Light emitting diode epitaxial wafer and preparation method thereof, and light emitting diode

Abstract

The application discloses a light-emitting diode epitaxial wafer and a preparation method thereof and a light-emitting diode, and relates to the field of semiconductor photoelectric devices. The light-emitting diode epitaxial wafer comprises a substrate and a nucleation layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer and a P-type GaN layer arranged on the substrate in sequence; the multi-quantum well layer is a periodic structure, and the period number is 2-15; each period comprises a quantum well layer and a quantum barrier layer which are stacked in sequence; each quantum barrier layer comprises: a plurality of AlN nanorods which are arrayed on the quantum well layer; a plurality of AlGaN nanorods which are one-to-one correspondingly stacked on the AlN nanorods; and a GaN two-dimensional layer which is stacked on the AlGaN nanorods, and the GaN two-dimensional layer grows and merges along a preset direction of the top of the AlGaN nanorods to form a quantum barrier layer with nanoholes. By implementing the application, the light-emitting efficiency of the light-emitting diode can be improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic devices, and more particularly to a light-emitting diode epitaxial wafer and its fabrication method, and a light-emitting diode. Background Technology

[0002] Currently, GaN-based light-emitting diodes (LEDs) are widely used in solid-state lighting and display fields, attracting increasing attention. GaN-based LEDs have achieved industrial-scale production and are used in backlights, general lighting, and landscape lighting.

[0003] In light-emitting diodes (LEDs), the multiple quantum well layer serves as the active light-emitting region. It is a periodic structure consisting of repeated stacked potential well and barrier layers, and is the most important structure in epitaxial growth. The inventors discovered the following problems:

[0004] (1) The traditional InGaN potential well layer and GaN barrier layer have severe lattice mismatch, which leads to piezoelectric polarization and defect accumulation in the multiple quantum well layer, affecting the luminous efficiency of the light-emitting diode, especially at low current density.

[0005] (2) Because the electron mobility is greater than that of holes and P-type doping is difficult to activate, the electron mobility is greater than that of holes in the multi-quantum well layer, and electron overflow is prone to occur, which affects the luminescence efficiency. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an epitaxial wafer for a light-emitting diode and a method for preparing the same, which can improve the luminous efficiency of the light-emitting diode.

[0007] Another technical problem that this invention aims to solve is to provide a light-emitting diode with high luminous efficiency.

[0008] To address the aforementioned problems, this invention discloses a light-emitting diode epitaxial wafer, comprising a substrate and a nucleation layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially disposed on the substrate; the multiple quantum well layer has a periodic structure with a period number of 2 to 15, and each period includes sequentially stacked quantum well layers and quantum barrier layers; each quantum barrier layer includes:

[0009] Multiple AlN nanopillars are arrayed on the quantum well layer;

[0010] Each AlGaN nanopillar corresponds to one of the multiple AlGaN nanopillars stacked on the AlN nanopillars;

[0011] A two-dimensional GaN layer is stacked on the AlGaN nanopillar, and the GaN two-dimensional layer grows and merges along a predetermined direction at the top of the AlGaN nanopillar to form a quantum barrier layer with nanopores.

[0012] As an improvement to the above technical solution, the aspect ratio of the AlN nanopillar is greater than that of the AlGaN nanopillar.

[0013] As an improvement to the above technical solution, the AlN nanopillars have a height of 10-20 nm, a diameter of 2-5 nm, an Al component ratio of 0.6-0.7, and a distance of 10-200 nm between adjacent AlN nanopillars.

[0014] As an improvement to the above technical solution, the AlGaN nanopillars have a height of 5-10 nm, a diameter of 2-5 nm, and an Al component ratio of 0.25-0.3%.

[0015] As an improvement to the above technical solution, the thickness of the GaN two-dimensional layer is 2-5 nm.

[0016] As an improvement to the above technical solution, the diameter of the AlGaN nanopillars gradually increases from 2-5 nm to 10-20 nm along the epitaxial growth direction.

[0017] Accordingly, the present invention also discloses a method for preparing a light-emitting diode epitaxial wafer, which includes:

[0018] A substrate is provided on which a nucleation layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer are sequentially grown. The multiple quantum well layer has a periodic structure, with each period comprising sequentially stacked quantum well layers and quantum barrier layers. Each quantum barrier layer includes:

[0019] Multiple AlN nanopillars are arrayed on the quantum well layer;

[0020] Each AlGaN nanopillar corresponds to one of the multiple AlGaN nanopillars stacked on the AlN nanopillars;

[0021] A two-dimensional GaN layer is stacked on the AlGaN nanopillar, and the GaN two-dimensional layer grows and merges along a predetermined direction at the top of the AlGaN nanopillar to form a quantum barrier layer with nanopores.

[0022] As an improvement to the above technical solution, the growth temperature of the AlN nanopillars is 500-700℃, and the growth pressure is 500-600 torr.

[0023] The growth temperature of the AlGaN nanopillars is 750–850 °C, and the growth pressure is 300–400 torr.

[0024] The growth temperature of the GaN two-dimensional layer is 1300–1400℃, and the growth pressure is 200–300 torr.

[0025] As an improvement to the above technical solution, the V / Ⅲ ratio is 1500-2500 during the growth of the AlN nanopillars;

[0026] During the growth of the AlGaN nanopillars, the V / Ⅲ ratio is 1000–1500;

[0027] During the growth of the GaN two-dimensional layer, the V / Ⅲ ratio is 200 to 500.

