CN112271240A - AlGaN-based deep ultraviolet LED epitaxial wafer and preparation method thereof - Google Patents

Abstract

The invention discloses an AlGaN-based deep ultraviolet LED epitaxial wafer and a preparation method thereof, wherein the AlGaN-based deep ultraviolet LED epitaxial wafer comprises: the GaN-based solar cell comprises an SiN layer growing on a sapphire substrate, a plurality of GaN nanorods growing on the SiN layer, a plurality of AlN nanorod shell layers correspondingly wrapping the outer layers of the GaN nanorods, a plurality of AlGaN nanorod shell layers correspondingly wrapping the outer layers of the AlN nanorod shell layers, an undoped AlGaN layer growing on the AlGaN nanorod shell layers, an n-type doped AlGaN layer growing on the undoped AlGaN layer, an AlGaN multi-quantum well layer growing on the n-type doped AlGaN layer, an electron blocking layer growing on the AlGaN multi-quantum well layer, a p-type doped AlGaN layer growing on the electron blocking layer and a p-type doped GaN layer growing on the p-type doped AlGaN layer. The invention adopts the nano-pillar structure to replace the traditional complex multilayer thin film buffer layer structure, reduces the lattice mismatch between sapphire and AlGaN, and improves the performance.

Description

AlGaN-based deep ultraviolet LED epitaxial wafer and preparation method thereof

Technical Field

The invention relates to the technical field of semiconductor devices, in particular to an AlGaN-based deep ultraviolet LED epitaxial wafer and a preparation method thereof.

Background

The deep ultraviolet light has wide application prospect in the fields of national defense technology, information technology, bio-pharmaceuticals, environmental monitoring, public health, sterilization, disinfection and the like. The traditional ultraviolet light sources used at present are gas lasers and mercury lamps, and have the defects of large volume, high energy consumption, pollution and the like. An AlGaN-based compound semiconductor ultraviolet Light Emitting Diode (LED) is a solid ultraviolet light source and has the advantages of small volume, high efficiency, long service life, environmental friendliness, low energy consumption, no pollution and the like. The AlGaN material with high Al component is an irreplaceable material system for preparing high-performance deep ultraviolet LEDs, has great requirements in civil and military aspects, such as the medical and health fields of sterilization, cancer detection, skin disease treatment and the like, and has the advantages of no mercury pollution, adjustable wavelength, small volume, good integration, low energy consumption, long service life and the like.

In recent years, the development of AlGaN-based deep ultraviolet LEDs has made some progress, but the commercialization of AlGaN-based deep ultraviolet LEDs is still hindered by performance problems such as low external quantum efficiency and low light emitting power, and high-quality epitaxial materials are the basis for preparing high-performance deep ultraviolet LEDs. Currently, high-quality AlGaN materials are generally manufactured by a hetero-epitaxial method, and at present, a sapphire substrate is mostly used as an epitaxial substrate of an AlGaN-based deep ultraviolet LED, but because a large lattice mismatch exists between sapphire and an epitaxially grown AlGaN material, buffer layers of various structures are generally required to be used between the sapphire substrate and AlGaN to reduce the lattice mismatch between the sapphire substrate and the AlGaN. Therefore, in order to realize the growth of high-quality AlGaN materials and high-performance deep ultraviolet LED epitaxial wafers on sapphire substrates, it is still necessary to overcome the serious defects such as lattice mismatch, crystal dislocation, and stacking fault, which severely limits the large-scale application of the commercial production of ultraviolet LEDs.

Disclosure of Invention

The invention aims to provide an AlGaN-based deep ultraviolet LED epitaxial wafer and a preparation method thereof, and aims to solve the problem that the performance of the AlGaN-based deep ultraviolet LED epitaxial wafer in the prior art needs to be improved.

