CN105742416A - Preparation method for gallium nitride based LED epitaxial wafer with high light emitting efficiency - Google Patents

Preparation method for gallium nitride based LED epitaxial wafer with high light emitting efficiency Download PDF

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CN105742416A
CN105742416A CN201610132463.2A CN201610132463A CN105742416A CN 105742416 A CN105742416 A CN 105742416A CN 201610132463 A CN201610132463 A CN 201610132463A CN 105742416 A CN105742416 A CN 105742416A
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CN105742416B (en
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卢太平
朱亚丹
赵广洲
许并社
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Taiyuan University of Technology
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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
    • H01L33/20—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 particular shape, e.g. curved or truncated substrate
    • H01L33/22—Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

The invention belongs to the field of a photoelectronic device, and specifically relates to a preparation method for a gallium nitride based LED epitaxial wafer with high light emitting efficiency. The structure prepared by the method comprises a low-temperature GaN core-forming layer, a hollow-out-structured GaN rough layer, a non-doped GaN layer, an N type GaN layer, a multi-quantum-well active layer, an electron barrier layer and a P type GaN layer which are stacked in sequence, wherein the step of enabling the hollow-out-structured GaN rough layer to grow comprises the steps of enabling a first 3D-strucured GaN layer to grow firstly, then enabling the first 3D-strucured GaN layer to be processed at a high temperature by an H2 gas, then enabling a second 3D-strucured GaN layer to grow, finally enabling a rapid combination layer of the 3D-strucured GaN layers to grow, and enabling holes which are distributed in a relative uniform manner to be generated in the combination process between islands. According to the preparation method, the 3D-strucured GaN layers are processed by the H2, so that the obtained GaN island-shaped structure is more uniform in dimensional and space distribution, and the holes generated in the combination process of the 3D-strucured GaN layers are distributed more uniformly; and in addition, due to the hollow-out-structured GaN rough layer, the total internal reflection can be reduced, and the light extraction efficiency of the GaN based LED is improved.

Description

A kind of preparation method of high-luminous-efficiency GaN-based LED epitaxial wafer
Technical field
The invention belongs to field of optoelectronic devices, the preparation method being specifically related to a kind of high-luminous-efficiency GaN-based LED epitaxial wafer.
Background technology
Gallium nitride based light emitting diode (LightEmittingDiode, LED) there is the features such as high brightness, low energy consumption, long-life, fast response time and environmental protection, be widely used in multiple fields such as indoor and street lighting, traffic signal and outdoor display, automobile lamp illumination, liquid crystal backlight.Therefore, large power white light LED is considered as the lighting source of 21 century.
In order to obtain the LED of high brightness, it is critical to improve internal quantum efficiency and the external quantum efficiency of device.The LED internal quantum efficiency of current blue light GaN base is up to more than 80%, but the external quantum efficiency of high-power LED chip generally only has about 40%.The light extraction efficiency that the principal element that restriction external quantum efficiency improves is chip is relatively low, this is because the refractive index of GaN material (n=2.5) differs bigger with the refractive index (n=1.75) of the refractive index of air (n=1) and Sapphire Substrate, causing that air and GaN interface and sapphire and GaN interface occur the critical angle of total reflection to only have 23.6 ° and 44.4 ° respectively, the light that active area produces only has minority can escape out body material.In order to improve the light extraction efficiency of chip, the main technical schemes adopted both at home and abroad at present has growth distribution bragg reflection layer (DBR) structure, patterned substrate (PSS) technology, surface texture technology and photonic crystal technology etc..The rule degree of figure is required significantly high by PSS, in addition Sapphire Substrate is harder, no matter is dry etching or wet-etching technology, has certain difficulty in the concordance and uniformity of full wafer figure, and manufacturing process is significantly high to equipment and technological requirement, causes high expensive.DBR and photonic crystal processing technology relative complex, relatively costly, and surface texture technology adopts dry etching or wet corrosion technique, there is also very big challenge.
Summary of the invention
Present invention aims to the drawbacks described above existed in prior art, it is provided that the preparation method of a kind of high-luminous-efficiency GaN-based LED epitaxial wafer, and the method is simple, preparation cost is relatively low.
