Light emitting diode epitaxial wafer and preparation method thereof, LED

Abstract

The application discloses a light emitting diode epitaxial wafer and a preparation method thereof and an LED, and the light emitting diode epitaxial wafer comprises a substrate, a buffer layer, a composite non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer and a P-type GaN layer which are sequentially stacked on the substrate; the composite non-doped GaN layer comprises a first intrinsic GaN layer, a reflection layer and a second intrinsic GaN layer which are sequentially stacked on the buffer layer, and the reflection layer comprises an AlN reflection layer, an Al reflection layer and a SiO2 reflection layer. The light emitting diode epitaxial wafer provided by the application can reduce dislocation density, reduce non-radiation recombination of quantum wells, improve light extraction efficiency of the light emitting diode and improve light emitting efficiency of the light emitting diode.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, and in particular to a light-emitting diode epitaxial wafer and its preparation method, and LEDs. Background Technology

[0002] InGaN-based light-emitting diodes, or LEDs for short, are semiconductor devices that convert electrical energy into light energy. As a new type of lighting source, they have advantages such as small size, light weight, good directionality, long lifespan, energy saving, and environmental friendliness, and have broad application prospects. As a new type of green light source, LEDs, with their unique characteristics, will lead the future development trend in the lighting field and will become the "fourth generation light source" after incandescent lamps, fluorescent lamps, and high-intensity discharge lamps.

[0003] Currently, due to improvements in material growth quality and device fabrication processes, the internal quantum efficiency of GaN has reached very high values. High-quality LEDs generally achieve internal quantum efficiencies exceeding 90%, and GaN-based blue LEDs have also reached over 80%. However, their luminous efficiency remains relatively low. Light extraction efficiency has become the main factor limiting their luminous efficiency.

[0004] The large lattice mismatch and difference in thermal expansion coefficients between the substrate and GaN result in numerous defects in the GaN epitaxial layer, leading to a decrease in the radiative recombination efficiency of the quantum well layer. Furthermore, GaN is a high-refractive-index material; most of the light emitted from the active region of the GaN epitaxial layer undergoes total internal reflection at the air interface, becoming trapped inside the LED. After multiple total internal reflections, it is absorbed and lost. Factors contributing to light absorption include the epitaxial layer, quantum well, chip electrodes, and substrate absorption, all of which reduce the external quantum efficiency of the LED. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an epitaxial wafer for light-emitting diodes that can reduce dislocation density, reduce nonradiative recombination in quantum wells, improve the light extraction efficiency of light-emitting diodes, and enhance the luminous efficiency of light-emitting diodes.

[0006] The technical problem to be solved by the present invention is to provide a method for preparing an epitaxial wafer of a light-emitting diode, which has a simple process and can stably produce an epitaxial wafer of a light-emitting diode with good luminous efficiency.

[0007] To solve the above-mentioned technical problems, the present invention provides a light-emitting diode epitaxial wafer, comprising a substrate and a buffer layer, a composite undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially stacked on the substrate.

[0008] The composite undoped GaN layer includes a first intrinsic GaN layer, a reflective layer, and a second intrinsic GaN layer sequentially stacked on the buffer layer. The reflective layer includes an AlN reflective layer, an Al reflective layer, and a SiO2 reflective layer.

[0009] In one embodiment, the thickness of the first intrinsic GaN layer is 0.5 μm to 5 μm;

[0010] The thickness of the reflective layer is 10 nm to 100 nm;

[0011] The thickness of the second intrinsic GaN layer is 0.5 μm to 5 μm.

[0012] In one embodiment, the thickness of the AlN reflective layer: the thickness of the Al reflective layer: the thickness of the SiO2 reflective layer = (1~10): 1: (1~10).

[0013] In one embodiment, the AlN reflective layer, the Al reflective layer, and the SiO2 reflective layer are stacked sequentially to form a periodic layer, and the reflective layer includes a plurality of the periodic layers.

[0014] In one embodiment, the reflective layer comprises 1 to 50 of the periodic layers.