The embodiment of the invention provides an AlGaN-based deep ultraviolet LED epitaxial wafer, which comprises: the GaN-based solar cell comprises an SiN layer growing on a sapphire substrate, a plurality of GaN nanorods growing on the SiN layer, a plurality of AlN nanorod shell layers correspondingly wrapping the outer layers of the GaN nanorods, a plurality of AlGaN nanorod shell layers correspondingly wrapping the outer layers of the AlN nanorod shell layers, an undoped AlGaN layer growing on the AlGaN nanorod shell layers, an n-type doped AlGaN layer growing on the undoped AlGaN layer, an AlGaN multi-quantum well layer growing on the n-type doped AlGaN layer, an electron blocking layer growing on the AlGaN multi-quantum well layer, a p-type doped AlGaN layer growing on the electron blocking layer and a p-type doped GaN layer growing on the p-type doped AlGaN layer.

Preferably, the diameter of the single GaN nanorod ranges from 50nm to 200nm, and the height of the single GaN nanorod ranges from 300 nm to 2000 nm.

Preferably, the thickness of the single AlN nanocolumn shell layer is 50-150 nm.

Preferably, the thickness of a single AlGaN nanocolumn shell layer is 50-150 nm.

Preferably, the thickness of the undoped AlGaN layer is 500-800 nm.

Preferably, the thickness of the n-type doped AlGaN layer is 3-5 μm.

Preferably, the AlGaN multi-quantum well layer is made of Al with 7-10 periods_0.3Ga_0.7N well layer and Al_0.5Ga_0.5N barrier layers.

Preferably, the Al is_0.3Ga_0.7The thickness of the N well layer is 2-3 nm, and the Al is_0.5Ga_0.5The thickness of the N barrier layer is 10-13 nm.

Preferably, the electron blocking layer is Al_0.4Ga_0.6And the thickness of the electron blocking layer is 20-50 nm.

The embodiment of the invention provides a preparation method of the AlGaN-based deep ultraviolet LED epitaxial wafer, which comprises the following steps:

selecting a sapphire substrate;

growing a SiN layer on the sapphire substrate;

growing a plurality of GaN nano-pillars on the SiN layer;

correspondingly growing a plurality of AlN nanocolumn shell layers on the outer layers of the GaN nanocolumns;

correspondingly growing a plurality of AlGaN nanocolumn shell layers on the plurality of AlN nanocolumn shell layers;

growing a non-doped AlGaN layer on the plurality of AlGaN nanorod shell layers;

growing an n-type doped AlGaN layer on the undoped AlGaN layer;

growing an AlGaN multi-quantum well layer on the n-type doped AlGaN layer;

growing an electron barrier layer on the AlGaN multi-quantum well layer;

growing a p-type doped AlGaN layer on the electron blocking layer;

and growing a p-type doped GaN layer on the p-type doped AlGaN layer.

The embodiment of the invention provides an AlGaN-based deep ultraviolet LED epitaxial wafer and a preparation method thereof, wherein the AlGaN-based deep ultraviolet LED epitaxial wafer comprises: the GaN-based solar cell comprises an SiN layer growing on a sapphire substrate, a plurality of GaN nanorods growing on the SiN layer, a plurality of AlN nanorod shell layers correspondingly wrapping the outer layers of the GaN nanorods, a plurality of AlGaN nanorod shell layers correspondingly wrapping the outer layers of the AlN nanorod shell layers, an undoped AlGaN layer growing on the AlGaN nanorod shell layers, an n-type doped AlGaN layer growing on the undoped AlGaN layer, an AlGaN multi-quantum well layer growing on the n-type doped AlGaN layer, an electron blocking layer growing on the AlGaN multi-quantum well layer, a p-type doped AlGaN layer growing on the electron blocking layer and a p-type doped GaN layer growing on the p-type doped AlGaN layer. According to the invention, a nano-pillar structure is adopted to replace a traditional complex multilayer thin film buffer layer structure, so that the lattice mismatch between sapphire and AlGaN is reduced, the defects of the prior art are overcome, and the high-performance AlGaN-based deep ultraviolet LED epitaxial wafer is obtained.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an AlGaN-based deep ultraviolet LED epitaxial wafer according to an embodiment of the present invention;

fig. 2 is a schematic flow chart of a method for preparing an AlGaN-based deep ultraviolet LED epitaxial wafer according to an embodiment of the present invention;

fig. 3 is an electroluminescence spectrum of the AlGaN-based deep ultraviolet LED epitaxial wafer prepared according to the embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

