Green light GaN epitaxial wafer and preparation method thereof

Abstract

This invention relates to the field of semiconductor technology, and provides a green GaN epitaxial wafer and its fabrication method. The epitaxial wafer includes a substrate, and a buffer layer, a first strain control layer, an undoped GaN layer, a second strain control layer, a third strain control layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially deposited on the substrate. The first strain control layer is a superlattice layer composed of periodically alternating first AlGaN layers and GaN layers; the second strain control layer is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers; the third strain control layer is a superlattice layer composed of periodically alternating C / Si co-doped AlInGaN layers and InGaN layers; the electron blocking layer includes Si-doped AlGaN layers and AlGaN / Al... x In y Ga 1‑x‑y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1‑x‑y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1‑x‑y The N-layers are periodically alternating. The green GaN epitaxial wafer and its preparation method provided by this invention can effectively release the stress of the epitaxial layer, improve the crystal quality of the epitaxial layer, and enhance the luminescence efficiency.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology and relates to a green GaN epitaxial wafer and its preparation method. Background Technology

[0002] GaN-based materials play a crucial role in third-generation semiconductors. These materials primarily include AlN, GaN, InN, and their alloys, such as AlGaN, InGaN, and AlInGaN. They possess a wide luminescence range, theoretically covering the ultraviolet band (200 nm) to the infrared band (1770 nm), with a continuously adjustable bandgap between 0.7 eV and 6.2 eV. Therefore, as a typical representative of third-generation semiconductors, GaN-based materials, due to their large bandgap and high electron mobility, are core materials with immense application potential in the future semiconductor field. For example, gallium nitride (GaN)-based devices are widely used in wireless communication, radar, and other electronic systems in the microwave to millimeter-wave frequency bands, and have a very broad development prospect in optoelectronics and microelectronics.

[0003] However, most major LED manufacturers and research institutions currently use sapphire as the substrate material. Due to the high lattice mismatch of 13.3% and thermal expansion coefficient mismatch of GaN between sapphire and GaN, as the In content increases, the lattice mismatch between the InGaN well layer and the GaN barrier layer will increase rapidly, resulting in a rapid increase in compressive strain in the InGaN well layer.

[0004] This has two adverse consequences. First, compressive strain induces strong piezoelectric polarization and generates a large number of mismatched dislocations. Second, the combined effect of spontaneous polarization and piezoelectric polarization causes spatial separation of the wave functions of electrons and holes in the quantum well, thereby reducing the radiative recombination efficiency of electrons and holes. In addition, the energy bands become severely bent, reducing the quantum well's ability to confine charge carriers and thus generating a large leakage current. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a green GaN epitaxial wafer and its preparation method, which can effectively release the stress of the epitaxial layer, improve the crystal quality of the epitaxial layer, and enhance the luminescence efficiency.

[0006] To solve the above problems, the present invention is achieved through the following technical solution: The present invention provides a green GaN epitaxial wafer, comprising a substrate, and a buffer layer, a first strain control layer, an undoped GaN layer, a second strain control layer, a third strain control layer, a multiple quantum well layer, an electron blocking layer and a P-type GaN layer sequentially deposited on the substrate; The first strain control layer is a superlattice layer composed of alternating first AlGaN layers and GaN layers; The second strain control layer is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers; The third strain control layer is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers and InGaN layers. The electron blocking layer includes a Si-doped AlGaN layer and an AlGaN / Al layer. x In y Ga 1-x-y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The structure consists of N layers arranged in a periodic alternation.

[0007] In some embodiments, the number of superlattice layers of the first strain control layer is 3 to 5, the thickness of the first AlGaN layer is 10 nm to 100 nm, and the thickness of the GaN layer is 2 nm to 8 nm. The second strain control layer has a superlattice layer period number of 10 to 20, the thickness of the N-type GaN layer is 100 nm to 300 nm, and the thickness of the AlN layer is 10 nm to 15 nm. The number of superlattice layers in the third strain control layer is 3 to 20, and the thickness of the C / Si co-doped AlInGaN layer is 10 nm to 100 nm. The thickness of the Si-doped AlGaN layer in the electron blocking layer is 5 nm to 50 nm, and the AlGaN / Al x In y Ga 1-x-y The number of periods in the N-composite superlattice layer is 2–5, and the thickness of the second AlGaN layer is 5 nm–15 nm. x In y Ga 1-x-y The thickness of the N layer is 1 nm to 15 nm.

