CN105870269B - Improve the LED epitaxial growing method of hole injection - Google Patents

Improve the LED epitaxial growing method of hole injection Download PDF

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CN105870269B
CN105870269B CN201610355656.4A CN201610355656A CN105870269B CN 105870269 B CN105870269 B CN 105870269B CN 201610355656 A CN201610355656 A CN 201610355656A CN 105870269 B CN105870269 B CN 105870269B
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CN105870269A (en
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林传强
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Xiangneng Hualei Optoelectrical Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
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    • 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
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    • H01L33/00—Semiconductor devices having potential barriers 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 having potential barriers 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 having potential barriers 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 having potential barriers 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 having potential barriers 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 having potential barriers 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
    • H01L33/12—Semiconductor devices having potential barriers 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 stress relaxation structure, e.g. buffer layer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers 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 having potential barriers 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 having potential barriers 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
    • H01L33/145—Semiconductor devices having potential barriers 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 with a current-blocking structure
    • H—ELECTRICITY
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Abstract

The present invention discloses the LED epitaxial growing method for improving hole injection, including：After Sapphire Substrate annealing；It is passed through TMGa and NH3Growing low temperature GaN nucleating layers；After in-situ annealing handles 5 10min, epitaxial growth high temperature GaN buffer layers；It is passed through NH3 and TMGa, the undoped u GaN layers of growth high temperature；It is passed through NH3, TMGa and SiH4, the n GaN layers of growth Si doping；Grow multicycle Quantum Well MQW luminescent layer；Growth thickness is that mixing for 20 120nm and does not mix the superlattice layer of Mg at Mg；Grow p-type AlGaN layer；Grow high temperature p-type GaN layer；Grow p-type GaN contact layers；Terminate growth after carrying out 5 10min of annealing in nitrogen atmosphere；Single light-emitting diode chip for backlight unit is made in obtained light emitting diode epitaxial structure after over cleaning, deposition, lithography and etching.The present invention improves the luminous efficiency of LED.

Description

Light emitting diode epitaxial growth method for improving hole injection
Technical Field
The invention relates to the technical field of semiconductor chip manufacturing, in particular to a light emitting diode epitaxial growth method for improving hole injection.
Background
As a semiconductor electronic device for converting electric energy into Light energy, Light-Emitting diodes (LEDs) are popular because of their low operating voltage (some are a few volts), low operating current (some are a few milliamps), good shock and shock resistance, high reliability, long life, and capability of conveniently modulating the intensity of Light emission, compared with conventional incandescent bulbs and neon lamps. With the rapid development of the third generation semiconductor technology, semiconductor lighting has the advantages of energy conservation, environmental protection, high brightness, long service life and the like, and becomes the focus of social development, and the development of the upstream, middle and downstream industries in the whole industry is also driven. The GaN (gallium nitride) -based LED chip is the 'power' of semiconductor illumination, and in recent years, the performance of the LED chip is greatly improved, the production cost is also reduced, and the LED chip makes a prominent contribution to the semiconductor illumination of thousands of households. However, in order to increase the market proportion of LED lighting and to accelerate the replacement of traditional light sources such as incandescent lamps and fluorescent lamps, LED devices need to further increase the lighting efficiency and reduce the cost per lumen.
As shown in fig. 1 and 2, fig. 1 is a schematic flow chart of a conventional epitaxial growth method for an LED structure; fig. 2 is an epitaxial structure of an LED fabricated by a conventional LED structure epitaxial growth method. The epitaxial growth method of the traditional LED structure comprises the following steps:
step 101, annealing the sapphire substrate in a hydrogen atmosphere at 1050-1150 ℃ to clean the surface of the substrate.
Step 102, reducing the temperature to 500-620 ℃, and introducing NH3And TMGa, under the conditions of growth pressure of 400-650Torr and V/III mole ratio of 500-3000, growing a low-temperature GaN nucleation layer with thickness of 20-40nm (the ratio of V/III group elements is N)3-And Ga3+In the LED field, the commonly used group V source is NH3Group III source is TMGa).
And step 103, stopping introducing TMGa after the growth of the low-temperature GaN nucleation layer is finished, and carrying out in-situ annealing treatment: the annealing temperature is raised to 1000-1100 ℃, and the annealing time is 5-10 min; after annealing, adjusting the temperature to 900-1050 ℃, continuously introducing TMGa, and growing the high-temperature GaN buffer layer with the thickness of 0.2-1um in an epitaxial growth mode under the conditions that the growth pressure is 400-650Torr and the V/III molar ratio is 500-3000.