[0015] In one embodiment, the growth temperature of the first intrinsic GaN layer is 1000℃~1200℃;

[0016] The growth temperature of the second intrinsic GaN layer is 1000℃~1200℃;

[0017] The growth temperature of the reflective layer is 900℃~1100℃.

[0018] In one embodiment, the growth atmosphere of the first intrinsic GaN layer or the second intrinsic GaN layer is a mixture of N2, H2 and NH3 gas, wherein the ratio of N2, H2 and NH3 gas is 1:(1-5):(1-10);

[0019] The growth atmosphere of the AlN reflective layer is a mixture of N2 and NH3 gas, with the ratio of N2 to NH3 gas being (1-5):(1-5).

[0020] The growth atmosphere of the Al reflective layer is N2;

[0021] The growth atmosphere of the SiO2 reflective layer is a mixture of N2 and O2 gas, with the ratio of N2 to O2 gas being (1-5):(1-5).

[0022] In one embodiment, the growth pressure of the first intrinsic GaN layer, the reflective layer, or the second intrinsic GaN layer is 50 to 300 torr.

[0023] To address the above problems, this invention provides a method for fabricating a light-emitting diode epitaxial wafer, comprising the following steps:

[0024] S1. Prepare the substrate;

[0025] S2. A buffer layer, a composite 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 deposited on the substrate.

[0026] The composite undoped GaN layer includes a first intrinsic GaN layer, a reflective layer, and a second intrinsic GaN layer sequentially stacked on the buffer layer. The reflective layer includes an AlN reflective layer, an Al reflective layer, and a SiO2 reflective layer.

[0027] Accordingly, the present invention also provides an LED, which includes the above-described light-emitting diode epitaxial wafer.

[0028] Implementing this invention has the following beneficial effects:

[0029] The light-emitting diode epitaxial wafer provided by the present invention has a composite undoped GaN layer with a specific structure. The composite undoped GaN layer includes a first intrinsic GaN layer, a reflective layer, and a second intrinsic GaN layer sequentially stacked on the buffer layer. The reflective layer includes an AlN reflective layer, an Al reflective layer, and a SiO2 reflective layer.

[0030] First, by adjusting the thickness of the first and second intrinsic GaN layers, compressive stress can be released through stacking faults, reducing line defects, improving crystal quality, and lowering reverse leakage current. Furthermore, the reduction in compressive stress is beneficial for the formation of In-rich light-emitting centers in the InGaN quantum well, increasing the device's luminous intensity. Second, GaN is a high-refractive-index material. Most of the light emitted from the active region of the GaN epitaxial layer undergoes total internal reflection at the air interface, becoming trapped inside the LED. After multiple total internal reflections, it is absorbed and lost, significantly reducing the LED's external quantum efficiency. The deposited reflective layers include an AlN reflective layer with a refractive index n=2, an Al reflective layer with a refractive index n=1.07, and a SiO2 reflective layer with a refractive index n=1.6, all lower than the GaN refractive index. Further, the AlN, Al, and SiO2 reflective layers form a superlattice structure. This high-reflectivity film, composed of alternating layers of high and low refractive index materials, reduces the absorption of light emitted by the LED by the substrate, improving the LED's light extraction efficiency. Ultimately, the LED epitaxial wafer provided by this invention can reduce dislocation density, decrease nonradiative recombination in quantum wells, improve the light extraction efficiency of LEDs, and enhance the luminous efficiency of LEDs. Attached Figure Description

[0031] Figure 1This is a schematic diagram of the structure of the light-emitting diode epitaxial wafer provided by the present invention;

[0032] Figure 2 A schematic diagram of the electron blocking layer of the light-emitting diode epitaxial wafer provided by the present invention;

[0033] Figure 3 A flowchart illustrating the method for fabricating a light-emitting diode epitaxial wafer provided by the present invention;

[0034] Figure 4 The flowchart shows step S2 of the method for preparing a light-emitting diode epitaxial wafer provided by the present invention.