[0008] In some embodiments, the thickness of the buffer layer is 10–50 nm; The thickness of the undoped GaN layer is 1 μm to 5 μm; The multiple quantum well layer is formed by periodically alternating InGaN quantum well layers and AlGaN quantum barrier layers, with a period number of 5 to 20. The thickness of the InGaN quantum well layer is 2 nm to 5 nm, and the thickness of the AlGaN quantum barrier layer is 5 nm to 15 nm. The thickness of the P-type GaN layer is 10 nm to 50 nm.

[0009] In some embodiments, the N-type GaN layer of the second strain control layer is a Si-doped N-type GaN layer with a Si doping concentration of 1 x 10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm 3 ; The third strain-tuning layer is a C / Si co-doped AlInGaN layer with a Si doping concentration of 1x10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm 3 The C doping concentration is 1x10 16 atoms / cm 3 ~1x10 17 atoms / cm 3 ; The Si-doped AlGaN layer of the electron blocking layer has a Si doping concentration of 1x10⁻⁶. 16 atoms / cm 3 ~1x10 17 atoms / cm 3 ; The p-type GaN layer is a Mg-doped p-type GaN layer with a Mg doping concentration of 1 x 10⁻⁶. 19 atoms / cm 3 ~1x10 21 atoms / cm 3 .

[0010] In some embodiments, the first AlGaN layer of the first strain-controlled layer has an Al content of 0.01 to 0.2, and the Al content decreases along the epitaxial growth direction. The third strain-controlled layer, a C / Si co-doped AlInGaN layer, has an Al content of 0.01–0.2%, which increases along the epitaxial growth direction. The Si-doped AlGaN layer of the electron blocking layer has an Al content of 0.01 to 0.5%. The electron blocking layer AlGaN / Al x In y Ga 1-x-y N-composite superlattice layer, wherein the Al content of the second AlGaN layer is 0.01–0.5, Al x In y Ga 1-x-yThe Al component content of the N layer is 0.01–0.5%, wherein the Al x In y Ga 1-x-y The Al content of the N layer decreases along the epitaxial growth direction; The AlGaN quantum barrier layer with multiple quantum wells has an Al content of 0.01 to 0.1%.

[0011] In some embodiments, the In content of the C / Si co-doped AlInGaN layer of the third strain control layer is 0.01 to 0.1, and the In content decreases along the epitaxial growth direction. The InGaN layer of the third strain control layer has an In content of 0.01 to 0.1. Al of the electron blocking layer x In y Ga 1-x-y The N-layer has an In content of 0.01 to 0.2, wherein the In content increases along the epitaxial growth direction. The InGaN quantum well layer with multiple quantum well layers has an In content of 0.01 to 0.3%.

[0012] Accordingly, the present invention also provides a method for preparing a green GaN epitaxial wafer, comprising the following steps: (1) Deposit a buffer layer on the substrate; (2) Introduce gas to heat-treat the buffer layer; (3) Deposit a first strain control layer on the buffer layer; (4) Deposit an undoped GaN layer on the first strain control layer; (5) Deposit a second strain control layer on the undoped GaN layer; (6) Deposit a third strain control layer on the second strain control layer; (7) Deposit a multi-quantum-well layer in the third strain control layer; (8) Deposit an electron blocking layer in the multi-quantum well layer; (9) Deposit a P-type GaN layer in the electron blocking layer; The first strain control layer is a superlattice layer composed of alternating first AlGaN layers and GaN layers. The second strain control layer is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers; The third strain control layer is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers and InGaN layers. The electron blocking layer includes a Si-doped AlGaN layer and an AlGaN / Al layer.x In y Ga 1-x-y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The structure consists of N layers arranged in a periodic alternation.

