CN116190511B - High-light-efficiency LED epitaxial wafer, preparation method and LED chip - Google Patents
High-light-efficiency LED epitaxial wafer, preparation method and LED chip Download PDFInfo
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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
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- 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
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- H—ELECTRICITY
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- 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
- H01L33/04—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
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Abstract
The invention provides a high-light-efficiency LED epitaxial wafer, a preparation method and an LED chip, wherein the epitaxial wafer comprises a substrate, and a buffer layer, a composite three-dimensional nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, an active layer, an electronic barrier layer, a P-type AlGaN layer and a P-type contact layer which are sequentially deposited on the substrate, wherein the composite three-dimensional nucleation layer comprises an Mg quantum dot nucleation layer and an Mg quantum dot nucleation layer which are sequentially deposited x Al 1‑x N-coated nucleation layer, alN three-dimensional nucleation layer and Al y Ga 1‑y An N three-dimensional nucleation layer. Because the mobility of Mg atoms on the surface is far higher than that of Al atoms, a layer of nucleation points with larger spacing can be formed on the buffer layer, the premature merging of the nucleation points to form dislocation is avoided, the lattice mismatch with the substrate is reduced for the subsequent deposition of the AlN three-dimensional nucleation layer, the crystal quality is improved, the probability of generating cracks is reduced, and the luminous efficiency of the deep ultraviolet light-emitting diode is improved.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a high-light-efficiency LED epitaxial wafer, a preparation method and an LED chip.
Background
Group III nitrides (including AlN, gaN, inN and its alloys) based on GaN are one of the most important wide bandgap semiconductor material systems, and their unique bandgap ranges, excellent optical and electrical properties and excellent mechanical properties of materials make them widely applicable in the fields of optical devices, electronic devices, and semiconductor devices under special conditions.
The AlGaN material with high Al component and high quality is one of the most important basic works for manufacturing AlGaN-based deep ultraviolet LED devices. Compared with the growth of a GaN film on a sapphire substrate, the growth difficulty of the high-quality AlGaN film is higher, and a large number of defects exist in the AlGaN film in the growth process.
The lattice mismatch between AlGaN and sapphire is larger than that between GaN and sapphire, stress generated by the mismatch is released through dislocation generation, and a large number of dislocations are finally generated. Both of the two can reduce the crystal quality of the AlGaN epitaxial layer, even lead to cracking of the AlGaN epitaxial layer film, and influence the photoelectric performance of the deep ultraviolet light emitting diode.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a high-light-efficiency LED epitaxial wafer, a preparation method and an LED chip, and aims to solve the technical problems that in the prior art, due to lattice mismatch between AlGaN and sapphire and too large adhesion coefficient on the surface of Al atoms in the AlGaN growth process, proper lattice point positions are difficult to reach, and due to nearby nucleation growth and other reasons, a large number of dislocation is generated in the AlGaN growth process, the crystal quality of an AlGaN epitaxial layer is affected, and the photoelectric performance of a deep ultraviolet light-emitting diode is further affected.
In order to achieve the above objective, in one aspect, an embodiment of the present invention provides a high light efficiency LED epitaxial wafer, including a substrate, and a buffer layer, a composite three-dimensional nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, an active layer, an electron blocking layer, a P-type AlGaN layer, and a P-type contact layer sequentially deposited on the substrate, where the composite three-dimensional nucleation layer includes a Mg quantum dot nucleation layer, and a Mg contact layer sequentially deposited on the buffer layer x Al 1-x N-coated nucleation layer, alN three-dimensional nucleation layer and Al y Ga 1-y An N three-dimensional nucleation layer.
