DBR structure without the transition layer, thereby improving the light emitting efficiency of the VCSEL chip.

It will be appreciated by those skilled in the art that in the present disclosure, the terms "transverse," "longitudinal," "upper," "lower," and the like are used for convenience in describing the present invention and simplifying the description based on the azimuth or positional relationship shown in the drawings, and do not indicate or imply that the apparatus or element to be referred to must have a specific azimuth, be constructed and operated in a specific azimuth, and thus the above terms should not be construed as limiting the present invention.

It should be noted that, in the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described as different from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (11)

1. A VCSEL epitaxial structure comprising:

a substrate;

an N-type DBR reflective layer, a resonant cavity layer, and a P-type DBR reflective layer sequentially stacked on the substrate along a first direction, the resonant cavity layer comprising an active region, the first direction being perpendicular to the substrate and directed from the substrate to the P-type DBR reflective layer;

wherein the P-type DBR reflection layer comprises a first DBR stack structure and a first AlGaAs transition layer, the first DBR stack structure comprises alternately laminated Al _x GaAs layer and Al _y A GaAs layer, the first AlGaAs transition layer is arranged on the Al _x GaAs layer and Al _y Between GaAs layers, where x<y；

The doping concentration of the P-type DBR reflection layer is sequentially increased along the first direction, and the thickness of the first AlGaAs transition layer is reduced along with the increase of the doping concentration of the P-type DBR reflection layer.

2. A VCSEL epitaxial structure in accordance with claim 1, wherein: the thickness of the first AlGaAs transition layer linearly decreases with the increase of the doping concentration of the P-type DBR reflection layer;

or, the thickness of the first AlGaAs transition layer is reduced stepwise along with the increase of the doping concentration of the P-type DBR reflection layer;

or, the thickness of the first AlGaAs transition layer decreases in a parabolic shape as the doping concentration of the P-type DBR reflection layer increases.

3. A VCSEL epitaxial structure in accordance with claim 1, wherein: the Al is _x GaAs layer, the Al _y The GaAs layer and the first AlGaAs transition layer are doped in a P type, and the doping concentration of the first AlGaAs transition layer is larger than that of the Al adjacent to the first AlGaAs transition layer _x GaAs layer and Al _y Doping concentration of GaAs layer.

4. A VCSEL epitaxial structure in accordance with claim 1, wherein: the thickness of the first AlGaAs transition layer is in a range of 5-25nm, including the end point value.

5. A VCSEL epitaxial structure in accordance with claim 1, wherein: the N-type DBR reflection layer comprises a second DBR stack structure and a second AlGaAs transition layer, wherein the second DBR stack structure comprises alternately laminated Al _a GaAs layer and Al _b A GaAs layer, the second AlGaAs transition layer is arranged on the Al _a GaAs layer and Al _b Between GaAs layers, wherein a<b。

6. A VCSEL epitaxial structure in accordance with claim 5, wherein: the doping concentration of the N-type DBR reflecting layer is sequentially increased along the opposite direction of the first direction, and the thickness of the second AlGaAs transition layer is in a decreasing trend along with the increase of the doping concentration of the N-type DBR reflecting layer.

7. A VCSEL epitaxial structure in accordance with claim 5, whichIs characterized in that: the Al is _a GaAs layer, the Al _b The GaAs layer and the second AlGaAs transition layer are doped with N type, and the doping concentration of the second AlGaAs transition layer is larger than that of the Al adjacent to the second AlGaAs transition layer _a GaAs layer and Al _b Doping concentration of GaAs layer.

8. A VCSEL epitaxial structure in accordance with claim 1, wherein: in the first direction, the resonant cavity layer comprises an N-type limiting layer, the active region, a P-type limiting layer and an oxide layer which are sequentially stacked.

9. A VCSEL epitaxial structure in accordance with claim 1, wherein: the VCSEL epitaxial structure further comprises:

a buffer layer between the substrate and the N-type DBR reflective layer;

and the ohmic contact layer is positioned on one side of the P-type DBR reflection layer away from the resonant cavity layer.

10. The preparation method of the VCSEL epitaxial structure is characterized by comprising the following steps of:

providing a substrate;

an N-type DBR reflecting layer, a resonant cavity layer and a P-type DBR reflecting layer are sequentially grown on the substrate by adopting MOCVD equipment through a metal organic chemical vapor deposition method, and the resonant cavity layer comprises an active region;

wherein the P-type DBR reflection layer comprises a first DBR stack structure and a first AlGaAs transition layer, the first DBR stack structure comprises alternately laminated Al _x GaAs layer and Al _y A GaAs layer, the first AlGaAs transition layer is arranged on the Al _x GaAs layer and Al _y Between GaAs layers, where x<y；

The doping concentration of the P-type DBR reflection layer is sequentially increased along the first direction, and the thickness of the first AlGaAs transition layer is reduced along with the increase of the doping concentration of the P-type DBR reflection layer.

11. A VCSEL chip, characterized in that the VCSEL chip comprises a VCSEL epitaxial structure according to any of claims 1-9.

Images