CN117239027A - LED epitaxial wafer, preparation method thereof and LED - Google Patents

LED epitaxial wafer, preparation method thereof and LED Download PDF

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CN117239027A
CN117239027A CN202311516890.7A CN202311516890A CN117239027A CN 117239027 A CN117239027 A CN 117239027A CN 202311516890 A CN202311516890 A CN 202311516890A CN 117239027 A CN117239027 A CN 117239027A
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doped
epitaxial wafer
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CN117239027B (en
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郑文杰
程龙
高虹
刘春杨
胡加辉
金从龙
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Jiangxi Zhao Chi Semiconductor Co Ltd
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Jiangxi Zhao Chi Semiconductor Co Ltd
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Abstract

The invention discloses a light-emitting diode epitaxial wafer and a preparation method thereof, and an LED, wherein the light-emitting diode epitaxial wafer comprises a substrate, and a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, a P-type GaN layer and a P-type contact layer are sequentially arranged on the substrate; the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, the first composite layer comprises an SiN layer and an Mg-doped Ga-polar AlGaN layer which are alternately stacked, and the second composite layer comprises an h-BN layer and an Mg-doped nitrogen-polar AlInGaN layer which are alternately stacked. The LED epitaxial wafer provided by the invention can improve hole generation efficiency, reduce ohmic contact voltage and improve reflectivity.

Description

LED epitaxial wafer, preparation method thereof and LED
Technical Field
The invention relates to the technical field of photoelectricity, in particular to a light-emitting diode epitaxial wafer, a preparation method thereof and an LED.
Background
GaN (gallium nitride) -based LEDs have huge application potential in the fields of high-brightness blue light emitting diodes, blue light lasers and other optoelectronic devices due to the characteristics of wide band gap, high luminous efficiency, high electron saturation drift speed, stable chemical properties and the like, and are widely focused by people. The forward voltage is an important parameter for measuring the performance of the LED under the driving of the same current density. The lower the forward voltage, the smaller the power consumption of the chip, and the more competitive the market. And the quality of the epitaxial structure is a determining factor directly influencing the quality of the chip. Thus, lowering the forward voltage of the chip by lowering the forward voltage of the GaN-based LED epitaxial structure is the most direct and efficient approach. The forward voltage drop of the epitaxial wafer mainly comes from an N-type GaN bottom layer, a quantum well active region, a P-type GaN layer, an electron blocking layer and the like. The presence of certain factors increases the inherent voltage drop, e.g., the polarizing electric field. InGaN/GaN light emitting diodes have a polarizing electric field between them due to lattice mismatch between the potential well and the potential barrier. The existence of the polarized electric field causes the energy band structure to be greatly changed, so that the shape of the potential barrier becomes a large triangle. These triangular barriers have a great impeding effect on the flow of carriers in the active region, resulting in an increase in forward voltage. In addition, for example, the P-type GaN material is very low in Mg activation efficiency, so that it is often difficult to achieve high hole concentration, resulting in a P-terminal with a high resistivity and a high parasitic resistance.
Disclosure of Invention
The invention aims to solve the technical problem of providing a light-emitting diode epitaxial wafer which can improve hole generation efficiency, reduce ohmic contact voltage and improve reflectivity.
The invention also aims to provide a preparation method of the light-emitting diode epitaxial wafer, which has simple process and can stably prepare the light-emitting diode epitaxial wafer with good luminous efficiency.
In order to solve the technical problems, the invention provides a light-emitting diode epitaxial wafer, which comprises a substrate, wherein a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, a P-type GaN layer and a P-type contact layer are sequentially arranged on the substrate;
the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, the first composite layer comprises an SiN layer and an Mg-doped Ga-polar AlGaN layer which are alternately stacked, and the second composite layer comprises an h-BN layer and an Mg-doped nitrogen-polar AlInGaN layer which are alternately stacked.
In one embodiment, the P-type contact layer is a P-type contact layer subjected to high-temperature annealing treatment, and the high-temperature annealing treatment process comprises the following steps: at N 2 Annealing treatment is carried out at 800-900 ℃ in the atmosphere;
the annealing treatment time is 8-10 min.