[0035] Among them: substrate 1, buffer layer 2, composite undoped GaN layer 3, N-type GaN layer 4, multiple quantum well layer 5, electron blocking layer 6, P-type GaN layer 7, first intrinsic GaN layer 31, reflective layer 32, second intrinsic GaN layer 33, AlN reflective layer 321, Al reflective layer 322 and SiO2 reflective layer 323. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0037] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0038] In this invention, "preferred" is merely a description of a more effective implementation method or embodiment, and should be understood as not constituting a limitation on the scope of protection of this invention.

[0039] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0040] In this invention, numerical ranges are involved, and unless otherwise specified, they include the two endpoints of the numerical range.

[0041] To address the above problems, the present invention provides a light-emitting diode epitaxial wafer, such as... Figures 1-2 As shown, it includes a substrate 1 and a buffer layer 2, a composite 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, which are sequentially stacked on the substrate 1.

[0042] The composite undoped GaN layer 3 includes a first intrinsic GaN layer 31, a reflective layer 32, and a second intrinsic GaN layer 33 sequentially stacked on the buffer layer 2. The reflective layer 32 includes an AlN reflective layer 321, an Al reflective layer 322, and a SiO2 reflective layer 323.

[0043] The light-emitting diode epitaxial wafer provided by the present invention has a composite undoped GaN layer with a specific structure, and the specific structure of the composite undoped GaN layer will be described in detail below.

[0044] In one embodiment, the thickness of the first intrinsic GaN layer 31 is 0.5 μm to 5 μm; exemplaryly, the thickness of the first intrinsic GaN layer 31 is 1 μm, 2 μm, 3 μm, or 4 μm, but not limited thereto; the thickness of the second intrinsic GaN layer 33 is 0.5 μm to 5 μm; exemplaryly, the thickness of the second intrinsic GaN layer 33 is 1 μm, 2 μm, 3 μm, or 4 μm, but not limited thereto. Preferably, the thickness of the first intrinsic GaN layer 31 is 1 μm to 1.5 μm; the thickness of the second intrinsic GaN layer 33 is 1 μm to 1.5 μm. It should be noted that, firstly, the thickness of the first intrinsic GaN layer 31 and / or the second intrinsic GaN layer 33 is relatively thick. As the thickness increases, the compressive stress is released through stacking faults, reducing line defects, improving crystal quality, and reducing reverse leakage current. Moreover, the reduction of compressive stress is beneficial to the formation of In-rich light-emitting centers in the InGaN quantum well, thereby improving the luminous intensity of the device.

[0045] In one embodiment, the thickness of the reflective layer 32 is 10nm to 100nm; exemplaryly, the thickness of the reflective layer 32 is 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, or 90nm, but is not limited thereto; preferably, the thickness of the AlN reflective layer 321: the thickness of the Al reflective layer 322: the thickness of the SiO2 reflective layer 323 = (1~10):1:(1~10). Under this condition, the light escape efficiency of the light-emitting diode can be improved, and the light loss due to multiple absorptions in the epitaxial layer can be reduced.

[0046] Furthermore, in one embodiment, the AlN reflective layer 321, the Al reflective layer 322, and the SiO2 reflective layer 323 are stacked sequentially to form a periodic layer, and the reflective layer includes a plurality of the periodic layers; preferably, the reflective layer 32 includes 1 to 50 of the periodic layers; more preferably, the reflective layer 32 includes 10 to 30 of the periodic layers.

[0047] It should be noted that GaN is a high refractive index material with a refractive index n = 2.3. Most of the light emitted from the active region of the GaN epitaxial layer undergoes total internal reflection at the air interface, becoming trapped inside the LED. After multiple total internal reflections, it is absorbed and lost, significantly reducing the external quantum efficiency of the LED. The deposited reflective layers include an AlN reflective layer 321 with a refractive index n = 2, an Al reflective layer 322 with a refractive index n = 1.07, and a SiO2 reflective layer 323 with a refractive index n = 1.6, all lower than the refractive index of GaN. Furthermore, the AlN reflective layer 321, Al reflective layer 322, and SiO2 reflective layer 323 are alternately stacked to form a superlattice structure. This high-reflectivity film, composed of alternating high and low refractive index materials, reduces the absorption of light emitted by the LED by the substrate, improving the light extraction efficiency of the LED.

