CN118888658B

CN118888658B - LED epitaxial wafer, epitaxial growth method and LED chip

Info

Publication number: CN118888658B
Application number: CN202411356495.1A
Authority: CN
Inventors: 唐慧慧; 霍丽艳; 崔晓慧; 袁健
Original assignee: Jiangxi Qianzhao Photoelectric Co ltd
Current assignee: Jiangxi Qianzhao Photoelectric Co ltd
Priority date: 2024-09-27
Filing date: 2024-09-27
Publication date: 2024-12-20
Anticipated expiration: 2044-09-27
Also published as: CN118888658A

Abstract

The present invention provides an LED epitaxial wafer, an epitaxial growth method and an LED chip. A substrate and an N-type layer, a multi-quantum well layer and a P-type layer are sequentially deposited on the substrate. The N-type layer is a periodic superlattice structure in which an LT-AlN layer, a PALE-AlN layer, a GaN quantum dot and an n-Al _x Ga _(1- x) N layer are sequentially deposited. Since a plurality of GaN quantum dots are distributed at the interface between the PALE-AlN layer and the n-Al _x Ga _(1-x) N layer, electrons required for radiation recombination can be provided. The introduction of quantum dots can effectively bind electrons and decelerate the electrons injected into the active region of the multi-quantum well layer without affecting hole injection, thereby improving the carrier injection efficiency of the device.

Description

LED epitaxial wafer, epitaxial growth method and LED chip

Technical Field

The invention relates to the technical field of LEDs, in particular to an LED epitaxial wafer, an epitaxial growth method and an LED chip.

Background

Nitride is a novel semiconductor material for developing microelectronic devices and optoelectronic devices, and research and application of nitride are hot spots of global semiconductor research at present. The material has the characteristics of wide direct band gap, strong atomic bond, high heat conductivity, good chemical stability (hardly corroded by any acid), and the like, and strong irradiation resistance, and has wide prospect in the application fields of photoelectrons, high-temperature high-power devices and high-frequency microwave devices.

But in the development of both InGaN and AlGaN optoelectronic devices, the problem of high density defects due to the lack of a homogenous substrate is encountered. In addition, experiments show that in nitride materials, the effective masses of electrons and holes are greatly different, so that electrons are extremely easy to overflow from an active region, and holes are difficult to inject, so that the recombination process of electrons and holes often occurs at a P-GaN position rather than in the active region.

AlGaN materials are widely used as Electron Barrier Layers (EBLs) in GaN Light Emitting Diodes (LEDs) and other devices due to their forbidden bandwidths (3.4 eV to 6.2 eV) compared with GaN materials. However, the presence of the EBL also has a certain resistance to hole injection, and the EBL requires an AlGaN material having a high Al composition.

Disclosure of Invention

Based on the above, the invention aims to provide an LED epitaxial wafer, an epitaxial growth method and an LED chip, which aim to reduce the speed of electrons injected into an active region of a multiple quantum well layer without affecting hole injection, so that the carrier injection efficiency of a device is improved.

According to the embodiment of the invention, the LED epitaxial wafer comprises a substrate, and an N-type layer, a multiple quantum well layer and a P-type layer which are sequentially deposited on the substrate, wherein the N-type layer is a periodic superlattice structure formed by sequentially depositing an LT-AlN layer, a PALE-AlN layer, a GaN quantum dot and an N-Al _xGa_（1-x） N layer, and x is more than or equal to 0 and less than or equal to 1;

In the process of depositing the GaN quantum dots, firstly, only introducing a Ga source to form Ga liquid drops on the PALE-AlN layer;

immediately introducing an N source after Ga drops are formed;

and heating and annealing in an N source environment to form the GaN quantum dots.

Further, in the step of forming Ga droplets on the PALE-AlN layer by only introducing the Ga source, the growth time is 5-18 s, and the growth temperature is 500-650 ℃.

Further, in the step of immediately introducing the N source after the Ga drops are formed, NH ₃ is immediately introduced, the introduction time is 8-30 s, and the growth temperature is lower than that when the Ga drops are formed.

Further, in the step of heating and annealing in the N source environment to form the GaN quantum dots, heating to 850-1200 ℃ and annealing in the NH ₃ environment, wherein the annealing time is 10-60 s.