In one embodiment, the SiN layer has a thickness of 1nm to 10nm;
the thickness of the Mg-doped Ga-polarity AlGaN layer is 5 nm-20 nm;
the Mg doping concentration of the Mg-doped Ga-polar AlGaN layer is 2 multiplied by 10 15 atoms/cm 3 ~2×10 16 atoms/cm 3 。
In one embodiment, the thickness of the h-BN layer is 1nm to 10nm;
the thickness of the Mg-doped nitrogen polarity AlInGaN layer is 1 nm-50 nm;
the Mg doping concentration of the Mg-doped nitrogen polarity AlInGaN layer is 2 multiplied by 10 18 atoms/cm 3 ~2×10 19 atoms/cm 3 。
In one embodiment, the Mg doping concentration of the Mg doped Ga-polarity AlGaN layer is less than the Mg doping concentration of the Mg doped nitrogen-polarity AlInGaN layer;
the Mg doping concentration in the Mg-doped Ga-polar AlGaN layer gradually rises along the growth direction;
the Mg doping concentration in the Mg-doped nitrogen polarity AlInGaN layer gradually increases along the growth direction.
In one embodiment, the Al composition in the Mg-doped Ga-polarity AlGaN layer is gradually reduced in the growth direction;
the Al component in the Mg-doped nitrogen polarity AlInGaN layer gradually rises along the growth direction;
the In composition within the Mg-doped nitrogen polarity AlInGaN layer remains uniform throughout.
In order to solve the problems, the invention also provides a preparation method of the light-emitting diode epitaxial wafer, which comprises the following steps:
s1, preparing a substrate;
s2, sequentially depositing a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, a P-type GaN layer and a P-type contact layer on the substrate;
the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, the first composite layer comprises an SiN layer and an Mg-doped Ga-polar AlGaN layer which are alternately stacked, and the second composite layer comprises an h-BN layer and an Mg-doped nitrogen-polar AlInGaN layer which are alternately stacked.
In one embodiment, the first composite layer is made by the following method:
controlling the temperature of the reaction chamber to be 800-1000 ℃ and the pressure to be 100-500 torr, introducing an N source and an Si source, and growing a SiN layer;
controlling the temperature of the reaction chamber to 980-1000 ℃ and the pressure to 100-500 torr, and introducing a Ga source, an Al source and a Mg source in a nitrogen atmosphere to grow a Mg-doped Ga polar AlGaN layer;
alternately growing the SiN layer and the Mg-doped Ga-polarity AlGaN layer to obtain a first composite layer.
In one embodiment, the second composite layer is made by the following method:
the temperature of the reaction chamber is controlled to be 800-1000 ℃, the pressure is controlled to be 100-500 torr, and the atmosphere is N 2 With NH 3 The volume ratio of (1): b source is introduced into the mixed gas in the step (1-10), and an h-BN layer is grown;
controlling the temperature of the reaction chamber at 800-900 ℃ and the pressure at 100-500 torr, and introducing an N source, a Ga source, an Al source, an In source and an Mg source In an ammonia atmosphere to grow an Mg-doped nitrogen polarity AlInGaN layer;
and alternately growing the h-BN layer and the Mg-doped nitrogen polarity AlInGaN layer to obtain a second composite layer.
Correspondingly, the invention further provides an LED, and the LED comprises the LED epitaxial wafer.
The implementation of the invention has the following beneficial effects:
the light-emitting diode epitaxial wafer provided by the invention is provided with a P-type contact layer with a specific composition, wherein the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, the first composite layer comprises an alternately laminated SiN layer and an Mg-doped Ga-polar AlGaN layer, and the second composite layer comprises an alternately laminated h-BN layer and an Mg-doped nitrogen-polar AlInGaN layer.
Firstly, the SiN layer can continuously block upward extension of defects, so that leakage channels are reduced. The Mg-doped Ga-polarity AlGaN layer has Ga polarity, and the Ga polarity can improve the crystal quality. The h-BN layer has a two-dimensional material layered structure, the layers are connected by virtue of Van der Waals force, and the AlInGaN material is grown on the h-BN layer, so that mismatch stress can be effectively relieved, and crystal quality is improved. The Mg-doped nitrogen polarity AlInGaN layer has nitrogen polarity, and the nitrogen polarity can improve the In incorporation efficiency, improve the surface roughness and the reflectivity, and reduce the polarization effect between the two.