104, after the growth of the high-temperature GaN buffer layer is finished, introducing NH3And TMGa, under the conditions of 1050-1200 ℃ of temperature, 100-500Torr of growth pressure and 300-3000V/III molar ratio, growing a non-doped u-GaN layer with the thickness of 1-3 um.
105, after the growth of the high-temperature non-doped GaN layer is finished, introducing NH3TMGa and SIH4At 1050-1200 deg.C, growth pressure of 100-600Torr, V/III molar ratio of 300-3000, and Si doping concentration of 8 x 1018-2*1019cm-3Under the condition, an n-GaN layer with stable doping concentration is grown, and the thickness is 2-4 um.
106, after the N-GaN layer grows, TMIn and TEGa are used as MO sources (the MO sources are high-purity metal organic compounds or compound semiconductor microstructure materials, and are support materials for growing semiconductor microstructure materials by Metal Organic Chemical Vapor Deposition (MOCVD), Metal Organic Molecular Beam Epitaxy (MOMBE) and other technologies), silane is used as an N-type dopant to grow for multiple weeksQuantum well MQW light emitting layers. The multicycle quantum well of the luminescent layer consists of In of 5-15 cyclesyGa1-yN/GaN well barrier structure, wherein the quantum well is InyGa1-yThe thickness of the N (y is 0.1-0.3) layer is 2-5nm, the growth temperature is 700-800 ℃, the growth pressure is 100-500Torr, and the V/III molar ratio is 300-5000; the thickness of the barrier layer GaN is 8-15nm, the growth temperature is 800-950 ℃, the growth pressure is 100-500Torr, the V/III molar ratio is 300-5000, and the barrier layer GaN is subjected to low-concentration Si doping (the Si component is 0.5% -3%).
Step 107, after the growth of the multi-period quantum well MQW light-emitting layer is finished, TMAl, TMGa and CP are used2Mg is an MO source, and a p-type AlGaN layer with the thickness of 50-200nm is grown under the conditions that the growth temperature is 900-1100 ℃, the growth time is 3-10min, the pressure is 20-200Torr, and the V/III molar ratio is 1000-20000. Wherein, the molar composition of Al in the p-type AlGaN layer is 10-30%, and the molar composition of Mg is 0.05-0.3%. Wherein, the p-type AlGaN layer is an electron blocking layer of the LED.
Step 108, after the growth of the p-type AlGaN layer is finished, TMGa and CP are used2Mg is MO source, the growth temperature is 850-1000 deg.C, the growth pressure is 100-500Torr, the V/III molar ratio is 300-5000, and the Mg doping concentration is 1017-1018cm-3Growing a high-temperature p-type GaN layer with the thickness of 100-800nm under the condition of (1).
Step 109, after the growth of the P-type GaN layer is finished, TMGa and CP are used2Mg is an MO source, and a p-type GaN contact layer with the thickness of 5-20nm is grown under the conditions that the growth temperature is 850-1050 ℃, the growth pressure is 100-500Torr, and the V/III molar ratio is 1000-5000.
110, after the epitaxial growth is finished, reducing the temperature of the reaction chamber to 650-800 ℃, carrying out annealing treatment for 5-10min in a pure nitrogen atmosphere, and then reducing the temperature to room temperature to finish the growth; the epitaxial structure is manufactured into a single small-size chip through subsequent semiconductor processing technologies such as cleaning, deposition, photoetching and etching.
Referring to fig. 2, the epitaxial structure of the LED prepared by the conventional LED structure epitaxial growth method includes: 201 is sapphire substrate, 202 is GaN buffer layer, 203 is u-GaN layer, 204 is n-GaN layer, 205 is quantum well multicycle quantum well MQW luminescent layer, 206 is p-type AlGaN layer, 207 is p-type GaN layer doped with Mg at high temperature, and 208 is p-type GaN contact layer.
At present, the LED market requires that the driving voltage of an LED chip is low, and particularly, the smaller the driving voltage under large current is, the better the driving voltage is, and the higher the lighting effect is, the better the lighting effect is. The market value of the LED is reflected in (light efficiency)/unit price, the better the light efficiency is, the higher the price is, so that the high light efficiency of the LED is always the target pursued by LED research institutes of LED manufacturers and universities. High luminous efficiency means high optical power and low driving voltage, but the optical power is limited to a certain extent by the hole concentration of the P layer, because the LED emits light mainly because electrons and holes recombine in the MQW to emit light. The driving voltage is limited by the hole mobility of the P layer to a certain extent, the concentration of injected holes is increased, and the recombination efficiency of holes and electrons of the light-emitting layer is increased; the light emitting power is increased, and the hole mobility of the P layer is increased to reduce the driving voltage.