The present invention adopts the following technical scheme that realization: the preparation method of a kind of high-luminous-efficiency GaN-based LED epitaxial wafer, comprises the following steps:
Step one: Sapphire Substrate is cleaned substrate surface in reaction chamber atmosphere of hydrogen, and reaction cavity temperature is 1060-1100 DEG C, and the time is 5min-10min；
Step 2: reaction chamber temperature is reduced to 520-550 DEG C, then at clean Grown on Sapphire Substrates low temperature GaN nucleating layer, nucleating layer thickness is 20-40nm, and growth pressure is 400-700Torr；
Step 3: reaction chamber temperature is increased to 950-1000 DEG C, and stablizes 2min, carries out the high annealing of GaN nucleating layer, passes into NH in this process3Gas decomposes completely preventing GaN nucleating layer.Then passing to metal organic source TMGa, start to grow the GaN layer of a 3D structure on GaN nucleating layer surface, growth thickness is 200-300nm, and growth pressure is 400-700Torr, and the GaN layer of a 3D structure includes little GaN island and great GaN island；
Step 4: reaction chamber temperature is increased to 1030-1110 DEG C, passes into NH in temperature-rise period3Gas, to prevent the GaN layer of a 3D structure from decomposing, heats up and closes NH after terminating3Passing into of gas, and only pass into H2The GaN of 3D structure is carried out processing 5-10min, in the process H by gas2The GaN layer of the oneth 3D structure can be performed etching by gas, little GaN island can be etched away, great GaN island then remains, little GaN island and great GaN island do not have clear and definite size to define, simply in etching process, size little GaN island is easily etched away, therefore the GaN island being etched away is little GaN island, the Wei great GaN island, GaN island remained；
Step 5: reaction chamber temperature is reduced to 950-1000 DEG C, passes into NH3Gas and metal organic source TMGa, at H2The GaN layer 500-1000nm of continued growth the 2nd 3D structure in the GaN layer of the 3D structure after gas treatment, growth pressure is 400-700Torr, obtains the 3D structure GaN layer expanded；
Step 6: reaction chamber temperature is increased to 1050-1200 DEG C, the GaN layer of the 3D structure expanded mushrooms out unadulterated GaN, 3D island structure is healed rapidly, and ultimately form interior void than the more uniform and GaN rough layer of engraved structure that surface is smooth, growth thickness is 1 ~ 2um, and growth pressure is 50-300Torr；
Step 7: grow the GaN layer of involuntary doping, thickness is 1 ~ 2um, and growth temperature is 1050-1200 DEG C, and growth pressure is 50-300Torr；
Step 8: the GaN layer of growth Si doping, this layer of carrier concentration is 1018-1019cm-3, thickness is 1-3um, and growth temperature is 1050-1200 DEG C, and growth pressure is 50-300Torr；
Step 9: the multiple quantum well active layer in 3-6 cycle of growth, wherein barrier layer is GaN, well layer is InGaN, In component is calculated as 10-30% with mass fraction, well layer thickness is 2-5nm, and temperature is 700-800 DEG C, and barrier layer thickness is 8-13nm, growth temperature is 800-950 DEG C, and in growth course, pressure is 200-500Torr；
Step 10: the p-AlGaN electronic barrier layer that growth 20-50nm is thick, in this layer, Al component is calculated as 10-20% with mass fraction, and hole concentration is 1017-1018cm-3, growth temperature is 850 DEG C-1000 DEG C, and pressure is 50-300Torr；
Step 11: the GaN layer of growth Mg doping, thickness is 100-300nm, and growth temperature is 850-1000 DEG C, and growth pressure is 100-500Torr, and hole concentration is 1017-1018cm-3；
Step 12: after epitaxial growth terminates, is down to 650-800 DEG C by the temperature of reaction chamber, is annealed processing 5-15min, is then down to room temperature, terminate growth, obtain epitaxial wafer in nitrogen atmosphere.