[0048] In summary, the LED epitaxial wafer with a specific composite undoped GaN layer structure provided by this invention can reduce dislocation density, reduce nonradiative recombination in quantum wells, improve the light extraction efficiency of LEDs, and enhance the luminous efficiency of LEDs.

[0049] Accordingly, the present invention provides a method for fabricating a light-emitting diode epitaxial wafer, such as... Figure 3 As shown, it includes the following steps:

[0050] S1. Prepare substrate 1;

[0051] In one embodiment, the substrate 1 is selected as a sapphire substrate; sapphire is currently the most commonly used substrate material, and sapphire substrates have mature manufacturing processes, low prices, are easy to clean and process, and have good stability at high temperatures.

[0052] S2. A buffer layer 2, a composite undoped GaN layer 3, an N-type GaN layer, a multiple quantum well layer 5, an electron blocking layer 6, and a P-type GaN layer 7 are sequentially deposited on the substrate 1.

[0053] In one implementation, such as Figure 4 As shown, step S2 includes the following steps:

[0054] S21. Deposit a buffer layer 2 on substrate 1.

[0055] Preferably, an AlN buffer layer with a thickness of 10 nm to 20 nm is deposited in the PVD material. The AlN buffer layer provides nucleation centers with the same orientation as the substrate, releasing the stress caused by the lattice mismatch between GaN and the substrate, as well as the thermal stress caused by the mismatch of thermal expansion coefficients. Further growth provides a flat nucleation surface, reducing the contact angle of nucleation growth, allowing the island-shaped GaN grains to connect into a surface within a smaller thickness, thus transforming into two-dimensional epitaxial growth.

[0056] S22. Deposit a composite undoped GaN layer 3 on the buffer layer 2.

[0057] Preferably, before depositing the composite undoped GaN layer, the sapphire substrate with the AlN buffer layer is transferred into MOCVD and pretreated in H2 atmosphere for 1 min to 10 min at a temperature of 1000℃ to 1200℃. This can improve the crystal quality of the AlN buffer layer and effectively improve the crystal quality of the subsequently deposited GaN epitaxial layer.

[0058] Preferably, the growth temperature of the first intrinsic GaN layer is 1000℃~1200℃;

[0059] The growth temperature of the second intrinsic GaN layer is 1000℃~1200℃;

[0060] The growth temperature of the reflective layer is 900℃~1100℃.

[0061] Preferably, the growth atmosphere of the first intrinsic GaN layer or the second intrinsic GaN layer is a mixture of N2, H2 and NH3 gas, wherein the ratio of N2, H2 and NH3 gas is 1:(1~5):(1~10);

[0062] The growth atmosphere of the AlN reflective layer is a mixture of N2 and NH3 gas, with the ratio of N2 to NH3 gas being (1-5):(1-5).

[0063] The growth atmosphere of the Al reflective layer is N2;

[0064] The growth atmosphere of the SiO2 reflective layer is a mixture of N2 and O2 gas, with the ratio of N2 to O2 gas being (1-5):(1-5).

[0065] It should be noted that the growth atmosphere of the first intrinsic GaN layer or the second intrinsic GaN layer is a mixture of N2, H2 and NH3 gas. The introduction of H2 improves the mobility of Ga, promotes the lateral growth of the GaN epitaxial layer, and improves the quality of GaN crystal.

[0066] The growth atmosphere of the AlN reflective layer is a mixture of N2 and NH3 gases, with no H2, which reduces the side reactions between the Al source and H2 and decreases the crystal quality of the AlN layer.

[0067] The Al reflective layer is grown in an N2 atmosphere, and the Al source is decomposed at high temperature to deposit the Al radioactive layer.

[0068] The growth atmosphere of the SiO2 reflective layer is a mixture of N2 and O2 gas. A suitable gas ratio improves the crystal quality of the SiO2 reflective layer.

[0069] Preferably, the growth pressure of the first intrinsic GaN layer, the reflective layer, or the second intrinsic GaN layer is 50 torr to 300 torr.

