CN112802929A - Epitaxial wafer of light emitting diode and preparation method thereof - Google Patents

Epitaxial wafer of light emitting diode and preparation method thereof Download PDF

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CN112802929A
CN112802929A CN202110164464.6A CN202110164464A CN112802929A CN 112802929 A CN112802929 A CN 112802929A CN 202110164464 A CN202110164464 A CN 202110164464A CN 112802929 A CN112802929 A CN 112802929A
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layer
algan
growth
epitaxial wafer
type
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丁涛
龚程成
尹涌
梅劲
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HC Semitek Zhejiang Co Ltd
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HC Semitek Zhejiang Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0095—Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0075—Processes for devices with an active region comprising only III-V compounds comprising nitride compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/025—Physical imperfections, e.g. particular concentration or distribution of impurities
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/04—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
    • H01L33/06—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of group III and group V of the periodic system
    • H01L33/32—Materials of the light emitting region containing only elements of group III and group V of the periodic system containing nitrogen

Abstract

The disclosure provides an epitaxial wafer of a light emitting diode and a preparation method thereof, belonging to the technical field of photoelectron manufacturing. The preparation method comprises the following steps: providing a substrate; the method comprises the following steps that a high-temperature AlN buffer layer, a transition layer, an n-type AlGaN layer, a multi-quantum well layer and a p-type layer are epitaxially grown on a substrate in sequence, the transition layer is of a periodic structure, the periodic structure comprises AlN layers and AlGaN layers which are alternately stacked, and the growth pressure of each AlGaN layer is gradually reduced along the growth direction of an epitaxial wafer. The AlN layer in the transition layer can promote dislocation defect bending that high temperature AlN buffer layer extended, increases dislocation mutual annihilation probability to reach the purpose that reduces the dislocation defect, and the growth pressure on the AlGaN layer of growing earlier is higher, promotes the three-dimensional island growth on AlGaN layer, and the growth pressure on the AlGaN layer of growing afterwards is lower, makes the AlGaN layer gradually transition from three-dimensional growth to two-dimensional growth, reduces dislocation density, improves crystal quality.

Description

Epitaxial wafer of light emitting diode and preparation method thereof
Technical Field
The disclosure relates to the technical field of photoelectron manufacturing, and in particular relates to an epitaxial wafer of a light emitting diode and a preparation method thereof.
Background
The Light Emitting Diode (LED) is a new product with great influence in the photoelectronic industry, has the characteristics of small volume, long service life, rich and colorful colors, low energy consumption and the like, and is widely applied to the fields of illumination, display screens, signal lamps, backlight sources, toys and the like. The core structure of the LED is an epitaxial wafer, and the manufacturing of the epitaxial wafer has great influence on the photoelectric characteristics of the LED.
The epitaxial wafer typically includes a buffer layer, an n-type layer, a multiple quantum well layer, and a p-type layer. The n-type layer in the epitaxial wafer of the ultraviolet light emitting diode is usually an AlGaN layer.
At present, the epitaxial growth technology of the ultraviolet LED is not mature enough, and the grown epitaxial wafer has more dislocation defects, so that the quality of crystals is poor, and the luminous efficiency is low.
Disclosure of Invention
The embodiment of the disclosure provides an epitaxial wafer of a light emitting diode and a preparation method thereof, which can reduce dislocation defects, improve the crystal quality of the epitaxial wafer and improve the light emitting efficiency of an ultraviolet LED. The technical scheme is as follows:
in one aspect, an embodiment of the present disclosure provides a method for preparing an epitaxial wafer of a light emitting diode, where the method includes:
providing a substrate;
and sequentially epitaxially growing a high-temperature AlN buffer layer, a transition layer, an n-type AlGaN layer, a multi-quantum well layer and a p-type layer on the substrate, wherein the transition layer is of a periodic structure, the periodic structure comprises AlN layers and AlGaN layers which are alternately stacked, and the growth pressure of each AlGaN layer is gradually reduced along the growth direction of the epitaxial wafer.
Optionally, in the transition layer, growth pressure difference values of adjacent AlGaN layers are all equal.
Optionally, in the transition layer, a difference in growth pressure between adjacent AlGaN layers is 8mbar to 12 mbar.