[0028] Accordingly, the present invention also discloses a light-emitting diode, which includes the above-mentioned light-emitting diode epitaxial wafer.

[0029] Implementing this invention has the following beneficial effects:

[0030] 1. In the epitaxial wafer of the light-emitting diode of the present invention, a quantum barrier layer with nanopores is formed by AlN nanopillars, AlGaN nanopillars, and a GaN two-dimensional layer. This significantly reduces the direct contact area between the quantum well layer and the quantum barrier layer, thereby reducing the lattice mismatch between them, reducing the polarization effect caused by the lattice mismatch, reducing non-radiative combinations, and improving luminous efficiency, especially the luminous efficiency under low current. Furthermore, the quantum barrier layer with nanopores can better release stress and reduce band tilt than a bulk two-dimensional quantum barrier layer. Therefore, the light-emitting diode exhibits enhanced wavelength consistency and reduced color difference when injected with different currents.

[0031] 2. The quantum barrier layer of the present invention incorporates AlN nanopillars and AlGaN nanopillars with high Al content, which have higher energy levels and can effectively alleviate electron migration rate and reduce electron overflow.

[0032] 3. In the epitaxial wafer of the light-emitting diode of the present invention, a quantum barrier layer with nanopores is formed by AlN nanopillars, AlGaN nanopillars and GaN two-dimensional layer, which increases the diffuse reflection of the light-emitting diode in the multi-quantum-well region, especially greatly enhances the lateral light emission and increases the light emission efficiency. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a light-emitting diode epitaxial wafer in one embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure of a multi-quantum well layer in one embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the structure of a multi-quantum well layer in another embodiment of the present invention;

[0036] Figure 4 This is a flowchart of a method for preparing an epitaxial wafer for a light-emitting diode according to an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0038] refer to Figure 1 and Figure 2 This invention discloses a light-emitting diode epitaxial wafer, comprising a substrate 1 and a nucleation layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a multiple quantum well layer 5, an electron blocking layer 6, and a P-type GaN layer 7 sequentially disposed on the substrate 1. The multiple quantum well layer 5 has a periodic structure with 2 to 15 periods, and each period includes a quantum well layer 51 and a quantum barrier layer 52 stacked sequentially.

[0039] Each quantum barrier layer 52 includes: multiple AlN nanopillars 521 arrayed on the quantum well layer 51, multiple AlGaN nanopillars 522 stacked one-to-one on the AlN nanopillars 521, and a GaN two-dimensional layer 523 stacked on the AlGaN nanopillars 522. The GaN two-dimensional layer 523 grows and merges along a predetermined direction at the top of the AlGaN nanopillars 522 to form a quantum barrier layer 52 with nanopores 524.

[0040] The AlN nanopillars 521 have a height of 5–30 nm. When their height is less than 5 nm, it is difficult to form a quantum barrier layer 52 with nanopores 524; when their height is greater than 30 nm, the potential barrier of the quantum barrier layer 52 is too high, reducing the luminescence efficiency. Exemplarily, the height of the AlN nanopillars 521 is 8 nm, 10 nm, 12 nm, 15 nm, 20 nm, 22 nm, 26 nm, or 28 nm, but is not limited thereto. Preferably, the height of the AlN nanopillars 521 is 10–20 nm.

[0041] The AlN nanopillars 521 have a diameter of 1–10 nm, and the distance between adjacent AlN nanopillars 521 is 5–220 nm. When their diameter is too small or the adjacent spacing is too large, it is difficult for the subsequent GaN two-dimensional layers 523 to connect and form a two-dimensional structure, affecting the crystal quality of the multiple quantum well layer 5 and reducing the luminescence efficiency. When their diameter is too large or the adjacent spacing is too small, it is difficult to form effective light scattering. For example, the diameter of the AlN nanopillars 521 is 2 nm, 4 nm, 6 nm, 8 nm, or 9 nm, but is not limited to these. Preferably, it is 2–5 nm. For example, the distance between adjacent AlN nanopillars 521 is 15 nm, 30 nm, 45 nm, 60 nm, 80 nm, 125 nm, 130 nm, or 180 nm, but is not limited to these. Preferably, it is 10–200 nm.

[0042] The Al component in AlN nanopillars 521 comprises 0.5–0.8%, with exemplary values ​​of 0.55, 0.59, 0.63, 0.67, 0.72, or 0.78, but not limited thereto. Preferably, it comprises 0.6–0.7%.

[0043] The height of the AlGaN nanopillars 522 is 3–15 nm, with exemplary values ​​of 5 nm, 7 nm, 9 nm, 11 nm, or 13 nm, but not limited thereto. Preferably, it is 5–10 nm.

[0044] AlGaN nanopillars 522 can be cylindrical structures with uniform diameter or frustum structures with gradually changing diameter. In one embodiment of the present invention, the AlGaN nanopillars 522 are cylindrical structures with uniform diameter, the same as the diameter of the AlN nanopillars 521, i.e., 2–5 nm. (Reference) Figure 4 In another embodiment of the present invention, the AlGaN nanopillars 522 are frustum structures with a gradually changing diameter. Specifically, the diameter of the AlGaN nanopillars gradually increases from 2-5 nm to 10-20 nm along the epitaxial growth direction. Based on the above structure, the AlGaN nanopillars 522 can not only further improve the light extraction efficiency, but also effectively improve the crystal quality of the GaN two-dimensional layer 523, thereby improving the crystal quality of the multi-quantum well layer 5 and enhancing the luminescence efficiency.