Further, the thickness of the LT-AlN layer is 5 nm-30 nm, and the growth temperature is 300-800 ℃.

Further, the thickness of the PALE-AlN layer is 30-500 nm, and the growth temperature is 900-1200 ℃.

Further, the number of cycles of the PALE-AlN layers is 6-50, one PALE cycle is 8-25 s, TMAL is directly introduced into the reaction cavity, NH ₃ is introduced in a pulse mode, and the NH ₃ introduction time is smaller than the closing time.

Further, the thickness of the N-Al _xGa_（1-x） N layer is 10 nm-100 nm, the doping element is Si, and the electron concentration formed by doping is 1X 10 ¹⁷cm^-3～1×10²⁰cm^-3.

According to an embodiment of the invention, an epitaxial growth method of an LED epitaxial wafer is used for preparing the LED epitaxial wafer, and comprises the following steps:

The growth substrate, and an N-type layer, a multiple quantum well layer and a P-type layer which are sequentially deposited on the substrate, wherein the N-type layer is a superlattice structure formed by sequentially depositing an LT-AlN layer, a PALE-AlN layer, a GaN quantum dot and an N-Al _xGa_（1-x） N layer, and x is more than or equal to 0 and less than 1;

immediately introducing an N source after Ga drops are formed;

According to the embodiment of the invention, the LED chip comprises the LED epitaxial wafer.

Compared with the prior art, the LED epitaxial wafer has the advantages that tensile stress can be released through the LT-AlN layer and the PALE-AlN layer instead of the traditional buffer layer, cracking of an epitaxial film can be prevented, meanwhile, lattice difference between the whole N-type layer and a substrate can be reduced, crystal defect density is further reduced, crystal quality of an epitaxial material is improved, non-radiative composite efficiency is reduced, in addition, the PALE method can effectively inhibit gas phase pre-reaction, enhance migration capacity of Al atoms on the surface and provide a template for growth of subsequent GaN quantum dots, finally, electron deceleration can be achieved due to the fact that the dimension of the GaN quantum dots in all directions is close to the Bohr radius of electrons, and movement of electrons is limited in the quantum dots in three dimensions, so that state density distribution of electrons shows delta function distribution. The state density distribution is no longer continuous, electrons can only be transited and radiated at a limited energy level, and then non-radiative recombination of carriers is weakened, so that high internal quantum efficiency is brought.

Drawings

Fig. 1 is a schematic structural diagram of an N-type layer of an LED epitaxial wafer according to an embodiment of the present invention;

fig. 2 is a flowchart of an implementation of an epitaxial growth method of an LED epitaxial wafer according to an embodiment of the present invention.

Detailed Description

In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Several embodiments of the invention are presented in the figures. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "mounted" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1, a schematic structure diagram of an N-type layer of an LED epitaxial wafer according to an embodiment of the present invention is shown, the LED epitaxial wafer includes a substrate, and an N-type layer 1, a multiple quantum well layer and a P-type layer sequentially deposited on the substrate, wherein the N-type layer is a superlattice structure formed by sequentially depositing an LT-AlN layer 11, a PALE-AlN layer 12, a GaN quantum dot 13 and an N-Al _xGa_（1-x） N layer 14, and the N-type layer has an electron deceleration effect.

The LT-AlN layer 11 is a low-temperature grown AlN layer, specifically, the thickness of the LT-AlN layer 11 is 5nm to 30nm, and exemplary thicknesses of the LT-AlN layer 11 are 5nm, 10nm, 15nm, 20nm, 25nm, or 30nm, but not limited thereto, and it should be noted that "5nm to 30nm" means values between 5nm and 30nm and end points of 5nm and 30nm, and the meaning expressed by the symbol appearing later is consistent, and is not repeated, and the growth temperature of the LT-AlN layer 11 is 300 ℃ to 800 ℃.

In an embodiment of the present invention, the PALE-AlN layer 12 has a thickness of 30nm to 500nm, and the thickness of the PALE-AlN layer 12 is exemplified by, but not limited to, 30nm, 100nm, 200nm, 300nm, 400nm, 500nm, etc., and the growth temperature is 900 ℃ to 1200 ℃, and it should be noted that the PALE-AlN layer 12 is an AlN layer prepared by PALE (Pulsed Atomic Layer Epitaxy, pulse atomic layer epitaxy) process. More specifically, PALE-AlN layers 12 have 6-50 cycles, one PALE cycle is 8-25 s, TMAL is directly introduced into the reaction chamber, NH ₃ is introduced in a pulse form, and the NH ₃ introduction time is smaller than the closing time.