Secondly, the SiN layer and the Mg-doped Ga-polar AlGaN layer in the first composite layer form a superlattice structure, and ionization energy of an Mg acceptor in the AlGaN layer material can be further reduced by forming a superlattice microstrip. Since the SiN layer and the Mg-doped Ga-polarity AlGaN layer constituting the superlattice structure have different forbidden bandwidths, discontinuity of energy bands will be generated at the interface of the SiN layer and the Mg-doped Ga-polarity AlGaN layer, and the conduction band and the valence band thereof will generate periodic oscillations with the same superlattice period. Further, by controlling the Al component in the superlattice structure of the SiN layer and the Mg doped Ga polar AlGaN layer, the required amplitude and period valence band edge oscillation can be obtained, and the valence band oscillation can enable the superlattice to form a hole microstrip, so that the concentration of holes is improved.
Thirdly, the P-type contact layer is a P-type contact layer subjected to high-temperature annealing treatment, and the high-temperature annealing can cause the increase of the surface roughness of the epitaxial wafer, so that the reflectivity is increased, and the luminous efficiency is improved.
And the intentional lightly doped structure of the Mg-doped Ga-polar AlGaN layer can release the compressive stress generated when the P-type GaN layer is connected with the P-type contact layer to a certain extent. The Mg-doped nitrogen polarity AlInGaN layer has higher Mg concentration doping, can improve the hole concentration of the P-type contact layer, reduce the contact resistivity of the second composite layer and metal, narrow a barrier region generated by the second composite layer and metal, increase the probability that carriers pass through the barrier region through tunneling and pass through the contact of the metal and the semiconductor, reduce the working voltage of the high-power LED chip, and further improve the luminous efficiency of the high-power LED chip. On the other hand, the carrier concentration is enhanced to a certain extent, the longitudinal current expansion capability is enhanced, and the purpose of reducing the working voltage of the light-emitting diode is achieved.
Drawings
Fig. 1 is a schematic structural diagram of an led epitaxial wafer according to the present invention;
fig. 2 is a flowchart of a method for preparing an led epitaxial wafer according to the present invention;
fig. 3 is a flowchart of step S2 of the method for manufacturing a light emitting diode epitaxial wafer according to the present invention.
Detailed Description
The present invention will be described in further detail below in order to make the objects, technical solutions and advantages of the present invention more apparent.
Unless otherwise indicated or contradicted, terms or phrases used herein have the following meanings:
in the present invention, "preferred" is merely to describe embodiments or examples that are more effective, and it should be understood that they are not intended to limit the scope of the present invention.
In the invention, the technical characteristics described in an open mode comprise a closed technical scheme composed of the listed characteristics and also comprise an open technical scheme comprising the listed characteristics.
In the present invention, the numerical range is referred to, and both ends of the numerical range are included unless otherwise specified.
In order to solve the above problems, the present invention provides a light emitting diode epitaxial wafer, as shown in fig. 1, comprising a substrate 100, wherein a buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a multiple quantum well layer 500, an electron blocking layer 600, a P-type GaN layer 700 and a P-type contact layer 800 are sequentially disposed on the substrate 100;
the P-type contact layer 800 includes a first composite layer 801 and a second composite layer 802 sequentially deposited on the P-type GaN layer 700, the first composite layer 801 includes an alternately stacked SiN layer and Mg-doped Ga-polarity AlGaN layer, and the second composite layer 802 includes an alternately stacked h-BN layer and Mg-doped nitrogen-polarity AlInGaN layer.
The specific structure of the P-type contact layer 800 is as follows:
in one embodiment, the P-type contact layer is a P-type contact layer subjected to high-temperature annealing treatment, and the high-temperature annealing treatment process comprises the following steps: at N 2 Annealing treatment is carried out at 800-900 ℃ in the atmosphere; the annealing treatment time is 8-10 min. Preferably, the high-temperature annealing treatment process comprises the following steps: at N 2 Annealing at 820-880 deg.c in atmosphere; the annealing treatment time is 9min. The high-temperature annealing under the conditions can cause the surface roughness of the epitaxial wafer to be increased, the reflectivity is increased, and the luminous efficiency is improved.
In one embodiment, the SiN layer has a thickness of 1nm to 10nm; exemplary thicknesses of the SiN layer are 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, but are not limited thereto; the SiN layer can continuously block upward extension of defects, and reduce leakage channels.
In one embodiment, the thickness of the Mg-doped Ga-polar AlGaN layer is 5 nm-20 nm; exemplary thicknesses of the Mg-doped Ga-polar AlGaN layer are 7nm, 9nm, 11nm, 13nm, 15nm, 17nm, 19nm, but are not limited thereto; the Mg-doped Ga-polarity AlGaN layer has Ga polarity, and the Ga polarity can improve the crystal quality.