Therefore, it is an urgent problem in the art to provide a method for epitaxial growth of a light emitting diode that reduces the operating voltage of the LED and improves the light emitting efficiency of the LED.
Disclosure of Invention
In view of this, the invention provides a light emitting diode epitaxial growth method for improving hole injection, which solves the defects of low hole mobility, high working voltage and low light emitting efficiency of the conventional LED chip.
In order to solve the above technical problem, the present invention provides a method for epitaxial growth of a light emitting diode for improving hole injection, including:
annealing the sapphire substrate in a hydrogen atmosphere with the purity of more than 99.999 percent at the temperature of 1050-1150 ℃, and cleaning the surface of the substrate;
the temperature is reduced to 500-620 ℃ and TMGa is introduced with a purity of 99.More than 999% NH3Growing a low-temperature GaN nucleating layer with the thickness of 20-40 nm;
stopping introducing TMGa, and raising the temperature to 1000-1100 ℃ for in-situ annealing treatment for 5-10 min; after in-situ annealing, adjusting the temperature to 900-1050 ℃, and epitaxially growing a high-temperature GaN buffer layer with the thickness of 0.2-1 um;
NH3 and TMGa are introduced, and a high-temperature non-doped u-GaN layer with the thickness of 1-3um is grown;
introduction of NH3TMGa and SiH4Growing an n-GaN layer with stable Si doping concentration and 2-4um thickness;
TMIn and TEGa are used as MO source and SiH4Growing a multi-period quantum well MQW light emitting layer for an N-type dopant;
using TMIn, TMGa and CP2Mg is an MO source, and a superlattice layer of InGaN, Mg/InGaN, doped with Mg and not doped with Mg, with the thickness of 20-120nm is grown under the conditions that the growth temperature is 700-900 ℃, the pressure is 100-500Torr, the molar ratio of V/III is 300-5000, the molar component of Mg is 0.3% -1%, and the molar component of In is 1-10%, wherein the superlattice layer thickness ratio of InGaN, Mg/InGaN is 1:1-5:1, and the period number is 4-50;
using TMGa and CP2Mg is an MO source, and a p-type AlGaN layer with the thickness of 50-200nm is grown;
using TMGa and CP2Mg is an MO source, and a high-temperature p-type GaN layer with the thickness of 100-800nm is grown, wherein the Mg doping concentration is 1017-1018cm-3；
Using TMGa and CP2Mg is an MO source, and a p-type GaN contact layer with the thickness of 5-20nm is grown;
annealing in nitrogen atmosphere with purity of 99.999% for 5-10min, and finishing growth;
the obtained light emitting diode epitaxial structure is cleaned, deposited, photoetched and etched to form a single light emitting diode chip.
Further, wherein the growing of the low-temperature GaN nucleation layer with the thickness of 20-40nm comprises:
growing a low-temperature GaN nucleating layer with the thickness of 20-40nm under the conditions that the growth pressure is 400-650Torr and the V/III molar ratio is 500-3000.
Further, wherein, epitaxial growth thickness is 0.2-1 um's high temperature GaN buffer layer, includes:
continuously introducing TMGa, and epitaxially growing a high-temperature GaN buffer layer with the thickness of 0.2-1um under the conditions that the pressure is 400-650Torr and the V/III molar ratio is 500-3000.
Further, wherein the growing of the high temperature undoped u-GaN layer with a thickness of 1-3um comprises:
growing a high-temperature non-doped u-GaN layer with the thickness of 1-3um under the conditions that the growth temperature is 1050-1200 ℃, the growth pressure is 100-500Torr, and the V/III molar ratio is 300-3000.
Further, wherein, the n-GaN layer with stable doping concentration and 2-4um thickness comprises:
at 1050-1200 deg.C, growth pressure of 100-600Torr, V/III molar ratio of 300-3000, and Si doping concentration of 8 x 1018-2*1019cm-3Under the conditions of (1), an n-GaN layer with a thickness of 2-4um is grown.
Further wherein the grown multi-cycle quantum well MQW light emitting layer comprises:
the multi-period quantum well MQW light-emitting layer consists of 5-15 periods of InyGa1-yN/GaN quantum well/barrier layer structure, y is 0.1-0.3; wherein,
growing quantum well In with thickness of 2-5nm at growth temperature of 700-800 deg.C, growth pressure of 100-500Torr and V/III molar ratio of 300-5000yGa1-yN layers;
under the conditions that the growth temperature is 800-950 ℃, the growth pressure is 100-500Torr and the V/III molar ratio is 300-5000, barrier layer GaN with the thickness of 8-15nm is grown, and low-concentration Si doping with the Si component of 0.5-3% is carried out on the barrier layer GaN.