Epitaxial process of the present invention all carries out in the MOCVD reaction chamber of metal organic chemical vapor deposition technique (MOCVD), LED epitaxial structure order from bottom to top includes Sapphire Substrate, low temperature GaN nucleating layer, the GaN rough layer of engraved structure, undoped GaN layer, N-type GaN layer, multiple quantum well active layer, electronic barrier layer and P type GaN layer successively, with trimethyl gallium (TMGa), triethyl-gallium (TEGa), trimethyl aluminium (TMAl), trimethyl indium (TMIn) and ammonia (NH in epitaxial process of the present invention3) respectively Ga, Al, In and N source, silane (SiH4) and two luxuriant magnesium (CP2Mg) for N, P-type dopant.
The present invention passes through process above, and growth interior void is than more uniform and that surface is smooth engraved structure GaN rough layer on a sapphire substrate, and the GaN rough layer of this engraved structure can reduce total internal reflection, is conducive to improving the light extraction efficiency of GaN base LED.Additionally adopt the GaN3D structure growth technique of two steps, contribute to changing the direction of growth of dislocation so that the dislocation density of active area reduces, improve the crystal mass of epitaxial wafer.
Accompanying drawing explanation
Fig. 1 is the flow chart of prior art growth epitaxial wafer, and it stacks gradually growing low temperature GaN nucleating layer, undoped GaN, N-type GaN, multiple quantum well active layer, electronic barrier layer, P type GaN layer on a sapphire substrate.
Fig. 2 is the flow chart that the present invention grows epitaxial wafer, its stack gradually on a sapphire substrate growing low temperature GaN nucleating layer, the GaN layer of a 3D structure, the GaN layer of the 2nd 3D structure, 3D structure GaN layer quickly merge layer, undoped GaN, N-type GaN, multiple quantum well active layer, electronic barrier layer, P type GaN layer.
Fig. 3 is the schematic diagram on epitaxial wafer after the GaN layer of growth the oneth 3D structure.
Fig. 4 is H2Schematic diagram after the GaN layer of high-temperature process the oneth 3D structure.
Fig. 5 is the schematic diagram after the GaN layer of growth the 2nd 3D structure.
Fig. 6 is the empty schematic diagram being internally formed after the GaN layer of 3D structure quickly merges.
Fig. 7 is the figure of the LED chip optical output power profiles versus made by epitaxial wafer of the epitaxial wafer being respectively adopted method provided by the invention growth and commonsense method growth.
Detailed description of the invention
Embodiment one:
The preparation method of a kind of high-luminous-efficiency GaN-based LED epitaxial wafer, comprises the following steps:
Step one: Sapphire Substrate is cleaned substrate surface in MOCVD reaction chamber atmosphere of hydrogen, and reaction cavity temperature is 1060 DEG C, and the time is 10min；
Step 2: reaction chamber temperature is reduced to 520 DEG C, then at clean Grown on Sapphire Substrates low temperature GaN nucleating layer, nucleating layer thickness is 20nm, and growth pressure is 400Torr；
Step 3: reaction chamber temperature is increased to 950 DEG C, passes into NH in temperature-rise period3Gas decomposes completely preventing GaN nucleating layer, then passing to metal organic source TMGa, start to grow the GaN layer of a 3D structure on GaN nucleating layer surface, growth thickness is 200nm, growth pressure is 400Torr, and the GaN layer of a 3D structure includes little GaN island and great GaN island；
Step 4: reaction chamber temperature is increased to 1030 DEG C, passes into NH in temperature-rise period3Gas, to prevent the GaN layer of a 3D structure from decomposing, heats up and closes NH after terminating3Passing into of gas, and only pass into H2The GaN layer of the oneth 3D structure is carried out processing 10min, in the process H by gas2The GaN layer of 3D structure can be performed etching by gas, and the GaN island that the GaN layer of a 3D structure is medium and small can be etched away, and great GaN island then remains；
Step 5: reaction chamber temperature is reduced to 950 DEG C, passes into NH3Gas and metal organic source TMGa, at H2The GaN layer 500nm of continued growth the 2nd 3D structure in the GaN layer of the 3D structure after gas treatment, growth pressure is 400Torr, obtains the 3D structure GaN layer expanded；
Step 6: reaction chamber temperature is increased to 1050 DEG C, the GaN layer of the 3D structure expanded mushrooms out unadulterated GaN, 3D island structure is healed rapidly, and ultimately form interior void than the more uniform and GaN rough layer of engraved structure that surface is smooth, growth thickness is 1um, and growth pressure is 50Torr；
Step 7: grow the GaN layer of involuntary doping, thickness is 1um, and growth temperature is 1050 DEG C, and growth pressure is 50Torr；
