CN112331748A - Epitaxial structure of light emitting diode and preparation method thereof - Google Patents

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

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CN112331748A
CN112331748A CN202011363610.XA CN202011363610A CN112331748A CN 112331748 A CN112331748 A CN 112331748A CN 202011363610 A CN202011363610 A CN 202011363610A CN 112331748 A CN112331748 A CN 112331748A
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刘园旭
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Anhui University of Traditional Chinese Medicine AHUTCM
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Anhui University of Traditional Chinese Medicine AHUTCM
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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
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
    • H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound 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
    • H01L33/04—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
    • H01L33/14—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 carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
    • 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 invention provides a preparation method of an epitaxial structure of a light-emitting diode, which comprises the steps of providing a substrate, growing a buffer layer and an N-type AlGaN conducting layer on the substrate in sequence, and growing SiN on the N-type AlGaN conducting layerxMask layer and in-situ etching are carried out on SiN with incompact growthxThe part is etched to expose the N-type AlGaN layer, and the N-type AlGaN repairing layer and Al are continuously grown in an epitaxial mannerxGa1‑xN/AlyGa1‑yN multiple quantum well active layers, wherein x is 0.37-0.38, and y is 0.55-0.6; AlGaN electron blocking layer, P-type AlGaN hole expanding layer and P-type gallium nitride conducting layer. The LED epitaxial structure prepared by the preparation method provided by the invention has improved luminous efficiency.

Description

Epitaxial structure of light emitting diode and preparation method thereof
Technical Field
The invention relates to the technical field of semiconductor device preparation, in particular to an epitaxial structure of a light emitting diode and a preparation method thereof.
Background
Ultraviolet (UV) refers to an electromagnetic wave having a wavelength of 10 nanometers (nm) to 400nm, and the shorter the wavelength of the electromagnetic wave, the stronger the radiation, and UV can be classified into UVA (320 to 400nm), UVB (280 to 320nm), and UVC (100 to 280nm) according to the wavelength of the electromagnetic wave. Wherein, the UVC wavelength is between 100nm and 280nm, can destroy the DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) molecular structure of microorganisms, so that bacteria die or can not be propagated to achieve the aim of sterilization, and therefore, the UVC has wide application in the fields of sterilization, water purification, air purification, medical treatment and the like.
Mercury lamps have been one of the UV sterilization methods, but mercury is highly toxic and unsuitable for long-term development, and a safer and environmentally friendly method is needed to replace mercury lamps. With the continuous development of Light Emitting Diode (LED) technology, the light emitting wavelength of the LED has been expanded from the visible light band to the deep ultraviolet band, and the deep ultraviolet LED has the advantages of low energy consumption, small volume, good integration, long service life, environmental protection, no toxicity and the like as a novel ultraviolet light source, and has a wide application prospect in various fields, but the current deep ultraviolet LED has a low light emitting efficiency and limits the application of the deep ultraviolet LED. Therefore, a preparation method for improving the brightness of the deep ultraviolet LED is urgently needed to be developed.
Disclosure of Invention
Aiming at the defects and shortcomings in the prior art, the invention provides a preparation method of a light-emitting diode epitaxial structure, which is used for solving the problem of low light emitting efficiency of a deep ultraviolet light-emitting diode.
In order to achieve the above and other related objects, the present invention provides a method for preparing an epitaxial structure of a light emitting diode, comprising the steps of:
providing a substrate, and annealing the substrate;
growing a buffer layer on the substrate after the annealing treatment;
growing an N-type AlGaN conducting layer on the buffer layer;
growing SiN on the N-type AlGaN conducting layerxMask layer and for the SiNxCarrying out in-situ etching on the mask layer to expose a part of area of the N-type AlGaN conducting layer;
SiN after said etchingxGrowing an N-type AlGaN repairing layer on the mask layer;
growing Al on the N-type AlGaN repairing layerxGa1-xN/AlyGa1-yN multiple quantum well active layers, wherein x is 0.37-0.38, and y is 0.55-0.60;
in the AlxGa1-xN/AlyGa1-yGrowing an AlGaN electron barrier layer on the N multi-quantum well active layer;
growing a P-type AlGaN hole expansion layer on the AlGaN electron blocking layer;
and growing a P-type gallium nitride conducting layer on the P-type AlGaN hole expansion layer.
In an embodiment of the invention, growing the buffer layer on the annealed substrate includes:
growing an aluminum nitride buffer layer on the substrate after the annealing treatment;
growing an AlGaN buffer layer on the aluminum nitride buffer layer, wherein the thickness of the AlGaN buffer layer is 300-350 nanometers (nm), and the Al component content of the AlGaN buffer layer is reduced from 80-85% to 60-65% from the beginning to the end of growth.