[0013] In some embodiments, the temperature for heat treatment of the buffer layer is 1000℃~1100℃; The deposition temperature of the first strain-controlled layer is 900℃~1000℃, and the deposition pressure is 100 torr~500 torr; The deposition temperature of the undoped GaN layer is 1050℃~1200℃, and the deposition pressure is 100 torr~600 torr. The deposition temperature of the second strain-controlled layer is 850℃~1150℃, and the deposition pressure is 100 torr~500 torr; The deposition temperature of the third strain control layer is 800℃~900℃, and the deposition pressure is 100torr~600torr; The multi-quantum well layer is formed by periodically alternating InGaN quantum well layers and AlGaN quantum barrier layers. The deposition temperature of the InGaN quantum well layer is 790℃~810℃ and the deposition pressure is 50 torr~300 torr. The deposition temperature of the AlGaN quantum barrier layer is 800℃~900℃ and the deposition pressure is 50 torr~300 torr. The electron blocking layer is deposited at a temperature of 900℃ to 1000℃ and at a pressure of 50 torr to 500 torr. The deposition temperature of the P-type GaN layer is 900℃~1050℃, and the deposition pressure is 100 torr~600 torr.

[0014] In some embodiments, in steps (2) to (9), the gas introduced is a mixture of N2, H2, and NH3 or a mixture of N2 and NH3; When the introduced gas is a mixture of N2, H2, and NH3, its volume ratio is 1:(1-20):(1-10). When the gas introduced is a mixture of N2 and NH3, the volume ratio is 1:(1~10).

[0015] In some embodiments, the N-type GaN layer of the second strain control layer is a Si-doped N-type GaN layer with a Si doping concentration of 1 x 10⁻⁶.17 atoms / cm 3 ~1x10 19 atoms / cm 3 ; The third strain-tuning layer is a C / Si co-doped AlInGaN layer with a Si doping concentration of 1x10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm 3 The C doping concentration is 1x10 16 atoms / cm 3 ~1x10 17 atoms / cm 3 ; The Si-doped AlGaN layer of the electron blocking layer has a Si doping concentration of 1x10⁻⁶. 16 atoms / cm 3 ~1x10 17 atoms / cm 3 ; The p-type GaN layer is a Mg-doped p-type GaN layer with a Mg doping concentration of 1 x 10⁻⁶. 19 atoms / cm 3 ~1x10 21 atoms / cm 3 .

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a green GaN epitaxial wafer, wherein the first strain control layer is a superlattice layer composed of alternating first AlGaN layers and GaN layers; the second strain control layer is a superlattice layer composed of alternating N-type GaN layers and AlN layers; the third strain control layer is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers and InGaN layers; and the electron blocking layer includes Si-doped AlGaN layers and AlGaN / Al x In y Ga 1-x-y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The structure consists of N layers arranged in a periodic alternation.

[0017] The second strain control layer of this invention is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers. During the epitaxial growth process, the thinner AlN layer at the interface of the N-type GaN layer can distort or annihilate the extended dislocations, thereby improving the crystal quality. This not only weakens the influence of the polarization electric field, reduces electron scattering, and improves electron transport efficiency, but also helps to improve the subsequent growth quality.

[0018] The Si-doped AlGaN layer of the electron blocking layer in this invention and the AlGaN / Al x In y Ga 1-x-y The high Al content end of the Al-GaN composite superlattice layer forms a high potential barrier, strongly preventing electron leakage. Simultaneously, the decreasing Al content and increasing In content lower the hole injection barrier. Furthermore, the AlGaN / Al... x In y Ga 1-x-y The superlattice structure of the N-composite superlattice layer reduces polarization charge at the interface and suppresses nonradiative recombination. Furthermore, Si doping in the Si-doped AlGaN layer improves hole injection efficiency, reduces operating voltage, and enhances luminescence efficiency.

[0019] (2) This invention provides a method for preparing a green GaN epitaxial wafer, wherein a buffer layer, a first strain control layer, an undoped GaN layer, a second strain control layer, a third strain control layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer are sequentially deposited on a substrate. Specifically, a gas is introduced before depositing the first strain control layer to heat-treat the buffer layer. Since the buffer layer itself has poor crystal quality, typically being polycrystalline or amorphous, the gas and heat treatment can improve the crystal quality of the buffer layer. Subsequently, the first strain control layer is deposited on the buffer layer. By controlling the Al composition content of the first AlGaN layer of the first strain control layer to decrease along the epitaxial growth direction, the lattice mismatch between the substrate and GaN is gradually alleviated, thereby releasing heteroepitaxial stress and suppressing dislocation propagation, thus improving the crystal quality of the epitaxial layer.