Optionally, the growth pressure of the AlGaN layer is 20mbar to 200 mbar.
Optionally, the growth temperature of the AlGaN layer is 1100 ℃ to 1200 ℃.
Optionally, the molar ratio V/III when growing the AlN layer is 200-400.
On the other hand, the embodiment of the present disclosure further provides an epitaxial wafer of a light emitting diode, where the epitaxial wafer includes a substrate, and a high-temperature AlN buffer layer, a transition layer, an n-type AlGaN layer, a multiple quantum well layer, and a p-type layer sequentially formed on the substrate, where the transition layer is a periodic structure, the periodic structure includes AlN layers and AlGaN layers that are alternately stacked, and a growth pressure of each AlGaN layer is gradually reduced along a growth direction of the epitaxial wafer.
Optionally, the number of cycles of the transition layer is 5-20.
Optionally, the Al composition in the AlGaN layer is 40% to 95%.
Optionally, the AlN layer has a thickness of 10nm to 100nm, and the AlGaN layer has a thickness of 10nm to 100 nm.
The beneficial effects brought by the technical scheme provided by the embodiment of the disclosure at least comprise:
the transition layer is arranged between the high-temperature AlN buffer layer and the n-type AlGaN layer and comprises a periodic structure formed by alternately laminating AlN layers and AlGaN layers, on one hand, the AlN layer in the transition layer can promote dislocation defects extending from the high-temperature AlN buffer layer to bend, and the probability of mutual annihilation of dislocations is increased, so that the purpose of reducing the dislocation defects is achieved, on the other hand, the growth pressure of the AlGaN layer growing firstly in the transition layer is higher, the three-dimensional island growth of the AlGaN layer is promoted, the growth pressure of the AlGaN layer growing later is lower, so that the AlGaN layer gradually transits from three-dimensional growth to two-dimensional growth, the dislocation density is reduced, the crystal quality is improved, the crystal quality of the n-type AlGaN layer growing subsequently is favorably improved, the carrier concentration is improved, and the luminous efficiency of the ultraviolet LED is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an epitaxial wafer of a light emitting diode provided in an embodiment of the present disclosure;
fig. 2 is a flowchart of a method for manufacturing an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure;
fig. 3 is a flowchart of another method for manufacturing an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure;
fig. 4 is a schematic view illustrating a manufacturing process of an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure;
fig. 5 is a schematic view illustrating a manufacturing process of an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure;
fig. 6 is a schematic view illustrating a manufacturing process of an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure;
fig. 7 is a schematic view illustrating a process for preparing an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure;
fig. 8 is a schematic view illustrating a process for manufacturing an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure;
fig. 9 is a schematic view illustrating a process for preparing an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure;
fig. 10 is a schematic view of a process for preparing an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure.
Detailed Description
To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of an epitaxial wafer of a light emitting diode provided in an embodiment of the present disclosure. As shown in fig. 1, the epitaxial wafer includes a substrate 10, and a high-temperature AlN buffer layer 20, a transition layer 30, an n-type AlGaN layer 40, a multiple quantum well layer 50, and a p-type layer 60 sequentially formed on the substrate 10.
The transition layer 30 has a periodic structure. The periodic structure includes AlN layers 301 and AlGaN layers 302 alternately stacked, and the growth pressure of each AlGaN layer 302 is gradually reduced in the direction of epitaxial wafer growth.
The transition layer is arranged between the high-temperature AlN buffer layer and the n-type AlGaN layer and comprises a periodic structure formed by alternately laminating AlN layers and AlGaN layers, on one hand, the AlN layer in the transition layer can promote dislocation defects extending from the high-temperature AlN buffer layer to bend, and the probability of mutual annihilation of dislocations is increased, so that the purpose of reducing the dislocation defects is achieved, on the other hand, the growth pressure of the AlGaN layer growing firstly in the transition layer is higher, the three-dimensional island growth of the AlGaN layer is promoted, the growth pressure of the AlGaN layer growing later is lower, so that the AlGaN layer gradually transits from three-dimensional growth to two-dimensional growth, the dislocation density is reduced, the crystal quality is improved, the crystal quality of the n-type AlGaN layer growing subsequently is favorably improved, the carrier concentration is improved, and the luminous efficiency of the ultraviolet LED is improved.