An embodiment of the present invention provides an AlGaN-based deep ultraviolet LED epitaxial wafer, as shown in fig. 1, including: the solar cell comprises a SiN layer 102 grown on a sapphire substrate 101, a plurality of GaN nanorods 103 grown on the SiN layer 102, a plurality of AlN nanorod shell layers 104 correspondingly wrapped on the outer layers of the GaN nanorods 103, a plurality of AlGaN nanorod shell layers 105 correspondingly wrapped on the outer layers of the AlN nanorod shell layers 104, a non-doped AlGaN layer 106 grown on the AlGaN nanorod shell layers 105, an n-type doped AlGaN layer 107 grown on the non-doped AlGaN layer 106, an AlGaN multi-quantum well layer 108 grown on the n-type doped AlGaN layer 107, an electron blocking layer 109 grown on the AlGaN multi-quantum well layer 108, a p-type doped AlGaN layer 110 grown on the electron blocking layer 109, and a p-type doped GaN layer 111 grown on the p-type doped AlGaN layer 110.

Because the sapphire and the AlGaN have larger lattice mismatch, the embodiment of the invention adopts the nano-pillar structure to replace the traditional complex multilayer thin film buffer layer structure, reduces the lattice mismatch between the sapphire and the AlGaN, overcomes the defects of the prior art, and obtains the high-performance AlGaN-based deep ultraviolet LED.

Generally, because of higher lattice mismatch between sapphire and AlGaN, an AlGaN material with high crystal quality is epitaxially grown on a sapphire substrate, and a multilayer and complex buffer layer structure is generally adopted; compared with a thin film material, the nano-column has a high specific surface area, and the high specific surface area enables lattice strain generated by lattice mismatch between the nano-column and a substrate to be effectively relaxed on the side wall of the nano-column, so that the threading dislocation density can be obviously reduced, and the nano-column material with high crystal quality is obtained.

Because it is difficult to directly grow the AlGaN nanorod material with high crystal quality on the sapphire substrate, the AlN nanorod shell layer 104 and the AlGaN nanorod shell layer 105 are continuously grown outside the high-quality GaN nanorod 103, so that the high-quality AlGaN nanorod (i.e., the AlGaN nanorod shell layer 105) is obtained; the high-crystal-quality AlGaN nanocolumn shell layer 105 is taken as a basis, and the non-doped AlGaN layer 106 is epitaxially grown on the AlGaN nanocolumn shell layer 105 in the transverse direction, so that the high-crystal non-doped AlGaN layer 106 can be obtained, and the preparation of a high-performance AlGaN-based photoelectric device is facilitated.

In one embodiment, the SiN layer 102 is 2-10 nm thick.

In one embodiment, the diameter of the single GaN nanorod 103 is 50-200 nm, and the height thereof is 300-2000 nm. The GaN nanorods 103 may be uniformly distributed on the SiN layer. In addition, the distance between adjacent GaN nanorods 103 may be 400-600 nm.

In one embodiment, the thickness of the single AlN nanocolumn shell layer 104 is 50-150 nm. This thickness refers to the thickness of the cladding on the single GaN nano-pillar 103, i.e., the side thickness and the top thickness.

In one embodiment, the thickness of the AlGaN nanocolumn shell layer 105 is 50-150 nm. This thickness refers to the thickness of the single AlN nanocolumn shell 104 that is covered, i.e., the side thickness and the top thickness.

In one embodiment, the thickness of the undoped AlGaN layer 106 is 500 to 800 nm.

