CN111082318B - Epitaxial structure of deep ultraviolet multi-quantum well semiconductor laser and preparation method thereof - Google Patents

Abstract

The invention discloses an epitaxial structure of a deep ultraviolet multiple quantum well semiconductor laser, which comprises: the substrate is a single crystal N-type substrate; the N-type transition layer, the N-type lower limiting layer, the lower waveguide layer, the lower barrier layer, the multi-quantum well layer, the upper barrier layer, the upper waveguide layer, the P-type upper limiting layer and the P-type heavily doped layer are sequentially grown on the upper surface of the substrate; a P surface electrode is prepared on the upper surface of the P type heavily doped layer; and an N-face electrode prepared on the lower surface of the N-type substrate. The structure of the invention ensures that the semiconductor laser can have certain output power, and the semiconductor laser has higher brightness.

Description

Epitaxial structure of deep ultraviolet multi-quantum well semiconductor laser and preparation method thereof

Technical Field

The invention relates to the technical field of semiconductor photoelectron, in particular to epitaxial structure growth of a deep ultraviolet multiple quantum well semiconductor laser and a preparation method thereof.

Background

The deep ultraviolet semiconductor laser structure is suitable for scientific research, industry and OEM system integration development. In the scientific research aspect, the ultraviolet laser can be used for the research of atomic/analytical spectroscopy, chemical kinetics and the like. In the industrial sector, the data storage disks based on magnetic disks produced by uv lasers are 20 times more spacious than blue lasers. In the future, the deep ultraviolet laser technology will promote the development of new-generation nanotechnology, material science, biotechnology, chemical analysis, plasma physics and other disciplines.

Currently, AlN (aluminum nitride) is known as the semiconductor material with the widest energy band (6.2eV) among direct band gaps, which corresponds to the wavelength of 210nm at deep ultraviolet wavelengths. In the active region structure of the semiconductor laser, the wrapping layer outside the quantum well is required to be made of a material with a wider band gap than the quantum well layer to serve as the barrier layer and the waveguide layer, so that AlN serves as the quantum well and no suitable barrier layer and waveguide layer material exists at present. So far, no deep ultraviolet semiconductor laser structure with the wavelength of 210nm appears. And the non-semiconductor deep ultraviolet semiconductor laser has large volume, heavy weight and high cost, and is not beneficial to the progress and development of related applications and products.

Therefore, how to develop an Al-based alloy_xN_yDeep ultraviolet abundance of materialsThe growth of epitaxial structure of sub-well semiconductor laser and its preparation method are the problems that the technicians in this field need to solve urgently.

Disclosure of Invention

In view of the above, the present invention provides an epitaxial structure of a deep ultraviolet multiple quantum well semiconductor laser, including:

a substrate with a doping concentration (1-5) E18cm^-3300-700 μm thick;

the N-type transition layer, the N-type lower limiting layer, the lower waveguide layer, the lower barrier layer, the quantum well layer, the upper barrier layer, the upper waveguide layer, the P-type upper limiting layer and the P-type heavily doped layer are sequentially grown on the upper surface of the substrate;

a P surface electrode is prepared on the upper surface of the P type heavily doped layer;

and an N-face electrode prepared on the lower surface of the N-type substrate.

The invention has the beneficial effects that: the structure in the invention enables the semiconductor laser to have certain output power, so that the semiconductor laser has higher brightness, and the structure in the invention is simple.

Preferably, the thickness of the quantum well layer is 2-10nm, and the material of the quantum well layer is Al_xN_yWherein x/y is 0.95-1.

Preferably, the thickness of the N-type transition layer is 100-500 nm; the N-type transition layer is made of Al_xN_yWherein, x/y is 1-0.45, the value of x/y decreases with the thickness, and the decrease is determined by the thickness.

Preferably, the thickness of the N-type lower limiting layer is 1.2-3 μm, and the material of the N-type lower limiting layer is Al_xN_yWherein x/y is 0.45-0.3; the thickness of the P-type upper limiting layer is 1.2-3 μm, and the material of the P-type upper limiting layer is Al_xN_yWherein x/y is 0.3-0.45.