In one embodiment, the alternating period of the SiN layer and the Mg doped Ga-polarity AlGaN layer is 4-7.
Further, the SiN layer and the Mg-doped Ga-polar AlGaN layer in the first composite layer form a superlattice structure, and ionization energy of an Mg acceptor in the AlGaN layer material can be further reduced by forming a superlattice microstrip. Since the SiN layer and the Mg-doped Ga-polarity AlGaN layer constituting the superlattice structure have different forbidden bandwidths, discontinuity of energy bands will be generated at the interface of the SiN layer and the Mg-doped Ga-polarity AlGaN layer, and the conduction band and the valence band thereof will generate periodic oscillations with the same superlattice period. Further, by controlling the Al component in the superlattice structure of the SiN layer and the Mg-doped Ga-polar AlGaN layer, the required amplitude and period valence band edge oscillation can be obtained, and the valence band oscillation can enable the superlattice to form a hole microstrip, so that the concentration of holes is improved. Preferably, the Al component of the Mg-doped Ga-polar AlGaN layer is 0.01-0.5, and under the condition, the hole concentration is improved.
In one embodiment, the thickness of the h-BN layer is 1nm to 10nm; exemplary thicknesses of the h-BN are 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, but are not limited thereto; the h-BN layer is of a two-dimensional material layered structure, layers are connected by means of Van der Waals force, and the AlInGaN material grows on the h-BN layer, so that mismatch stress can be effectively relieved, and crystal quality is improved.
In one embodiment, the thickness of the Mg-doped nitrogen polarity AlInGaN layer is 1 nm-50 nm; exemplary thicknesses of the Mg-doped nitrogen-polarity AlInGaN layer are 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, but are not limited thereto; the Mg-doped nitrogen polarity AlInGaN layer has nitrogen polarity, and the nitrogen polarity can improve the In incorporation efficiency, improve the surface roughness and the reflectivity, and reduce the polarization effect between the two.
In one embodiment, the alternating period of the h-BN layer and the Mg-doped nitrogen polarity AlInGaN layer is 4-7.
Further, in one embodiment, the Mg doping concentration of the Mg doped Ga-polarity AlGaN layer is less than the Mg doping concentration of the Mg doped nitrogen-polarity AlInGaN layer. Preferably, the Mg is doped with Ga poleThe Mg doping concentration of the AlGaN layer is 2×10 15 atoms/cm 3 ~2×10 16 atoms/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The Mg doping concentration of the Mg-doped nitrogen polarity AlInGaN layer is 2 multiplied by 10 18 atoms/cm 3 ~2×10 19 atoms/cm 3 . More preferably, the Mg doping concentration of the Mg-doped Ga-polar AlGaN layer is 3×10 15 atoms/cm 3 ~1×10 16 atoms/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The Mg doping concentration of the Mg-doped nitrogen polarity AlInGaN layer is 3 multiplied by 10 18 atoms/cm 3 ~1×10 19 atoms/cm 3 . The intentional lightly doped structure of the Mg-doped Ga-polar AlGaN layer can release the compressive stress generated when the P-type GaN layer is connected with the P-type contact layer to a certain extent. The Mg-doped nitrogen polarity AlInGaN layer has higher Mg concentration doping, can improve the hole concentration of the P-type contact layer, reduce the contact resistivity of the second composite layer and metal, narrow a barrier region generated by the second composite layer and metal, increase the probability that carriers pass through the barrier region through tunneling and pass through the contact of the metal and the semiconductor, reduce the working voltage of the high-power LED chip, and further improve the luminous efficiency of the high-power LED chip. On the other hand, the carrier concentration is enhanced to a certain extent, the longitudinal current expansion capability is enhanced, and the purpose of reducing the working voltage of the light-emitting diode is achieved.
In one embodiment, the Mg doping concentration in the Mg-doped Ga-polarity AlGaN layer increases gradually along the growth direction; the Mg doping concentration in the Mg-doped nitrogen polarity AlInGaN layer gradually increases along the growth direction. Thus being beneficial to gradually increasing the doping concentration of Mg, leading the Mg to more effectively generate holes more fully and improving the hole injection efficiency.