In an embodiment of the invention, silane is used as a silicon dopant when growing the N-type AlGaN conductive layer on the buffer layer, wherein the silicon doping concentration in the N-type AlGaN conductive layer is 3E 18-1E 19cm-3The content of the Al component in the N-type AlGaN conducting layer is 50-55%, and the thickness is 1000-2500 nm.
In an embodiment of the invention, SiN is grown on the N-type AlGaN conductive layerxMask layer and for the SiNxThe mask layer is subjected to in-situ etching, and the in-situ etching comprises the following steps:
controlling the temperature to be 1080-1100 ℃ and the pressure to be 50-100 mbar;
introducing hydrogen as a carrier gas, and taking ammonia gas and silane as reaction gases, wherein the flow rate of the ammonia gas is 2000-2500 sccm, and the flow rate of the silane is 200-250 sccm; the SiN grownxThe thickness of the mask layer is 3-5 nm;
stopping introducing silane, keeping the flow of ammonia unchanged, continuously introducing for 3-5 minutes (min), and introducing the SiNxAnd etching the mask layer in situ, wherein a part of the grown region which is not compact is etched through to expose the N-type AlGaN conducting layer.
In one embodiment of the present invention, the SiNxWhen an N-type AlGaN repairing layer grows on the mask layer, the N-type AlGaN repairing layer is on the SiNxEtching the mask layer to form surface growth of N-type AlGaN conducting layer, and etching the non-etched SiN layerxMask layer shielding part formationA void; the content of Al in the N-type AlGaN repairing layer is 48-50%, and the doping amount of Si is 1E 18-3E 18cm-3(ii) a The thickness of the N-type AlGaN repairing layer is 50-100 nm.
In an embodiment of the invention, Al is grown on the N-type AlGaN repair layerxGa1-xN/AlyGa1-yThe N multi-quantum well active layer is Al alternately grownxGa1-xN quantum well layer and AlyGa1-yN quantum barrier layer of AlxGa1-xThe thickness of the N quantum well layer is 2-3 nm, and Al isyGa1-yThe thickness of the N quantum barrier layer is 4-10 nm, and the growth cycle of the multiple quantum well is 3-10; growing the AlyGa1-ySilane is introduced as a dopant in the process of the N quantum barrier layer, and the AlyGa1-yThe doping concentration of silicon in the N quantum barrier layer is 5E 17-6E 17cm-3。
In an embodiment of the present invention, the Al isxGa1-xN/AlyGa1-yThe content of Al in the AlGaN electron blocking layer grown on the N multi-quantum well active layer is reduced to 55-60% from 75-80% from the beginning to the end of growth, and the thickness of the AlGaN electron blocking layer is 20-30 nm.
In an embodiment of the invention, magnesium is used as a magnesium dopant when a P-type AlGaN hole expansion layer is grown on the AlGaN electron blocking layer, wherein the doping concentration of magnesium in the P-type AlGaN hole expansion layer is 1E 19-5E 19cm-3The content of Al components in the P-type AlGaN hole expansion layer is 60-65%, and the thickness of the P-type AlGaN hole expansion layer is 30-50 nm.
In an embodiment of the present invention, the growing the P-type gan conductive layer on the P-type AlGaN hole expansion layer includes:
controlling the growth temperature to be 960-1000 ℃ and the growth pressure to be 200 mbar;
introducing trimethyl gallium and ammonia gas to provide a gallium source and a nitrogen source, and introducing magnesium diclocide as a magnesium dopant, wherein the flow rate of trimethyl gallium is 150-200 sccm, the flow rate of ammonia gas is 20000-22000 sccm, and the flow rate of magnesium diclocide is 600-800 sccm;
the doping concentration of magnesium in the P-type gallium nitride conducting layer is 5E 19-1E 20cm-3The thickness of the P-type gallium nitride conducting layer is 100-300 nm.
The invention also provides an epitaxial structure of the light emitting diode prepared based on the preparation method.