Compared with the prior art, the invention has the beneficial effects that: depositing the Mg quantum dot nucleation layer on the buffer layer, wherein the mobility of Mg atoms on the surface is far higher than that of Al atoms, so that a nucleation point with larger spacing can be formed on the buffer layer, and then the Mg amount is formedWrapping the Mg on the sub-point nucleation layer x Al 1-x The N cladding nucleation layer enables nucleation points to continue to grow, dislocation is prevented from being formed by premature combination of the nucleation points, lattice mismatch between the AlN three-dimensional nucleation layer and a substrate can be well reduced for subsequent deposition, and crystal quality of the AlN three-dimensional nucleation layer is improved. The AlN three-dimensional nucleation layer and the Al deposited y Ga 1-y The N three-dimensional nucleation layer enables nucleation points to be continuously enlarged and combined, and the dislocation density generated after combination is low due to the fact that the density of the nucleation points is controlled in the early stage, so that the crystal quality of the AlGaN epitaxial layer is improved, the probability of cracking of the AlGaN epitaxial layer is reduced, non-radiative recombination of the deep ultraviolet light emitting diode due to dislocation is further reduced, and the light emitting efficiency of the deep ultraviolet light emitting diode is improved.
Further, the Mg quantum dot nucleation layer comprises a plurality of Mg quantum dots which are uniformly distributed at intervals, the diameter of each Mg quantum dot is 1-100 nm, and the distance between every two adjacent Mg quantum dots is 10-1000 nm.
Further, the thickness of the Mg quantum dot nucleation layer is 1 nm-100 nm, and the Mg x Al 1-x The thickness of the N-coated nucleation layer is 10 nm-100 nm, the thickness of the AlN three-dimensional nucleation layer is 10 nm-100 nm, and the Al y Ga 1-y The thickness of the N three-dimensional nucleation layer is 0.5 um-5 um.
Still further, the Mg x Al 1-x The value range of x in the N-coated nucleation layer is 0.01-0.5, and the Al y Ga 1-y The value range of y in the N three-dimensional nucleation layer is 0.1-0.9.
Still further, the active layer includes M periodic structures including Al alternately laminated a Ga 1-a N quantum well layer and Al b Ga 1-b An N quantum barrier layer; wherein, the value range of a is 0.2-0.6, the value range of b is 0.4-0.8, and the value range of M is 3-15.
On the other hand, the embodiment of the invention provides a preparation method of a high-light-efficiency LED epitaxial wafer, which is used for preparing the high-light-efficiency LED epitaxial wafer, and comprises the following steps of:
providing a substrate required for growth, and depositing a buffer layer on the substrate;
depositing a Mg quantum dot nucleation layer on the buffer layer with a first growth condition;
sequentially depositing Mg on the Mg quantum dot nucleation layer under a second growth condition x Al 1-x N-coated nucleation layer, alN three-dimensional nucleation layer and Al y Ga 1-y N three-dimensional nucleation layer, the Mg quantum dot nucleation layer and the Mg x Al 1-x N-coated nucleation layer, alN three-dimensional nucleation layer and Al y Ga 1-y The N three-dimensional nucleation layer forms a composite three-dimensional nucleation layer;
depositing an undoped AlGaN layer on the composite three-dimensional nucleation layer;
depositing an N-type AlGaN layer on the undoped AlGaN layer;
depositing an active layer on the N-type AlGaN layer;
depositing an electron blocking layer on the active layer;
depositing a P-type AlGaN layer on the electron blocking layer;
and depositing a P-type contact layer on the P-type AlGaN layer.
Further, the first growth condition comprises a first growth gas, a first growth temperature and a first growth pressure, wherein the first growth gas is N 2 The first growth temperature is 900-1200 ℃, and the first growth pressure is 50-500 torr.
Further, the second growth conditions include a second growth gas, a second growth temperature and a second growth pressure, the second growth gas consisting of N 2 、H 2 NH and NH 3 And mixing to form the second growth temperature of 900-1200 ℃ and the second growth pressure of 50-500 torr.
Further, N in the second growth gas 2 、H 2 NH and NH 3 The mixing ratio of (2) is 1:1:1-1:10:10.
The embodiment of the invention also provides an LED chip, which comprises the high-light-efficiency LED epitaxial wafer.
Drawings
Fig. 1 is a schematic structural diagram of a high light efficiency LED epitaxial wafer in embodiment 1 of the present invention;
fig. 2 is a flow chart of a method for preparing a high light efficiency LED epitaxial wafer in embodiment 2 of the present invention;
description of main reference numerals:
the invention will be further described in the following detailed description in conjunction with the above-described figures.