Step 8: the GaN layer of growth Si doping, this layer of carrier concentration is 1018cm-3, thickness is 1um, and growth temperature is 1050 DEG C, and growth pressure is 50Torr；
Step 9: the multiple quantum well active layer in 3 cycles of growth, wherein barrier layer is GaN, and well layer is InGaN, In component is calculated as 30% with mass fraction, and well layer thickness is 2nm, and growth temperature is 700 DEG C, barrier layer thickness is 8nm, and growth temperature is 800 DEG C, and in growth course, pressure is 200Torr；
Step 10: the p-AlGaN electronic barrier layer that growth 20nm is thick, in this layer, Al component is calculated as 10% with mass fraction, and hole concentration is 1017cm-3, growth temperature is 850 DEG C, and pressure is 50Torr；
Step 11: the GaN layer of growth Mg doping, thickness is 100nm, and growth temperature is 850 DEG C, and growth pressure is 100Torr, and hole concentration is 1017cm-3；
Step 12: after epitaxial growth terminates, is down to 650 DEG C by the temperature of reaction chamber, is annealed processing 15min in nitrogen atmosphere, then room temperature it is down to, terminating growth, obtain epitaxial wafer, epitaxial wafer makes single small-size chips after cleaning, deposition, photoetching and etching.
Embodiment two:
The preparation method of a kind of high-luminous-efficiency GaN-based LED epitaxial wafer, comprises the following steps:
Step one: Sapphire Substrate is cleaned substrate surface in MOCVD reaction chamber atmosphere of hydrogen, and reaction cavity temperature is 1100 DEG C, and the time is 5min；
Step 2: reaction chamber temperature is reduced to 550 DEG C, then at clean Grown on Sapphire Substrates low temperature GaN nucleating layer, nucleating layer thickness is 40nm, and growth pressure is 700Torr；
Step 3: reaction chamber temperature is increased to 1000 DEG C, passes into NH in temperature-rise period3Gas decomposes completely preventing GaN nucleating layer, then passing to metal organic source TMGa, start to grow the GaN layer of a 3D structure on GaN nucleating layer surface, growth thickness is 300nm, growth pressure is 700Torr, and the GaN layer of a 3D structure includes little GaN island and great GaN island；
Step 4: reaction chamber temperature is increased to 1050 DEG C, passes into NH in temperature-rise period3Gas, to prevent the GaN layer of a 3D structure from decomposing, heats up and closes NH after terminating3Passing into of gas, and only pass into H2The GaN layer of the oneth 3D structure is carried out processing 9min, in the process H by gas2The GaN layer of 3D structure can be performed etching by gas, and the GaN island that the GaN layer of a 3D structure is medium and small can be etched away, and great GaN island then remains；
Step 5: reaction chamber temperature is reduced to 1000 DEG C, passes into NH3Gas and metal organic source TMGa, at H2The GaN layer 1000nm of continued growth the 2nd 3D structure in the GaN layer of the 3D structure after gas treatment, growth pressure is 700Torr, obtains the 3D structure GaN layer expanded；
Step 6: reaction chamber temperature is increased to 1200 DEG C, the GaN layer of the 3D structure expanded mushrooms out unadulterated GaN, 3D island structure is healed rapidly, and ultimately form interior void than the more uniform and GaN rough layer of engraved structure that surface is smooth, growth thickness is 2um, and growth pressure is 300Torr；
Step 7: grow the GaN layer of involuntary doping, thickness is 2um, and growth temperature is 1200 DEG C, and growth pressure is 300Torr；
Step 8: the GaN layer of growth Si doping, this layer of carrier concentration is 1019cm-3, thickness is 3um, and growth temperature is 1200 DEG C, and growth pressure is 300Torr；
Step 9: the multiple quantum well active layer in 4 cycles of growth, wherein barrier layer is GaN, and well layer is InGaN, In component is calculated as 10% with mass fraction, and well layer thickness is 5nm, and growth temperature is 800 DEG C, barrier layer thickness is 13nm, and growth temperature is 950 DEG C, and in growth course, pressure is 500Torr；
Step 10: the p-AlGaN electronic barrier layer that growth 50nm is thick, in this layer, Al component is calculated as 20% with mass fraction, and hole concentration is 1018cm-3, growth temperature is 1000 DEG C, and pressure is 300Torr；
Step 11: the GaN layer of growth Mg doping, thickness is 300nm, and growth temperature is 1000 DEG C, and growth pressure is 500Torr, and hole concentration is 1018cm-3；
Step 12: after epitaxial growth terminates, is down to 800 DEG C by the temperature of reaction chamber, is annealed processing 5min in nitrogen atmosphere, then room temperature it is down to, terminating growth, obtain epitaxial wafer, epitaxial wafer makes single small-size chips after cleaning, deposition, photoetching and etching.