As mentioned above, the invention provides a preparation method of a light emitting diode epitaxial structure, which realizes the coverage of the LED light-emitting wavelength in 200-280 nm by adjusting the Al component in AlGaN and changing the forbidden bandwidth of the AlGaN material, and SiN is grown on an N-type AlGaN conducting layer in the preparation processxA mask layer is etched in situ on the SiNx mask layer, and the SiNx mask layer is etched in the SiN layerxExposing the N-type AlGaN conducting layer at the position with the mask layer defect by etching, and then continuing to epitaxially grow an N-type AlGaN repairing layer on the etched SiNxThe region exposed on the surface of the N-type AlGaN grows, and the part which is not etched through and is shielded by SiNx can not continue to grow, so that the N-type AlGaN repairing layer, the active layer and the like continue to grow in the lateral direction and the longitudinal direction along with the increase of the growth thickness, and the N-type AlGaN repairing layer and the active layer continue to grow in the region which is shielded by SiNxxThe mask shelters from the part and can form the hole because epitaxial growth can not continue, follow-up continuation epitaxial growth P type conducting layer, fill up the hole, the hole carrier can not only get into the active layer from the top in the P type conducting layer, and can get into more active layers through the side of hole and compound the luminescence with the electron, improve the recombination rate in electron and hole and improve dark ultraviolet LED's luminous efficacy.
Drawings
The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
fig. 1 is a flow chart of a method for manufacturing an LED epitaxial structure according to the present invention.
Fig. 2 is a flow chart illustrating a method for fabricating a buffer layer according to an embodiment of the invention.
Fig. 3 is a schematic structural diagram of an AlN buffer layer in an embodiment of the present invention.
FIG. 4 is a schematic structural diagram of an epitaxial wafer after a SiNx mask layer is grown and in-situ etched according to the present invention.
FIG. 5 shows the grown Al of the present inventionxGa1-xN/AlyGa1-yAnd the structure schematic diagram of the epitaxial wafer behind the N multi-quantum well active layer.
FIG. 6 is a schematic view of an epitaxial structure of an LED after the growth of the present invention is completed.
Fig. 7 shows a hole diffusion schematic of a prior art epitaxial structure without chemical etching.
Fig. 8 shows a hole diffusion diagram of an epitaxial structure of an LED prepared according to the present invention.
Reference numerals
1 patterned sapphire substrate
2AlN buffer layer
21 first AlN layer
22 second AlN layer
23 third AlN layer
3AlGaN buffer layer
4N type AlGaN conductive layer
5SiNxMask layer
6N type AlGaN repairing layer
7AlxGa1-xN/AlyGa1-yN multiple quantum well active layer
8AlGaN electron blocking layer
9P type AlGaN hole expansion layer
10P type GaN conductive layer
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict. It is also to be understood that the terminology used in the examples is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. Test methods in which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under conditions recommended by the respective manufacturers.
When numerical ranges are given in the examples, it is understood that both endpoints of each of the numerical ranges and any value therebetween can be selected unless the invention otherwise indicated. 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 and the description of the present invention, and any methods, apparatuses, and materials similar or equivalent to those described in the examples of the present invention may be used to practice the present invention.
The invention provides a preparation method of an LED epitaxial structure, and Al is grownxGa1-xN/AlyGa1-yBefore N multiple quantum well active layer, a layer of SiN is grown on N type conductive layerxMask layer, in-situ etching, and subsequent continuous epitaxial growth of un-etched SiNxHoles can be formed in the positions shielded by the mask layer, holes in the P-type conducting layer can enter the active layer from the top and can enter more active layers from the side through the holes to be compounded with electrons, and the recombination rate of the electron holes is improved, so that the luminous efficiency of the LED is improved.
The invention provides a preparation method of an LED epitaxial structure, which can be carried out in Metal Organic Chemical Vapor Deposition (MOCVD) equipment by using trimethylaluminum (TMAl), trimethylgallium (TMGa) and ammonia (NH)3) Hydrogen (H) as aluminum (Al) source, gallium (Ga) source and nitrogen (N) source2) Nitrogen (N)2) Or the mixture of the two is used as carrier gas.
Referring to fig. 1 to 6, the present invention provides a method for manufacturing an LED epitaxial structure, including the following steps:
s1, providing a substrate, and annealing the substrate;
s2, growing a buffer layer on the substrate;
s3, growing an N-type AlGaN conducting layer 4 on the buffer layer;
s4, growing SiN on the N-type AlGaN conducting layer 4x Mask layer 5, and for the SiNxCarrying out in-situ etching on the mask layer 5;
s5, SiN after etchingxGrowing an N-type AlGaN repairing layer 6 on the mask layer 5;
s6, growing Al on the N-type AlGaN repairing layer 6xGa1-xN/AlyGa1-yN multiple quantum well active layer 7, wherein x is 0.37-0.38, y is 0.55-0.60;
s7 at the above AlxGa1-xN/AlyGa1-yAn AlGaN electronic barrier layer 8 grows on the N multi-quantum well active layer 7;
s8, growing a P-type AlGaN hole expansion layer 9 on the AlGaN electron blocking layer 8;
and S9, growing a P-type GaN conducting layer 10 on the P-type AlGaN hole expanding layer 9.