[0070] S23. Deposit an N-type GaN layer 4 on the composite undoped GaN layer 3.

[0071] Preferably, the N-type GaN layer is grown at a temperature of 1050℃ to 1200℃, a pressure of 100 torr to 600 torr, a thickness of 2 μm to 3 μm, and a Si doping concentration of 1×10⁻⁶. 19 atoms / cm 3 ~5×10 19 atoms / cm 3 The N-type GaN layer provides sufficient electrons for LED light emission. The resistivity of the N-type GaN layer is higher than that of the transparent electrode on the GaN layer. Therefore, sufficient Si doping can effectively reduce the resistivity of the N-type GaN layer. In addition, the sufficient thickness of the N-type GaN layer can effectively release stress and improve the luminous efficiency of the LED.

[0072] S24. Grow a multi-quantum-well layer 5 on the N-type GaN layer 4.

[0073] Preferably, the multiple quantum well layer comprises alternating stacked InGaN quantum well layers and AlGaN quantum barrier layers, with 6 to 12 stacking periods. The InGaN quantum well layer is grown at a temperature of 790°C to 810°C, with a thickness of 2 nm to 5 nm and a growth pressure of 50 torr to 300 torr. The AlGaN quantum barrier layer is grown at a temperature of 800°C to 900°C, with a thickness of 5 nm to 15 nm and a growth pressure of 50 torr to 300 torr, and has an Al content of 0.01 to 0.1%. The multiple quantum well layer is a region where electrons and holes recombine. A well-designed structure can significantly increase the overlap of electron and hole wave functions, thereby improving the luminous efficiency of the LED device.

[0074] S25. An electron blocking layer 6 is grown on the multi-quantum well layer 5.

[0075] Preferably, the electron blocking layer is an AlInGaN layer with a thickness of 10 nm to 20 nm, wherein the Al component concentration gradually changes from 0.01 to 0.05 along the growth direction of the epitaxial layer, the In component concentration is 0.01 to 0.02, the growth temperature is 950℃ to 1000℃, and the growth pressure is 200 torr to 250 torr. This can effectively limit electron overflow, reduce the blocking of holes, improve the injection efficiency of holes into the electron well, reduce carrier Auger recombination, and improve the luminous efficiency of the light-emitting diode.

[0076] S26. Grow a P-type GaN layer 7 on the electron blocking layer 6.

[0077] Preferably, the p-type GaN layer is grown at a temperature of 900℃ to 1050℃, with a thickness of 10nm to 50nm, a growth pressure of 100 torr to 600 torr, and a Mg doping concentration of 1×10⁻⁶. 19 atoms / cm 3 ~1×10 21 atoms / cm 3 Excessive Mg doping concentration can compromise crystal quality, while low doping concentration can affect hole concentration. Furthermore, for LED structures containing V-shaped pits, the higher growth temperature of the GaN layer is beneficial for merging these pits, resulting in a smooth LED epitaxial wafer.

[0078] Accordingly, the present invention also provides an LED comprising the aforementioned light-emitting diode epitaxial wafer. The photoelectric efficiency of the LED is effectively improved, and other electrical properties are also excellent.

[0079] The present invention is further illustrated below with specific embodiments:

[0080] Example 1

[0081] This embodiment provides a light-emitting diode epitaxial wafer, including a substrate and a buffer layer, a composite undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially stacked on the substrate.

[0082] The composite undoped GaN layer includes a first intrinsic GaN layer, a reflective layer, and a second intrinsic GaN layer sequentially stacked on the buffer layer. The reflective layer includes an AlN reflective layer, an Al reflective layer, and a SiO2 reflective layer.

[0083] The thickness of the first intrinsic GaN layer is 1.5 μm; the thickness of the second intrinsic GaN layer is 1 μm.

[0084] The AlN reflective layer, Al reflective layer and SiO2 reflective layer are stacked sequentially to form a periodic layer. The reflective layer includes 20 such periodic layers. The thickness of the reflective layer is 50 nm. The ratio of the thickness of the AlN reflective layer to the thickness of the Al reflective layer to the thickness of the SiO2 reflective layer is 2:1:3.