Detailed Description
In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Several embodiments of the invention are presented in the figures. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "mounted" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
Referring to fig. 1, in the embodiment 1 of the present invention, a high-light-efficiency LED epitaxial wafer is used for preparing a deep ultraviolet light emitting diode. The high-light-efficiency LED epitaxial wafer comprises a substrate 100, wherein the substrate 100 is a sapphire substrate, an AlN substrate, a Si substrate or a SiC substrate, preferably, the substrate 100 is a sapphire substrate, and sapphire is the most commonly used substrate material at present, and the sapphire substrate has the advantages of mature preparation process, low price, easiness in cleaning and high stability at high temperature.
The high-light-efficiency LED epitaxial wafer further comprises a buffer layer 200, a composite three-dimensional nucleation layer 300, an undoped AlGaN layer 400, an N-type AlGaN layer 500, an active layer 600, an electron blocking layer 700, a P-type AlGaN layer 800 and a P-type contact layer 900 which are sequentially deposited on the substrate 100.
Specifically, the buffer layer 200 is an AlN buffer layer 200, the buffer layer 200 provides nucleation centers oriented in the same direction as the substrate 100, and the thickness of the buffer layer 200 is 90 nm to 110nm. The thickness of the undoped AlGaN layer 400 is 1 um-5 um, along with the increase of the thickness of the undoped AlGaN layer 400, compressive stress can be released through stacking faults, line defects are reduced, crystal quality is improved, reverse leakage is reduced, but the consumption of metal organic source materials is larger by improving the thickness of the undoped AlGaN layer 400, and the epitaxial cost of the light emitting diode is greatly improved, so that the epitaxial wafer can have higher crystal quality on the premise of saving production cost by controlling the thickness of the undoped AlGaN layer 400. The thickness of the N-type AlGaN layer 500 is 1 um-5 um, the N-type AlGaN layer 500 provides sufficient electrons and holes for the ultraviolet LED to emit light to generate recombination, and the thickness of the N-type AlGaN layer 500 can effectively release stress and improve the luminous efficiency of the light emitting diode.
The active layer 600 includes M periodic structures, the active layer 600 has a thickness of 21 nm-300 nm, and the periodic structures include alternately laminated Al a Ga 1-a N quantum well layer and Al b Ga 1-b An N quantum barrier layer, preferably the Al a Ga 1-a The thickness of the N quantum well layer is 2 nm-5 nm, and the Al b Ga 1-b The thickness of the N quantum barrier layer is 5 nm-15 nm. The active layer 600 is a region where electrons and holes are recombined, and is formed by laminating the Al a Ga 1-a N quantum well layer and Al b Ga 1-b The N quantum barrier layer can significantly increase electrons andthe overlapping degree of the cavity wave functions further improves the luminous efficiency. Preferably, the Al a Ga 1-a The value range of a in the N quantum well layer is 0.2-0.6, and the Al b Ga 1-b The value range of b in the N quantum barrier layer is 0.4-0.8, and the value range of M in the periodic structure is 3-15.
The thickness of the electron blocking layer 700 is 25-35 nm, preferably, the electron blocking layer 700 is an AlGaN electron blocking layer 700, and by arranging the electron blocking layer 700, not only can the electron overflow be effectively limited, but also the blocking of holes can be reduced, the injection efficiency of the holes to the quantum well is improved, the auger recombination of carriers is reduced, and the luminous efficiency of the light emitting diode is improved. The thickness of the P-type AlGaN layer 800 is 20 nm-200 nm, and the P-type AlGaN layer 800 can effectively fill up the epitaxial layer to obtain the deep ultraviolet LED epitaxial wafer with a smooth surface. The thickness of the P-type contact layer 900 is 5 nm-50 nm, and the P-type contact layer 900 can effectively reduce contact resistance.