Illustratively, the substrate 10 is a sapphire substrate, a silicon substrate, or a silicon carbide substrate. The substrate 10 may be a flat substrate or a patterned substrate.
As an example, in the embodiments of the present disclosure, the substrate 10 is a sapphire substrate. The sapphire substrate is a common substrate, the technology is mature, and the cost is low. The substrate can be a patterned sapphire substrate or a sapphire flat sheet substrate.
The thickness of the high-temperature AlN buffer layer 20 can be 1-5 μm, the grown high-temperature AlN buffer layer 20 has different thicknesses, and the quality of the finally formed epitaxial layer is different, if the thickness of the high-temperature AlN buffer layer 20 is too thin, the surface of the high-temperature AlN buffer layer 20 is loose and rough, so that a good template cannot be provided for the growth of a subsequent structure, along with the increase of the thickness of the high-temperature AlN buffer layer 20, the surface of the high-temperature AlN buffer layer 20 gradually becomes more compact and smoother, which is beneficial to the growth of the subsequent structure, but if the thickness of the high-temperature AlN buffer layer 20 is too thick, the surface of the high-temperature AlN buffer layer 20 is too compact, which is also not beneficial to the growth of the subsequent structure, and the lattice defects in the epitaxial.
As an example, in the embodiment of the present disclosure, the thickness of the high-temperature AlN buffer layer 20 is 2.5 μm.
Optionally, the transition layer 30 has a thickness of 0.2 μm to 2.0 μm. The thickness of transition layer 30 sets up is too thin, and is less to dislocation defect's reducing effect, and is not obvious to ultraviolet LED's luminous efficacy's improvement effect, and the thickness of transition layer 30 sets up thickly, can increase resistance, can increase transition layer 30 in addition to the absorption of light.
As an example, in the disclosed embodiment, the thickness of the transition layer 30 is 1 μm.
Optionally, the number of cycles of the transition layer 30 is 5-20. In the transition layer 30, the number of the AlN layer 301 and the AlGaN layer 302 stacked alternately is too small, which is not obvious for reducing dislocation defects, and too large increases complexity of the manufacturing process and manufacturing cost, and also causes an excessively large total thickness of the transition layer 30, which increases resistance and increases absorption of light by the transition layer 30, in the case where the thicknesses of the AlN layer 301 and the AlGaN layer 302 are fixed.
By way of example, in the disclosed embodiment, the number of cycles of the transition layer 30 is 10.
Optionally, the AlN layer 301 has a thickness of 10nm to 100nm, and the AlGaN layer 302 has a thickness of 10nm to 100 nm. The thickness of the single AlN layer 301 and the single AlGaN layer 302 is not too thick, which is disadvantageous for lattice transition, resulting in an increase in dislocation defects.
As an example, in the embodiment of the present disclosure, the AlN layer 301 has a thickness of 50nm, and the AlGaN layer 302 has a thickness of 50 nm.
Optionally, the Al composition in the AlGaN layer 302 is 40% to 95%.
The Al composition in different AlGaN layers 302 may be the same or different, for example, the Al composition in different AlGaN layers 302 increases, decreases, increases and then decreases, or decreases and then increases along the direction of epitaxial wafer growth.
As an example, in the disclosed embodiment, the Al composition in each AlGaN layer 302 is 70%.
Alternatively, the thickness of the n-type AlGaN layer 40 may be 600nm to 800nm, and in the embodiment of the present disclosure, the thickness of the n-type AlGaN layer 40 is 700 nm.
OptionallyAnd the doping concentration of Si in the n-type AlGaN layer 40 is 1017cm-3～1018cm-3. Too high a doping concentration of Si may reduce crystal quality, resulting in an increase in defects, and too low a doping concentration of Si may reduce the conductivity of the n-type AlGaN layer 40. The doping concentration of Si is controlled to 1017cm-3～1018cm-3The n-type AlGaN layer 40 can have a good crystal quality and also have sufficient conductivity.