[0045] The Al component in AlGaN nanopillars 522 comprises 0.2–0.4%, with exemplary values ​​of 0.22, 0.26, 0.3, 0.34, 0.38, or 0.39, but not limited thereto. Preferably, it comprises 0.25–0.3%.

[0046] Preferably, in one embodiment of the present invention, the aspect ratio of AlN nanopillars 521 is greater than that of AlGaN nanopillars 522. Based on this structure, the luminous efficiency of the light-emitting diode can be further improved.

[0047] The thickness of the GaN two-dimensional layer 523 is 1–15 nm, with exemplary thicknesses of 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, or 14 nm, but not limited thereto. Preferably, it is 2–5 nm.

[0048] The substrate 1 can be a sapphire substrate, a silicon substrate, a SiC substrate, a ZnO substrate, or a GaN substrate, but is not limited to these.

[0049] The nucleation layer 2 can be an AlN layer and / or an AlGaN layer, but is not limited thereto. Preferably, it is an AlN layer with a thickness of 20–100 nm, such as 25 nm, 30 nm, 35 nm, 40 nm, 50 nm, 70 nm or 85 nm, but is not limited thereto.

[0050] The thickness of the undoped GaN layer 3 is 300–800 nm, with exemplary values ​​of 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 700 nm, or 750 nm, but not limited to these.

[0051] The doping element of the N-type GaN layer 4 is Si, but it is not limited to Si. The doping concentration of the N-type GaN layer 4 is 5 × 10⁻⁶. 18 ~5×10 19 cm -3 An example is 7×10 18 cm -3 9×10 18 cm -3 1.5×10 19 cm -3 3×10 19 cm -3 Or 4×10 19 cm -3 However, it is not limited to this. The thickness of the N-type GaN layer 4 is 1 to 3 μm, with exemplary thicknesses of 1.2 μm, 1.6 μm, 2 μm, 2.4 μm, 2.8 μm or 2.9 μm, but it is not limited to this.

[0052] The quantum well layer 51 is an InGaN layer with a thickness of 2–5 nm. Examples include 2.5 nm, 3 nm, 3.5 nm, 4 nm, or 4.5 nm, but it is not limited to these.

[0053] The electron blocking layer 6 is an AlGaN layer or an AlInGaN layer, but is not limited to these. Preferably, it is Al... a Ga 1-a N layer (a = 0.05–0.2) and In b Ga 1-b A periodic structure with alternating N layers (b = 0.1–0.5) and a period number of 3–15. The thickness of electron blocking layer 6 is 20–100 nm.

[0054] The doping element in the p-type GaN layer 7 is Mg, but it is not limited to this. The doping concentration of Mg in the p-type GaN layer 7 is 1×10⁻⁶. 19 ~1×10 21 cm -3 An example is 5×10 19 cm -3 8×10 19 cm -3 2×10 20 cm -3 6×10 20 cm -3 Or 9×10 20 cm-3 However, it is not limited to this. The thickness of the p-type GaN layer 7 is 20 to 100 nm, with examples being 25 nm, 30 nm, 35 nm, 40 nm, 55 nm, 70 nm or 85 nm, but not limited to this.

[0055] Accordingly, refer to Figure 4 The present invention also discloses a method for preparing a light-emitting diode epitaxial wafer, which includes the following steps:

[0056] S1: Provides a substrate;

[0057] Preferably, in one embodiment of the present invention, the substrate is loaded into the MOCVD reaction chamber and pretreated in an H2 atmosphere for 5 to 8 minutes at a processing temperature of 1000 to 1200°C and a processing pressure of 200 to 600 torr.

[0058] S2: A nucleation layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer are grown sequentially on the substrate;

[0059] Specifically, step S2 includes:

[0060] S21: Growing a nucleation layer on the substrate;

[0061] Among them, AlGaN layers grown by MOCVD or AlN layers grown by PVD can be used as nucleation layers, but are not limited to these.

[0062] Preferably, in one embodiment of the present invention, an AlGaN layer is grown by MOCVD as a nucleation layer at a growth temperature of 500–700°C and a growth pressure of 200–400 torr. During growth, NH3 is introduced into the MOCVD reaction chamber as an N source, N2 and H2 as carrier gases, TMGa is introduced as a Ga source, and TMAl is introduced as an Al source.

[0063] S22: Growing an undoped GaN layer on the nucleation layer;

[0064] In one embodiment of the present invention, an undoped GaN layer is grown in MOCVD at a growth temperature of 1100–1150°C and a growth pressure of 100–500 torr. During growth, NH3 is introduced into the MOCVD reaction chamber as an N source, N2 and H2 are introduced as carrier gases, and TMGa is introduced as a Ga source.

[0065] S23: Growing an N-type GaN layer on an undoped GaN layer;

[0066] In one embodiment of the present invention, an N-type GaN layer is grown in MOCVD at a growth temperature of 1100–1150 °C and a growth pressure of 100–500 torr. During growth, NH3 is introduced into the MOCVD reaction chamber as an N source, N2 and H2 are introduced as carrier gases, TMGa is introduced as a Ga source, and SiH4 is introduced as an N-type doping source.

[0067] S24: Growth of multiple quantum well layers on N-type GaN layers;

[0068] In one embodiment of the present invention, quantum well layers and quantum barrier layers are periodically grown in MOCVD to form a multi-quantum well layer. The InGaN well layer is grown at a temperature of 700–800°C and a growth pressure of 100–300 torr. During growth, NH3 is introduced into the MOCVD reaction chamber as an N source, N2 as a carrier gas, TMGa as a Ga source, and TMIn as an In source.