Preferably, the thickness of the lower waveguide layer is 0.1-0.8 μm, and the material of the lower waveguide layer is Al_xN_yWherein x/y is 0.55-0.7, and the value of x/y increases with the thickness; the thickness of the upper waveguide layer is 0.1-0.8 μmThe material is Al_xN_yWherein, x/y is 0.7-0.55, and the value of x/y decreases with the thickness.

Preferably, the thickness of the lower barrier layer is 10-20nm, and the material of the lower barrier layer is Al_xN_yWherein x/y is 0.8-0.85; the thickness of the upper barrier layer is 10-20nm, and the material of the upper barrier layer is Al_xN_yWherein x/y is 0.85-0.8.

Preferably, the multiple quantum well layer is 2-6 layers, the multiple quantum well layer is composed of barrier layers between a plurality of single quantum wells and quantum hydrazine, the thickness of the single quantum well layer is 2-10nm, and the single quantum well layer is made of Al_xN_yWherein x/y is 0.95-1; the thickness of the barrier layer is 8-15nm, and the material of the barrier layer is Al_xN_yWherein x/y is 0.83-0.88.

The beneficial effects are that: for Al_xN_yThe material structure can realize the characteristic of high temperature resistance by controlling the ratio of x to y and having a wider band gap than an AlN single crystal material.

Preferably, the N-type substrate is a monocrystalline silicon wafer, an aluminum nitride wafer, a silicon carbide wafer, a gallium arsenide wafer or a gallium nitride wafer.

Preferably, the N-surface electrode and the P-surface electrode are both composed of a titanium layer with the thickness of 50nm and a gold layer with the thickness of 300 nm.

The invention also provides a catalyst based on Al_xN_yThe preparation method of the epitaxial structure of the deep ultraviolet multi-quantum well semiconductor laser comprises the following steps:

step (1) carrying out heat treatment on a substrate in an MOCVD deposition system at the temperature of 500-1250 ℃;

sequentially growing an N-type transition layer, an N-type lower limiting layer, a lower waveguide layer, a lower barrier layer, a quantum well layer, an upper barrier layer, an upper waveguide layer, a P-type upper limiting layer and a P-type heavily doped layer on the substrate by controlling the flow of the Al source beam and the ammonia gas;

and (3) arranging an N-surface electrode on the lower surface of the substrate through a photoetching process, and preparing a P-surface electrode on the upper surface of the P-type heavily doped layer.

The preparation method disclosed by the invention is simple and easy to operate, has small realization difficulty and is suitable for large-scale industrial production.

Preferably, in the step (1), the heat treatment time is 5-20 min.

Preferably, in the step (2), the operations of controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAl) and the flow of ammonia gas are as follows: the flow rate of ammonia gas is controlled to be 0-5000sccm, and the beam flow rate of trimethylaluminum (TMAl) or Triethylaluminum (TEAL) is controlled to be (0.2-60) x10^-4mol/min。

Preferably, in the step (2), the specific operations of controlling the flow of trimethylaluminum (TMAl) or triethylaluminum (TEAl) and the flow of ammonia gas are as follows:

growing an N-type transition layer: controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) at (0.2-60) x10^{- 4}The mol/min, the ammonia gas flow is controlled at 800-1500sccm, the silane doping beam flow is controlled at (0.2-60) x10^-7mol/min；

Growing an N-type lower limiting layer: controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) at (0.2-60) x10^{- 4}The mol/min, the ammonia gas flow is controlled at 1500-^-7mol/min；

Growing a lower waveguide layer: controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) at (0.2-60) x10^-4The mol/min, the ammonia gas flow is controlled at 2500-;

growing a lower barrier layer: controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) at (0.2-60) x10^-4mol/min, controlling the flow of ammonia gas at 3500 and 4000 sccm;

and (3) growing a quantum well layer: controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) at (0.2-60) x10^-4The mol/min, the ammonia gas flow is controlled at 4000-;

growing an upper barrier layer: controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) at (0.2-60) x10^-4The mol/min, the ammonia gas flow is controlled at 4000-;

growing an upper waveguide layer: controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) at (0.2-60) x10^-4The mol/min and the ammonia flow are controlled to 3500-sccm；