In one embodiment, the thickness of the n-doped AlGaN layer 107 is 3 to 5 μm. The n-type doped AlGaN layer 107 is doped with Si at a doping concentration of 1 × 10¹⁷～1×10²⁰cm^-3。

In one embodiment, the AlGaN MQW layer 108 is made of 7-10 periods of Al_0.3Ga_0.7N well layer and Al_0.5Ga_0.5N barrier layers. That is, the AlGaN MQW layer 108 is one layer of Al_0.3Ga_0.7N well layer and one layer of Al_0.5Ga_0.5The N barrier layers form a unit, the unit is continuously repeated, and 7-10 units are arranged in total.

In one embodiment, the Al_0.3Ga_0.7The thickness of the N well layer is 2-3 nm, and the Al is_0.5Ga_0.5The thickness of the N barrier layers is 10 to13 nm. The above thickness refers to the thickness of each layer, i.e. each layer of Al_0.3Ga_0.7The thickness of the N well layer is 2-3 nm, and each layer of Al_0.5Ga_0.5The thickness of the N barrier layer is 10-13 nm.

In one embodiment, the electron blocking layer 109 is Al_0.4Ga_0.6And the thickness of the electron blocking layer 109 is 20-50 nm. In order to avoid that the injected electrons cannot be efficiently radiatively recombined in the active region, the electron blocking layer 109 is provided in the embodiment of the present invention.

In one embodiment, the thickness of the p-type doped AlGaN layer 110 is 300to 350 nm. The electron blocking layer 109 is an AlGaN layer having an Al composition of 0.4, and has a large lattice mismatch with GaN, in order to reduce Al_0.4Ga_0.6The lattice mismatch between the N-electron blocking layer 109 and the p-doped GaN layer 111, and therefore the p-doped AlGaN layer 110 is interposed therebetween.

In one embodiment, the thickness of the p-type doped GaN layer 111 is 300-350 nm. In order to obtain a p-type contact layer material with a high doping concentration and a high crystalline quality, GaN is used as the p-type layer material.

An embodiment of the present invention further provides a method for preparing the AlGaN based deep ultraviolet LED epitaxial wafer, as shown in fig. 2, the method includes:

s201, selecting a sapphire substrate;

s202, growing a SiN layer on the sapphire substrate;

s203, growing a plurality of GaN nano columns on the SiN layer;

s204, correspondingly growing a plurality of AlN nanocolumn shell layers on the outer layers of the GaN nanocolumns;

s205, correspondingly growing a plurality of AlGaN nanocolumn shell layers on the plurality of AlN nanocolumn shell layers;

s206, growing a non-doped AlGaN layer on the plurality of AlGaN nano-column shell layers;

s207, growing an n-type doped AlGaN layer on the undoped AlGaN layer;

s208, growing an AlGaN multi-quantum well layer on the n-type doped AlGaN layer;

s209, growing an electronic barrier layer on the AlGaN multi-quantum well layer;

s210, growing a p-type doped AlGaN layer on the electron blocking layer;

and S211, growing a p-type doped GaN layer on the p-type doped AlGaN layer.

In step S201, a commercially available and common sapphire substrate may be used.

In the step S202, in the SiN layer growing step, the SiN layer is grown by a metal organic chemical vapor deposition method under the following process conditions: the pressure in the reaction chamber is 50-300 torr, and the temperature of the substrate is 1000-1160 ℃.

In step S203, in the GaN nanorod growth step, a metal organic chemical vapor deposition method is used to grow GaN nanorods on the SiN layer, and the process conditions are as follows: the pressure in the reaction chamber is 50-300 torr, the substrate temperature is 1000-1260 ℃, the beam current ratio V/III is 10-50, and the growth rate is 1-2 μm/h. Because the thickness of the SiN layer grown on the sapphire is very thin, a compact SiN layer cannot be formed, a partial sapphire region can be exposed on the surface of the SiN layer, and the GaN cannot perform nucleation growth on the surface of the SiN layer, namely, a mask is made on the sapphire substrate by adopting the thin SiN layer. The GaN nanorod can be grown under the condition of a low V/III ratio (V/III is 10-50); similarly, 2 layers of nanocolumns (namely an AlN nanocolumn shell layer and an AlGaN nanocolumn shell layer) are continuously wrapped on the GaN nanocolumns under the condition of low V/III ratio (V/III is 10-50).