[0069] Specifically, in one embodiment of the present invention, the growth method of each quantum barrier layer is as follows:

[0070] (I) Growth of AlN nanopillars on quantum well layers;

[0071] The AlN nanopillars were grown at a temperature of 500–700 °C and a pressure of 500–600 torr. During growth, NH3 was introduced as the N source, N2 and H2 as carrier gases, and TMAl as the Al source in the MOCVD reaction chamber. Based on these growth parameters, multiple spaced columnar three-dimensional structures could be grown on the quantum well layer.

[0072] Preferably, in one embodiment of the present invention, the V / III ratio is 1500 to 2500 during the growth of AlN nanopillars. Based on this control, the three-dimensional growth trend of AlN can be further enhanced.

[0073] (II) AlGaN nanopillars are grown on AlN nanopillars in a one-to-one correspondence;

[0074] The AlGaN nanopillars were grown at a temperature of 750–850 °C and a growth pressure of 300–400 torr. During growth, NH3 was introduced as the N source, N2 and H2 as the carrier gases, TMGa as the Ga source, and TMAl as the Al source in the MOCVD reaction chamber. Based on these growth conditions, nanopillar structures, namely AlGaN nanopillars, could be formed on top of the AlN nanopillars.

[0075] Preferably, in one embodiment of the present invention, the V / III ratio is 1000-1500 during the growth of AlGaN nanopillars; based on this control, the three-dimensional growth trend of AlGaN can be further enhanced.

[0076] (III) Growth of GaN two-dimensional layers on AlGaN nanopillars;

[0077] The GaN two-dimensional layer was grown at a temperature of 1300–1400 °C and a growth pressure of 200–300 torr. During growth, NH3 was introduced as the nitrogen source, N2 and H2 as carrier gases, and TMGa was introduced as the Ga source in the MOCVD reaction chamber. Based on these growth conditions, the GaN two-dimensional layer could be continuously grown and gradually merged on the top of the AlGaN nanopillar along a predetermined direction, thereby forming a quantum barrier layer with nanopores.

[0078] Preferably, in one embodiment of the present invention, the V / III ratio is 200 to 500 during the growth of the GaN two-dimensional layer. Based on this growth condition, the two-dimensional growth trend of the GaN two-dimensional layer can be improved.

[0079] S25: Growth of an electron blocking layer on a multi-quantum-well layer;

[0080] In one embodiment of the present invention, Al is periodically grown in MOCVD. a Ga 1-a N layer (a = 0.05–0.2) and In b Ga 1-b N layers (b = 0.1–0.5) are added until an electron blocking layer is obtained; both are grown at temperatures of 900–1000℃ and at pressures of 100–500 torr. Among these, Al is grown... a Ga 1-a In the N-layer stage, NH3 is introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa as the Ga source, and TMAl as the Al source. In is then grown. b Ga 1-b In the N layer, NH3 is introduced into the MOCVD reaction chamber as the N source, N2 as the carrier gas, TMGa as the Ga source, and TMIn as the In source.

[0081] S26: Grow a P-type GaN layer on the electron blocking layer;

[0082] In one embodiment of the present invention, a p-type GaN layer is grown in MOCVD at a growth temperature of 800–1000 °C and a growth pressure of 100–300 torr. During growth, NH3 is introduced into the MOCVD reaction chamber as an N source, N2 and H2 are introduced as carrier gases, TMGa is introduced as a Ga source, and CP2Mg is introduced as a p-type doping source.

[0083] The present invention will be further described below with reference to specific embodiments:

[0084] Example 1

[0085] This embodiment provides a light-emitting diode epitaxial wafer, referenced... Figure 1 and Figure 2 It includes a substrate 1 and a nucleation layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a multiple quantum well layer 5, an electron blocking layer 6, and a P-type GaN layer 7 sequentially disposed on the substrate 1.

[0086] In this design, substrate 1 is a sapphire substrate, nucleation layer 2 is an AlN layer with a thickness of 30 nm, undoped GaN layer 3 has a thickness of 400 nm, and N-type GaN layer 4 has a thickness of 2 μm, with Si as the dopant element and a Si doping concentration of 2.5 × 10⁻⁶. 19 cm -3 .

[0087] The multi-quantum-well layer 5 has a periodic structure with 10 periods, each period consisting of sequentially stacked quantum well layers (InGaN layers) and quantum barrier layers. The thickness of a single quantum well layer is 3 nm. Each quantum barrier layer 52 includes: multiple AlN nanopillars 521 arrayed on the quantum well layer 51; multiple AlGaN nanopillars 522 stacked one-to-one on the AlN nanopillars 521; and a GaN two-dimensional layer 523 stacked on the AlGaN nanopillars 522. The GaN two-dimensional layer 523 grows and merges along a predetermined direction at the top of the AlGaN nanopillars 522 to form a quantum barrier layer 52 with nanopores 524. The AlN nanopillars 521 have a height of 12 nm, a diameter of 5 nm, and a distance of 15 nm between adjacent AlN nanopillars 521. The Al content in the AlN nanopillars 521 is 0.62%. The AlGaN nanopillars 522 have a height of 12 nm, a diameter of 5 nm, and an Al content of 0.28%. The thickness of the GaN 2D layer 523 is 4 nm.

[0088] Among them, electron blocking layer 6 is Al a Ga 1-a N layers (a = 0.1) and In b Ga 1-b A periodic structure with N alternating layers (b = 0.3) and a period number of 8. A single Al a Ga 1-a The thickness of the N layer is 6nm, and a single In... b Ga 1-b The thickness of the N-layer is 6 nm. The dopant element of the p-type GaN layer 7 is Mg, with a doping concentration of 2 × 10⁻⁶. 20 cm -3 The thickness is 45nm.