Referring to fig. 1 and 4, the substrate in step S1 may be selected as the patterned sapphire substrate 1, and the annealing process is performed in a hydrogen atmosphere at 1000 ℃, 100mbar, 3-5min, so as to remove the smut and oxide layer on the surface of the substrate.
Referring to fig. 1 to 4, the step S2 of growing the buffer layer on the annealed substrate includes:
s21, growing an AlN buffer layer 2 on the substrate; and
s22, an AlGaN buffer layer 3 is grown on the AlN buffer layer 2.
Wherein, in the step S21, TMAl and NH are introduced into the reaction chamber to grow the AlN buffer layer 2 on the substrate3To provide an Al source and an N source while feeding H2As a carrier gas. In one embodiment, growing the AlN buffer layer 2 includes the steps of: growing a first AlN layer 21 on the substrate, wherein the temperature of the reaction chamber in the growth stage is controlled to be 900-950 ℃, the pressure is controlled to be 50-100 mbar, the flow rate of TMAl is 200-250 sccm, the molar ratio of V/III element is 3000-4000, and the thickness of the first AlN layer 21 grown in the growth stage is 20-40 nm; then, second Al is grown on the first AlN layer 21The temperature of a reaction chamber in the growth stage is 1100-1150 ℃, the pressure of the reaction chamber is kept unchanged, the flow rate of TMAl is 180-220 sccm, the molar ratio of V/III is 4000-5000, and the thickness of a second AlN layer 22 grown in the growth stage is 400-600 nm; and then growing a third AlN layer 23 on the second AlN layer 22, raising the temperature of the reaction chamber to 1220-1300 ℃, keeping the pressure of the reaction chamber unchanged, wherein the flow rate of the TMAl is 380-450 sccm, the molar ratio of V/III is 200-400, and the thickness of the third AlN layer 33 grown in the growth stage is 1.5-3.5 mu m. The first AlN layer 21 grows rapidly at a low temperature, and compared with a subsequent high-temperature growth layer with a relatively low-temperature A1N doped layer, dislocation blocking and substrate stress relief are facilitated; the second AlN layer 22 grows at a medium temperature, and gradually transits from a low temperature to a high temperature to be equivalent to a transition layer, so that the growth of the A1N buffer layer 2 is transited from three-dimension to two-dimension, the surface is roughened to be changed into flatness, the dislocation is cut off and penetrates upwards, the dislocation density of a subsequent upward epitaxial layer is reduced, and the gradual release and relief of stress are facilitated; the third AlN layer 23 is grown at high temperature, the surface migration capability of A1 atoms is strong at high temperature, two-dimensional growth is realized, and an A1N epitaxial layer material with low dislocation density, no crack and smooth surface can be obtained. The AlN buffer layer 2 grown in a segmented mode can block upward epitaxial dislocation better, is beneficial to gradual release of stress and is more beneficial to epitaxial growth of a high-quality epitaxial layer.
Step S22, growing AlGaN buffer layer 3 on AlN buffer layer 2, introducing TMGa, TMAl, NH into the reaction chamber3Providing Ga source, Al source and N source, and introducing H2As a carrier gas. The temperature of the reaction chamber in the growth stage is 1060-1100 ℃, the pressure is 50-100 mbar, the flow rate of TMGa is 50-60sccm, NH3The flow rate of the TMAl is 8000-9000 sccm, and the flow rate of the TMAl is reduced from the start of growth to the end of growth from 250-270 sccm to 130-150 sccm. In this stage, the Al content of the AlGaN buffer layer 3 is reduced from 80-85% to 60-65% from the beginning to the end, and the thickness of the AlGaN buffer layer 3 is 300-350 nm. The Al component content of the AlGaN buffer layer 3 gradually changes from high to low, the surface in contact with the AlN buffer layer 2 is the AlGaN buffer layer 3 with high Al component, and the surface in contact with the N-type AlGaN conducting layer 4 is lowAnd the Al component enables the lattice constant of the buffer layer to gradually approach the N-type AlGaN conducting layer 4, so that the difference between layers is reduced, and the crystal quality of the epitaxial layer is improved.
Referring to fig. 1 and 4, in step S3, an N-type AlGaN conductive layer 4 is grown on the buffer layer to provide electrons for the LED epitaxial structure, and TMGa, TMAl, and NH are introduced into the reaction chamber during the growth of the N-type AlGaN conductive layer3Providing Ga source, Al source and N source, and introducing Silane (SiH)4) As Si dopant, H is introduced2As a carrier gas. The temperature in the reaction chamber in the growth stage is 1080-1100 ℃, the pressure is 50-100 mbar, the flow rate of TMGa is 50-60sccm, the flow rate of TMAl is 120-140 sccm, and NH is added3The flow rate of the Al-doped N-type AlGaN conductive layer 4 is 2000-2500 sccm, the Al component content of the Si-doped N-type AlGaN conductive layer 4 grown at the stage is 50-55%, and the doping concentration of Si is 3E 18-1E 19cm-3The thickness is 1000 to 2500 nm.