[0020] The third strain-modulating layer of this invention has a low deposition temperature, which can effectively release the thermal stress caused by the difference in thermal expansion coefficients between the substrate and the epitaxial layer. Its compressive stress can offset some of the tensile stress from the substrate to the epitaxial layer. Furthermore, the C / Si co-doped AlInGaN layer of the third strain-modulating layer, due to C doping, can effectively release the stress in the epitaxial layer. In addition, by controlling the Al and In content of the C / Si co-doped AlInGaN layer, the luminous efficiency can be improved. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a green GaN epitaxial wafer in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, the present invention provides a green GaN epitaxial wafer, including a substrate 1, and a buffer layer 2, a first strain control layer 3, an undoped GaN layer 4, a second strain control layer 5, a third strain control layer 6, a multiple quantum well layer 7, an electron blocking layer 10, and a P-type GaN layer 11 sequentially deposited on the substrate 1.

[0024] The first strain control layer 3 is a superlattice layer composed of alternating first AlGaN layers 31 and GaN layers 32; the second strain control layer 5 is a superlattice layer composed of alternating N-type GaN layers 51 and AlN layers 52; the third strain control layer 6 is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers 61 and InGaN layers 62; and the electron blocking layer 10 includes a Si-doped AlGaN layer 8 and an AlGaN / Al... x In y Ga 1-x-y N-composite superlattice layer 9, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer 9 is composed of the second AlGaN layer 91 and Al x In y Ga 1-x-y The N layers are composed of 92 periodic alternations.

[0025] Specifically, the first strain control layer 3 gradually alleviates the lattice mismatch between the substrate and GaN, thereby releasing heteroepitaxial stress and suppressing dislocation propagation, thus improving the crystal quality of the epitaxial layer; the second strain control layer 5 improves crystal quality by twisting or annihilating the propagating dislocations, laying the foundation for improving the subsequent growth quality; the third strain control layer 6 introduces periodic compressive stress, which can offset part of the tensile stress from the substrate to the epitaxial layer, thereby suppressing cracks, reducing dislocation density, improving the integrity of the epitaxial layer, and improving luminescence efficiency; the electron blocking layer 10 can effectively release the stress of the epitaxial layer and improve luminescence efficiency.

[0026] Specifically, a substrate 1 is provided, which includes, but is not limited to, a sapphire substrate, a SiO2-sapphire composite substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, and a zinc oxide substrate. Preferably, the substrate 1 is a sapphire substrate, which is currently the most commonly used GaN-based LED substrate. Its preparation process is mature, its price is low, it is easy to clean and process, and it has good high-temperature stability.

[0027] In some embodiments, the thickness of the buffer layer 2 is 10–50 nm. Exemplarily, the thickness of the buffer layer 2 is 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm, but is not limited thereto.

[0028] In some embodiments, the number of superlattice layers in the first strain control layer 3 is 3 to 5, the thickness of the first AlGaN layer 31 is 10 nm to 100 nm, and the thickness of the GaN layer 32 is 2 nm to 8 nm.

[0029] For example, the thickness of the first AlGaN layer 31 is 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, or 100nm, but is not limited thereto.

[0030] For example, the thickness of the GaN layer 32 is 2nm, 4nm, 6nm, or 8nm, but is not limited thereto.

[0031] It should be noted that if the thickness of the first AlGaN layer 31 and GaN layer 32 is too small, the stress adjustment effect will be insignificant, which may easily lead to epitaxial layer cracks; if the thickness of the first AlGaN layer 31 and GaN layer 32 is too large, the epitaxial stress release will be uneven, resulting in a decrease in crystal quality and performance.

[0032] In some embodiments, the first AlGaN layer 31 of the first strain control layer 3 has an Al component content of 0.01 to 0.2, and the Al component content decreases along the epitaxial growth direction.