[0089] The method for fabricating an epitaxial wafer for a light-emitting diode in this embodiment includes the following steps:

[0090] (1) Provide a substrate;

[0091] Preferably, in one embodiment of the present invention, the substrate is loaded into the MOCVD reaction chamber, pretreated in an H2 atmosphere for 7 min, the treatment temperature is 1100°C, and the treatment pressure is 400 torr.

[0092] (2) Growing a nucleation layer on a substrate;

[0093] In this study, AlN layers were grown using PVD as nucleation layers.

[0094] (3) Grow an undoped GaN layer on the nucleation layer;

[0095] Undoped GaN layers were grown in MOCVD at a temperature of 1120℃ and a pressure of 300 torr. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 were introduced as the carrier gas, and TMGa was introduced as the Ga source.

[0096] (4) An N-type GaN layer is grown on an undoped GaN layer;

[0097] In this process, an N-type GaN layer was grown in MOCVD at a temperature of 1140℃ and a pressure of 300 torr. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa was introduced as the Ga source, and SiH4 was introduced as the N-type doping source.

[0098] (5) Growth of multiple quantum well layers on N-type GaN layers;

[0099] In this process, quantum well layers and quantum barrier layers are periodically grown in MOCVD to form multiple quantum well layers. The InGaN well layer is grown at a temperature of 760℃ and a growth pressure of 200 torr. During growth, NH3 is introduced as the N source, N2 as the carrier gas, TMGa as the Ga source, and TMIn as the In source into the MOCVD reaction chamber.

[0100] The growth method for each quantum barrier layer is as follows:

[0101] (I) Growth of AlN nanopillars on quantum well layers;

[0102] The growth temperature of the AlN nanopillars was 580℃, the growth pressure was 560 torr, the V / III ratio was 2000, and during growth, NH3 was introduced as the N source, N2 and H2 were introduced as carrier gases, and TMAl was introduced as the Al source in the MOCVD reaction chamber.

[0103] (II) AlGaN nanopillars are grown on AlN nanopillars in a one-to-one correspondence;

[0104] The growth temperature of AlGaN nanopillars was 800℃, the growth pressure was 380 torr, and the V / III ratio was 2000. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 were introduced as the carrier gas, TMGa was introduced as the Ga source, and TMAl was introduced as the Al source.

[0105] (III) Growth of GaN two-dimensional layers on AlGaN nanopillars;

[0106] The GaN two-dimensional layer was grown at a temperature of 1320℃, a growth pressure of 220 torr, and a V / III ratio of 300. During growth, NH3 was introduced as the N source, N2 and H2 were introduced as carrier gases, and TMGa was introduced as the Ga source in the MOCVD reaction chamber.

[0107] (6) Grow an electron blocking layer on a multi-quantum-well layer;

[0108] Among them, Al is periodically grown in MOCVD a Ga 1-a N layers and In b Ga 1-b The process continues until an electron blocking layer is obtained; both are grown at a temperature of 950℃ and a growth pressure of 300 torr. Specifically, Al is grown... a Ga 1-a In the N-layer stage, NH3 is introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa as the Ga source, and TMAl as the Al source. In is then grown. b Ga 1-b In the N layer, NH3 is introduced into the MOCVD reaction chamber as the N source, N2 as the carrier gas, TMGa as the Ga source, and TMIn as the In source.

[0109] (7) Grow a P-type GaN layer on the electron blocking layer;

[0110] In this process, a P-type GaN layer was grown in MOCVD at a temperature of 930℃ and a pressure of 200 torr. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa was introduced as the Ga source, and CP2Mg was introduced as the P-type doping source.

[0111] Example 2

[0112] This embodiment provides a light-emitting diode epitaxial wafer, referenced... Figure 1 and Figure 2 It includes a substrate 1 and a nucleation layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a multiple quantum well layer 5, an electron blocking layer 6, and a P-type GaN layer 7 sequentially disposed on the substrate 1.

[0113] In this design, substrate 1 is a sapphire substrate, nucleation layer 2 is an AlN layer with a thickness of 30 nm, undoped GaN layer 3 has a thickness of 400 nm, and N-type GaN layer 4 has a thickness of 2 μm, with Si as the dopant element and a Si doping concentration of 2.5 × 10⁻⁶. 19 cm -3 .

[0114] The multi-quantum-well layer 5 has a periodic structure with 10 periods, each period consisting of sequentially stacked quantum well layers (InGaN layers) and quantum barrier layers. The thickness of a single quantum well layer is 3 nm. Each quantum barrier layer 52 includes: multiple AlN nanopillars 521 arrayed on the quantum well layer 51; multiple AlGaN nanopillars 522 stacked one-to-one on the AlN nanopillars 521; and a GaN two-dimensional layer 523 stacked on the AlGaN nanopillars 522. The GaN two-dimensional layer 523 grows and merges along a predetermined direction at the top of the AlGaN nanopillars 522 to form a quantum barrier layer 52 with nanopores 524. The AlN nanopillars 521 have a height of 12 nm, a diameter of 4 nm, and a distance of 15 nm between adjacent AlN nanopillars 521. The Al content in the AlN nanopillars 521 is 0.62%. The AlGaN nanopillars 522 have a height of 8 nm, a diameter of 4 nm, and an Al content of 0.28%. The thickness of the GaN 2D layer 523 is 4 nm.