As an example, in the embodiment of the present disclosure, the doping concentration of Si in the n-type AlGaN layer 40 is 5 × 1017cm-3。
Optionally, the MQW layer 50 includes 3-8 AlxGa1-xN quantum well layer 51 and AlyGa1-yAnd the N quantum barrier layers 52, wherein x is more than 0 and less than y is less than 1. That is, the MQW layer 50 includes 3 to 8 periods of Al alternately stackedxGa1-xN quantum well layer 51 and AlyGa1-yAnd an N quantum barrier layer 52.
As an example, in the embodiment of the present disclosure, the multiple quantum well layer 50 includes 5 periods of Al alternately stackedxGa1-xN quantum well layer 51 and AlyGa1-yAnd an N quantum barrier layer 52.
Alternatively, AlxGa1-xThe thickness of the N quantum well layer 51 may be 2nm to 4 nm. Al (Al)yGa1-yThe thickness of the N quantum barrier layer 52 can be 9-14 nm.
Exemplarily, in the embodiments of the present disclosure, AlxGa1-xThe thickness of the N quantum well layer 51 was 3 nm. Al (Al)yGa1-yThe thickness of the N quantum barrier layer 52 is 11 nm.
Note that fig. 1 shows only a partial structure of the mqw layer 50, and is not intended to limit AlxGa1-xN quantum well layer 51 and AlyGa1-yThe number of cycles of the N quantum barrier layers 52 alternately stacked, and Al may be grown on the N-type AlGaN layer 40 in the case of growing the multiple quantum well layer 50yGa1-yAnd an N quantum barrier layer 52.
In the embodiment of the present disclosure, the p-type layer 60 includes a p-type barrier layer 61, a p-type AlGaN layer 62, and a p-type GaN layer 63 sequentially stacked on the multiple quantum well layer 50. The p-type barrier layer 61, the p-type AlGaN layer 62, and the p-type GaN layer 63 are all Mg doped.
Illustratively, the p-type barrier layer 61 is a p-type AlGaN barrier layer.
The p-type AlGaN barrier layer may have a thickness of 5nm to 15 nm. As an example, in the embodiments of the present disclosure, the thickness of the p-type AlGaN barrier layer is 10 nm. If the thickness of the p-type AlGaN blocking layer is too thin, the blocking effect on electrons is reduced, and if the thickness of the p-type AlGaN blocking layer is too thick, the absorption of light by the p-type AlGaN blocking layer is increased, which reduces the light emission efficiency of the LED.
In some examples, the p-type AlGaN layer 62 has a thickness of 20nm to 30 nm. As an example, in the disclosed embodiment, the thickness of the p-type AlGaN layer 62 is 25 nm.
Alternatively, the thickness of the p-type GaN layer 63 may be 20nm to 70 nm. As an example, in the embodiment of the present disclosure, the thickness of the p-type GaN layer 63 is 50 nm.
Fig. 2 is a flowchart of a method for manufacturing an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure. The method is used to manufacture the epitaxial wafer shown in fig. 1. As shown in fig. 2, the manufacturing method includes:
s11: a substrate 10 is provided.
S12: a high-temperature AlN buffer layer 20, a transition layer 30, an n-type AlGaN layer 40, a multiple quantum well layer 50, and a p-type layer 60 are epitaxially grown in this order on a substrate 10.
The transition layer 30 has a periodic structure. The periodic structure includes AlN layers 301 and AlGaN layers 302 alternately stacked, and the growth pressure of each AlGaN layer 302 is gradually reduced in the direction of epitaxial wafer growth.
The transition layer is arranged between the high-temperature AlN buffer layer and the n-type AlGaN layer and comprises a periodic structure formed by alternately laminating AlN layers and AlGaN layers, on one hand, the AlN layer in the transition layer can promote dislocation defects extending from the high-temperature AlN buffer layer to bend, and the probability of mutual annihilation of dislocations is increased, so that the purpose of reducing the dislocation defects is achieved, on the other hand, the growth pressure of the AlGaN layer growing firstly in the transition layer is higher, the three-dimensional island growth of the AlGaN layer is promoted, the growth pressure of the AlGaN layer growing later is lower, so that the AlGaN layer gradually transits from three-dimensional growth to two-dimensional growth, the dislocation density is reduced, the crystal quality is improved, the crystal quality of the n-type AlGaN layer growing subsequently is favorably improved, the carrier concentration is improved, and the luminous efficiency of the ultraviolet LED is improved.