Further, in the process of depositing the GaN quantum dots 13, ga liquid drops are formed on the PALE-AlN layer 12, wherein the growth time is 5-18 s, the growth temperature is 500-650 ℃, and NH ₃ is not introduced;

On the basis of Ga liquid drops, NH ₃ is immediately introduced, the introduction time is 8-30 s, and the growth temperature is lower than that when Ga liquid drops are formed;

and in an NH ₃ environment, heating to 850-1200 ℃ and annealing for 10-60 s. It is understood that GaN quantum dots 13 are distributed at the interface of PALE-AlN layer 12 and N-Al _xGa_（1-x） N layer 14.

In an embodiment of the present invention, the thickness of the N-Al _xGa_（1-x） N layer 14 is 10nm to 100nm, and the thickness of the N-Al _xGa_（1-x） N layer 14 is 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, etc., but not limited thereto, the doping element is Si, and the concentration of electrons formed by doping is 1×10 ¹⁷cm^-3～1×10²⁰cm^-3.

In one embodiment of the present invention, 0.ltoreq.x <1 in the N-Al _xGa_（1-x） N layer 14, the LT-AlN layer 11, PALE-AlN layer 12, gaN quantum dot 13 and N-Al _xGa_（1-x） N layer 14 are sequentially deposited in a period of 4 to 15, and the period is, for example, 4, 5,6, 7, 8, 9, 10, 11, 12, 13 or 14.

Correspondingly, the embodiment of the invention also provides an epitaxial growth method of the LED epitaxial wafer, which is used for preparing the LED epitaxial wafer, and referring to fig. 2, the implementation flow chart of the epitaxial growth method of the LED epitaxial wafer provided by the embodiment of the invention specifically comprises the following steps:

s1, providing a substrate and cleaning.

Wherein, the substrate can be one of a PSS plated AlN substrate, a sapphire substrate or a SIC substrate. Specifically, the substrate is heated to 1100 ℃, subjected to hydrogenation treatment for 5min, and surface impurities and the like are removed.

S2, growing an N-type layer on the substrate.

Specifically, firstly, introducing TMAL, and growing an LT-AlN layer, wherein the thickness of the LT-AlN layer is 5-30 nm, and the growth temperature is 300-800 ℃;

Then TMAL and NH ₃ are introduced, a PALE-AlN layer grows, the thickness of the PALE-AlN layer is 30-500 nm, the growth temperature is 900-1200 ℃, the period number of the PALE-AlN layer is 6-50, one PALE period is 8-25 s, TMAL is directly introduced into the reaction cavity, NH ₃ is introduced in a pulse mode, and the introduction time of NH ₃ is smaller than the closing time;

Further, ga liquid drops are formed on the PALE-AlN layer, wherein the growth time is 5-18 s, the growth temperature is 500-650 ℃, and NH ₃ is not introduced;

Heating to 850-1200 ℃ and annealing in an NH ₃ environment for 10-60 s to obtain GaN quantum dots;

And finally, TMAl, TEGa, siH ₄ is introduced to grow an N-Al _xGa_（1-x） N layer, the thickness of the N-Al _xGa_（1-x） N layer is 10 nm-100 nm, the doping element is Si, and the electron concentration formed by doping is 1X 10 ¹⁷cm^-3～1×10²⁰cm^-3.

And S3, growing a multi-quantum well layer on one side of the N-type layer, which is away from the substrate.

Specifically, the total thickness of the multi-quantum well layer grown by passing TEGa, TMIn, siH ₄ is 140nm, wherein the growth temperature of the quantum well layer is 780 ℃, and the growth temperature of the quantum barrier layer is 890 ℃.

And S4, growing a P-type layer on one side of the multi-quantum well layer, which is away from the substrate.

Specifically, a P-type GaN layer is grown by introducing TEGa and CP ₂ Mg, the thickness is 0.4 mu m, the growth temperature is 965 ℃, and the concentration of Mg is 2E19/cm ³.