[0033] This invention controls the Al composition content of the first AlGaN layer 31 of the first strain control layer 3 to make it decrease along the epitaxial growth direction, thereby gradually alleviating the lattice mismatch between the substrate 1 and GaN, releasing heteroepitaxial stress, suppressing dislocation extension, and improving the crystal quality of the epitaxial layer.

[0034] In some embodiments, the thickness of the undoped GaN layer 4 is 1 μm to 5 μm. Within this range, the dislocation density can be further reduced, and the crystal quality can be improved. If the thickness is too large, it will cause severe warping or even cracking of the epitaxial wafer, reducing the crystal quality.

[0035] In some embodiments, the number of superlattice layers in the second strain control layer 5 is 10 to 20, the thickness of the N-type GaN layer 51 is 100 nm to 300 nm, and the thickness of the AlN layer 52 is 10 nm to 15 nm.

[0036] For example, the thickness of the N-type GaN layer 51 is 100nm, 150nm, 200nm, 250nm, or 300nm, but is not limited thereto.

[0037] For example, the thickness of the AlN layer 52 is 10nm, 11nm, 12nm, 13nm, 14nm, or 15nm, but is not limited thereto.

[0038] It should be noted that during the epitaxial growth process, the AlN layer 52 of the second strain control layer 5 is relatively thin, which can distort or annihilate the extended dislocations at the interface of the N-type GaN layer 51, thereby improving the crystal quality. This not only weakens the influence of the polarization electric field, reduces electron scattering, and improves electron transport efficiency, but also helps to improve the subsequent growth quality.

[0039] In some embodiments, the N-type GaN layer 51 of the second strain control layer 5 is a Si-doped N-type GaN layer with a Si doping concentration of 1x10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm 3 Si doping can provide free electrons, thereby improving the conductivity of the epitaxial layer.

[0040] In some embodiments, the number of superlattice layers in the third strain control layer 6 is 3 to 20, the thickness of the C / Si co-doped AlInGaN layer 61 is 10 nm to 100 nm, and the thickness of the InGaN layer 62 is 1 nm to 10 nm.

[0041] For example, the thickness of the C / Si co-doped AlInGaN layer 61 is 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, or 100nm, but is not limited thereto.

[0042] The thickness of the InGaN layer 62 is 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, or 10nm, but is not limited to these.

[0043] The third strain control layer 6 of the present invention can counteract part of the tensile stress from the substrate to the epitaxial layer by introducing periodic compressive stress, thereby suppressing cracks, reducing dislocation density, improving epitaxial layer integrity, and enhancing luminescence efficiency.

[0044] In some embodiments, the Si doping concentration of the C / Si co-doped AlInGaN layer 61 of the third strain control layer 6 is 1x10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm3 The C doping concentration is 1x10 16 atoms / cm 3 ~1x10 17 atoms / cm 3 .

[0045] It should be noted that the C doping of the C / Si co-doped AlInGaN layer 61 enables the defects generated during the epitaxial growth of the third strain control layer 6 to converge, thereby reducing the dislocation density and effectively releasing the stress of the epitaxial layer.

[0046] In some embodiments, the C / Si co-doped AlInGaN layer 61 of the third strain control layer 6 has an Al content of 0.01 to 0.2, which increases along the epitaxial growth direction; and an In content of 0.01 to 0.1, which decreases along the epitaxial growth direction.

[0047] In some embodiments, the InGaN layer 62 of the third strain control layer 6 has an In content of 0.01 to 0.1%.

[0048] This invention ensures lattice matching and raises the energy band by controlling the Al and In content of the C / Si co-doped AlInGaN layer 61. The energy band is smoothed by gradually changing the composition content, reducing the loss of charge carriers when crossing the potential barrier. In addition, the V-shaped pit, as a natural stress release channel, can push the charge carriers towards the center of the well, thereby enhancing the wave function overlap integral, suppressing electron overflow, and improving luminescence efficiency.

[0049] In some embodiments, the multiple quantum well layer 7 is formed by periodically stacking InGaN quantum well layers and AlGaN quantum barrier layers, with a period number of 5 to 20, wherein the thickness of the InGaN quantum well layer is 2 nm to 5 nm, and the thickness of the AlGaN quantum barrier layer is 5 nm to 15 nm.