In one embodiment, the Al composition in the Mg-doped Ga-polarity AlGaN layer is gradually reduced in the growth direction; the Al component in the Mg-doped nitrogen polarity AlInGaN layer gradually rises along the growth direction; the In composition within the Mg-doped nitrogen polarity AlInGaN layer remains uniform throughout. The In atoms are larger, so that the surface roughness is improved and the light reflectivity is improved under the conditions on the basis of ensuring the lattice quality of each layer.
During the growth of the epitaxial layer, the amount of the metal source introduced into the reaction chamber may be controlled by a mass flow controller. Specifically, when the Mg-doped Ga-polar AlGaN layer is grown, the introducing amount of the Mg source is controlled, so that the introducing amount of the Mg source is changed from low to high, and the Mg doping concentration in the Mg-doped Ga-polar AlGaN layer is ensured to be gradually increased along the growth direction. Likewise, the introduction amount of the Al source can be controlled, so that the introduction amount of the Al source is changed from high to low, and the Al component in the Mg-doped Ga-polar AlGaN layer is ensured to be gradually reduced along the growth direction.
Correspondingly, the invention provides a preparation method of the light-emitting diode epitaxial wafer, as shown in fig. 2, comprising the following steps:
s1, preparing a substrate 100;
in one embodiment, the substrate is selected from (0001) plane sapphire substrate, alN substrate, (111) plane Si substrate, and (0001) plane SiC substrate. Preferably, the substrate is a sapphire substrate, which is the most commonly used substrate material at present, and has the advantages of mature preparation process, low price, easy cleaning and processing and good stability at high temperature.
S2, a buffer layer 200, an undoped GaN layer 300, an N-type GaN layer 400, a multiple quantum well layer 500, an electron blocking layer 600, a P-type GaN layer 700 and a P-type contact layer 800 are sequentially deposited on the substrate 100.
As shown in fig. 3, the step S2 specifically includes the following steps:
s21, depositing a buffer layer 200 on the substrate 100.
An AlN buffer layer is deposited in PVD, and the thickness of the AlN buffer layer is 20 nm-70 nm.
S22, depositing an undoped GaN layer 300 on the buffer layer 200.
In one embodiment, the temperature of the reaction chamber is controlled to 1100-1150 ℃, the pressure is controlled to 100-500 torr, an N source and a Ga source are introduced, and an undoped GaN layer with the thickness of 1-3 μm is grown.
S23, depositing an N-type GaN layer 400 on the undoped GaN layer 300.
In one implementation mode, the temperature of the reaction chamber is controlled to be 1000-1300 ℃, the pressure is controlled to be 50-500 torr, an N source, a Ga source and a Si source are introduced, and the N-type GaN layer with the thickness of 1-5 μm is grown.
S24, depositing a multiple quantum well layer 500 on the N-type GaN layer 400.
In one embodiment, the multiple quantum well layer is an InGaN quantum well layer and a GaN quantum barrier layer which are alternately stacked, and the stacking period is 3-15; the growth temperature of the InGaN quantum well layer is 700-800 ℃, the thickness of the InGaN quantum well layer is 2-5 nm, and the growth pressure is 100-500 torr; the growth temperature of the GaN quantum barrier layer is 800-900 ℃, the thickness of the GaN quantum barrier layer is 5-15 nm, and the growth pressure of the GaN quantum barrier layer is 100-500 torr.
S25, depositing an electron blocking layer 600 on the multiple quantum well layer 500.
In one embodiment, the temperature of the reaction chamber is controlled to be 1000-1100 ℃, the pressure is controlled to be 100-300 torr, an N source, an Al source and a Ga source are introduced, and an AlGaN electron blocking layer with the thickness of 10-100 nm is grown.
S26, a P-type GaN layer 700 is deposited on the electron blocking layer 600.
In one embodiment, the temperature of the reaction chamber is controlled to be 1000-1100 ℃, the pressure is controlled to be 100-600 torr, an N source, a Ga source and an Mg source are introduced, and a P-type GaN layer with the thickness of 20-200 nm is grown. Preferably, the Mg doping concentration is 1×10 19 atoms/cm 3 ~5×10 20 atoms/cm 3 。
And S27, depositing a P-type contact layer 800 on the P-type GaN layer 700.