It should be noted that, the above steps are all performed in MOCVD equipment, and the MO source used is trimethylgallium TEGa, triethylgallium TEGa, trimethyltmin, magnesium-bis-cyclopentadienyl (Cp ₂ Mg), trimethylaluminum (TMAl), TEGa and TEGa as Ga sources, the gaseous source is silane (SiH ₄), ammonia (NH ₃）、H₂、N₂), NH ₃ is N source, H ₂、N₂ is carrier gas, and the N-type and P-type doping sources are silane SiH ₄ and magnesium-bis-cyclopentadienyl Cp ₂ Mg, respectively.

In summary, the invention provides an LED epitaxial wafer, an epitaxial growth method and an LED chip, wherein a substrate, an N-type layer, a multiple quantum well layer and a P-type layer are arranged on the substrate, the N-type layer is a periodic superlattice structure formed by sequentially depositing an LT-AlN layer, a PALE-AlN layer, a GaN quantum dot and an N-Al _xGa_（1-x） N layer, and as a plurality of GaN quantum dots are distributed at the interface of the PALE-AlN layer and the N-Al _xGa_（1-x） N layer, electrons required by radiation recombination can be provided, electrons can be effectively bound by introducing the quantum dots, electrons injected into an active region of the multiple quantum well layer can be decelerated, and hole injection is not influenced, so that the carrier injection efficiency of the device is improved.

The invention is further illustrated by the following examples:

Example 1

The epitaxial growth method of the LED epitaxial wafer in the embodiment 1 comprises the following steps:

(1) A substrate is provided and cleaned.

Wherein the substrate is a PSS AlN plating substrate, specifically, the substrate is heated to 1100 ℃, and hydrogenation treatment is carried out for 5min to remove surface impurities and the like.

(2) And growing an N-type layer on the PSS plating AlN substrate.

Specifically, TMAL is firstly introduced, an LT-AlN layer is grown, the thickness of the LT-AlN layer is 10nm, and the growth temperature is 500 ℃;

Introducing TMAL and NH ₃, growing PALE-AlN layers, wherein the period of PALE is 10, the period time is 10s, the introducing time of NH ₃ is 4s, and the growth temperature is 1000 ℃;

Introducing TEGa, wherein the flow is 12 mu mol/min, not introducing NH ₃, growing Ga drops on the PALE-AlN layer, the growth time is 12s, the growth temperature is 580 ℃, and the growth pressure is 40Torr;

And (3) introducing TEGa with the flow of 12 mu mol/min, immediately introducing 1800sccm of NH ₃ on the basis of the Ga liquid drops, and rapidly cooling to 450 ℃ for 10 seconds to grow GaN quantum dots.

Reducing the flow of TEGa to 8 mu mol/min, keeping other growth parameters unchanged, heating to 900 ℃ and annealing in an NH ₃ environment of 1800sccm, wherein the annealing time is 15s;

And finally, introducing TMAl, TEGa, siH ₄ to grow an N-Al _xGa_（1-x） N layer, wherein the thickness of the N-Al _xGa_（1-x） N layer is 20nm, the doping element is Si, the electron concentration formed by doping is 2E19/cm ³, the growth temperature is 1085 ℃, and the period of the whole superlattice N-type layer is 5, namely the N-type layer consists of 5 LT-AlN layers, PALE-AlN layers, gaN quantum dots and N-Al _xGa_（1-x） N layers which are deposited in sequence.

(3) And growing a multi-quantum well layer on one side of the N-type layer, which is away from the substrate.

(4) And growing a P-type layer on one side of the multi-quantum well layer, which is away from the substrate.

Example 2

The same method for epitaxial growth of LED epitaxial wafer as in example 2 is different from example 1 in that (2) an N-type layer is grown on a PSS AlN-plated substrate, specifically TMAl and NH ₃ are introduced, PALE-AlN layers are grown, the PALE period is 30, the period time is 10s, the NH ₃ introduction time is 4s, and the temperature is 1000 ℃.

Example 3

The same method as in example 3 provides an epitaxial growth method for an LED epitaxial wafer, which is different from example 1 in that (2) an N-type layer is grown on a PSS AlN-plated substrate, specifically, TMAl and NH ₃ are introduced, a PALE-AlN layer is grown, the number of PALE cycles is 50, the cycle time is 10s, the NH ₃ introduction time is 4s, and the temperature is 1000 ℃.