Embodiment three:
The preparation method of a kind of high-luminous-efficiency GaN-based LED epitaxial wafer, comprises the following steps:
Step one: Sapphire Substrate is cleaned substrate surface in MOCVD reaction chamber atmosphere of hydrogen, and reaction cavity temperature is 1080 DEG C, and the time is 7min；
Step 2: reaction chamber temperature is reduced to 530 DEG C, then at clean Grown on Sapphire Substrates low temperature GaN nucleating layer, nucleating layer thickness is 30nm, and growth pressure is 500Torr；
Step 3: reaction chamber temperature is increased to 960 DEG C, passes into NH in temperature-rise period3Gas decomposes completely preventing GaN nucleating layer, then passing to metal organic source TMGa, start to grow the GaN layer of a 3D structure on GaN nucleating layer surface, growth thickness is 220nm, growth pressure is 500Torr, and the GaN layer of a 3D structure includes little GaN island and great GaN island；
Step 4: reaction chamber temperature is increased to 1070 DEG C, passes into NH in temperature-rise period3Gas, to prevent the GaN layer of a 3D structure from decomposing, heats up and closes NH after terminating3Passing into of gas, and only pass into H2The GaN layer of the oneth 3D structure is carried out processing 9min, in the process H by gas2The GaN layer of 3D structure can be performed etching by gas, and the GaN island that the GaN layer of a 3D structure is medium and small can be etched away, and great GaN island then remains；
Step 5: reaction chamber temperature is reduced to 960 DEG C, passes into NH3Gas and metal organic source TMGa, at H2The GaN layer 700nm of continued growth 3D structure in the GaN layer of the 3D structure after gas treatment, growth pressure is 500Torr, obtains the 3D structure GaN layer expanded；
Step 6: reaction chamber temperature is increased to 1100 DEG C, the GaN layer of the 3D structure expanded mushrooms out unadulterated GaN, 3D island structure is healed rapidly, and ultimately form interior void than the more uniform and GaN rough layer of engraved structure that surface is smooth, growth thickness is 1.2um, and growth pressure is 120Torr；
Step 7: grow the GaN layer of involuntary doping, thickness is 1.2um, and growth temperature is 1100 DEG C, and growth pressure is 120Torr；
Step 8: the GaN layer of growth Si doping, this layer of carrier concentration is 3 × 1018cm-3, thickness is 2um, and growth temperature is 1100 DEG C, and growth pressure is 120Torr；
Step 9: the multiple quantum well active layer in 5 cycles of growth, wherein barrier layer is GaN, and well layer is InGaN, In component is calculated as 25% with mass fraction, and well layer thickness is 3nm, and growth temperature is 730 DEG C, barrier layer thickness is 10nm, and growth temperature is 850 DEG C, and in growth course, pressure is 300Torr；
Step 10: the p-AlGaN electronic barrier layer that growth 30nm is thick, in this layer, Al component is calculated as 12% with mass fraction, and hole concentration is 2 × 1017cm-3, growth temperature is 930 DEG C, and pressure is 120Torr；
Step 11: the GaN layer of growth Mg doping, thickness is 200nm, and growth temperature is 930 DEG C, and growth pressure is 400Torr, and hole concentration is 3 × 1017cm-3；
Step 12: after epitaxial growth terminates, is down to 700 DEG C by the temperature of reaction chamber, is annealed processing 12min in nitrogen atmosphere, then room temperature it is down to, terminating growth, obtain epitaxial wafer, epitaxial wafer makes single small-size chips after cleaning, deposition, photoetching and etching.