Growing a P-type upper limiting layer: controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) at (0.2-60) x10^{- 4}The mol/min, the ammonia gas flow is controlled at 2500-₂Mg) doping beam current is controlled to be (0.2-60) x10^-7mol/min；

Growing a P-type heavily doped layer: controlling the flow of trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) at (0.2-60) x10^{- 4}The mol/min, the nitrogen flow is controlled at 1500-₂Mg) doping beam current is controlled to be (0.2-60) x10^-7mol/min。

The beneficial effects are that: the slower the trimethyl aluminum (TMAl) or triethyl aluminum (TEAl) beam is, the higher the quality of film deposition can be realized, but the time is long; the speed of the trimethyl aluminum (TMAl) or triethyl aluminum (TEAL) beam current controlled in the invention can realize high-quality film deposition, and can not cause large time loss.

Preferably, in the step (2),

the growth time of the N-type transition layer is 20-50min, and the growth temperature is 800-1250 ℃;

the growth time of the N-type lower limiting layer is 40-80min, and the growth temperature is 800-1250 ℃;

the growth time of the lower waveguide layer is 4-20min, and the growth temperature is 800-1250 ℃;

the growth time of the lower barrier layer is 1-6min, and the growth temperature is 800-1250 ℃;

the growth time of the quantum well layer is 0.5-2min, and the growth temperature is 800-1250 ℃;

the growth time of the upper barrier layer is 1-6min, and the growth temperature is 800-1250 ℃;

the growth time of the upper waveguide layer is 4-20min, and the growth temperature is 800-1250 ℃;

the growth time of the P-type upper limiting layer is 40-80min, and the growth temperature is 800-1250 ℃;

the growth time of the P-type heavily doped layer is 20-50min, and the growth temperature is 800-1250 ℃.

The beneficial effects are that: the film layer has high growth quality and accurate component control, and the epitaxial structure and the device of the multi-quantum well semiconductor laser with high photoelectric conversion efficiency, high brightness and high beam quality can be obtained.

Drawings

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

FIG. 1 is a schematic structural diagram of an epitaxial structure of a laser provided by the present invention;

FIG. 2 is a graph showing a spectrum in example 1 according to the present invention;

FIG. 3 is a graph showing current-power curves in example 1 according to the present invention;

FIG. 4 is a graph showing a spectrum in example 2 according to the present invention;

FIG. 5 is a graph showing current-power curves in example 2 according to the present invention;

the optical waveguide structure comprises a 1-N surface electrode, a 2-N type substrate, a 3-N type transition layer, a 4-N type lower limiting layer, a 5-lower waveguide layer, a 6-lower barrier layer, a 7-multi-quantum well layer, an 8-upper barrier layer, a 9-upper waveguide layer, a 10-P type upper limiting layer, an 11-P type heavily doped layer and a 12-P surface electrode.

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.

Example 1

Epitaxial structure of deep ultraviolet multiple quantum well semiconductor laser: including a thickness ofImpurity concentration 3E18cm^-3An N-type single crystal substrate 2 having a thickness of 660 μm; an N-type transition layer 3 (thickness of 300nm, Al) sequentially grown on the upper surface of the substrate_xN_yX/y in the material is 1-0.45, the value of x/y decreases with the increase of thickness), N-type lower limiting layer 4 (thickness is 1.6 μm, Al_xN_yX/y of the material is 0.40), and a lower waveguide layer 5 (thickness of 0.15 μm, Al)_xN_yX/y of the material is 0.55-0.7, the x/y value increases with increasing thickness), a lower barrier layer 6 (thickness of 10nm, Al)_xN_yThe material x/y is 0.85), a multiple quantum well layer 7(3 single quantum well layers, 2 barrier layers, a barrier layer is clamped between every two single quantum well layers, the thickness of the single quantum well layer is 6.5nm, the x/y is 0.1, the thickness of the barrier layer is 8nm, the x/y is 0.85), an upper barrier layer 8 (the thickness is 10nm, and Al is 0.85), and the like_xN_yX/y of the material is 0.85), and an upper waveguide layer 9 (thickness of 0.15 μm, Al)_xN_yX/y in the material is 0.70-0.55, the value of x/y decreases with increasing thickness), and a P-type upper limiting layer 10 (thickness of 1.6 μm, Al)_xN_yX/y of the material is 0.45) and a heavily P-doped layer 11 (thickness 350nm, Al)_xN_yX/y in the material is 0.45-1, and the value of x/y increases with the thickness);