The first composite layer is prepared by the following method:
controlling the temperature of the reaction chamber to be 800-1000 ℃ and the pressure to be 100-500 torr, introducing an N source and an Si source, and growing a SiN layer;
controlling the temperature of the reaction chamber to 980-1000 ℃ and the pressure to 100-500 torr, and introducing a Ga source, an Al source and a Mg source in a nitrogen atmosphere to grow a Mg-doped Ga polar AlGaN layer;
alternately growing the SiN layer and the Mg-doped Ga-polarity AlGaN layer to obtain a first composite layer.
In one embodiment, the second composite layer is made by the following method:
controlling the temperature of the reaction chamber toThe temperature is 800-1000 ℃, the pressure is controlled to be 100-500 torr, and the atmosphere is N 2 With NH 3 The volume ratio of (1): b source is introduced into the mixed gas in the step (1-10), and an h-BN layer is grown;
controlling the temperature of the reaction chamber at 800-900 ℃ and the pressure at 100-500 torr, and introducing an N source, a Ga source, an Al source, an In source and an Mg source In an ammonia atmosphere to grow an Mg-doped nitrogen polarity AlInGaN layer;
and alternately growing the h-BN layer and the Mg-doped nitrogen polarity AlInGaN layer to obtain a second composite layer.
Correspondingly, the invention further provides an LED, and the LED comprises the LED epitaxial wafer. The photoelectric efficiency of the LED is effectively improved, and other items have good electrical properties.
The invention is further illustrated by the following examples:
example 1
The embodiment provides a light-emitting diode epitaxial wafer, which comprises a substrate, wherein a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, a P-type GaN layer and a P-type contact layer are sequentially arranged on the substrate;
the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, wherein the first composite layer comprises 5 SiN layers and Mg-doped Ga-polarity AlGaN layers which are alternately stacked in cycles, and the second composite layer comprises 5 h-BN layers and Mg-doped nitrogen-polarity AlInGaN layers which are alternately stacked in cycles.
The P-type contact layer is subjected to high-temperature annealing treatment, and the high-temperature annealing treatment process comprises the following steps: at N 2 Annealing was performed at 850℃for 9min in the atmosphere.
The thickness of the SiN layer is 6nm;
the thickness of the Mg-doped Ga-polar AlGaN layer is 15nm, and the Mg doping concentration is 1 multiplied by 10 16 atoms/cm 3 。
The thickness of the h-BN layer is 6nm;
the thickness of the Mg-doped nitrogen polarity AlInGaN layer is 30nm, and the Mg doping concentration is 1 multiplied by 10 19 atoms/cm 3 ；
The Mg doping concentration in the Mg-doped Ga-polar AlGaN layer gradually rises along the growth direction;
the Mg doping concentration in the Mg-doped nitrogen polarity AlInGaN layer gradually increases along the growth direction.
Example 2
The embodiment provides a light-emitting diode epitaxial wafer, which comprises a substrate, wherein a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, a P-type GaN layer and a P-type contact layer are sequentially arranged on the substrate;
the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, wherein the first composite layer comprises 5 SiN layers and Mg-doped Ga-polarity AlGaN layers which are alternately stacked in cycles, and the second composite layer comprises 5 h-BN layers and Mg-doped nitrogen-polarity AlInGaN layers which are alternately stacked in cycles.
The P-type contact layer is subjected to high-temperature annealing treatment, and the high-temperature annealing treatment process comprises the following steps: at N 2 Annealing was performed at 850℃for 9min in the atmosphere.
The thickness of the SiN layer is 6nm;
the thickness of the Mg-doped Ga-polar AlGaN layer is 15nm, and the Mg doping concentration is 1 multiplied by 10 16 atoms/cm 3 。
The thickness of the h-BN layer is 6nm;
the thickness of the Mg-doped nitrogen polarity AlInGaN layer is 30nm, and the Mg doping concentration is 1 multiplied by 10 19 atoms/cm 3 ；
The Al component in the Mg-doped Ga-polar AlGaN layer is gradually reduced along the growth direction;
the Al component in the Mg-doped nitrogen polarity AlInGaN layer gradually rises along the growth direction;
the In composition within the Mg-doped nitrogen polarity AlInGaN layer remains uniform throughout.
Example 3
The embodiment provides a light-emitting diode epitaxial wafer, which comprises a substrate, wherein a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, a P-type GaN layer and a P-type contact layer are sequentially arranged on the substrate;
the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, wherein the first composite layer comprises 5 SiN layers and Mg-doped Ga-polarity AlGaN layers which are alternately stacked in cycles, and the second composite layer comprises 5 h-BN layers and Mg-doped nitrogen-polarity AlInGaN layers which are alternately stacked in cycles.