In the step S204, in the AlN nanopillar shell layer growing step, an AlN nanopillar shell layer is grown on the GaN nanopillar by using a metal organic chemical vapor deposition method, under process conditions: the pressure in the reaction chamber is 50-300 torr, the substrate temperature is 1000-1260 ℃, the beam current ratio V/III is 10-50, and the growth rate is 1-2 μm/h.

In step S205, in the step of growing the AlGaN nanorod shell, an AlGaN nanorod shell is grown on the AlN nanorod by using a metal organic chemical vapor deposition method, and the process conditions are as follows: the pressure in the reaction chamber is 50-300 torr, the substrate temperature is 1000-1260 ℃, the beam current ratio V/III is 10-50, and the growth rate is 1-2 μm/h.

In step S206, in the step of epitaxially growing the undoped AlGaN layer, a metal organic chemical vapor deposition method is used to grow the undoped AlGaN layer on the AlGaN nanorod, and the process conditions are as follows: the pressure in the reaction chamber is 50-300 torr, the substrate temperature is 1000-1260 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 2-4 μm/h.

In step S207, in the step of epitaxially growing the n-type doped AlGaN layer, an n-type doped AlGaN layer is grown on the undoped AlGaN layer by using a metal organic chemical vapor deposition method, where the process conditions are as follows: the pressure of the reaction chamber is 50-300 torr, the temperature of the substrate is 1000-1260 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 2-4 mu m/h; the n-type doped AlGaN layer is doped with Si with the doping concentration of 1 multiplied by 10¹⁷～1×10²⁰cm^-3。

In the step S208, in the step of epitaxial growth of the AlGaN multi-quantum well layer, Al is grown on the n-type doped AlGaN layer for 7-10 periods by using a metal organic chemical vapor deposition method_0.3Ga_0.7N well layer/Al_0.5Ga_0.5N base layers, the process conditions are as follows: the pressure in the reaction chamber is 50-300 torr, the substrate temperature is 1000-1260 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 2-4 μm/h.

In the step S209, in the electron blocking layer epitaxial growth step, Al is grown on the AlGaN multi-quantum well layer by using a metal organic chemical vapor deposition method_0.4Ga_0.6The process conditions of the N electron blocking layer are as follows: the pressure in the reaction chamber is 50-300 torr, the substrate temperature is 1000-1260 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 2-4 μm/h.

In step S210, in the step of epitaxially growing the p-type doped AlGaN layer, a metal organic chemical vapor deposition method is used to grow the p-type doped AlGaN layer on the electron blocking layer, and the process conditions are as follows: the pressure in the reaction chamber is 50-300 torr, the temperature of the Si substrate is 1000-1260 ℃, the beam current ratio V/III is 3000-5000, and the growth rate is 2-4 μm/h.

In step S211, in the p-type doped GaN layer epitaxial growth step, a p-type doped GaN layer is grown on the p-type doped AlGaN layer by a metal organic chemical vapor deposition method, and the process conditions are as follows: the pressure in the reaction chamber is 50 to 300torr, the temperature of the Si substrate is 1000 to 1060 ℃, the beam current ratio V/III is 3000 to 5000, and the growth rate is 2 to 4 μm/h.

The electroluminescence spectrum of the AlGaN-based deep ultraviolet LED epitaxial wafer finally prepared in the embodiment of the invention is shown in FIG. 3.