The composite three-dimensional nucleation layer 300 comprises a Mg quantum dot nucleation layer 310 and Mg which are deposited in sequence x Al 1-x N-clad nucleation layer 320, alN three-dimensional nucleation layer 330 and Al y Ga 1-y N three-dimensional nucleation layer 340. Depositing the Mg quantum dot nucleation layer 310 on the buffer layer 200, since the mobility of Mg atoms on the surface is much higher than that of Al atoms, a layer of nucleation points with larger spacing can be formed on the buffer layer 200, and then the Mg quantum dot nucleation layer 310 is coated with the Mg x Al 1-x The N-cladding nucleation layer 320 allows nucleation sites to continue to grow, avoids premature merging of nucleation sites to form dislocations, and may well reduce lattice mismatch with the substrate 100 for subsequent deposition of the AlN three-dimensional nucleation layer 330, improving the crystal quality of the AlN three-dimensional nucleation layer 330. The AlN three-dimensional nucleation layer 330 and the Al deposited y Ga 1-y The N three-dimensional nucleation layer 340 continues to expand and merge nucleation points, and the dislocation density generated after merging is lower due to the early control of the density of the nucleation points, so that the crystal quality of the AlGaN epitaxial layer is improved, the probability of cracking of the AlGaN epitaxial layer is reduced, the non-radiative recombination of the deep ultraviolet light emitting diode due to dislocation is further reduced, and the two deep ultraviolet light emitting modes are improvedThe luminous efficiency of the polar tube.
Preferably, the thickness of the Mg quantum dot nucleation layer 310 is 1nm, the Mg x Al 1-x The thickness of the N-coated nucleation layer 320 is 10nm, the thickness of the AlN three-dimensional nucleation layer 330 is 10nm, and the thickness of the Al y Ga 1-y The thickness of the N three-dimensional nucleation layer 340 is 0.5um, and the structure itself is in a concave-convex shape during the growth process of the composite three-dimensional nucleation layer, by controlling the Mg quantum dot nucleation layer 310 and the Mg x Al 1-x N-clad nucleation layer 320, alN three-dimensional nucleation layer 330 and Al y Ga 1-y The thickness of the N three-dimensional nucleation layer 340 can avoid the excessive thickness to cause more surface roughness points of the composite three-dimensional nucleation layer, thereby causing the need to use more undoped AlGaN layers 400 to fill the concave-convex points, which affects the crystal quality. The Mg is x Al 1-x The value of x in the N-coated nucleation layer 320 ranges from 0.01 to 0.5, and the Al y Ga 1-y The value range of y in the N three-dimensional nucleation layer 340 is 0.1-0.9 by controlling the Mg x Al 1-x N cladding nucleation layer 320 and Al y Ga 1-y The composition of the atoms in the N three-dimensional nucleation layer 340 may make its overall structure more stable. The Mg quantum dot nucleation layer 310 includes a plurality of Mg quantum dots uniformly distributed at intervals, the diameter of each Mg quantum dot is 1nm, the distance between adjacent Mg quantum dots is 10nm, and the Mg quantum dots provide nucleation points for subsequent growth.
Referring to fig. 2, embodiment 2 of the present invention provides a method for preparing a high-light-efficiency LED epitaxial wafer, which is used for preparing the high-light-efficiency LED epitaxial wafer in the above embodiment, and includes the following steps:
s10: providing a substrate required for growth, and depositing a buffer layer on the substrate;
the buffer layer releases stress generated by lattice mismatch between AlGaN and the substrate and thermal stress generated by thermal expansion coefficient mismatch, provides a flat nucleation surface for further growth, reduces the contact angle of nucleation growth, enables GaN grains growing in an island shape to be connected into a plane in a smaller thickness, converts the GaN grains into two-dimensional epitaxial growth, improves the crystal quality of a subsequently deposited AlGaN layer, reduces dislocation density, and improves the recombination efficiency of subsequent radiation.
In the embodiment, MOCVD (Metal-organic Chemical Vapor Deposition Metal organic vapor deposition, MOCVD for short) equipment is adopted, and high-purity H 2 (Hydrogen), high purity N 2 (Nitrogen) high purity H 2 And high purity N 2 Is used as carrier gas, high-purity NH 3 As N source, trimethylgallium (TMGa) and triethylgallium (TEGa) as gallium source, trimethylaluminum (TMAL) as aluminum source, silane (SiH) 4 ) As an N-type dopant, magnesium-bis-cyclopentadienyl (CP 2 Mg) was epitaxially grown as a P-type dopant.