preparing a P-surface electrode 12 on the upper surface of the P-type heavily doped layer 11;

and preparing an N-face electrode 1 on the lower surface of the N-type substrate 2.

Based on Al_xN_yThe epitaxial structure growth of the deep ultraviolet multiple quantum well semiconductor laser of the material and the preparation method thereof are as follows:

(1) carrying out heat treatment on the substrate for 5min at 1100 ℃;

(2) sequentially growing an N-type transition layer 3, an N-type lower limiting layer 4, a lower waveguide layer 5, a lower barrier layer 6, a multi-quantum well layer 7, an upper barrier layer 8, an upper waveguide layer 9, a P-type upper limiting layer 10 and a P-type heavily doped layer 11 on a substrate by controlling the flow of trimethylaluminum (TMAl) beam and ammonia gas by adopting an MOCVD method;

wherein, growing the N-type transition layer 3: trimethylaluminum (TMAl) beam control 3x10^-4The mol/min, the ammonia gas flow is controlled at 800-The doping beam current is controlled to be 3x10^-7mol/min, growth time of 12min and growth temperature of 1050 ℃;

and growing an N-type lower limiting layer 4: controlling the current of trimethylaluminum (TMAl) at 3x10^-4mol/min, ammonia gas flow is controlled to be 2000sccm, and silane doping beam current is controlled to be 3x10^-7mol/min, growth time of 40min and growth temperature of 1050 ℃;

growing the lower waveguide layer 5: controlling the current of trimethylaluminum (TMAl) at 3x10^-4Controlling the flow rate of ammonia gas at 2700sccm, the growth time at 1050 ℃ and the growth temperature at 6 min;

growing the lower barrier layer 6: controlling the current of trimethylaluminum (TMAl) at 3x10^-4Controlling the flow rate of ammonia gas at 3300sccm, the growth time at 1050 ℃ and the growth temperature at 2 min;

growing the multiple quantum well layer 7: single quantum well layer, trimethylaluminum (TMAl) beam controlled at 3x10^-4And controlling the flow rate of ammonia gas at 4000sccm, the growth time at 65s and the growth temperature at 1050 ℃ in mol/min. Barrier layer, trimethyl aluminum (TMAl) beam current controlled at 3x10^-4Controlling the flow of ammonia gas at 3300sccm, the growth time at 70s and the growth temperature at 1050 ℃ in mol/min;

growing the upper barrier layer 8: controlling the current of trimethylaluminum (TMAl) at 3x10^-4Controlling the flow rate of ammonia gas at 3300sccm, the growth time at 1050 ℃ and the growth temperature at 2 min;

growing the upper waveguide layer 9: controlling the current of trimethylaluminum (TMAl) at 3x10^-4Controlling the flow rate of ammonia gas at 2700sccm, the growth time at 1050 ℃ and the growth temperature at 6 min;

growing the P-type upper confinement layer 10: controlling the current of trimethylaluminum (TMAl) at 3x10^-4mol/min, controlling ammonia gas flow at 2500sccm, controlling magnesium metallocene doping beam flow at 3x10^-7mol/min, growth time of 40min and growth temperature of 1050 ℃;

growing the P-type heavily doped layer 11: controlling the current of trimethylaluminum (TMAl) at 3x10^-4The mol/min, the ammonia gas flow is controlled at 1500-^-7mol/min, growth time 20min, growth temperature 1050 ℃.