Fig. 3 is a flowchart of another method for manufacturing an epitaxial wafer of a light emitting diode according to an embodiment of the present disclosure, where the method is used for manufacturing the epitaxial wafer shown in fig. 1. The manufacturing method provided in fig. 3 will be described in detail with reference to fig. 4 to 10:
s21: a substrate 10 is provided.
Alternatively, the substrate 10 is a sapphire substrate, a silicon substrate, or a silicon carbide substrate. The substrate 10 may be a flat substrate or a patterned substrate.
As an example, in the embodiments of the present disclosure, the substrate 10 is a sapphire substrate. The sapphire substrate is a common substrate, the technology is mature, and the cost is low. The substrate can be a patterned sapphire substrate or a sapphire flat sheet substrate.
In step S21, the sapphire substrate may be pretreated, placed in an MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber, and subjected to a baking process for 12 to 18 minutes. As an example, in the embodiment of the present disclosure, the baking process was performed on the sapphire substrate for 15 minutes.
Specifically, the baking temperature can be 1000-1200 ℃, and the pressure in the MOCVD reaction chamber during baking can be 100-200 mbar.
S22: a high temperature AlN buffer layer 20 is epitaxially grown on the substrate 10.
As shown in fig. 4, a high-temperature AlN buffer layer 20 is grown on the substrate 10.
The thickness of the high-temperature AlN buffer layer 20 can be 1-5 μm, the grown high-temperature AlN buffer layer 20 has different thicknesses, and the quality of the finally formed epitaxial layer is different, if the thickness of the high-temperature AlN buffer layer 20 is too thin, the surface of the high-temperature AlN buffer layer 20 is loose and rough, a good template cannot be provided for the growth of a subsequent structure, along with the increase of the thickness of the high-temperature AlN buffer layer 20, the surface of the high-temperature AlN buffer layer 20 gradually becomes more compact and smoother, which is beneficial to the growth of the subsequent structure, but if the thickness of the high-temperature AlN buffer layer 20 is too thick, the surface of the high-temperature AlN buffer layer 20 is too compact, which is also not beneficial to the growth of the subsequent structure, and the lattice defects in the epitaxial layer cannot be reduced.
As an example, in the embodiment of the present disclosure, the thickness of the high-temperature AlN buffer layer 20 is 2.5 μm.
Optionally, the growth temperature of the high-temperature AlN buffer layer 20 is 1200 to 1300 ℃. As an example, in the embodiments of the present disclosure, the growth temperature of the high-temperature AlN buffer layer 20 is 1250 ℃.
Optionally, the growth pressure of the high-temperature AlN buffer layer 20 is 50mbar to 200 mbar. As an example, in the embodiments of the present disclosure, the growth pressure of the high-temperature AlN buffer layer 20 is 150 mbar.
S23: a transition layer 30 is grown on the high-temperature AlN buffer layer 20.
As shown in fig. 5, a transition layer 30 is grown on the high-temperature AlN buffer layer 20.
The transition layer 30 has a periodic structure. The periodic structure includes AlN layers 301 and AlGaN layers 302 alternately stacked, and the growth pressure of each AlGaN layer 302 is gradually reduced in the direction of epitaxial wafer growth.
The number of cycles of the transition layer 30 is 5 to 20. In the transition layer 30, the number of the AlN layer 301 and the AlGaN layer 302 stacked alternately is too small, which is not obvious for reducing dislocation defects, and too large increases complexity of the manufacturing process and manufacturing cost, and also causes an excessively large total thickness of the transition layer 30, which increases resistance and increases absorption of light by the transition layer 30, in the case where the thicknesses of the AlN layer 301 and the AlGaN layer 302 are fixed.
By way of example, in the disclosed embodiment, the number of cycles of the transition layer 30 is 10.