[0050] For example, the thickness of the InGaN quantum well layer is 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, or 5nm, but is not limited thereto.

[0051] For example, the thickness of the AlGaN quantum barrier layer is 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, or 15nm, but is not limited thereto.

[0052] In some embodiments, the AlGaN quantum barrier layer of the multi-quantum well layer 7 has an Al content of 0.01 to 0.1, and the InGaN quantum well layer of the multi-quantum well layer 7 has an In content of 0.01 to 0.3.

[0053] Preferably, the InGaN quantum well layer of the multi-quantum well layer 7 has an In content of 0.15 to 0.3%.

[0054] This invention periodically and alternately stacks InGaN quantum well layers and AlGaN quantum barrier layers to form a quantum confinement structure, confining electrons and holes within multiple quantum well layers for radiative recombination. By controlling the thickness and In content of the InGaN quantum well layers, the emission wavelength can be tuned. At the same time, by controlling the Al content and thickness of the AlGaN quantum barrier layer, the band structure is optimized to suppress polarization effects, thereby improving the internal quantum efficiency while determining the green light band.

[0055] In some embodiments, the thickness of the Si-doped AlGaN layer 8 of the electron blocking layer 10 is 5 nm to 50 nm, and the AlGaN / Al x In y Ga 1-x-y The number of periods in the N-composite superlattice layer 9 is 2 to 5, and the thickness of the second AlGaN layer 91 is 5 nm to 15 nm. x In y Ga 1-x-y The thickness of the N-layer 92 is 1nm to 15nm.

[0056] For example, the thickness of the Si-doped AlGaN layer 8 is 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, or 50nm, but is not limited thereto.

[0057] For example, the thickness of the second AlGaN layer 91 is 5nm, 10nm, or 15nm, but is not limited thereto.

[0058] For example, the Al x In y Ga 1-x-y The thickness of the N-layer 92 is 1nm, 3nm, 5nm, 7nm, 9nm, 11nm, 13nm, 15nm, but is not limited to these.

[0059] In some embodiments, the Si-doped AlGaN layer 8 of the electron blocking layer 10 has a Si doping concentration of 1 x 10⁻⁶. 16 atoms / cm 3 ~1x10 17 atoms / cm 3 Its Al component content is 0.01 to 0.5%.

[0060] Specifically, the Si doping of the Si-doped AlGaN layer 8 can change the hole injection path from C-plane injection to V-shaped pit injection, thereby increasing the hole injection ratio, reducing the operating voltage, and improving the luminous efficiency.

[0061] In some embodiments, the electron blocking layer 10 is AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer 9, wherein the Al content of the second AlGaN layer 91 is 0.01–0.5%, and the Al content is... x In y Ga 1-x-y The Al content of layer N92 is 0.01 to 0.5, and the Al content decreases along the epitaxial growth direction. The In content is 0.01 to 0.2, and the In content increases along the epitaxial growth direction.

[0062] The Si-doped AlGaN layer 8 of the electron blocking layer 10 of this invention and AlGaN / Al x In y Ga 1-x-y The Al composition at the high end of the Al-based superlattice layer 9 forms a high potential barrier, strongly preventing electron leakage. The decreasing Al content and increasing In content achieve a bandgap transition, which not only significantly reduces the hole injection barrier and improves hole injection efficiency, but also reduces electron overflow and increases effective recombination. Furthermore, the AlGaN / Al x In y Ga 1-x-y The superlattice structure of the N-composite superlattice layer 9 reduces nonradiative recombination efficiency by decreasing the polarization charge at the interface.

[0063] In some embodiments, the thickness of the P-type GaN layer 11 is 10 nm to 50 nm. Exemplarily, the thickness of the P-type GaN layer 11 is 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm, but is not limited thereto.

[0064] In some embodiments, the p-type GaN layer 11 is a Mg-doped p-type GaN layer with a Mg doping concentration of 1 x 10⁻⁶. 19 atoms / cm 3 ~1x10 21 atoms / cm 3 Within the aforementioned range, magnesium doping provides holes, enabling P-type conductivity and providing low-resistance channels for holes, thereby improving injection efficiency and luminescence efficiency.