Further, the growing of the p-type AlGaN layer with the thickness of 50-200nm comprises the following steps:
growing a p-type AlGaN layer with the thickness of 50-200nm under the conditions that the growth temperature is 900-1100 ℃, the pressure is 20-200Torr, the V/III molar ratio is 1000-20000, and the growth time is 3-10min, wherein the molar component of Al of the p-type AlGaN layer is 10-30%, and the molar component of Mg is 0.05-0.3%.
Further, wherein the growing the high temperature p-type GaN layer with the thickness of 100-800nm comprises:
growing a high temperature p-type GaN layer with a thickness of 100-800nm under the conditions of a growth temperature of 850-1000 ℃, a growth pressure of 100-500Torr and a V/III molar ratio of 300-5000.
Further, wherein the growing of the p-type GaN contact layer with the thickness of 5-20nm comprises:
growing a p-type GaN contact layer with a thickness of 5-20nm under the conditions of a growth temperature of 850-1050 ℃, a growth pressure of 100-500Torr and a V/III molar ratio of 1000-5000.
Further, the growth is finished after annealing treatment is carried out for 5-10min in a nitrogen atmosphere with the purity of more than 99.999%, and the method comprises the following steps:
reducing the reaction temperature to 650-800 ℃, annealing for 5-10min in a nitrogen atmosphere with the purity of more than 99.999 percent, and then reducing the temperature to room temperature to finish the growth.
Compared with the prior art, the light-emitting diode epitaxial growth method for improving hole injection realizes the following beneficial effects:
(1) according to the light emitting diode epitaxial growth method for improving hole injection, after a multi-quantum well layer grows, a layer of InGaN (indium gallium nitride)/InGaN superlattice layer structure doped with Mg or not doped with Mg grows, so that the hole concentration is provided, the transverse expansion of hole carriers under the action of a superlattice is improved through the growth of the superlattice, the uniform distribution of holes is utilized, the hole diffusion length and the hole mobility are improved, the hole injection level of a quantum well region is improved, the working voltage of an LED is reduced, and the light emitting efficiency of the LED is improved.
(2) According to the light emitting diode epitaxial growth method for improving hole injection, the Mg/InGaN superlattice layer structure of Mg-doped InGaN and Mg-undoped InGaN is grown in the LED epitaxial layer, so that the hole injection level of the quantum well region is improved, the recombination efficiency of holes and electrons is increased, the light power of a high-power LED chip is improved, and the driving voltage of the high-power LED chip is reduced.
(3) The light emitting diode epitaxial growth method for improving hole injection improves the injection and migration rate of holes in the light emitting diode epitaxial layer only by growing the InGaN/InGaN superlattice layer structure doped with Mg and not doped with Mg in the LED epitaxial layer, and has the advantages of simple operation and strong practicability.
Of course, it is not necessary for any product in which the present invention is practiced to achieve all of the above-described technical effects simultaneously.
Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.
FIG. 1 is a schematic flow chart of a conventional method for epitaxial growth of an LED structure;
FIG. 2 is an epitaxial structure of an LED fabricated by a conventional LED structure epitaxial growth method;
FIG. 3 is a schematic flow chart of an alternative embodiment of a method for epitaxial growth of a light emitting diode for improving hole injection according to the present invention;
FIG. 4 is a schematic structural diagram of an LED fabricated by the epitaxial growth method of the light emitting diode according to the present invention;
fig. 5 is a schematic flowchart of an alternative embodiment of a method for epitaxial growth of a light emitting diode for improving hole injection according to embodiment 2 of the present invention;
FIG. 6 is a graph comparing the luminance distributions of sample 1 and sample 2 in example 3 of the present invention;
FIG. 7 is a graph comparing the driving voltages of sample 1 and sample 2 in example 3 of the present invention.
Detailed Description
Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
Example 1
Fig. 3 is a schematic flow chart of an alternative embodiment of the method for epitaxial growth of a light emitting diode for improving hole injection according to the present invention. The Mg/InGaN superlattice layer structure of the Mg-doped InGaN or the Mg/InGaN is grown in the LED epitaxial layer, so that the hole injection level of the quantum well region is improved, the working voltage of a Light Emitting Diode (LED) is reduced, and the light emitting efficiency of the LED is improved. The light emitting diode epitaxial growth method for improving hole injection in the embodiment includes the following steps:
step 301, annealing the sapphire substrate in a hydrogen atmosphere with the purity of more than 99.999% at 1050-1150 ℃, and cleaning the surface of the substrate.
Step 302, reducing the temperature to 500-620 ℃, and introducing TMGa and NH with the purity of more than 99.999 percent3And growing a low-temperature GaN nucleating layer with the thickness of 20-40 nm.