Optionally, the growth pressure of the AlGaN layer 302 is 20mbar to 200 mbar. The growth pressure of the AlGaN layer 302 affects the growth of the AlGaN layer 302, and when the pressure is high, the AlGaN layer 302 exhibits three-dimensional island-like growth, and when the pressure is low, the AlGaN layer 302 exhibits two-dimensional growth. By changing the growth pressure of each AlGaN layer 302 in this range, the AlGaN layer 302 in the transition layer 30 can be smoothly transitioned from three-dimensional island growth to two-dimensional growth, so that the dislocation density is further reduced, and the crystal quality is improved.
Optionally, the growth pressure difference of the adjacent AlGaN layers 302 in the transition layer 30 is equal.
The growth pressure of each AlGaN layer 302 is sequentially decreased by the same magnitude, so that the AlGaN layer 302 is more smoothly transited from three-dimensional island-like growth to two-dimensional growth.
Optionally, the growth pressure difference between adjacent AlGaN layers 302 in the transition layer 30 is 8mbar to 12 mbar. As an example, in an embodiment of the present disclosure, the growth pressure difference of adjacent AlGaN layers 302 is 10 mbar. The growth pressure of the adjacent AlGaN layer 302 decreases too fast, which is not favorable for the AlGaN layer 302 to smoothly transition from three-dimensional island growth to two-dimensional growth.
In the embodiment of the present disclosure, from the side of the high-temperature AlN buffer layer 20 toward the n-type AlGaN layer 40, the growth pressure of the AlGaN layer 302 is decreased from 140mbar to 50mbar, and the growth pressure difference between the adjacent AlGaN layers 302 is 10 mbar.
Optionally, the growth temperature of the AlGaN layer 302 is 1100 ℃ to 1200 ℃. As an example, in the embodiments of the present disclosure, the growth temperature of the AlGaN layer 302 is 1180 ℃.
In the transition layer 30, the growth temperature of each AlGaN layer 302 may be the same or different. As an example, in the embodiment of the present disclosure, the growth temperature of each AlGaN layer 302 is the same, and is 1180 ℃, and the AlGaN layers 302 are grown at the same growth temperature, which is more convenient to operate and simpler in process.
Optionally, the molar ratio V/III when growing the AlGaN layer 302 is 500-2000. As an example, in the embodiments of the present disclosure, the v/iii molar ratio when growing the AlGaN layer 302 is 1000.
Optionally, the growth temperature of the AlN layer 301 is 1200 ℃ to 1300 ℃. As an example, in the embodiments of the present disclosure, the growth temperature of the AlN layer 301 is 1220 ℃.
In the transition layer 30, the growth temperature of each AlN layer 301 may be the same or different. As an example, in the embodiment of the present disclosure, the growth temperature of each AlN layer 301 is the same, and is 1220 ℃, and the growth temperature of each AlN layer 301 is the same, which is more convenient to operate and simpler in process.
Optionally, the molar ratio V/III when growing the AlN layer 301 is 200 to 400. As an example, in the embodiments of the present disclosure, the v/iii molar ratio when growing AlN layer 301 is 300.
S24: an n-type AlGaN layer 40 is grown on the transition layer 30.
As shown in fig. 6, an n-type AlGaN layer 40 is grown on the transition layer 30.
Optionally, the growth temperature of the n-type AlGaN layer 40 is 1000 ℃ to 1100 ℃. As an example, in the embodiment of the present disclosure, the growth temperature of the n-type AlGaN layer 40 is 1060 ℃.
Alternatively, the growth pressure of the n-type AlGaN layer 40 may be 80mbar to 110 mbar. As an example, in the embodiments of the present disclosure, the growth pressure of the n-type AlGaN layer 40 is 100 mbar.
When the n-type AlGaN layer 40 is grown, silane doping is performed, and the Si doping concentration in the n-type AlGaN layer 40 may be 1017cm-3～1018cm-3. As an example, in the embodiment of the present disclosure, the Si doping concentration in the n-type AlGaN layer 40 is 5 × 1017cm-3。
The thickness of the n-type AlGaN layer 40 may be 600nm to 800nm, and in the embodiment of the present disclosure, the thickness of the n-type AlGaN layer 40 is 700 nm.
S25: a multiple quantum well layer 50 is grown on the n-type AlGaN layer 40.