S20: depositing a Mg quantum dot nucleation layer on the buffer layer with a first growth condition;
the first growth condition comprises a first growth gas, a first growth temperature and a first growth pressure, wherein the first growth gas is N 2 The first growth temperature is 900 ℃, the first growth pressure is 50torr, and the thickness of the Mg quantum dot nucleation layer is 1nm.
S30: sequentially depositing Mg on the Mg quantum dot nucleation layer under a second growth condition x Al 1-x N-coated nucleation layer, alN three-dimensional nucleation layer and Al y Ga 1-y N three-dimensional nucleation layer, the Mg quantum dot nucleation layer and the Mg x Al 1-x N-coated nucleation layer, alN three-dimensional nucleation layer and Al y Ga 1-y The N three-dimensional nucleation layer forms a composite three-dimensional nucleation layer;
the second growth conditions include a second growth gas, a second growth temperature and a second growth pressure, the second growth gas consisting of N 2 、H 2 NH and NH 3 Mixing to form the second growth temperature of 900 ℃ and the second growth pressure of 50torr. The Mg is x Al 1-x The thickness of the N coating nucleation layer is 10nm, the thickness of the AlN three-dimensional nucleation layer is 10nm, and the Al y Ga 1-y The thickness of the N three-dimensional nucleation layer was 0.5um.
It will be appreciated that for convenience of growth, the first growth temperature is the same as the second growth temperatureThe first growth pressure is the same as the second growth pressure. N in the second growth gas 2 、H 2 NH and NH 3 The mixing ratio of (2) is 1:1:1. Under the condition of overhigh temperature and pressure, the composite three-dimensional nucleation layer can grow sideward, and then the composite three-dimensional nucleation layer is finally flat, and the integral structure of the composite three-dimensional nucleation layer can be ensured by controlling the first growth condition and the second growth condition.
Depositing the Mg quantum dot nucleation layer on the buffer layer, forming a nucleation point with larger spacing on the buffer layer due to the fact that the mobility of Mg atoms on the surface is far higher than that of Al atoms, and subsequently wrapping the Mg quantum dot nucleation layer x Al 1-x The N cladding nucleation layer enables nucleation points to continue to grow, dislocation is prevented from being formed by premature combination of the nucleation points, lattice mismatch between the AlN three-dimensional nucleation layer and a substrate can be well reduced for subsequent deposition, and crystal quality of the AlN three-dimensional nucleation layer is improved. The AlN three-dimensional nucleation layer and the Al deposited y Ga 1-y The N three-dimensional nucleation layer enables nucleation points to be continuously enlarged and combined, and the dislocation density generated after combination is low due to the fact that the density of the nucleation points is controlled in the early stage, so that the crystal quality of the AlGaN epitaxial layer is improved, the probability of cracking of the AlGaN epitaxial layer is reduced, non-radiative recombination of the deep ultraviolet light emitting diode due to dislocation is further reduced, and the light emitting efficiency of the deep ultraviolet light emitting diode is improved.
S40: depositing an undoped AlGaN layer on the composite three-dimensional nucleation layer;
on the composite three-dimensional nucleation layer, i.e. the Al y Ga 1-y The undoped AlGaN layer is deposited on the N three-dimensional nucleation layer by adopting a metal organic vapor deposition (MOCVD) method, the growth temperature is 1000-1300 ℃, the growth pressure is 50-500 torr, the growth temperature of the undoped AlGaN layer is higher, the growth pressure is lower, and the crystal quality of the prepared epitaxial wafer is better.
S50: depositing an N-type AlGaN layer on the undoped AlGaN layer;
depositing the N-type AlGaN layer at a growth temperature of 1000-1300 DEG CThe pressure is 90-110 torr, the doping element of the N-type AlGaN layer is Si, and the doping concentration of Si in the N-type AlGaN layer is 1E+19~5E+20 atoms/cm 3 . The resistivity of the N-type AlGaN layer is high, so that the enough Si doping can effectively reduce the resistivity of the N-type AlGaN layer.