Referring to fig. 1 and 4, in step S4, SiN is grown on the N-type AlGaN conductive layer 4x Mask layer 5, and for SiNxThe mask layer 5 is etched in situ, the temperature of the reaction chamber at the stage is 1080-1100 ℃, the pressure is 50-100 mbar, H is introduced2As carrier gas, NH is introduced3And SiH4Is a reaction gas of NH3The flow rate of (1) is 2000-2500 sccm, SiH4The flow rate of (1) is 200-250 sccm, SiNxThe thickness of the mask layer 5 is 3-5 nm; after the reaction is completed, SiH is stopped4By introducing, maintaining NH3And H2Continuously introducing for 3-5min, and passing through H2To SiNxThe mask layer 5 is etched in situ. Since the SiNx mask layer 5 is thin, the growth time is short, and SiNxThere are many defects, H, in the mask layer 52Etching on the position with more defects, and SiN with more defects along with the prolonging of the etching timexThe mask layer 5 is etched through to expose the underlying N-type AlGaN conductive layer 4.
Referring to FIGS. 1 and 4, in step S5, SiN is addedxAn N-type AlGaN repairing layer 6 grows on the mask layer 5, the lateral extension is mainly used when the N-type AlGaN repairing layer 6 grows, and the lateral extension is preferentially carried out on SiNxThe mask layer 5 is etched to expose the surface of the N-type AlGaN conductive layer 4 to grow, but is not etched throughSiNxThe mask layer 5 does not grow at the position shielded by SiN along with the increase of growth thicknessxThe part shielded by the mask layer 5 forms a cavity. In one embodiment, when the AlGaN repairing layer 6 is grown, the temperature of the reaction chamber is 1100 to 1120 ℃, and the pressure is 50 to 100 mbar; introduction of NH3The flow rate of (1) is 1000-1500 sccm, the flow rate of TMGa is 45-55 sccm, the flow rate of TMAl is 120-140 sccm, and SiH is introduced4As a Si dopant. The Al component content of the N-type AlGaN repairing layer 6 is 48-50%, and the doping concentration of Si is 1E 18-3E 18cm-3The thickness of the N-type AlGaN repairing layer 6 is 50-100 nm.
Referring to fig. 1 and 5, in step S6, Al is grown on the N-type AlGaN repair layer 6xGa1-xN/AlyGa1-yThe N multi-quantum well active layer 7 is Al grown alternatelyxGa1-xN quantum well layer and AlyGa1-yN quantum barrier layer of AlxGa1-xX in N is 0.37-0.38, AlyGa1-yY in N is 0.55-0.6, each layer of AlxGa1-xThe thickness of the N quantum well is 2-3 nm, and each layer of AlyGa1-yThe thickness of the N quantum barrier is 4-10 nm, and AlxGa1-xN quantum well layer and AlyGa1-yThe period of the alternate growth of the N quantum barrier layers is 3-10. Introducing TMGa, TMAl and NH into the reaction chamber in the growth stage3Providing Ga source, Al source and N source, and introducing H2And N2As a carrier gas, wherein H2And N2The flow ratio of (2) is 4: 1. The temperature of the reaction chamber in the growth stage is 1080-1100 ℃, the pressure is 50-100 mbar, and Al growsxGa1-xWhen the N quantum well layer is adopted, the TMGa flow is 20-24 sccm, and the TMAl flow is 22-25 sccm; growing AlyGa1-yGrowing Al with TMGa flow of 20-24 sccm and TMAl flow of 60-65 sccm in the case of N quantum barrier layeryGa1-ySiH is also required to be introduced when the N quantum barrier layer is formed4As Si dopant, AlyGa1-yThe doping concentration of Si in the N quantum barrier layer is 5E 17-6E 17cm-3。
Referring to FIGS. 1, 5 and 6, step S7 is performed on AlxGa1-xN/AlyGa1-yGrowing an AlGaN electron blocking layer 8 on the N multi-quantum well active layer 7, wherein the growth temperature of the AlGaN electron blocking layer 8 is 1050-1080 ℃, the pressure is 50-100 mbar, the flow rate of TMGa is 50-60sccm, and NH is added3The flow rate of the AlGaN electron blocking layer 8 is 2000-3000sccm, the flow rate of TMAl is gradually changed from 230-260 sccm to 130-150sccm from the beginning to the end of growth, the content of Al components in the AlGaN electron blocking layer 8 is reduced from 75-80% to 55-60% from the beginning to the end of growth, and the thickness of the AlGaN electron blocking layer 8 is 20-30 nm.