As shown in fig. 7, a multiple quantum well layer 50 is grown on the n-type AlGaN layer 40.
In practice, the MQW layer 50 may include a plurality of layers of Al alternately stackedxGa1-xN quantum well layer 51 and multilayer AlyGa1-yAnd the N quantum barrier layers 52, wherein x is more than 0 and less than y is less than 1.
Alternatively, AlxGa1-xN quantum well layer 51 and AlyGa1-yThe number of the alternately stacked N quantum barrier layers 52 may be 3 to 8. Exemplarily, in the embodiments of the present disclosure, AlxGa1-xN quantum well layer 51 and AlyGa1-yThe number of cycles of the N quantum barrier layers 52 stacked alternately is 5.
Note that fig. 7 shows only a partial structure of the mqw layer 50, and is not intended to limit AlxGa1-xN quantum well layer 51 and AlyGa1-yThe number of cycles of the N quantum barrier layers 52 alternately stacked, and Al may be grown on the N-type AlGaN layer 40 in the case of growing the multiple quantum well layer 50yGa1-yAnd an N quantum barrier layer 52.
Alternatively, AlxGa1-xThe thickness of the N quantum well layer 51 may be 2nm to 4 nm. Al (Al)yGa1-yThe thickness of the N quantum barrier layer 52 can be 9-14 nm.
Exemplarily, in the embodiments of the present disclosure, AlxGa1-xThe thickness of the N quantum well layer 51 was 3 nm. Al (Al)yGa1-yThe thickness of the N quantum barrier layer 52 is 11 nm.
After the mqw layer 50 is grown, a p-type layer 60 is grown on the mqw layer 50, and in the embodiment of the present disclosure, the p-type layer 60 includes a p-type barrier layer 61, a p-type AlGaN layer 62, and a p-type GaN layer 63 sequentially stacked on the mqw layer 50. The p-type barrier layer 61, the p-type AlGaN layer 62, and the p-type GaN layer 63 are all Mg doped. The growth of the p-type layer 60 includes steps S26 to S28 as follows.
S26: a p-type barrier layer 61 is grown on the multiple quantum well layer 50.
As shown in fig. 8, a p-type barrier layer 61 is grown on the multiple quantum well layer 50.
Alternatively, the p-type barrier layer 61 may be a p-type AlGaN barrier layer.
Specifically, the growth temperature of the p-type barrier layer 61 may be 960 ℃ to 990 ℃, and in the embodiment of the present disclosure, the growth temperature of the p-type barrier layer 61 is 980 ℃, as an example.
Specifically, the growth pressure of the p-type barrier layer 61 may be 100mbar to 200 mbar. As an example, in the embodiments of the present disclosure, the growth pressure of the p-type barrier layer 61 is 150 mbar.
Alternatively, the p-type barrier layer 61 may have a thickness of 5nm to 15 nm. As an example, in the embodiments of the present disclosure, the thickness of the p-type barrier layer 61 is 10 nm. If the thickness of the p-type blocking layer 61 is too thin, the blocking effect on electrons is reduced, and if the thickness of the p-type blocking layer 61 is too thick, the absorption of light by the p-type blocking layer 61 is increased, thereby reducing the light emitting efficiency of the LED.
S27: a p-type AlGaN layer 62 is grown on the p-type barrier layer 61.
As shown in fig. 9, a p-type AlGaN layer 62 is grown on the p-type barrier layer 61.
Specifically, the growth temperature of the p-type AlGaN layer 62 may be 880 ℃ to 920 ℃, and in the embodiment of the present disclosure, the growth temperature of the p-type AlGaN layer 62 is 900 ℃, as an example.
Specifically, the growth pressure of the p-type AlGaN layer 62 may be 180mbar to 220 mbar. As an example, in the embodiments of the present disclosure, the growth pressure of the p-type AlGaN layer 62 is 200 mbar.
Alternatively, the thickness of the p-type AlGaN layer 62 may be 20nm to 30 nm. As an example, in the disclosed embodiment, the thickness of the p-type AlGaN layer 62 is 25 nm.
S28: a p-type GaN layer 63 is grown on the p-type AlGaN layer 62.
As shown in fig. 10, a p-type GaN layer 63 is grown on the p-type AlGaN layer 62.