(3) An N-face electrode 1 is prepared on the lower surface of the substrate through a photoetching process, and a P-face electrode 12 is prepared on the upper surface of the P-type heavily doped layer 11. The performance of a deep ultraviolet semiconductor laser having the above epitaxial structure and a wavelength of 210nm was measured.

It can be seen from fig. 2 that the highest luminance and a narrower lasing spectrum are exhibited in the vicinity of the wavelength of 210 nm.

It can be seen from fig. 3 that the low-threshold current working state of about 60mA is realized under the conditions of the above structure and process preparation method, and normal lasing and working of the deep ultraviolet semiconductor laser device are realized.

Example 2

Epitaxial structure of deep ultraviolet multiple quantum well semiconductor laser: including a thickness of doping concentration 3E18cm^-3An N-type single crystal Si substrate 2 having a thickness of 640 μm; an N-type transition layer 3 (with a thickness of 500nm and Al) sequentially grown on the upper surface of the substrate_xN_yX/y in the material is 1-0.40, the value of x/y is gradually reduced along with the thickness, and an N-type lower limiting layer 4 (the thickness is 2 mu m, Al)_xN_yX/y of the material is 0.40), and a lower waveguide layer 5 (thickness of 0.25 μm, Al)_xN_yX/y of the material is 0.55-0.68, and the value of x/y increases with thickness), and a lower barrier layer 6 (thickness of 10nm, Al)_xN_yX/y of the material is 0.83), a multiple quantum well layer 7(3 quantum well layers, thickness is 7nm, x/y is 0.95, barrier layers are sandwiched between adjacent quantum well layers, thickness is 8nm, x/y is 0.85), and an upper barrier layer 8 (thickness is 10nm, Al is 0nm, Al is_xN_yX/y of the material is 0.83), and an upper waveguide layer 9 (thickness of 0.25 μm, Al)_xN_yX/y in the material is 0.68-0.55, the value of x/y is uniformly decreased along with the thickness), and a P-type upper limiting layer 10 (the thickness is 2 mu m, Al_xN_yX/y of material 0.55) and heavily P-doped layer 11 (thickness 400nm, Al)_xN_yX/y in the material is 0.55-1, and the value of x/y increases with the thickness);

preparing a P-surface electrode 12 on the upper surface of the P-type heavily doped layer 11;

and preparing an N-face electrode 1 on the lower surface of the N-type substrate 2.

The preparation method of the epitaxial structure of the deep ultraviolet semiconductor laser comprises the following steps:

(1) carrying out heat treatment on the substrate for 5min at 1150 ℃;

(2) sequentially growing an N-type transition layer 3, an N-type lower limiting layer 4, a lower waveguide layer 5, a lower barrier layer 6, a multi-quantum well layer 7, an upper barrier layer 8, an upper waveguide layer 9, a P-type upper limiting layer 10 and a P-type heavily doped layer 11 on a substrate by controlling the flow of triethyl aluminum (TEAL) beams and ammonia gas by adopting an MOCVD method;

wherein, growing the N-type transition layer 3: the triethyl aluminum (TEAL) flow is controlled at 2x10^-4The mol/min, the ammonia gas flow is controlled at 800-1500sccm, the ammonia gas flow is increased with time, and the silane atom doping beam current is controlled at 2x10^-7mol/min, growth time of 25min and growth temperature of 1150 ℃;

and growing an N-type lower limiting layer 4: the triethyl aluminum (TEAL) flow is controlled at 2x10^-4mol/min, ammonia gas flow is controlled to be 2000sccm, and silane atom doping beam flow is controlled to be 2x10^-7mol/min, growth time of 60min, growth temperature of 1150 ℃;

growing the lower waveguide layer 5: the triethyl aluminum (TEAL) flow is controlled at 2x10^-4Controlling the flow rate of ammonia gas at 2700sccm, the growth time at 12min and the growth temperature at 1150 ℃;

growing the lower barrier layer 6: the triethyl aluminum (TEAL) flow is controlled at 2x10^-4Controlling the flow rate of ammonia gas at 3300sccm, the growth time at 2min and the growth temperature at 1150 ℃;