Step 303, stopping introducing TMGa, and raising the temperature to 1000-1100 ℃ for in-situ annealing for 5-10 min; after in-situ annealing, the temperature is adjusted to 900-1050 ℃, and a high-temperature GaN buffer layer with the thickness of 0.2-1um is epitaxially grown.
The low-temperature GaN nucleating layer and the high-temperature GaN buffer layer form a GaN buffer layer of the LED.
And step 304, introducing NH3 and TMGa, and growing a high-temperature undoped u-GaN layer with the thickness of 1-3 um.
Step 305, introducing NH3TMGa and SiH4And growing an n-GaN layer with stable doping concentration and thickness of 2-4 um.
Step 306, using TMIn and TEGa as MO source and SiH4Is doped N-typeAnd growing a multi-period quantum well MQW light-emitting layer by using the growth agent.
Step 307, using TMIn, TMGa and CP2Mg is an MO source, and a superlattice layer of InGaN, Mg/InGaN, doped with Mg and not doped with Mg, with the thickness of 20-120nm is grown under the conditions that the growth temperature is 700-900 ℃, the pressure is 100-500Torr, the molar ratio of V/III is 300-5000, the molar component of Mg is 0.3% -1%, and the molar component of In is 1-10%, wherein the superlattice layer thickness ratio of InGaN, Mg/InGaN is 1:1-5:1, and the period number is 4-50.
Step 308, using TMGa and CP2Mg is an MO source, and a p-type AlGaN layer with the thickness of 50-200nm is grown, wherein the p-type AlGaN layer is also an electron blocking layer of the LED.
Step 309, Using TMGa and CP2Mg is an MO source, and a high-temperature p-type GaN layer with the thickness of 100-800nm is grown, wherein the Mg doping concentration is 1017-1018cm-3。
Step 310, using TMGa and CP2Mg is an MO source, and a p-type GaN contact layer with the thickness of 5-20nm is grown.
And 311, annealing in a nitrogen atmosphere with the purity of more than 99.999% for 5-10min, ending the growth, and cleaning, depositing, photoetching and etching the obtained light-emitting diode epitaxial structure to obtain a single light-emitting diode chip.
The compound starting materials used in this example include: trimethyl gallium (TMGa) as metal organic source, triethyl gallium (TEGa) as metal organic source, trimethyl indium (TMIn) as indium source, trimethyl aluminum (TMAl) as aluminum source, silane (SiH4) as N-type dopant, and magnesium dicylocene (CP) as P-type dopant2Mg), the substrate is sapphire.
Referring to fig. 4, fig. 4 is a schematic structural diagram of an LED manufactured by the epitaxial growth method of the light emitting diode according to this embodiment. In FIG. 4, 401 is a sapphire substrate, 402 is a GaN buffer layer, 403 is a u-GaN layer, 404 is an n-GaN layer, 405 is a quantum well multicycle quantum well MQW light emitting layer, 406 is an InGaN/InGaN superlattice layer, 407 is a p-type AlGaN layer, 408 is a high temperature Mg-doped p-type GaN layer, and 409 is a p-type GaN contact layer.
In the field of LED technology, LED luminescence is mainly due to recombination of electrons and holes in the MQW light-emitting layer. Generally, the higher the mobility and the higher the concentration, the lower the resistance, and both electrons and holes are the same, so the resistance is low and the natural operating voltage is low. For the same reason, if the concentration is constant, the mobility is high and the natural resistance is low. Only holes which enter the MQW luminescent layer and are combined with electrons are calculated as effective holes, the number of the holes which enter the MQW luminescent layer is increased due to the improvement of hole mobility of the LED epitaxial layer prepared by the method in the embodiment, and the opportunity of combining with electrons is increased, so that the brightness of the prepared LED is improved, and the luminous efficiency is related to the brightness and the voltage, is in direct proportion to the brightness, and is in inverse proportion to the voltage.
Example 2
Fig. 5 is a schematic flow chart of a method for epitaxial growth of a light emitting diode for improving hole injection according to embodiment 2 of the present invention. In this embodiment, a specific method for implementing each step of the epitaxial growth of the light emitting diode is provided. The light emitting diode epitaxial growth method for improving hole injection in the embodiment comprises the following steps:
step 501, annealing the sapphire substrate in a hydrogen atmosphere with the purity of more than 99.999% at 1050-1150 ℃, and cleaning the surface of the substrate.
Step 502, reducing the temperature to 500-620 ℃, and introducing TMGa and NH with the purity of more than 99.999 percent3Growing a low-temperature GaN nucleation layer with a thickness of 20-40nm under the conditions of a growth pressure of 400-650Torr and a V/III molar ratio of 500-3000.