The P-type contact layer is subjected to high-temperature annealing treatment, and the high-temperature annealing treatment process comprises the following steps: at N 2 Annealing was performed at 850℃for 9min in the atmosphere.
The thickness of the SiN layer is 6nm;
the thickness of the Mg-doped Ga-polar AlGaN layer is 15nm, and the Mg doping concentration is 1 multiplied by 10 16 atoms/cm 3 。
The thickness of the h-BN layer is 6nm;
the thickness of the Mg-doped nitrogen polarity AlInGaN layer is 30nm, and the Mg doping concentration is 1 multiplied by 10 19 atoms/cm 3 ；
The Mg doping concentration in the Mg-doped Ga-polar AlGaN layer gradually rises along the growth direction;
the Mg doping concentration in the Mg-doped nitrogen polarity AlInGaN layer gradually rises along the growth direction;
the Al component in the Mg-doped Ga-polar AlGaN layer is gradually reduced along the growth direction;
the Al component in the Mg-doped nitrogen polarity AlInGaN layer gradually rises along the growth direction;
the In composition within the Mg-doped nitrogen polarity AlInGaN layer remains uniform throughout.
Comparative example 1
This comparative example provides a light emitting diode epitaxial wafer, and the rest of example 1 is different in that: the P-type contact layer is an AlGaN layer. The remainder was referred to example 1.
Comparative example 2
This comparative example provides a light emitting diode epitaxial wafer, and the rest of example 1 is different in that: the P-type contact layer comprises a SiN layer and a composite layer which are sequentially deposited on the P-type GaN layer, and the composite layer comprises an h-BN layer and an Mg-doped nitrogen polarity AlInGaN layer which are alternately stacked. The remainder was referred to example 1.
Comparative example 3
This comparative example provides a light emitting diode epitaxial wafer, and the rest of example 1 is different in that: the P-type contact layer comprises an Mg-doped Ga-polar AlGaN layer and a composite layer which are sequentially deposited on the P-type GaN layer, and the composite layer comprises an h-BN layer and an Mg-doped nitrogen-polar AlInGaN layer which are alternately stacked. The remainder was referred to example 1.
Comparative example 4
This comparative example provides a light emitting diode epitaxial wafer, and the rest of example 1 is different in that: the P-type contact layer comprises a composite layer and an h-BN layer which are sequentially deposited on the P-type GaN layer, and the composite layer comprises an SiN layer and an Mg-doped Ga-polarity AlGaN layer which are alternately stacked. The remainder was referred to example 1.
Comparative example 5
This comparative example provides a light emitting diode epitaxial wafer, and the rest of example 1 is different in that: the P-type contact layer comprises a composite layer and an Mg-doped nitrogen polarity AlInGaN layer which are sequentially deposited on the P-type GaN layer, and the composite layer comprises an SiN layer and an Mg-doped Ga polarity AlGaN layer which are alternately stacked. The remainder was referred to example 1.
The light emitting diode epitaxial wafers prepared in examples 1 to 3 and comparative examples 1 to 5 were prepared into 10mil×24mil chips using the same chip process conditions, 300 LED chips were extracted, and tested at 120mA/60mA current, and the luminous efficiency improvement rates of each example and comparative example were calculated with reference to comparative example 1, and the specific test results are shown in table 1.
Table 1 results of Performance test of LEDs prepared in examples 1 to 3 and comparative examples 1 to 5
As can be seen from the above results, the light emitting diode epitaxial wafer provided by the invention has a P-type contact layer with a specific composition, wherein the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, the first composite layer comprises an alternately laminated SiN layer and an Mg doped Ga polarity AlGaN layer, and the second composite layer comprises an alternately laminated h-BN layer and an Mg doped nitrogen polarity AlInGaN layer. Compared with the light-emitting diode epitaxial wafer with the traditional buffer layer, the light-emitting diode epitaxial wafer provided by the invention can improve hole generation efficiency, reduce ohmic contact voltage and improve reflectivity.
While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that changes and modifications may be made without departing from the principles of the invention, such changes and modifications are also intended to be within the scope of the invention.