[0085] The growth atmosphere of the first intrinsic GaN layer or the second intrinsic GaN layer is a mixture of N2, H2 and NH3 gases, wherein the ratio of N2, H2 and NH3 gases is 1:3:5;

[0086] The growth atmosphere of the AlN reflective layer is a mixture of N2 and NH3 gases, with a ratio of N2 to NH3 of 2:3.

[0087] The growth atmosphere of the Al reflective layer is N2;

[0088] The growth atmosphere of the SiO2 reflective layer is a mixture of N2 and O2 gases, with a ratio of 2:3.

[0089] Example 2

[0090] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 1 in that: the thickness of the first intrinsic GaN layer is 1 μm; the thickness of the second intrinsic GaN layer is 0.5 μm; and the thickness of the reflective layer is 35 nm. All other aspects are the same as in Embodiment 1.

[0091] Example 3

[0092] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 1 in that: the thickness of the first intrinsic GaN layer is 2 μm; the thickness of the second intrinsic GaN layer is 1.5 μm; and the thickness of the reflective layer is 60 nm. All other aspects are the same as in Embodiment 1.

[0093] Example 4

[0094] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 1 in that the thickness of the AlN reflective layer: the thickness of the Al reflective layer: the thickness of the SiO2 reflective layer = 1:1:3. All other aspects are the same as in Embodiment 1.

[0095] Example 5

[0096] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 1 in that the thickness of the AlN reflective layer: the thickness of the Al reflective layer: the thickness of the SiO2 reflective layer = 3:1:2. All other aspects are the same as in Embodiment 1.

[0097] Example 6

[0098] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 1 in that: the AlN reflective layer, Al reflective layer, and SiO2 reflective layer are sequentially stacked to form a periodic layer, and the reflective layer includes 15 such periodic layers. Everything else is the same as in Embodiment 1.

[0099] Example 7

[0100] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 1 in that: the AlN reflective layer, Al reflective layer, and SiO2 reflective layer are sequentially stacked to form a periodic layer, and the reflective layer includes 25 such periodic layers. Everything else is the same as in Embodiment 1.

[0101] Example 8

[0102] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 1 in that: the growth atmosphere of the first intrinsic GaN layer or the second intrinsic GaN layer is a mixture of N2, H2, and NH3 gases, wherein the ratio of N2, H2, and NH3 gases is 1:1:3; the growth atmosphere of the AlN reflective layer is a mixture of N2 and NH3 gases, wherein the ratio of N2 to NH3 gases is 1:3. All other aspects are the same as in Embodiment 1.

[0103] Example 9

[0104] This embodiment provides a light-emitting diode epitaxial wafer, which differs from Embodiment 1 in that: the growth atmosphere of the first intrinsic GaN layer or the second intrinsic GaN layer is a mixture of N2, H2, and NH3 gases, wherein the ratio of N2, H2, and NH3 gases is 1:3:3; the growth atmosphere of the AlN reflective layer is a mixture of N2 and NH3 gases, wherein the ratio of N2 to NH3 gases is 1:1. All other aspects are the same as in Embodiment 1.

[0105] Comparative Example 1

[0106] The difference between this comparative example and Example 1 is that the undoped GaN layer is a 2.5 μm undoped GaN layer, while the rest is the same as in Example 1.

[0107] The light-emitting diode epitaxial wafers prepared in Examples 1 to 9 and Comparative Example 1 were fabricated into 10×24mil chips using the same chip process conditions. 300 LED chips were randomly selected from each example, and the photoelectric performance of the chips was tested at 120mA / 60mA current. The luminous efficacy improvement rate of Examples 1 to 9 compared with Comparative Example 1 was calculated. The specific test results are shown in Table 1.

[0108] Table 1 Performance test results of LEDs prepared in Examples 1 to 9

[0109]

[0110]

[0111] As can be seen from the above results, the light-emitting diode epitaxial wafer provided by the present invention has a composite undoped GaN layer with a specific structure. The composite undoped GaN layer includes a first intrinsic GaN layer, a reflective layer, and a second intrinsic GaN layer stacked sequentially on the buffer layer. The reflective layer includes an AlN reflective layer, an Al reflective layer, and a SiO2 reflective layer.