Step 503, stopping introducing TMGa, and raising the temperature to 1000-1100 ℃ for in-situ annealing for 5-10 min; after in-situ annealing, adjusting the temperature to 900-1050 ℃, continuously introducing TMGa, and epitaxially growing a high-temperature GaN buffer layer with the thickness of 0.2-1um under the conditions that the pressure is 400-650Torr and the V/III molar ratio is 500-3000.
Step 504, NH3 and TMGa are introduced, and a high-temperature non-doped u-GaN layer with the thickness of 1-3um is grown under the conditions that the growth temperature is 1050-1200 ℃, the growth pressure is 100-500Torr, and the V/III molar ratio is 300-3000.
Step 505, introducing NH3TMGa and SiH4At 1050-1200 deg.C, growth pressure of 100-600Torr, V/III molar ratio of 300-3000, and Si doping concentration of 8 x 1018-2*1019cm-3Under the conditions of (1), an n-GaN layer with a thickness of 2-4um is grown.
Step 506, using TMIn and TEGa as MO source and SiH4Is N-type dopant, and grows quantum well In with thickness of 2-5nm under the conditions of growth temperature of 700-800 deg.C, growth pressure of 100-500Torr and V/III molar ratio of 300-5000yGa1-yAnd N layers, wherein y is 0.1-0.3.
Preferably, the quantum well InyGa1-yIn the N layer, y is 0.2 to 0.22.
And 507, growing barrier layer GaN with the thickness of 8-15nm under the conditions that the growth temperature is 800-950 ℃, the growth pressure is 100-500Torr and the V/III molar ratio is 300-5000, and doping the barrier layer GaN with low-concentration Si with the Si component of 0.5-3%.
Wherein, the In is formed by 5-15 periodsyGa1-yThe N/GaN quantum well/barrier layer structure forms the multi-period quantum well MQW light-emitting layer.
Step 508, using TMIn, TMGa and CP2Mg is an MO source, and the superlattice layer of InGaN, Mg/InGaN with the thickness of 20-120nm and without Mg is grown under the conditions that the growth temperature is 700-900 ℃, the pressure is 100-500Torr, the V/III molar ratio is 300-5000, the molar component of Mg is 0.3% -1%, and the molar component of In is 1-10%, wherein the superlattice layer thickness of InGaN, Mg/InGaN is InGaNThe ratio is 1:1-5:1, and the cycle number is 4-50.
Step 509, use TMGa and CP2Mg is an MO source, and a p-type AlGaN layer with the thickness of 50-200nm is grown under the conditions that the growth temperature is 900-1100 ℃, the pressure is 20-200Torr, the V/III molar ratio is 1000-20000, and the growth time is 3-10min, wherein the molar composition of Al of the p-type AlGaN layer is 10-30%, and the molar composition of Mg is 0.05-0.3%.
Step 510, using TMGa and CP2Mg is an MO source, and a high-temperature p-type GaN layer with the thickness of 100-800nm is grown under the conditions that the growth temperature is 850-1000 ℃, the growth pressure is 100-500Torr, and the molar ratio of V/III is 300-5000, wherein the Mg doping concentration is 1017-1018cm-3；
Step 511, using TMGa and CP2Mg is an MO source, and a p-type GaN contact layer with the thickness of 5-20nm is grown under the conditions that the growth temperature is 850-1050 ℃, the growth pressure is 100-500Torr, and the V/III molar ratio is 1000-5000.
And 512, reducing the reaction temperature to 650-800 ℃, annealing for 5-10min in a nitrogen atmosphere with the purity of more than 99.999%, reducing the temperature to room temperature to finish growth, and cleaning, depositing, photoetching and etching the obtained light-emitting diode epitaxial structure to prepare a single light-emitting diode chip.
According to the LED prepared by the embodiment, the Mg/InGaN superlattice layer structure of InGaN doped with Mg and not doped with Mg grows in the LED epitaxial layer, so that the hole injection level of the quantum well region is improved, the recombination efficiency of holes and electrons is increased, the optical power of a high-power LED chip is improved, and the driving voltage of the high-power LED chip is reduced.