growing the multiple quantum well layer 7: single quantum well layer, triethyl aluminum (TEAL) beam controlled at 2x10^-4mol/min, controlling the flow of ammonia gas at 3800sccm, the growth time at 80s and the growth temperature at 1150 ℃. Barrier layer, triethyl aluminum (TEAL) beam current controlled at 2x10^-4Controlling the flow of ammonia gas at 3300sccm, the growth time at 80s, the growth temperature at 1150 ℃ and alternately growing the quantum well layer and the barrier layer at mol/min;

growing the upper barrier layer 8: the triethyl aluminum (TEAL) flow is controlled at 2x10^-4Controlling the flow rate of ammonia gas at 3300sccm, the growth time at 2min and the growth temperature at 1150 ℃;

growing the upper waveguide layer 9: the triethyl aluminum (TEAL) flow is controlled at 2x10^-4Controlling the flow rate of ammonia gas at 2700sccm, the growth time at 12min and the growth temperature at 1150 ℃;

growing the P-type upper confinement layer 10: the triethyl aluminum (TEAL) flow is controlled at 2x10^-4mol/min, ammonia gas flow is controlled to be 2000sccm, and the magnesium metallocene doping beam flow is controlled to be 2x10^-7mol/min, growth time of 50min, growth temperature of 1150 ℃;

growing the P-type heavily doped layer 11: the triethyl aluminum (TEAL) flow is controlled at 2x10^-4The mol/min, the ammonia gas flow is controlled at 1500-^-7mol/min, growth time of 30min and growth temperature of 1150 ℃.

(3) An N-face electrode 1 is prepared on the lower surface of the substrate through a photoetching process, and a P-face electrode 12 is prepared on the upper surface of the P-type heavily doped layer 11. The performance of a deep ultraviolet semiconductor laser having the above epitaxial structure and a wavelength of 210nm was measured.

It can be seen from fig. 4 that the waveguide layer is broadened, exhibiting maximum brightness at wavelengths around 214-215.5nm, with significant spectral redshifts and broadening.

As can be seen from fig. 5, the waveguide layer is widened, the threshold current working state of about 280mA is realized under the conditions of the structure and the process preparation method, and the normal lasing and working of the deep ultraviolet semiconductor laser device in a wider spectral range are realized.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and 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 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 (2)

1. An epitaxial structure of a deep ultraviolet multiple quantum well semiconductor laser, comprising:

the substrate is an N-type substrate;

the N-type transition layer, the N-type lower limiting layer, the lower waveguide layer, the lower barrier layer, the multi-quantum well layer, the upper barrier layer, the upper waveguide layer, the P-type upper limiting layer and the P-type heavily doped layer are sequentially grown on the upper surface of the substrate;

a P-surface electrode arranged on the upper surface of the P-type heavily doped layer;

and an N-face electrode arranged on the lower surface of the substrate;

the thickness of the N-type transition layer is 300-500 nm; the material is Al_xN_yWherein x/y is 1-0.40;

the thickness of the N-type lower limiting layer is 1.2-3 mu m; the material is Al_xN_yWherein x/y is 0.40-0.30; the thickness of the P-type upper limiting layer is 1.2-2 μm, and the material of the P-type upper limiting layer is Al_xN_yWherein x/y is 0.30-0.40;

the thickness of the lower waveguide layer is 0.1-0.8 μm; the material is Al_xN_yWherein x/y is 0.55-0.7; the thickness of the upper waveguide layer is 0.1-0.8 μm; the material is Al_xN_yWherein x/y is 0.7-0.55;

the thickness of the lower barrier layer is 10-20 nm; the material is Al_xN_yWherein x/y is 0.8-0.85; the thickness of the upper barrier layer is 10-20 nm; the material is Al_xN_yWherein x/y is 0.85-0.8;

the multiple quantum well layer is 2-6 layers and is composed of a plurality of single quantum wells and barrier layers among the quantum wells, and the thickness of the single quantum well layer is 2-10 nm; the material is Al_xN_yWherein x/y is 0.95-1; the thickness of the barrier layer is 8-15 nm; the material is Al_xN_yWherein x/y is 0.83-0.88.