S60: depositing an active layer on the N-type AlGaN layer;
the active layer includes M periodic structures including alternately laminated Al a Ga 1-a N quantum well layer and Al b Ga 1-b And an N quantum barrier layer. The Al is a Ga 1-a The growth temperature of the N quantum well layer is 950-1150 ℃ and the growth pressure is 50-300 torr; the Al is b Ga 1-b The growth temperature of the N quantum barrier layer is 1000-1300 ℃, and the growth pressure is 50-300 torr.
S70: depositing an electron blocking layer on the active layer;
the growth temperature of the electron blocking layer is 1000-1100 ℃, and the growth pressure is 100-300 torr.
S80: depositing a P-type AlGaN layer on the electron blocking layer;
the growth temperature of the P-type AlGaN layer is 1000-1100 ℃, the growth pressure is 100-600 torr, the doping element of the P-type AlGaN layer is Mg, and the doping concentration of Mg in the P-type AlGaN layer is 1E+19atoms/cm 3 ~5E+20atoms/cm 3 . By controlling the doping concentration of Mg, the damage to the crystal quality caused by the too high concentration of Mg can be avoided, and the influence on the hole concentration caused by the too low concentration of Mg can be avoided.
S90: and depositing a P-type contact layer on the P-type AlGaN layer.
The growth temperature of the P-type contact layer is 900-1100 ℃, the growth pressure is 100-600 torr, the doping element of the P-type contact layer is Mg, and the doping concentration of Mg in the P-type contact layer is 5E+19 atoms/cm 3 ~5E+20atoms/cm 3 . By doping Mg at a high concentration, the contact resistance of the P-type contact layer can be reduced.
The embodiment 3 of the present invention provides a method for preparing a high-light-efficiency LED epitaxial wafer, which is different from the method for preparing a high-light-efficiency LED epitaxial wafer in the embodiment 2 in that:
the thickness of the Mg quantum dot nucleation layer is 100nm, and the Mg x Al 1-x The thickness of the N coating nucleation layer is 100nm, the thickness of the AlN three-dimensional nucleation layer is 100nm, and the Al y Ga 1-y The thickness of the N three-dimensional nucleation layer is 5um.
The embodiment 4 of the present invention also provides a method for preparing a high light efficiency LED epitaxial wafer, which is different from the method for preparing a high light efficiency LED epitaxial wafer in the embodiment 2 in that:
the diameter of the Mg quantum dots is 100nm, and the distance between adjacent Mg quantum dots is 1000nm.
The embodiment 5 of the present invention also provides a method for preparing a high light efficiency LED epitaxial wafer, which is different from the method for preparing a high light efficiency LED epitaxial wafer in the embodiment 2 in that:
the first growth temperature and the second growth temperature are 1200 ℃, and the first growth pressure and the second growth pressure are 500torr.
The embodiment 6 of the present invention also provides a method for preparing a high light efficiency LED epitaxial wafer, which is different from the method for preparing a high light efficiency LED epitaxial wafer in the embodiment 2 in that:
n in the second growth gas 2 、H 2 NH and NH 3 The mixing ratio of (2) is 1:10:10.
The embodiment 7 of the invention provides an LED chip, which comprises the high-light-efficiency LED epitaxial wafer in the technical scheme.
Comparative example 1
The preparation method of the high-light-efficiency LED epitaxial wafer is different from the high-light-efficiency LED epitaxial wafer in the embodiment 2 in that:
the diameter of the Mg quantum dots is 200nm, and the distance between adjacent Mg quantum dots is 1500nm.
Comparative example 2
The preparation method of the high-light-efficiency LED epitaxial wafer is different from the high-light-efficiency LED epitaxial wafer in the embodiment 2 in that:
the first growth temperature is 1500 ℃, and the first growth pressure is 700torr.