Example 4

The same example 4 provides an epitaxial growth method of an LED epitaxial wafer, which is different from the example 1 in that (2) an N-type layer is grown on a PSS AlN-plated substrate, specifically, TEGa is introduced, the flow rate is 20 μmol/min, NH ₃ is not introduced, ga droplets are grown on a PALE-AlN layer, the growth time is 12s, the growth temperature is 580 ℃, and the growth pressure is 40Torr;

And (3) introducing TEGa with the flow of 20 mu mol/min, immediately introducing 1800sccm of NH ₃ on the basis of the Ga liquid drops, and rapidly cooling to 450 ℃ for 10 seconds to grow GaN quantum dots.

Example 5

In the same manner as in example 5, the difference from example 1 is that (2) an N-type layer is grown on a PSS-plated AlN substrate, specifically, TEGa is introduced at a flow rate of 12 μmol/min, NH ₃ is not introduced, ga droplets are grown on a PALE-AlN layer for 12s at a growth temperature of 650 ℃ and a growth pressure of 40Torr.

Example 6

The same method as in example 6 provides an epitaxial growth method of an LED epitaxial wafer, which is different from example 1 in that (2) an N-type layer is grown on a PSS AlN-plated substrate, specifically, TEGa is introduced at a flow rate of 12 μmol/min, 1800sccm of NH ₃ is immediately introduced on the basis of the above Ga droplet, the growth time is 10s, and then the temperature is rapidly reduced to 400 ℃ to grow GaN quantum dots.

Example 7

The same method as in example 7 provides an epitaxial growth method for an LED epitaxial wafer, which is different from example 1 in that (2) an N-type layer is grown on a PSS-plated AlN substrate, specifically, the TEGa flow rate is reduced to 12 μmol/min, other growth parameters are kept unchanged, and on this basis, the temperature is raised to 900 ℃ and annealed in an NH ₃ environment of 1800 seem, and the annealing time is 15s.

Example 8

The same method for epitaxial growth of LED epitaxial wafer as provided in this embodiment 8 is different from embodiment 1 in that (2) an N-type layer is grown on the PSS AlN-plated substrate, specifically, the period of the entire superlattice N-type layer is 15, that is, the N-type layer is composed of 15 LT-AlN layers, PALE-AlN layers, gaN quantum dots, and N-Al _xGa_（1-x） N layers deposited in sequence.

Comparative example 1

Comparative example 1 provides a conventional epitaxial growth method of an LED epitaxial wafer, specifically as follows:

(1) Providing a PSS AlN plating substrate, heating to 1100 ℃, carrying out hydrogenation treatment for 5min, removing surface impurities and the like, and playing a role in cleaning the substrate.

(2) And introducing TEGa, and growing a buffer layer with the thickness of 2nm and the growth temperature of 850 ℃.

(3) And introducing TEGa, and growing a U-shaped GaN layer with the thickness of 2300nm and the growth temperature of 1125 ℃.

(4) And introducing TEGa and SiH ₄ to grow an N-type GaN layer, wherein the thickness is 2000nm, the growth temperature is 1085 ℃, and the concentration of SiH ₄ is 2E19/cm ³.

(5) And introducing TEGa, TMIn, siH ₄ to grow the multi-quantum well layer, wherein the total thickness of the multi-quantum well layer is 140nm, the growth temperature of the quantum well layer is 780 ℃, and the growth temperature of the quantum barrier layer is 890 ℃.

(6) And introducing TEGa and CP ₂ Mg to grow a P-type GaN layer, wherein the thickness is 0.4 mu m, the growth temperature is 965 ℃, and the concentration of Mg is 2E19/cm ³.

The LED chips finally prepared in examples 1 to 8 were subjected to light efficiency test under the same conditions as those of the LED chip in comparative example 1, and the results are shown in the following table:

As can be seen from the table, the light-emitting efficiency of the LED chip prepared in the embodiment of the present invention is improved to a different extent compared with that of the comparative example 1, wherein the light-emitting efficiency of the LED chip prepared in the embodiment 1 is optimal, and the light-emitting efficiency is improved by 0.88% compared with that of the comparative example 1.