2. Based on Al_xN_yThe preparation method of the epitaxial structure of the deep ultraviolet multi-quantum well semiconductor laser is characterized by comprising the following steps of:

(1) carrying out heat treatment on the substrate for 5-20min at the temperature of 1000-1250 ℃;

(2) sequentially growing an N-type transition layer, an N-type lower limiting layer, a lower waveguide layer, a lower barrier layer, a multi-quantum well layer, an upper barrier layer, an upper waveguide layer, a P-type upper limiting layer and a P-type heavily doped layer on a substrate by controlling Al source beam current and ammonia gas flow;

(3) arranging an N-surface electrode on the lower surface of the substrate through a photoetching process, and arranging a P-surface electrode on the upper surface of the P-type heavily doped layer;

in the step (2), the Al source is trimethyl aluminum or triethyl aluminum; the N-type dopant adopted in the growth N-type transition layer and the N-type lower limiting layer is silane; the P-type dopant adopted in the growth P-type upper limiting layer and the P-type heavily doped layer is magnesium cyclopentadienyl; the ammonia flow rate was operated as follows: the ammonia gas flow is controlled to be 0-10000sccm, and the beam current control rate of the Al source is controlled to be (0.2-60) x10^-4mol/min；

In the step (2), the specific operations of controlling the flow of the Al source beam and the flow of the ammonia gas are as follows:

growing an N-type transition layer: the Al source beam current is controlled to be (0.2-60) x10^-4The mol/min, the ammonia gas flow is controlled at 800-1500sccm, and the N-type dopant flow is controlled at (0.2-60) x10^-7mol/min；

Growing an N-type lower limiting layer: the Al source beam current is controlled to be (0.2-60) x10^-4mol/min, the ammonia gas flow is controlled at 1500-^-7mol/min；

Growing a lower waveguide layer: the Al source beam current is controlled to be (0.2-60) x10^-4The mol/min, the ammonia gas flow is controlled at 2500-;

growing a lower barrier layer: the Al source beam current is controlled to be (0.2-60) x10^-4mol/min, ammonia flow controlPrepared at 3500 and 4000 sccm;

and (3) growing a quantum well layer: the Al source beam current is controlled to be (0.2-60) x10^-4The mol/min, the ammonia gas flow is controlled at 4000-;

growing an upper barrier layer: the beam current of the Al source is controlled to be (0.2-60) x10^-4The mol/min, the ammonia gas flow is controlled at 4000-;

growing an upper waveguide layer: the beam current of the Al source is controlled to be (0.2-60) x10^-4The mol/min, the ammonia gas flow is controlled to 3500 and 2500 sccm;

growing a P-type upper limiting layer: the Al source beam current is controlled to be (0.2-60) x10^-4The mol/min, the ammonia gas flow rate is controlled at 2500-^-7mol/min；

Growing a P-type heavily doped layer: the Al source beam current is controlled to be (0.2-60) x10^-4The mol/min, the ammonia gas flow is controlled at 1500-^-7mol/min；

In the step (2),

the growth time of the N-type transition layer is 20-50min, and the growth temperature is 800-1250 ℃;

the growth time of the N-type lower limiting layer is 40-80min, and the growth temperature is 800-1250 ℃;

the growth time of the lower waveguide layer is 20-50min, and the growth temperature is 800-1250 ℃;

the growth time of the lower barrier layer is 1-6min, and the growth temperature is 800-1250 ℃;

the growth time of the quantum well layer is 0.5-2min, and the growth temperature is 800-1250 ℃;

the growth time of the upper barrier layer is 1-6min, and the growth temperature is 800-1250 ℃;

the growth time of the upper waveguide layer is 20-50min, and the growth temperature is 800-1250 ℃;

the growth time of the P-type upper limiting layer is 40-60min, and the growth temperature is 800-1250 ℃;

the growth time of the P-type heavily doped layer is 20-50min, and the growth temperature is 800-1250 ℃.

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