Comparative example 3
The preparation method of the high-light-efficiency LED epitaxial wafer is different from the high-light-efficiency LED epitaxial wafer in the embodiment 2 in that:
the second growth temperature is 600 ℃, and the second growth pressure is 20torr.
Comparative example 4
The preparation method of the high-light-efficiency LED epitaxial wafer is different from the high-light-efficiency LED epitaxial wafer in the embodiment 2 in that:
the thickness of the Mg quantum dot nucleation layer is 150nm, and the Mg x Al 1-x The thickness of the N cladding nucleation layer is 150nm, the thickness of the AlN three-dimensional nucleation layer is 150nm, and the Al y Ga 1-y The thickness of the N three-dimensional nucleation layer is 10um.
Comparative example 5
The preparation method of the high-light-efficiency LED epitaxial wafer is different from the high-light-efficiency LED epitaxial wafer in the embodiment 2 in that:
depositing Al on the buffer layer d Ga 1-d An N three-dimensional nucleation layer, the Al d Ga 1-d The N three-dimensional nucleation layer forms the composite three-dimensional nucleation layer, and the Al d Ga 1-d In the comparative example, the deposition of the composite three-dimensional nucleation layer is a conventional preparation process, as the d in the N three-dimensional nucleation layer ranges from 0.5 to 0.8.
The high-light-efficiency LED epitaxial wafers prepared in the examples 2 to 6 and the comparative examples 1 to 5 are prepared into 15 mil X15 mil chips, 300 chips are prepared respectively, 120mA/60mA of current is introduced, and photoelectric efficiency tests are carried out, wherein the corresponding preparation parameters and test results are shown in the following table:
in practical application, the preparation methods and parameters corresponding to the above-mentioned examples 2-6 and comparative examples 1-5 are adopted to prepare the corresponding high-light-efficiency LED epitaxial wafer, the high-light-efficiency LED epitaxial wafer prepared by each example is prepared into a chip with the size of 15 mil by 15 mil, and 120mA/60mA of current is introduced to perform photoelectric efficiency test, and test data are shown in the table. In order to ensure the reliability of the verification result, the process and parameters of the present invention should be consistent except for the above parameters when the epitaxial wafers are prepared in the corresponding manner in examples 2 to 6 and comparative examples 1 to 5.
As can be seen from the above table, the high-light-efficiency LED epitaxial wafer prepared by the preparation method of the high-light-efficiency LED epitaxial wafer provided by the embodiments 2 to 6 of the present invention has improved brightness to a certain extent compared with the comparative example 5, i.e. compared with the conventional composite three-dimensional nucleation layer. And by controlling each parameter in a preset range, the stability of the whole structure can be effectively ensured, and the brightness improving effect is ensured.
In summary, in the high-light-efficiency LED epitaxial wafer and the preparation method thereof according to the embodiments of the present invention, the Mg quantum dot nucleation layer is deposited on the buffer layer, and since the mobility of Mg atoms on the surface is far higher than that of Al atoms, a nucleation point with a larger layer spacing can be formed on the buffer layer, and then the Mg quantum dot nucleation layer is coated with the Mg quantum dot nucleation layer x Al 1-x The N cladding nucleation layer enables nucleation points to continue to grow, dislocation is prevented from being formed by premature combination of the nucleation points, lattice mismatch between the AlN three-dimensional nucleation layer and a substrate can be well reduced for subsequent deposition, and crystal quality of the AlN three-dimensional nucleation layer is improved. The AlN three-dimensional nucleation layer and the Al deposited y Ga 1-y The N three-dimensional nucleation layer enables nucleation points to be continuously enlarged and combined, and the dislocation density generated after combination is low due to the fact that the density of the nucleation points is controlled in the early stage, so that the crystal quality of the AlGaN epitaxial layer is improved, the probability of cracking of the AlGaN epitaxial layer is reduced, non-radiative recombination of the deep ultraviolet light emitting diode due to dislocation is further reduced, and the light emitting efficiency of the deep ultraviolet light emitting diode is improved.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (9)
1. The high-light-efficiency LED epitaxial wafer is characterized by comprising a substrate, and a buffer layer, a composite three-dimensional nucleation layer, an undoped AlGaN layer, an N-type AlGaN layer, an active layer, an electron blocking layer, a P-type AlGaN layer and a P-type contact layer which are sequentially deposited on the substrate, wherein the composite three-dimensional nucleation layer comprises an Mg quantum dot nucleation layer and an Mg quantum dot nucleation layer which are sequentially deposited on the buffer layer x Al 1-x N-coated nucleation layer, alN three-dimensional nucleation layer and Al y Ga 1-y An N three-dimensional nucleation layer, the Mg x Al 1-x The value range of x in the N-coated nucleation layer is 0.01-0.5, and the Al y Ga 1-y The value range of y in the N three-dimensional nucleation layer is 0.1-0.9.