Embodiment four:
The preparation method of a kind of high-luminous-efficiency GaN-based LED epitaxial wafer, comprises the following steps:
Step one: Sapphire Substrate is cleaned substrate surface in MOCVD reaction chamber atmosphere of hydrogen, and reaction cavity temperature is 1070 DEG C, and the time is 8min；
Step 2: reaction chamber temperature is reduced to 540 DEG C, then at clean Grown on Sapphire Substrates low temperature GaN nucleating layer, nucleating layer thickness is 25nm, and growth pressure is 600Torr；
Step 3: reaction chamber temperature is increased to 970 DEG C, passes into NH in temperature-rise period3Gas decomposes completely preventing GaN nucleating layer, then passing to metal organic source TMGa, start to grow the GaN layer of a 3D structure on GaN nucleating layer surface, growth thickness is 240nm, growth pressure is 600Torr, and the GaN layer of a 3D structure includes little GaN island and great GaN island；
Step 4: reaction chamber temperature is increased to 1090 DEG C, passes into NH in temperature-rise period3Gas, to prevent the GaN layer of a 3D structure from decomposing, heats up and closes NH after terminating3Passing into of gas, and only pass into H2The GaN layer of the oneth 3D structure is carried out processing 7min, in the process H by gas2The GaN layer of 3D structure can be performed etching by gas, and the GaN island that the GaN layer of a 3D structure is medium and small can be etched away, and great GaN island then remains；
Step 5: reaction chamber temperature is reduced to 970 DEG C, passes into NH3Gas and metal organic source TMGa, at H2The GaN layer 800nm of continued growth the 2nd 3D structure in the GaN layer of the 3D structure after gas treatment, growth pressure is 600Torr, obtains the 3D structure GaN layer expanded；
Step 6: reaction chamber temperature is increased to 1150 DEG C, the GaN layer of the 3D structure expanded mushrooms out unadulterated GaN, 3D island structure is healed rapidly, and ultimately form interior void than the more uniform and GaN rough layer of engraved structure that surface is smooth, growth thickness is 1.4um, and growth pressure is 190Torr；
Step 7: grow the GaN layer of involuntary doping, thickness is 1.4um, and growth temperature is 1150 DEG C, and growth pressure is 190Torr；
Step 8: the GaN layer of growth Si doping, this layer of carrier concentration is 5 × 1018cm-3, thickness is 1.5um, and growth temperature is 1150 DEG C, and growth pressure is 190Torr；
Step 9: the multiple quantum well active layer in 6 cycles of growth, wherein barrier layer is GaN, and well layer is InGaN, In component is calculated as 15% with mass fraction, and well layer thickness is 4nm, and growth temperature is 780 DEG C, barrier layer thickness is 9nm, and growth temperature is 920 DEG C, and in growth course, pressure is 450Torr；
Step 10: the p-AlGaN electronic barrier layer that growth 40nm is thick, in this layer, Al component is calculated as 14% with mass fraction, and hole concentration is 5 × 1017cm-3, growth temperature is 970 DEG C, and pressure is 190Torr；
Step 11: the GaN layer of growth Mg doping, thickness is 260nm, and growth temperature is 970 DEG C, and growth pressure is 300Torr, and hole concentration is 8 × 1017cm-3；
Step 12: after epitaxial growth terminates, is down to 780 DEG C by the temperature of reaction chamber, is annealed processing 7min in nitrogen atmosphere, then room temperature it is down to, terminating growth, obtain epitaxial wafer, epitaxial wafer makes single small-size chips after cleaning, deposition, photoetching and etching.