Example 3
In this example, a contrast test of brightness and driving voltage was performed on the LED prepared by the conventional method and the LED prepared by the scheme of the present invention, respectively. The method comprises the following specific steps:
sample 1 was prepared according to the conventional LED growth method, and sample 2 was prepared according to the method described in this patent; the parameters of the epitaxial growth method of the sample 1 and the sample 2 are different from each other in that: sample 2 after the MQW light emitting layer was grown, a Mg/InGaN superlattice layer structure doped with Mg and not doped with Mg was grown by the method of the present invention, and referring to sample 1 and sample 2 in Table 1 for details, an ITO (indium tin oxide, commonly called ITO) layer with a thickness of 150nm was plated under the same pre-process conditions, a Cr/Pt/Au electrode with a thickness of 70nm was plated under the same conditions, and a SiO was plated under the same conditions2And (3) protecting the layer by 30nm, grinding and cutting the sample into chip particles of 762 μm (30mi 30mil) under the same condition, respectively selecting 150 crystal grains from the sample 1 and the sample 2 at the same position, and packaging into the white light LED under the same packaging process. And finally, testing the photoelectric properties of the sample 1 and the sample 2 by using an integrating sphere under the condition that the driving current is 350 mA. The growth parameters for sample 1 and sample 2 are tabulated below:
TABLE 1 growth parameter comparison Table for sample 1 and sample 2
Table 1 illustrates: the sample 1 is an electron blocking layer (p-type AlGaN layer) directly grown after a multi-quantum well barrier layer is grown in a traditional growth mode; sample 2 was prepared by inserting a layer of InGaN Mg/InGaN superlattice layer with a period of 20 between the multiple quantum well barrier layer and the electron blocking layer in the manner of LED epitaxial layer growth according to the present invention.
The results of comparing the luminance and the driving voltage of the sample 1 and the sample 2 obtained by the present test are shown in fig. 6 and 7. Wherein, fig. 6 is a comparison graph of the brightness distribution of the sample 1 and the sample 2 in the present embodiment; fig. 7 is a graph comparing the driving voltages of sample 1 and sample 2 in this example. As is evident from the test result graph: compared with the LED prepared by the method in the prior art, the LED prepared by the invention has the advantages that the working voltage is reduced, and the luminous efficiency is improved.
As can be seen from the above embodiments, the method for epitaxial growth of a light emitting diode for improving hole injection according to the present invention has the following beneficial effects:
(1) according to the light emitting diode epitaxial growth method for improving hole injection, after a multi-quantum well layer grows, a layer of InGaN (indium gallium nitride)/InGaN superlattice layer structure doped with Mg or not doped with Mg grows, so that the hole concentration is provided, the transverse expansion of hole carriers under the action of a superlattice is improved through the growth of the superlattice, the uniform distribution of holes is utilized, the hole diffusion length and the hole mobility are improved, the hole injection level of a quantum well region is improved, the working voltage of an LED is reduced, and the light emitting efficiency of the LED is improved.
(2) According to the light emitting diode epitaxial growth method for improving hole injection, the Mg/InGaN superlattice layer structure of Mg-doped InGaN and Mg-undoped InGaN is grown in the LED epitaxial layer, so that the hole injection level of the quantum well region is improved, the recombination efficiency of holes and electrons is increased, the light power of a high-power LED chip is improved, and the driving voltage of the high-power LED chip is reduced.
(3) The light emitting diode epitaxial growth method for improving hole injection improves the injection and migration rate of holes in the light emitting diode epitaxial layer only by growing the InGaN/InGaN superlattice layer structure doped with Mg and not doped with Mg in the LED epitaxial layer, and has the advantages of simple operation and strong practicability.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, apparatus, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims (10)

1. A light emitting diode epitaxial growth method for improving hole injection is characterized by comprising the following steps:
annealing the sapphire substrate in a hydrogen atmosphere with the purity of more than 99.999 percent at the temperature of 1050-1150 ℃, and cleaning the surface of the substrate;
reducing the temperature to 500-620 ℃, and introducing TMGa and NH with the purity of more than 99.999 percent3Growing a low-temperature GaN nucleating layer with the thickness of 20-40 nm;
stopping introducing TMGa, and raising the temperature to 1000-1100 ℃ for in-situ annealing treatment for 5-10 min; after in-situ annealing, adjusting the temperature to 900-1050 ℃, and epitaxially growing a high-temperature GaN buffer layer with the thickness of 0.2-1 um;
introducing NH3 and TMGa, and growing a high-temperature non-doped u-GaN layer with the thickness of 1-3um at the growth temperature of 1050-1200 ℃;
introduction of NH3TMGa and SiH4Growing an n-GaN layer with stable Si doping concentration and 2-4um thickness;
TMIn and TEGa are used as MO source and SiH4Growing a multi-period quantum well MQW light emitting layer for an N-type dopant;
using TMIn, TMGa and CP2Mg is an MO source, and a superlattice layer of InGaN, Mg/InGaN, doped with Mg and not doped with Mg, with the thickness of 20-120nm is grown under the conditions that the growth temperature is 700-900 ℃, the pressure is 100-500Torr, the molar ratio of V/III is 300-5000, the molar component of Mg is 0.3% -1%, and the molar component of In is 1-10%, wherein the superlattice layer thickness ratio of InGaN, Mg/InGaN is 1:1-5:1, and the period number is 4-50;
using TMGa and CP2Mg is an MO source, and a p-type AlGaN layer with the thickness of 50-200nm is grown;
using TMGa and CP2Mg is an MO source, and a high-temperature p-type GaN layer with the thickness of 100-800nm is grown, wherein the Mg doping concentration is 1017-1018cm-3The growth temperature is 850-1000 ℃;
using TMGa and CP2Mg is an MO source, and a p-type GaN contact layer with the thickness of 5-20nm is grown;
annealing in nitrogen atmosphere with purity of 99.999% for 5-10min, and finishing growth;
the obtained light emitting diode epitaxial structure is cleaned, deposited, photoetched and etched to form a single light emitting diode chip.