Referring to fig. 1 and 6, in step S8, a P-type AlGaN hole expansion layer 9, TMGa, TMAl, NH, is grown on the AlGaN electron blocking layer 83Providing Ga source, Al source and N source, introducing magnesium metallocene (Cp2Mg) as Mg dopant, and introducing H2As a carrier gas. The temperature of the reaction chamber in the growth stage is 1050-1080 ℃, the pressure is 50-100 mbar, the flow rate of TMGa is 60-65 slm, and the flow rate of TMAl is 150-200 slm. The content of Al component in the P-type AlGaN hole expanding layer 9 is 60-65%, the thickness of the layer is 30-50 nm, and the doping concentration of Mg is 1E 19-5E 19cm-3. The P-type AlGaN hole expansion layer 9 can improve the uniformity of P-pole hole injection, thereby improving the internal quantum efficiency.
Referring to fig. 1 and 6, in step S9, a P-type GaN conductive layer 10 is grown on the P-type AlGaN hole expansion layer 9 to provide holes for the LED epitaxial structure. In the growth stage, TMGa and NH are required to be introduced into the reaction chamber3Providing Ga source and N source, simultaneously introducing Cp2Mg serving as dopant, and introducing H2As a carrier gas. The growth temperature of the stage is 960-1000 ℃, the growth pressure is 200mbar, the flow of TMGa is 150-200 sccm, and NH is added3The flow rate of the catalyst is 20000 to 22000sccm, and the flow rate of Cp2Mg is 600 to 800 sccm. The doping concentration of Mg in the P-type GaN conductive layer 10 is 5E 19-1E 20cm-3The thickness of the P-type GaN conductive layer 10 is 100-300 nm. The growth stage is carried out at a lower temperature, and holes above the N-type AlGaN conducting layer can be filled, so that the P-type GaN conducting layer 10 can grow and be connected into a whole at the holes and the surface simultaneously.
Referring to fig. 3 to 6, the present invention further provides an LED epitaxial structure prepared by the above preparation method, including:
a substrate;
a buffer layer on the substrate;
the N-type AlGaN conducting layer 4 is positioned on the buffer layer;
the N-type AlGaN repairing layer 6 is positioned on the N-type AlGaN conducting layer 4;
AlxGa1-xN/AlyGa1-ythe N multi-quantum well active layer 7 is positioned on the N type AlGaN repairing layer 6, wherein x is 0.37-0.38, and y is 0.55-0.66;
AlGaN electron blocking layer 8 at AlxGa1-xN/AlyGa1-yN multiple quantum well active layer 7;
the P-type AlGaN hole expansion layer 9 is positioned on the AlGaN electron blocking layer 8;
the P-type GaN conducting layer 10 is positioned on the P-type AlGaN hole expanding layer 9;
and a hole is formed in the area, shielded by the SiNx mask layer 5, above the N-type AlGaN conducting layer 4.
Referring to fig. 6, in one embodiment, the substrate is a patterned sapphire substrate 1;
referring to fig. 3 and 6, in an embodiment, the buffer layer comprises an AlN buffer layer 2 on the patterned sapphire substrate 1 and an AlGaN buffer layer 3 on the AlN buffer layer 2, wherein the AlN buffer layer 2 comprises a first AlN layer 21, a second AlN layer 22 on the first AlN layer 21, and a third AlN layer 23 on the second AlN layer 22, the first AlN layer 21 has a thickness of 20 to 40nm, the second AlN layer 22 has a thickness of 400 to 600nm, and the third AlN layer 23 has a thickness of 1.5 to 3.5 μm; the Al component in the AlGaN buffer layer 3 is reduced to 60-65% from 80-85% from bottom to top, and the thickness of the AlGaN buffer layer 3 is 300-350 nm.
Referring to FIGS. 4 to 6, in an embodiment, the content of Al component in the N-type AlGaN conductive layer 4 is 50 to 55%, and the doping concentration of Si is 3E18 to 1E19cm-3The thickness of the N-type AlGaN conducting layer 4 is 1000-2500 nm. SiNxThe thickness of the mask layer 5 is 3 to 5 nm. The doping concentration of Si in the N-type AlGaN repairing layer 6 is 1E 18-3E 18cm-3The thickness of the N-type AlGaN repairing layer 6 is 50-100 nm.