[0115] Among them, electron blocking layer 6 is Al a Ga 1-a N layers (a = 0.1) and In b Ga 1-b A periodic structure with N alternating layers (b = 0.3) and a period number of 8. A single Al a Ga 1-a The thickness of the N layer is 6nm, and a single In... b Ga 1-b The thickness of the N-layer is 6 nm. The dopant element of the p-type GaN layer 7 is Mg, with a doping concentration of 2 × 10⁻⁶. 20 cm -3 The thickness is 45nm.

[0116] The method for fabricating an epitaxial wafer for a light-emitting diode in this embodiment includes the following steps:

[0117] (1) Provide a substrate;

[0118] Preferably, in one embodiment of the present invention, the substrate is loaded into the MOCVD reaction chamber, pretreated in an H2 atmosphere for 7 min, the treatment temperature is 1100°C, and the treatment pressure is 400 torr.

[0119] (2) Growing a nucleation layer on a substrate;

[0120] In this study, AlN layers were grown using PVD as nucleation layers.

[0121] (3) Grow an undoped GaN layer on the nucleation layer;

[0122] Undoped GaN layers were grown in MOCVD at a temperature of 1120℃ and a pressure of 300 torr. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 were introduced as the carrier gas, and TMGa was introduced as the Ga source.

[0123] (4) An N-type GaN layer is grown on an undoped GaN layer;

[0124] In this process, an N-type GaN layer was grown in MOCVD at a temperature of 1140℃ and a pressure of 300 torr. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa was introduced as the Ga source, and SiH4 was introduced as the N-type doping source.

[0125] (5) Growth of multiple quantum well layers on N-type GaN layers;

[0126] In this process, quantum well layers and quantum barrier layers are periodically grown in MOCVD to form multiple quantum well layers. The InGaN well layer is grown at a temperature of 760℃ and a growth pressure of 200 torr. During growth, NH3 is introduced as the N source, N2 as the carrier gas, TMGa as the Ga source, and TMIn as the In source into the MOCVD reaction chamber.

[0127] The growth method for each quantum barrier layer is as follows:

[0128] (I) Growth of AlN nanopillars on quantum well layers;

[0129] The growth temperature of the AlN nanopillars was 580℃, the growth pressure was 560 torr, the V / III ratio was 2000, and during growth, NH3 was introduced as the N source, N2 and H2 were introduced as carrier gases, and TMAl was introduced as the Al source in the MOCVD reaction chamber.

[0130] (II) AlGaN nanopillars are grown on AlN nanopillars in a one-to-one correspondence;

[0131] The growth temperature of AlGaN nanopillars was 800℃, the growth pressure was 380 torr, and the V / III ratio was 2000. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 were introduced as the carrier gas, TMGa was introduced as the Ga source, and TMAl was introduced as the Al source.

[0132] (III) Growth of GaN two-dimensional layers on AlGaN nanopillars;

[0133] The GaN two-dimensional layer was grown at a temperature of 1320℃, a growth pressure of 220 torr, and a V / III ratio of 300. During growth, NH3 was introduced as the N source, N2 and H2 were introduced as carrier gases, and TMGa was introduced as the Ga source in the MOCVD reaction chamber.

[0134] (6) Grow an electron blocking layer on a multi-quantum-well layer;

[0135] Among them, Al is periodically grown in MOCVD a Ga 1-a N layers and In b Ga 1-b The process continues until an electron blocking layer is obtained; both are grown at a temperature of 950℃ and a growth pressure of 300 torr. Specifically, Al is grown... a Ga 1-a In the N-layer stage, NH3 is introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa as the Ga source, and TMAl as the Al source. In is then grown. b Ga 1-b In the N layer, NH3 is introduced into the MOCVD reaction chamber as the N source, N2 as the carrier gas, TMGa as the Ga source, and TMIn as the In source.

[0136] (7) Grow a P-type GaN layer on the electron blocking layer;

[0137] In this process, a P-type GaN layer was grown in MOCVD at a temperature of 930℃ and a pressure of 200 torr. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa was introduced as the Ga source, and CP2Mg was introduced as the P-type doping source.

[0138] Example 3

[0139] This embodiment provides a light-emitting diode epitaxial wafer, referenced... Figure 1 and Figure 3 It includes a substrate 1 and a nucleation layer 2, an undoped GaN layer 3, an N-type GaN layer 4, a multiple quantum well layer 5, an electron blocking layer 6, and a P-type GaN layer 7 sequentially disposed on the substrate 1.

[0140] In this design, substrate 1 is a sapphire substrate, nucleation layer 2 is an AlN layer with a thickness of 30 nm, undoped GaN layer 3 has a thickness of 400 nm, and N-type GaN layer 4 has a thickness of 2 μm, with Si as the dopant element and a Si doping concentration of 2.5 × 10⁻⁶. 19 cm -3 .

[0141] The multi-quantum-well layer 5 has a periodic structure with 10 periods, each period consisting of sequentially stacked quantum well layers (InGaN layers) and quantum barrier layers. The thickness of a single quantum well layer is 3 nm. Each quantum barrier layer 52 includes: multiple AlN nanopillars 521 arrayed on the quantum well layer 51; multiple AlGaN nanopillars 522 stacked one-to-one on the AlN nanopillars 521; and a GaN two-dimensional layer 523 stacked on the AlGaN nanopillars 522. The GaN two-dimensional layer 523 grows and merges along a predetermined direction at the top of the AlGaN nanopillars 522 to form a quantum barrier layer 52 with nanopores 524. The AlN nanopillars 521 have a height of 12 nm, a diameter of 4 nm, and a distance of 15 nm between adjacent AlN nanopillars 521. The Al content in the AlN nanopillars 521 is 0.62%. The AlGaN nanopillars 522 have a height of 8 nm, are frustum-shaped, and have a diameter that gradually increases from 4 nm to 13 nm. The Al composition is 0.28%. The GaN two-dimensional layer 523 has a thickness of 4 nm.