According to the embodiment of the invention, the core-shell structure nano column is used as a buffer layer to replace a traditional multilayer film buffer layer structure, and the core-shell structure nano column is beneficial to relieving stress generated in the growth process of an epitaxial layer and relieving defect density in the film, so that the growth of a high-crystal-quality AlGaN film and an AlGaN-based deep ultraviolet LED epitaxial wafer is realized; in the preparation method of the embodiment of the invention, in order to obtain the AlGaN material with high crystal quality, the core-shell structure nano column is used as the buffer layer, then the AlGaN film is continuously grown on the nano column by changing the epitaxial growth mode, and the epitaxial layer film with high quality and smooth interface is obtained, so that the deep ultraviolet LED with high performance and high luminous efficiency is prepared.

The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Claims (10)

1. An AlGaN-based deep ultraviolet LED epitaxial wafer is characterized by comprising: the GaN-based solar cell comprises an SiN layer growing on a sapphire substrate, a plurality of GaN nanorods growing on the SiN layer, a plurality of AlN nanorod shell layers correspondingly wrapping the outer layers of the GaN nanorods, a plurality of AlGaN nanorod shell layers correspondingly wrapping the outer layers of the AlN nanorod shell layers, an undoped AlGaN layer growing on the AlGaN nanorod shell layers, an n-type doped AlGaN layer growing on the undoped AlGaN layer, an AlGaN multi-quantum well layer growing on the n-type doped AlGaN layer, an electron blocking layer growing on the AlGaN multi-quantum well layer, a p-type doped AlGaN layer growing on the electron blocking layer and a p-type doped GaN layer growing on the p-type doped AlGaN layer.

2. The AlGaN-based deep ultraviolet LED epitaxial wafer according to claim 1, wherein the diameter of each GaN nanorod is 50-200 nm, and the height of each GaN nanorod is 300-2000 nm.

3. The AlGaN-based deep ultraviolet LED epitaxial wafer according to claim 1, wherein the thickness of a single AlN nanocolumn shell layer is 50-150 nm.

4. The AlGaN-based deep ultraviolet LED epitaxial wafer according to claim 1, wherein the thickness of a single AlGaN nanocolumn shell layer is 50-150 nm.

5. The AlGaN-based deep ultraviolet LED epitaxial wafer according to claim 1, wherein the thickness of the undoped AlGaN layer is 500-800 nm.

6. The AlGaN-based deep ultraviolet LED epitaxial wafer of claim 1, wherein the thickness of the n-type doped AlGaN layer is 3-5 μm.

7. The AlGaN-based deep ultraviolet LED epitaxial wafer of claim 1, wherein the AlGaN multi-quantum well layer consists of 7-10 periods of Al_0.3Ga_0.7N well layer and Al_0.5Ga_0.5N barrier layers.

8. The AlGaN-based deep ultraviolet LED epitaxial wafer of claim 7, wherein the Al is_0.3Ga_0.7The thickness of the N well layer is 2-3 nm, and the Al is_0.5Ga_0.5The thickness of the N barrier layer is 10-13 nm.

9. The AlGaN-based deep ultraviolet LED epitaxial wafer of claim 1, wherein the electron blocking layer is Al_0.4Ga_0.6And the thickness of the electron blocking layer is 20-50 nm.

10. The preparation method of the AlGaN-based deep ultraviolet LED epitaxial wafer according to any one of claims 1 to 9, comprising the following steps of:

selecting a sapphire substrate;

growing a SiN layer on the sapphire substrate;

growing a plurality of GaN nano-pillars on the SiN layer;

correspondingly growing a plurality of AlN nanocolumn shell layers on the outer layers of the GaN nanocolumns;

correspondingly growing a plurality of AlGaN nanocolumn shell layers on the plurality of AlN nanocolumn shell layers;

growing a non-doped AlGaN layer on the plurality of AlGaN nanorod shell layers;

growing an n-type doped AlGaN layer on the undoped AlGaN layer;

growing an AlGaN multi-quantum well layer on the n-type doped AlGaN layer;

growing an electron barrier layer on the AlGaN multi-quantum well layer;

growing a p-type doped AlGaN layer on the electron blocking layer;

and growing a p-type doped GaN layer on the p-type doped AlGaN layer.

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