Referring to fig. 5 and 6, in one embodiment,AlxGa1-xN/AlyGa1-yn multiple quantum well active layer 7 made of AlxGa1-xN quantum well layer and AlyGa1-yN quantum barrier layers alternately grown, each AlxGa1-xThe thickness of the N quantum well layer is 2-3 nm, and each Al layeryGa1-yThe thickness of the N quantum barrier layer is 4-10 nm, the growth period of the N quantum barrier layer and the growth period of the N quantum barrier layer are 3-10 nm, wherein AlyGa1-yThe N quantum barrier layer is Si-doped AlyGa1-yThe doping concentration of N and Si is 5E 17-6E 17cm-3。
Referring to fig. 6, in an embodiment, the content of the Al component in the AlGaN electron blocking layer 8 gradually changes from 75 to 80% to 55 to 60% from bottom to top, and the thickness of the AlGaN electron blocking layer 8 is 20 to 30 nm.
Referring to FIG. 6, in one embodiment, the content of Al component in the P-type AlGaN hole-expanding layer 9 is 60-65%, and the Mg doping concentration is 1E 19-5E 19cm-3The thickness of the P-type AlGaN hole expansion layer 9 is 30-50 nm.
Referring to FIG. 6, in an embodiment, the doping concentration of Mg in the P-type GaN conductive layer 10 is 5E 19-1E 20cm-3The thickness of the P-type GaN conductive layer 10 is 100-300 nm.
Referring to fig. 7 and 8, in the conventional LED epitaxial structure, holes in the P-type GaN conductive layer 10 are along AlxGa1-xN/AlyGa1-yThe N multi-quantum well active layers 7 move longitudinally, only a small number of holes move into the multi-quantum well active layer due to slow movement of the holes, and the number of electrons in the quantum well active layer is far larger than that of the holes, so that the recombination rate of the electron holes is low, and the luminous efficiency of the LED is low; in the LED epitaxial structure prepared by the preparation method, SiN is coated on the N-type AlGaN conducting layer 4xHoles are formed in the area shielded by the mask layer 5, and the holes in the P-type GaN conducting layer 10 can not only enter the active layer from the top, but also enter Al from the side through the holesxGa1-xN/AlyGa1-yThe N multi-quantum well active layers 7 are compounded with electrons in the active layers, so that the recombination rate of electron holes is greatly increased, and the luminous efficiency of the LED is improved.
In summary, the invention discloses a method for preparing an LED epitaxial structure, in which a layer of SiN is grown on an N-type AlGaN conductive layer during the preparation processxMask layer and to SiNxThe mask layer is subjected to in-situ etching to expose the lower N-type AlGaN conducting layer, and the N-type AlGaN conducting layer is subjected to SiN in the subsequent epitaxial growth processxHoles are formed in the area part shielded by the mask layer, and the holes are filled and connected into a whole by the P-type GaN conducting layer. The preparation method increases the diffusion space of the holes, enables more holes to enter the active layer to be compounded with electrons, improves the recombination rate of the electron holes, realizes the improvement of the internal quantum efficiency, and thus improves the luminous efficiency of the LED. Therefore, the invention effectively overcomes some practical problems in the prior art, thereby having high utilization value and use significance.
The foregoing embodiments are merely illustrative of the principles of this invention and its efficacy, rather than limiting it, and various modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the invention, which is defined in the appended claims.

Claims (10)

1. A preparation method of a light emitting diode epitaxial structure is characterized by comprising the following steps:
providing a substrate, and annealing the substrate;
growing a buffer layer on the substrate after the annealing treatment;
growing an N-type AlGaN conducting layer on the buffer layer;
growing a SiNx mask layer on the N-type AlGaN conducting layer, and carrying out in-situ etching on the SiNx mask layer to enable a partial area to be exposed out of the N-type AlGaN conducting layer;
the SiN after etchingxGrowing an N-type AlGaN repairing layer on the mask layer;
growing Al on the N-type AlGaN repairing layerxGa1-xN/AlyGa1-yN multiple quantum well active layers, wherein x is 0.37-0.38, and y is 0.55-0.60;
in the AlxGa1-xN/AlyGa1-yGrowing an AlGaN electron barrier layer on the N multi-quantum well active layer;
growing a P-type AlGaN hole expansion layer on the AlGaN electron blocking layer;
and growing a P-type gallium nitride conducting layer on the P-type AlGaN hole expansion layer.
2. The method of claim 1, wherein growing a buffer layer on the annealed substrate comprises:
growing an aluminum nitride buffer layer on the substrate after the annealing treatment;
growing an AlGaN buffer layer on the aluminum nitride buffer layer, wherein the thickness of the AlGaN buffer layer is 300-350 nanometers, and the Al component content of the AlGaN buffer layer is reduced from 80-85% to 60-65% from the beginning to the end of growth.