Alternatively, the growth temperature of the p-type GaN layer 63 may be 800 deg.C to 900 deg.C. As an example, in the embodiment of the present disclosure, the growth temperature of the p-type GaN layer 63 is 850 ℃.
Alternatively, the growth pressure of the p-type GaN layer 63 may be 250mbar to 350 mbar. As an example, in the embodiments of the present disclosure, the growth pressure of the p-type GaN layer 63 is 300 mbar.
Alternatively, the thickness of the p-type GaN layer 63 may be 20nm to 70 nm. As an example, in the embodiment of the present disclosure, the thickness of the p-type GaN layer 63 is 50 nm.
When the p-type barrier layer 61, the p-type AlGaN layer 62, and the p-type GaN layer 63 are grown, Mg doping is performed using cyclopentadienyl magnesium with trimethyl gallium or triethyl gallium as a gallium source.
S29: and annealing the epitaxial wafer.
Alternatively, annealing may be performed for 30 minutes in a nitrogen atmosphere to end the growth of the epitaxial wafer. And then the heating system and the gas supply system are closed, and the temperature of the reaction cavity is reduced to room temperature.
Annealing the epitaxial wafer, and performing subsequent processing on the epitaxial wafer to prepare the LED.
In particular implementations, embodiments of the present disclosure may employ high purity H2Or/and N2As carrier gas, TEGa or TMGa is used as Ga source, TMIn is used as In source, SiH4As n-type dopant TMAl as aluminium source, Cp2Mg as a p-type dopant.
The above description is intended to be exemplary only and not to limit the present disclosure, and any modification, equivalent replacement, or improvement made without departing from the spirit and scope of the present disclosure is to be considered as the same as the present disclosure.

Claims (10)

1. A preparation method of an epitaxial wafer of a light-emitting diode is characterized by comprising the following steps:
providing a substrate (10);
the method comprises the step of epitaxially growing a high-temperature AlN buffer layer (20), a transition layer (30), an n-type AlGaN layer (40), a multi-quantum well layer (50) and a p-type layer (60) on a substrate (10) in sequence, wherein the transition layer (30) is of a periodic structure, the periodic structure comprises AlN layers (301) and AlGaN layers (302) which are alternately stacked, and the growth pressure of each AlGaN layer (302) is gradually reduced along the growth direction of the epitaxial wafer.
2. The method according to claim 1, wherein the growth pressure difference of the AlGaN layers (302) adjacent to each other in the transition layer (30) is equal.
3. The method according to claim 2, wherein a difference in growth pressure between adjacent ones of the AlGaN layers (302) in the transition layer (30) is 8 to 12 mbar.
4. The method according to claim 1, wherein the growth pressure of the AlGaN layer (302) is 20 to 200 mbar.
5. The method according to claim 1, wherein the growth temperature of the AlGaN layer (302) is 1100-1200 ℃.
6. The production method according to claim 1, wherein a V/III molar ratio at the time of growing the AlN layer (301) is 200 to 400.
7. An epitaxial wafer of a light emitting diode, characterized in that the epitaxial wafer comprises a substrate (10) and a high-temperature AlN buffer layer (20), a transition layer (30), an n-type AlGaN layer (40), a multiple quantum well layer (50) and a p-type layer (60) which are sequentially formed on the substrate (10), wherein the transition layer (30) is a periodic structure, the periodic structure comprises AlN layers (301) and AlGaN layers (302) which are alternately stacked, and the growth pressure of each AlGaN layer (302) is gradually reduced along the growth direction of the epitaxial wafer.
8. The epitaxial wafer according to claim 7, characterized in that the number of periods of the transition layer (30) is 5 to 20.
9. The epitaxial wafer according to claim 7, characterized in that the Al composition in the AlGaN layer (302) is between 40% and 95%.
10. The epitaxial wafer according to claim 7, wherein the AlN layer (301) has a thickness of 10nm to 100nm and the AlGaN layer (302) has a thickness of 10nm to 100 nm.
CN202110164464.6A 2021-02-05 2021-02-05 Epitaxial wafer of light emitting diode and preparation method thereof Pending CN112802929A (en)

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