[0142] Among them, electron blocking layer 6 is Al a Ga 1-a N layers (a = 0.1) and In b Ga 1-b A periodic structure with N alternating layers (b = 0.3) and a period number of 8. A single Al a Ga 1-a The thickness of the N layer is 6nm, and a single In... b Ga 1-b The thickness of the N-layer is 6 nm. The dopant element of the p-type GaN layer 7 is Mg, with a doping concentration of 2 × 10⁻⁶. 20 cm -3 The thickness is 45nm.

[0143] The method for fabricating an epitaxial wafer for a light-emitting diode in this embodiment includes the following steps:

[0144] (1) Provide a substrate;

[0145] Preferably, in one embodiment of the present invention, the substrate is loaded into the MOCVD reaction chamber, pretreated in an H2 atmosphere for 7 min, the treatment temperature is 1100°C, and the treatment pressure is 400 torr.

[0146] (2) Growing a nucleation layer on a substrate;

[0147] In this study, AlN layers were grown using PVD as nucleation layers.

[0148] (3) Grow an undoped GaN layer on the nucleation layer;

[0149] Undoped GaN layers were grown in MOCVD at a temperature of 1120℃ and a pressure of 300 torr. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 were introduced as the carrier gas, and TMGa was introduced as the Ga source.

[0150] (4) An N-type GaN layer is grown on an undoped GaN layer;

[0151] In this process, an N-type GaN layer was grown in MOCVD at a temperature of 1140℃ and a pressure of 300 torr. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa was introduced as the Ga source, and SiH4 was introduced as the N-type doping source.

[0152] (5) Growth of multiple quantum well layers on N-type GaN layers;

[0153] In this process, quantum well layers and quantum barrier layers are periodically grown in MOCVD to form multiple quantum well layers. The InGaN well layer is grown at a temperature of 760℃ and a growth pressure of 200 torr. During growth, NH3 is introduced as the N source, N2 as the carrier gas, TMGa as the Ga source, and TMIn as the In source into the MOCVD reaction chamber.

[0154] The growth method for each quantum barrier layer is as follows:

[0155] (I) Growth of AlN nanopillars on quantum well layers;

[0156] The growth temperature of the AlN nanopillars was 580℃, the growth pressure was 560 torr, the V / III ratio was 2000, and during growth, NH3 was introduced as the N source, N2 and H2 were introduced as carrier gases, and TMAl was introduced as the Al source in the MOCVD reaction chamber.

[0157] (II) AlGaN nanopillars are grown on AlN nanopillars in a one-to-one correspondence;

[0158] The growth temperature of AlGaN nanopillars was 800℃, the growth pressure was 380 torr, and the V / III ratio was 1200. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 were introduced as the carrier gas, TMGa was introduced as the Ga source, and TMAl was introduced as the Al source.

[0159] (III) Growth of GaN two-dimensional layers on AlGaN nanopillars;

[0160] The GaN two-dimensional layer was grown at a temperature of 1320℃, a growth pressure of 220 torr, and a V / III ratio of 300. During growth, NH3 was introduced as the N source, N2 and H2 were introduced as carrier gases, and TMGa was introduced as the Ga source in the MOCVD reaction chamber.

[0161] (6) Grow an electron blocking layer on a multi-quantum-well layer;

[0162] Among them, Al is periodically grown in MOCVD a Ga 1-a N layers and In b Ga 1-b The process continues until an electron blocking layer is obtained; both are grown at a temperature of 950℃ and a growth pressure of 300 torr. Specifically, Al is grown... a Ga 1-a In the N-layer stage, NH3 is introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa as the Ga source, and TMAl as the Al source. In is then grown. b Ga 1-b In the N layer, NH3 is introduced into the MOCVD reaction chamber as the N source, N2 as the carrier gas, TMGa as the Ga source, and TMIn as the In source.

[0163] (7) Grow a P-type GaN layer on the electron blocking layer;

[0164] In this process, a P-type GaN layer was grown in MOCVD at a temperature of 930℃ and a pressure of 200 torr. During growth, NH3 was introduced into the MOCVD reaction chamber as the N source, N2 and H2 as the carrier gas, TMGa was introduced as the Ga source, and CP2Mg was introduced as the P-type doping source.

[0165] Comparative Example 1

[0166] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that the quantum barrier layer is a GaN layer with a thickness of 10 nm, which is grown by MOCVD at a growth temperature of 860 °C and a growth pressure of 200 torr. All other aspects are the same as in Example 1.

[0167] Comparative Example 2

[0168] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that each quantum barrier layer sequentially includes an AlN layer, an AlGaN layer, and a GaN layer stacked on a quantum well layer; the thickness of the AlN layer is 12 nm, the thickness of the AlGaN layer is 12 nm, and the thickness of the GaN layer is 4 nm, all three being layered structures.

[0169] The AlN layer was grown by MOCVD at a growth temperature of 1000℃, a growth pressure of 150 torr, and a V / III ratio of 250. The AlGaN layer was grown by MOCVD at a growth temperature of 1100℃, a growth pressure of 200 torr, and a V / III ratio of 200. The GaN layer was also grown by MOCVD at a growth temperature of 1100℃, a growth pressure of 200 torr, and a V / III ratio of 200.