Claims (10)

1. The light-emitting diode epitaxial wafer is characterized by comprising a substrate, wherein a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, a P-type GaN layer and a P-type contact layer are sequentially arranged on the substrate;
the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, the first composite layer comprises an SiN layer and an Mg-doped Ga-polar AlGaN layer which are alternately stacked, and the second composite layer comprises an h-BN layer and an Mg-doped nitrogen-polar AlInGaN layer which are alternately stacked.
2. The led epitaxial wafer of claim 1, wherein the P-type contact layer is a P-type contact layer subjected to a high temperature annealing process comprising: at N 2 Annealing treatment is carried out at 800-900 ℃ in the atmosphere;
the annealing treatment time is 8-10 min.
3. The light-emitting diode epitaxial wafer of claim 1, wherein the SiN layer has a thickness of 1nm to 10nm;
the thickness of the Mg-doped Ga-polarity AlGaN layer is 5 nm-20 nm;
the Mg doping concentration of the Mg-doped Ga-polar AlGaN layer is 2 multiplied by 10 15 atoms/cm 3 ~2×10 16 atoms/cm 3 。
4. The light-emitting diode epitaxial wafer of claim 1, wherein the thickness of the h-BN layer is 1nm to 10nm;
the thickness of the Mg-doped nitrogen polarity AlInGaN layer is 1 nm-50 nm;
the Mg doping concentration of the Mg-doped nitrogen polarity AlInGaN layer is 2 multiplied by 10 18 atoms/cm 3 ~2×10 19 atoms/cm 3 。
5. The light emitting diode epitaxial wafer of claim 1, wherein the Mg doping concentration of the Mg doped Ga-polar AlGaN layer is less than the Mg doping concentration of the Mg doped nitrogen-polar AlInGaN layer;
the Mg doping concentration in the Mg-doped Ga-polar AlGaN layer gradually rises along the growth direction;
the Mg doping concentration in the Mg-doped nitrogen polarity AlInGaN layer gradually increases along the growth direction.
6. The light-emitting diode epitaxial wafer of claim 1, wherein the Al composition in the Mg-doped Ga-polar AlGaN layer gradually decreases in the growth direction;
the Al component in the Mg-doped nitrogen polarity AlInGaN layer gradually rises along the growth direction;
the In composition within the Mg-doped nitrogen polarity AlInGaN layer remains uniform throughout.
7. A method for preparing the light-emitting diode epitaxial wafer according to any one of claims 1 to 6, comprising the following steps:
s1, preparing a substrate;
s2, sequentially depositing a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, a P-type GaN layer and a P-type contact layer on the substrate;
the P-type contact layer comprises a first composite layer and a second composite layer which are sequentially deposited on the P-type GaN layer, the first composite layer comprises an SiN layer and an Mg-doped Ga-polar AlGaN layer which are alternately stacked, and the second composite layer comprises an h-BN layer and an Mg-doped nitrogen-polar AlInGaN layer which are alternately stacked.
8. The method for preparing a light emitting diode epitaxial wafer of claim 7, wherein the first composite layer is prepared by the following method:
controlling the temperature of the reaction chamber to be 800-1000 ℃ and the pressure to be 100-500 torr, introducing an N source and an Si source, and growing a SiN layer;
controlling the temperature of the reaction chamber to 980-1000 ℃ and the pressure to 100-500 torr, and introducing a Ga source, an Al source and a Mg source in a nitrogen atmosphere to grow a Mg-doped Ga polar AlGaN layer;
alternately growing the SiN layer and the Mg-doped Ga-polarity AlGaN layer to obtain a first composite layer.
9. The method for preparing a light emitting diode epitaxial wafer according to claim 7, wherein the second composite layer is prepared by the following method:
the temperature of the reaction chamber is controlled to be 800-1000 ℃, the pressure is controlled to be 100-500 torr, and the atmosphere is N 2 With NH 3 The volume ratio of (1): b source is introduced into the mixed gas in the step (1-10), and an h-BN layer is grown;
controlling the temperature of the reaction chamber at 800-900 ℃ and the pressure at 100-500 torr, and introducing an N source, a Ga source, an Al source, an In source and an Mg source In an ammonia atmosphere to grow an Mg-doped nitrogen polarity AlInGaN layer;
and alternately growing the h-BN layer and the Mg-doped nitrogen polarity AlInGaN layer to obtain a second composite layer.
10. An LED, characterized in that the LED comprises a light emitting diode epitaxial wafer according to any one of claims 1 to 6.
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