Embodiment five:
The preparation method of a kind of high-luminous-efficiency GaN-based LED epitaxial wafer, comprises the following steps:
Step one: Sapphire Substrate is cleaned substrate surface in MOCVD reaction chamber atmosphere of hydrogen, and reaction cavity temperature is 1090 DEG C, and the time is 6min；
Step 2: reaction chamber temperature is reduced to 545 DEG C, then at clean Grown on Sapphire Substrates low temperature GaN nucleating layer, nucleating layer thickness is 35nm, and growth pressure is 650Torr；
Step 3: reaction chamber temperature is increased to 980 DEG C, passes into NH in temperature-rise period3Gas decomposes completely preventing GaN nucleating layer, then passing to metal organic source TMGa, start to grow the GaN layer of a 3D structure on GaN nucleating layer surface, growth thickness is 260nm, growth pressure is 550Torr, and the GaN layer of a 3D structure includes little GaN island and great GaN island；
Step 4: reaction chamber temperature is increased to 1110 DEG C, passes into NH in temperature-rise period3Gas, to prevent the GaN layer of a 3D structure from decomposing, heats up and closes NH after terminating3Passing into of gas, and only pass into H2The GaN layer of the oneth 3D structure is carried out processing 5min, in the process H by gas2The GaN layer of 3D structure can be performed etching by gas, and the GaN island that the GaN layer of a 3D structure is medium and small can be etched away, and great GaN island then remains；
Step 5: reaction chamber temperature is reduced to 980 DEG C, passes into NH3Gas and metal organic source TMGa, at H2The GaN layer 1000nm of continued growth the 2nd 3D structure in the GaN layer of the 3D structure after gas treatment, growth pressure is 650Torr, obtains the 3D structure GaN layer expanded；
Step 6: reaction chamber temperature is increased to 1080 DEG C, the GaN layer of the 3D structure expanded mushrooms out unadulterated GaN, 3D island structure is healed rapidly, and ultimately form interior void than the more uniform and GaN rough layer of engraved structure that surface is smooth, growth thickness is 1.6um, and growth pressure is 260Torr；
Step 7: grow the GaN layer of involuntary doping, thickness is 1.6um, and growth temperature is 1080 DEG C, and growth pressure is 260Torr；
Step 8: the GaN layer of growth Si doping, this layer of carrier concentration is 7 × 1018cm-3, thickness is 2.5um, and growth temperature is 1080 DEG C, and growth pressure is 260Torr；
Step 9: the multiple quantum well active layer in 5 cycles of growth, wherein barrier layer is GaN, and well layer is InGaN, In component is calculated as 20% with mass fraction, and well layer thickness is 3nm, and growth temperature is 760 DEG C, barrier layer thickness is 12nm, and growth temperature is 890 DEG C, and in growth course, pressure is 400Torr；
Step 10: the p-AlGaN electronic barrier layer that growth 30nm is thick, in this layer, Al component is calculated as 16% with mass fraction, and hole concentration is 3 × 1017cm-3, growth temperature is 950 DEG C, and pressure is 260Torr；
Step 11: the GaN layer of growth Mg doping, thickness is 220nm, and growth temperature is 950 DEG C, and growth pressure is 200Torr, and hole concentration is 5 × 1017cm-3；
Step 12: after epitaxial growth terminates, is down to 750 DEG C by the temperature of reaction chamber, is annealed processing 10min in nitrogen atmosphere, then room temperature it is down to, terminating growth, obtain epitaxial wafer, epitaxial wafer makes single small-size chips after cleaning, deposition, photoetching and etching.
Fig. 3-Fig. 6 is what the present invention grew engraved structure GaN rough layer process schematic, and wherein Fig. 3 is the schematic diagram after the GaN layer growing a 3D structure on epitaxial wafer, and the size on GaN island and distribution are all uneven as shown in Figure 3；Fig. 4 is H2Schematic diagram after the GaN layer of high-temperature process the oneth 3D structure, little GaN island is by H as shown in Figure 42Etching away, the quantity on island tails off, and size is evenly；Fig. 5 is the schematic diagram after the GaN layer of growth the 2nd 3D structure, and during GaN growth, preferred growth has the position on GaN island, other position poor growths, eventually forms larger-size, size and the comparatively uniform GaN three-dimensional island structure of distribution.Fig. 6 is the empty schematic diagram being internally formed after the GaN layer of 3D structure quickly merges.This interior void is than more uniform and that surface is smooth engraved structure GaN rough layer, it is possible to reduces total internal reflection, is conducive to improving the light extraction efficiency of GaN base LED.Additionally adopt the GaN3D structure growth technique of two steps, contribute to changing the direction of growth of dislocation so that the dislocation density of active area reduces, improve the crystal mass of epitaxial wafer.