2. The method of claim 1, wherein growing the low temperature GaN nucleation layer to a thickness of 20-40nm comprises:
growing a low-temperature GaN nucleating layer with the thickness of 20-40nm under the conditions that the growth pressure is 400-650Torr and the V/III molar ratio is 500-3000.
3. The method of claim 1, wherein epitaxially growing a high temperature GaN buffer layer with a thickness of 0.2-1um comprises:
continuously introducing TMGa, and epitaxially growing a high-temperature GaN buffer layer with the thickness of 0.2-1um under the conditions that the pressure is 400-650Torr and the V/III molar ratio is 500-3000.
4. The method of claim 1, wherein growing the high temperature undoped u-GaN layer with a thickness of 1-3um comprises:
growing a high-temperature non-doped u-GaN layer with the thickness of 1-3um under the conditions that the growth temperature is 1050-1200 ℃, the growth pressure is 100-500Torr, and the V/III molar ratio is 300-3000.
5. The method for epitaxial growth of a Light Emitting Diode (LED) with improved hole injection according to claim 1, wherein the growing of the n-GaN layer with stable doping concentration and thickness of 2-4um comprises:
at 1050-1200 deg.C, growth pressure of 100-600Torr, V/III molar ratio of 300-3000, and Si doping concentration of 8 x 1018-2*1019cm-3Under the conditions of (1), an n-GaN layer with a thickness of 2-4um is grown.
6. The method of claim 1, wherein the growing the multi-period quantum well MQW light-emitting layer comprises:
the multi-period quantum well MQW light-emitting layer consists of 5-15 periods of InyGa1-yN/GaN quantum well/barrier layer structure, y is 0.1-0.3; wherein,
growing quantum well In with thickness of 2-5nm at growth temperature of 700-800 deg.C, growth pressure of 100-500Torr and V/III molar ratio of 300-5000yGa1-yN layers;
under the conditions that the growth temperature is 800-950 ℃, the growth pressure is 100-500Torr and the V/III molar ratio is 300-5000, barrier layer GaN with the thickness of 8-15nm is grown, and low-concentration Si doping with the Si component of 0.5-3% is carried out on the barrier layer GaN.
7. The light-emitting diode epitaxial growth method for improving hole injection according to claim 1, wherein the growth of the p-type AlGaN layer with the thickness of 50-200nm comprises the following steps:
growing a p-type AlGaN layer with the thickness of 50-200nm under the conditions that the growth temperature is 900-1100 ℃, the pressure is 20-200Torr, the V/III molar ratio is 1000-20000, and the growth time is 3-10min, wherein the molar component of Al of the p-type AlGaN layer is 10-30%, and the molar component of Mg is 0.05-0.3%.
8. The light-emitting diode epitaxial growth method for improving hole injection according to claim 1, wherein the growing of the high temperature p-type GaN layer with the thickness of 100-800nm comprises:
growing a high temperature p-type GaN layer with a thickness of 100-800nm under the conditions of a growth temperature of 850-1000 ℃, a growth pressure of 100-500Torr and a V/III molar ratio of 300-5000.
9. The light-emitting diode epitaxial growth method for improving hole injection according to claim 1, wherein the growth of the p-type GaN contact layer with the thickness of 5-20nm comprises:
growing a p-type GaN contact layer with a thickness of 5-20nm under the conditions of a growth temperature of 850-1050 ℃, a growth pressure of 100-500Torr and a V/III molar ratio of 1000-5000.
10. The method for epitaxial growth of a light emitting diode with improved hole injection according to claim 1, wherein the step of annealing the substrate in a nitrogen atmosphere with a purity of 99.999% or more for 5-10min and then ending the growth comprises:
reducing the reaction temperature to 650-800 ℃, annealing for 5-10min in a nitrogen atmosphere with the purity of more than 99.999 percent, and then reducing the temperature to room temperature to finish the growth.
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