[0112] First, by adjusting the thickness of the first and second intrinsic GaN layers, compressive stress can be released through stacking faults, reducing line defects, improving crystal quality, and lowering reverse leakage current. Furthermore, the reduction in compressive stress is beneficial for the formation of In-rich light-emitting centers in the InGaN quantum well, increasing the device's luminous intensity. Second, GaN is a high-refractive-index material. Most of the light emitted from the active region of the GaN epitaxial layer undergoes total internal reflection at the air interface, becoming trapped inside the LED. After multiple total internal reflections, it is absorbed and lost, significantly reducing the LED's external quantum efficiency. The deposited reflective layers include an AlN reflective layer with a refractive index n=2, an Al reflective layer with a refractive index n=1.07, and a SiO2 reflective layer with a refractive index n=1.6, all lower than the GaN refractive index. Further, the AlN, Al, and SiO2 reflective layers form a superlattice structure. This high-reflectivity film, composed of alternating layers of high and low refractive index materials, reduces the absorption of light emitted by the LED by the substrate, improving the LED's light extraction efficiency. Ultimately, the LED epitaxial wafer provided by this invention can reduce dislocation density, decrease nonradiative recombination in quantum wells, improve the light extraction efficiency of LEDs, and enhance the luminous efficiency of LEDs.

[0113] 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, characterized in that, It includes a substrate and a buffer layer, a composite undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially stacked on the substrate; The composite undoped GaN layer includes a first intrinsic GaN layer, a reflective layer, and a second intrinsic GaN layer sequentially stacked on the buffer layer. The reflective layer includes an AlN reflective layer, an Al reflective layer, and a SiO2 reflective layer. The thickness of the first intrinsic GaN layer is 0.5 μm to 5 μm; The thickness of the reflective layer is 10nm~100nm; The thickness of the second intrinsic GaN layer is 0.5 μm to 5 μm; The thickness of the AlN reflective layer: the thickness of the Al reflective layer: the thickness of the SiO2 reflective layer = (1~10): 1: (1~10); The growth atmosphere of the first intrinsic GaN layer or the second intrinsic GaN layer is a mixture of N2, H2 and NH3 gas, wherein the ratio of N2, H2 and NH3 gas is 1:(1~5):(1~10). The growth atmosphere of the AlN reflective layer is a mixture of N2 and NH3 gas, with the ratio of N2 to NH3 gas being (1~5):(1~5). The growth atmosphere of the Al reflective layer is N2; The growth atmosphere of the SiO2 reflective layer is a mixture of N2 and O2 gas, with the ratio of N2 to O2 gas being (1~5):(1~5).

2. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The AlN reflective layer, Al reflective layer and SiO2 reflective layer are stacked sequentially to form a periodic layer, and the reflective layer includes multiple such periodic layers.

3. The light-emitting diode epitaxial wafer as described in claim 2, characterized in that, The reflective layer comprises 1 to 50 of the periodic layers.

4. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The growth temperature of the first intrinsic GaN layer is 1000℃~1200℃; The growth temperature of the second intrinsic GaN layer is 1000℃~1200℃; The growth temperature of the reflective layer is 900℃~1100℃.

5. The light-emitting diode epitaxial wafer as described in claim 1, characterized in that, The growth pressure of the first intrinsic GaN layer, the reflective layer, or the second intrinsic GaN layer is 50 torr to 300 torr.

6. A method for fabricating a light-emitting diode epitaxial wafer as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Prepare the substrate; S2. A buffer layer, a composite 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 deposited on the substrate. The composite undoped GaN layer includes a first intrinsic GaN layer, a reflective layer, and a second intrinsic GaN layer sequentially stacked on the buffer layer. The reflective layer includes an AlN reflective layer, an Al reflective layer, and a SiO2 reflective layer.

7. An LED, characterized in that, The LED includes a light-emitting diode epitaxial wafer as described in any one of claims 1 to 5.

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