It can be appreciated that after the N-type layer with the electron deceleration effect is added, a periodic superlattice structure formed by sequentially depositing an LT-AlN layer, a PALE-AlN layer, a GaN quantum dot and an N-Al _xGa_（1-x） N layer is adopted as an N-type electron injection layer, and meanwhile, the GaN quantum dot is inserted into the interface between AlN and AlGaN superlattices, so that a multicycle superlattice interface quantum dot structure is formed, and the structure of a typical N-type electron injection layer (N-GaN) in the prior art is mainly changed. The GaN quantum dot material has the advantages that lattice mismatch between a substrate and a multi-quantum well layer can be reduced by LT-AlN and PALE-AlN, dislocation density of an AlGaN material is reduced, migration capability of Al atoms on the surface of the substrate can be enhanced by a PALE method, possibility of pre-reaction is reduced, crystal quality of an epitaxial layer is improved, electrons required by radiation recombination can be improved for the multi-quantum well layer by growing n-AlGaN, buried quantum dots can be covered, protection effect is achieved on the quantum dots, and in a GaN quantum dot material (also called zero-dimensional material), size in three dimensions is equal to Debroil wavelength of the electrons and even smaller, therefore electron movement is restrained in the three dimensions, obvious deceleration effect can be achieved on the electrons, injection efficiency of holes can not be hindered, and accordingly carrier recombination efficiency is improved.

The embodiment of the invention also provides an LED chip, which comprises the LED epitaxial wafer in any embodiment.

The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims

1. An LED epitaxial wafer, characterized in that it comprises a substrate and an N-type layer, a multi-quantum well layer and a P-type layer sequentially deposited on the substrate, wherein the N-type layer is a periodic superlattice structure in which an LT-AlN layer, a PALE-AlN layer, a GaN quantum dot and an n-Al _x Ga _(1-x) N layer are sequentially deposited, and 0≤x＜1;

In the process of depositing the GaN quantum dots, firstly, only a Ga source is introduced to form Ga droplets on the PALE-AlN layer, wherein the growth time is 5s to 18s and the growth temperature is 500° C. to 650° C.;

After the Ga droplets are formed, the N source is introduced immediately, wherein NH ₃ is introduced immediately for a time of 8s to 30s, and the growth temperature is lower than the growth temperature when the Ga droplets are formed;

In an N source environment, the temperature is raised and annealing is performed to form GaN quantum dots. In an NH ₃ environment, the temperature is raised to 850°C~1200°C and annealing is performed, and the annealing time is 10s~60s.

2 . The LED epitaxial wafer according to claim 1 , wherein the thickness of the LT-AlN layer is 5 nm to 30 nm, and the growth temperature is 300° C. to 800° C.

3 . The LED epitaxial wafer according to claim 1 , wherein the thickness of the PALE-AlN layer is 30 nm to 500 nm, and the growth temperature is 900° C. to 1200° C.

4. The LED epitaxial wafer according to claim 3 is characterized in that the number of cycles of the PALE-AlN layer is 6 to 50, one PALE cycle is 8s to 25s, TMAl is continuously introduced into the reaction chamber, and _NH3 is introduced in pulse form, wherein the _NH3 introduction time is shorter than the closing time.

5. The LED epitaxial wafer according to claim 1, characterized in that The thickness is 10nm~100nm, the doping element is Si, and the electron concentration formed by doping is .

6. An epitaxial growth method for an LED epitaxial wafer, characterized in that it is used to prepare the LED epitaxial wafer according to any one of claims 1 to 5, and the epitaxial growth method comprises:

A growth substrate and an N-type layer, a multi-quantum well layer and a P-type layer sequentially deposited on the substrate, wherein the N-type layer is a superlattice structure in which a LT-AlN layer, a PALE-AlN layer, a GaN quantum dot and an n-Al _x Ga _(1-x) N layer are sequentially deposited, 0≤x＜1;

During the deposition of the GaN quantum dots, only a Ga source is introduced to form Ga droplets on the PALE-AlN layer;

After the Ga droplets are formed, the N source is immediately introduced;

In an N source environment, the temperature is increased and annealing is performed to form GaN quantum dots.

7. An LED chip, characterized by comprising the LED epitaxial wafer according to any one of claims 1 to 5.