3. The method according to claim 1, wherein silane is used as a silicon dopant when growing the N-type AlGaN conductive layer on the buffer layer, wherein the doping concentration of silicon in the N-type AlGaN conductive layer is 3E 18-1E 19cm-3The content of the Al component in the N-type AlGaN conducting layer is 50-55%, and the thickness of the N-type AlGaN conducting layer is 1000-2500 nm.
4. The method according to claim 1, wherein a SiNx mask layer is grown on the N-type AlGaN conductive layer, and the SiN is applied to the SiN layerxThe mask layer is subjected to in-situ etching, and the in-situ etching comprises the following steps:
controlling the temperature to be 1080-1100 ℃ and the pressure to be 50-100 mbar;
introducing hydrogen as a carrier gas, and taking ammonia gas and silane as reaction gases, wherein the flow rate of the ammonia gas is 2000-2500 sccm, and the flow rate of the silane is 200-250 sccm; the SiN grownxThe thickness of the mask layer is 3-5 nanometers;
stopping introducing silane, keeping the flow of ammonia unchanged, continuously introducing for 3-5 minutes, and introducing the SiNxEtching mask layer in situ, said SiNxWith untight growth of mask layerAnd etching the region to expose the N-type AlGaN conducting layer.
5. The method according to claim 1, wherein the SiN is in a liquid crystal display devicexWhen an N-type AlGaN repairing layer grows on the mask layer, the N-type AlGaN repairing layer grows on the surface of the N-type AlGaN conducting layer etched on the SiNx mask layer after etching, and the N-type AlGaN repairing layer is etched on the SiNx mask layer by the SiNxForming a cavity at the position shielded by the mask layer; the content of Al in the N-type AlGaN repairing layer is 48-50%, and the doping amount of Si is 1E 18-3E 18cm-3(ii) a The thickness of the N-type AlGaN repairing layer is 50-100 nanometers.
6. The method according to claim 1, wherein Al is grown on the N-type AlGaN repair layerxGa1- xN/AlyGa1-yThe N multi-quantum well active layer is Al alternately grownxGa1-xN quantum well layer and AlyGa1-yN quantum barrier layer of AlxGa1-xThe thickness of the N quantum well layer is 2-3 nanometers, and Al isyGa1-yThe thickness of the N quantum barrier layer is 4-10 nanometers, and the growth cycle of the multiple quantum well is 3-10; growing the AlyGa1-yIntroducing silane as a dopant in the process of the N quantum barrier layer, wherein the Al isyGa1-yThe doping concentration of silicon in the N quantum barrier layer is 5E 17-6E 17cm-3。
7. The method according to claim 1, wherein Al is present in the alloyxGa1-xN/AlyGa1-yThe content of Al components in the AlGaN electron blocking layer grown on the N multi-quantum well active layer is reduced to 55-60% from 75-80% from the beginning to the end of growth, and the thickness of the AlGaN electron blocking layer is 20-30 nanometers.
8. The method according to claim 1, wherein a magnesium dopant is a magnesium dopant when growing the P-type AlGaN hole-expanding layer on the AlGaN electron-blocking layer, wherein the P-type AlGaN hole is formed in the P-type AlGaN hole-expanding layerThe doping concentration of magnesium in the hole-expanding layer is 1E 19-5E 19cm-3The content of Al components in the P-type AlGaN hole expansion layer is 60-65%, and the thickness of the P-type AlGaN hole expansion layer is 30-50 nanometers.
9. The method of claim 1, wherein growing a P-type gallium nitride conductive layer on the P-type AlGaN hole expanding layer comprises: controlling the growth temperature to be 960-1000 ℃ and the growth pressure to be 200 mbar;
introducing trimethyl gallium and ammonia gas to provide a gallium source and a nitrogen source, and introducing magnesium diclocide as a magnesium dopant, wherein the flow rate of trimethyl gallium is 150-200 sccm, the flow rate of ammonia gas is 20000-22000 sccm, and the flow rate of magnesium diclocide is 600-800 sccm;
the doping concentration of magnesium in the P-type gallium nitride conducting layer is 5E 19-1E 20cm-3The thickness of the P-type gallium nitride conducting layer is 100-300 nanometers.
10. An epitaxial structure of a light emitting diode prepared according to the preparation method of any one of claims 1 to 9.
CN202011363610.XA 2020-11-27 2020-11-27 Epitaxial structure of light emitting diode and preparation method thereof Pending CN112331748A (en)

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