2. The high-light-efficiency LED epitaxial wafer according to claim 1, wherein the Mg quantum dot nucleation layer comprises a plurality of Mg quantum dots which are uniformly distributed at intervals, the diameter of each Mg quantum dot is 1-100 nm, and the distance between every two adjacent Mg quantum dots is 10-1000 nm.
3. The high-light-efficiency LED epitaxial wafer of claim 1, whereinThe thickness of the Mg quantum dot nucleation layer is 1 nm-100 nm, and the Mg is x Al 1-x The thickness of the N-coated nucleation layer is 10 nm-100 nm, the thickness of the AlN three-dimensional nucleation layer is 10 nm-100 nm, and the Al y Ga 1-y The thickness of the N three-dimensional nucleation layer is 0.5 um-5 um.
4. A high light efficiency LED epitaxial wafer according to any one of claims 1 to 3 wherein said active layer comprises M periodic structures comprising Al alternately laminated a Ga 1-a N quantum well layer and Al b Ga 1-b An N quantum barrier layer;
wherein, the value range of a is 0.2-0.6, the value range of b is 0.4-0.8, and the value range of M is 3-15.
5. A method for preparing a high-light-efficiency LED epitaxial wafer, which is used for preparing the high-light-efficiency LED epitaxial wafer according to any one of claims 1 to 4, and is characterized in that the method for preparing the high-light-efficiency LED epitaxial wafer comprises the following steps:
providing a substrate required for growth, and depositing a buffer layer on the substrate;
depositing a Mg quantum dot nucleation layer on the buffer layer with a first growth condition;
sequentially depositing Mg on the Mg quantum dot nucleation layer under a second growth condition x Al 1-x N-coated nucleation layer, alN three-dimensional nucleation layer and Al y Ga 1-y N three-dimensional nucleation layer, the Mg quantum dot nucleation layer and the Mg x Al 1-x N-coated nucleation layer, alN three-dimensional nucleation layer and Al y Ga 1-y The N three-dimensional nucleation layer forms a composite three-dimensional nucleation layer;
depositing an undoped AlGaN layer on the composite three-dimensional nucleation layer;
depositing an N-type AlGaN layer on the undoped AlGaN layer;
depositing an active layer on the N-type AlGaN layer;
depositing an electron blocking layer on the active layer;
depositing a P-type AlGaN layer on the electron blocking layer;
and depositing a P-type contact layer on the P-type AlGaN layer.
6. The method for preparing a high-light-efficiency LED epitaxial wafer according to claim 5, wherein the first growth condition comprises a first growth gas, a first growth temperature and a first growth pressure, and the first growth gas is N 2 The first growth temperature is 900-1200 ℃, and the first growth pressure is 50-500 torr.
7. The method for preparing a high-light-efficiency LED epitaxial wafer according to claim 5, wherein the second growth conditions comprise a second growth gas, a second growth temperature and a second growth pressure, wherein the second growth gas consists of N 2 、H 2 NH and NH 3 And mixing to form the second growth temperature of 900-1200 ℃ and the second growth pressure of 50-500 torr.
8. The method for preparing a high-light-efficiency LED epitaxial wafer according to claim 7, wherein N in the second growth gas 2 、H 2 NH and NH 3 The mixing ratio of (2) is 1:1:1-1:10:10.
9. An LED chip comprising the high-efficiency LED epitaxial wafer according to any one of claims 1 to 4.
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