[0170] Everything else is the same as in Example 1.

[0171] Comparative Example 3

[0172] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that it does not include a GaN two-dimensional layer. Consequently, the fabrication method does not include the step of fabricating this layer. All other aspects are the same as in Example 1.

[0173] Comparative Example 4

[0174] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that it does not include AlGaN nanopillars; correspondingly, the preparation method does not include the step of preparing this layer. All other aspects are the same as in Example 1.

[0175] Comparative Example 5

[0176] This comparative example provides a light-emitting diode epitaxial wafer, which differs from Example 1 in that it does not include AlN nanopillars; correspondingly, the preparation method does not include the step of preparing this layer. All other aspects are the same as in Example 1.

[0177] The epitaxial wafers of the light-emitting diodes obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were tested. The specific test methods are as follows:

[0178] (1) The emission wavelengths of the prepared epitaxial wafers at 1 mA and 5 mA were measured using an IM-1130 PL spectrometer, and the emission wavelength uniformity was calculated. Wherein, emission wavelength uniformity = emission wavelength (1 mA) - emission wavelength (5 mA);

[0179] (2) The epitaxial wafer was fabricated into a chip with a vertical structure of 5mil×7mil, and its luminous brightness was tested at currents of 120mA and 60mA respectively.

[0180] The specific results are as follows:

[0181] Example 1 198.5 68.5 3.5 Example 2 199.8 69.6 3.3 Example 3 202.5 72.5 2.9 Comparative Example 1 191.2 60.1 6.8 Comparative Example 2 193.1 58.4 5.3 Comparative Example 3 180.2 50.5 6.9 Comparative Example 4 192.6 61.3 5.5 Comparative Example 5 191.5 60.8 5.8

[0182] As can be seen from the table, when the quantum barrier layer in the traditional light-emitting diode structure (Comparative Example 1) is replaced with the quantum barrier layer structure of the present invention, the luminous brightness under different currents is significantly improved, especially the luminous brightness at low currents is significantly improved, and the present invention also improves the uniformity of the emission wavelength.

[0183] Furthermore, a comparison between Example 1 and Comparative Examples 2 to 5 shows that when the structure of the quantum barrier layer in this invention is changed, it is difficult to effectively improve the brightness.

[0184] The above description is a preferred embodiment of the invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A light-emitting diode epitaxial wafer, comprising a substrate and a nucleation layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially disposed on the substrate; characterized in that, The multiple quantum well layer has a periodic structure with 2 to 15 periods. Each period includes sequentially stacked quantum well layers and quantum barrier layers. Each quantum barrier layer includes: Multiple AlN nanopillars are arrayed on the quantum well layer; the AlN nanopillars have a height of 10~20nm, a diameter of 2~5nm, an Al composition ratio of 0.6~0.7, and a distance of 10~200nm between adjacent AlN nanopillars. Multiple AlGaN nanopillars are stacked one-to-one on the AlN nanopillars; the height of the AlGaN nanopillars is 5~10nm, the diameter is 2~5nm, and the Al component ratio is 0.25~0.

3. A two-dimensional GaN layer is stacked on the AlGaN nanopillar, and the GaN two-dimensional layer grows and merges along a predetermined direction at the top of the AlGaN nanopillar to form a quantum barrier layer with nanopores.

2. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The aspect ratio of the AlN nanopillar is greater than that of the AlGaN nanopillar.

3. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The thickness of the GaN two-dimensional layer is 2~5nm.

4. The light-emitting diode epitaxial wafer as described in any one of claims 1 to 3, characterized in that, The diameter of the AlGaN nanopillars gradually increases from 2-5 nm to 10-20 nm along the epitaxial growth direction.

5. A method for preparing a light-emitting diode epitaxial wafer, used to prepare a light-emitting diode epitaxial wafer as described in any one of claims 1 to 4, characterized in that, include: A substrate is provided on which a nucleation layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer and a P-type GaN layer are sequentially grown. The multiple quantum well layers have a periodic structure, with each period comprising sequentially stacked quantum well layers and quantum barrier layers; each quantum barrier layer includes: Multiple AlN nanopillars are arrayed on the quantum well layer; Each AlGaN nanopillar corresponds to one of the multiple AlGaN nanopillars stacked on the AlN nanopillars; A two-dimensional GaN layer is stacked on the AlGaN nanopillar, and the GaN two-dimensional layer grows and merges along a predetermined direction at the top of the AlGaN nanopillar to form a quantum barrier layer with nanopores.

6. The method for fabricating a light-emitting diode epitaxial wafer as described in claim 5, characterized in that, The growth temperature of the AlN nanopillars is 500~700℃, and the growth pressure is 500~600 torr; The growth temperature of the AlGaN nanopillars is 750~850℃, and the growth pressure is 300 torr~400 torr; The growth temperature of the GaN two-dimensional layer is 1300~1400℃, and the growth pressure is 200~300 torr.

7. The method for fabricating a light-emitting diode epitaxial wafer as described in claim 5 or 6, characterized in that, During the growth of the AlN nanopillars, the V / Ⅲ ratio was 1500~2500; During the growth of the AlGaN nanopillars, the V / Ⅲ ratio is 1000~1500; During the growth of the GaN two-dimensional layer, the V / Ⅲ ratio is 200~500.

8. A light-emitting diode, characterized in that, Includes the light-emitting diode epitaxial wafer as described in any one of claims 1 to 4.

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