Fig. 7 is the figure of the LED chip optical output power profiles versus made by epitaxial wafer of the epitaxial wafer being respectively adopted method provided by the invention growth and commonsense method growth.Test condition for randomly selecting 180 samples, chip size 8x10mil, test electric current 20mA.The chip optical output power average adopting traditional method is 18.1mW, and adopt the present invention to provide the chip optical output power average of method to be 22.9mW, namely adopt the LED chip optical output power that the chip optical output power that method provided by the invention grows is formed than commonsense method to improve about 26.5%.

Claims (1)

1. the preparation method of a high-luminous-efficiency GaN-based LED epitaxial wafer, it is characterised in that comprise the following steps:
Step one: Sapphire Substrate carries out substrate surface cleaning in reaction chamber atmosphere of hydrogen, and reaction cavity temperature is 1060-1100 DEG C, and the time is 5min-10min；
Step 2: reaction chamber temperature is reduced to 520-550 DEG C, then at clean Grown on Sapphire Substrates low temperature GaN nucleating layer, nucleating layer thickness is 20-40nm, and growth pressure is 400-700Torr；
Step 3: reaction chamber temperature is increased to 950-1000 DEG C, and stablizes 2min, carries out the high annealing of GaN nucleating layer, passes into NH in this process3Gas decomposes completely preventing GaN nucleating layer, then passing to metal organic source TMGa, start to grow the GaN layer of a 3D structure on GaN nucleating layer surface, growth thickness is 200-300nm, growth pressure is 400-700Torr, and the GaN layer of a 3D structure includes little GaN island and great GaN island；
Step 4: reaction chamber temperature is increased to 1030-1110 DEG C, passes into NH in temperature-rise period3Gas, to prevent the GaN layer of a 3D structure from decomposing, heats up and closes NH after terminating3Passing into of gas, and only pass into H2The GaN layer of the oneth 3D structure is carried out processing 5-10min, in the process H by gas2The GaN layer of 3D structure can be performed etching by gas, and the GaN island that the GaN layer of a 3D structure is medium and small can be etched away, and great GaN island then remains；
Step 5: reaction chamber temperature is reduced to 950-1000 DEG C, passes into NH3Gas and metal organic source TMGa, at H2The GaN layer 500-1000nm of continued growth the 2nd 3D structure in the GaN layer of the 3D structure after gas treatment, growth pressure is 400-700Torr, obtains the 3D structure GaN layer expanded；
Step 6: reaction chamber temperature is increased to 1050-1200 DEG C, the GaN layer of the 3D structure expanded mushrooms out unadulterated GaN, 3D island structure is healed rapidly, and ultimately form interior void than the more uniform and GaN rough layer of engraved structure that surface is smooth, growth thickness is 1 ~ 2um, and growth pressure is 50-300Torr；
Step 7: grow the GaN layer of involuntary doping, thickness is 1 ~ 2um, and growth temperature is 1050-1200 DEG C, and growth pressure is 50-300Torr；
Step 8: the GaN layer of growth Si doping, this layer of carrier concentration is 1018-1019cm-3, thickness is 1-3um, and growth temperature is 1050-1200 DEG C, and growth pressure is 50-300Torr；
Step 9: the multiple quantum well active layer in 3-6 cycle of growth, wherein barrier layer is GaN, well layer is InGaN, In component is calculated as 10-30% with mass fraction, well layer thickness is 2-5nm, and growth temperature is 700-800 DEG C, and barrier layer thickness is 8-13nm, growth temperature is 800-950 DEG C, and in growth course, pressure is 200-500Torr；
Step 10: the p-AlGaN electronic barrier layer that growth 20-50nm is thick, in this layer, Al component is calculated as 10-20% with mass fraction, and hole concentration is 1017-1018cm-3, growth temperature is 850 DEG C-1000 DEG C, and pressure is 50-300Torr,；
Step 11: the GaN layer of growth Mg doping, thickness is 100-300nm, and growth temperature is 850-1000 DEG C, and growth pressure is 100-500Torr, and hole concentration is 1017-1018cm-3；
Step 12: after epitaxial growth terminates, is down to 650-800 DEG C by the temperature of reaction chamber, is annealed processing 5-15min, is then down to room temperature, terminate growth, obtain epitaxial wafer in nitrogen atmosphere.
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