[0065] Accordingly, the present invention also provides a method for preparing a green GaN epitaxial wafer, comprising the following steps: S1. Deposit a buffer layer 2 on substrate 1; Specifically, a buffer layer 2 is deposited on the substrate 1, and the deposition method used includes, but is not limited to, physical vapor deposition (PVD) and metal-organic chemical vapor deposition (MOCVD). Preferably, physical vapor deposition is used.

[0066] Preferably, the present invention uses AlN as a buffer layer 2, which can provide nucleation centers with the same orientation as the substrate 1, effectively releasing the stress caused by lattice mismatch and thermal expansion coefficient mismatch between GaN and the substrate 1. At the same time, the further growth of the buffer layer 2 can provide a flat nucleation surface, reduce the contact angle of GaN nucleation growth, and enable the island-shaped GaN grains to connect into a surface within a small thickness and transform into two-dimensional epitaxial growth.

[0067] S2. Introduce gas to heat-treat the buffer layer 2; In some embodiments, the temperature for heat treatment of the buffer layer 2 is 1000℃~1100℃, and the gas introduced is N2, H2, NH3, with a volume ratio of 1:(1~20):(1~10). Within the above range, two-dimensional epitaxial growth can be promoted, making its surface smoother and its grain orientation more consistent.

[0068] In this invention, gas is introduced before depositing the first strain control layer 3 to heat-treat the buffer layer 2. Since the crystal quality of the buffer layer 2 itself is poor, it is usually in a polycrystalline or amorphous state. The gas and heat treatment can improve the crystal quality of the buffer layer and lay the foundation for subsequent epitaxial growth.

[0069] S3. Deposit a first strain control layer 3 on the buffer layer 2; In some embodiments, a first strain control layer 3 is deposited on the buffer layer 2 using MOCVD. The deposition temperature of the first strain control layer 3 is 900°C to 1000°C, the deposition pressure is 100 torr to 500 torr, and the introduced gas is N2, H2, NH3, with a volume ratio of 1:(1 to 20):(1 to 10).

[0070] Specifically, the first strain control layer 3 is a superlattice layer composed of a first AlGaN layer 31 and a GaN layer 32 arranged in a periodic alternation. In this invention, the first strain control layer 3 is deposited on the buffer layer 2. By controlling the Al composition content of the first AlGaN layer 31 of the first strain control layer 3 to decrease gradually along the epitaxial growth direction, the lattice mismatch between the substrate 1 and GaN is alleviated stepwise, thereby releasing heteroepitaxial stress, suppressing dislocation propagation, and improving the crystal quality of the epitaxial layer.

[0071] S4. Deposit an undoped GaN layer 4 on the first strain control layer 3; In some embodiments, an undoped GaN layer 4 is deposited on the first strain control layer 3 using MOCVD. The deposition temperature of the undoped GaN layer 4 is 1050℃~1200℃, the deposition pressure is 100 torr~600 torr, and the introduced gas is N2, H2, NH3, with a volume ratio of 1:(1~20):(1~10).

[0072] S5. Deposit a second strain control layer 5 on the undoped GaN layer 4; In some embodiments, the deposition temperature of MOCVD in the second strain control layer 5 is 850°C to 1150°C, the deposition pressure is 100 torr to 500 torr, and the introduced gas is N2, H2, NH3, with a volume ratio of 1:(1 to 20):(1 to 10).

[0073] Specifically, the second strain control layer 5 is a superlattice layer composed of periodically alternating N-type GaN layers 51 and AlN layers 52, wherein the Si doping concentration of the N-type GaN layer 51 in the second strain control layer 5 is 1x10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm 3 Si doping can provide free electrons, thereby improving the conductivity of the epitaxial layer.

[0074] S6. Deposit a third strain control layer 6 on the second strain control layer 5; In some embodiments, a third strain control layer 6 is deposited on the second strain control layer 5 using MOCVD. The deposition temperature of the third strain control layer 6 is 800℃~900℃, the deposition pressure is 100torr~600torr, and the introduced gas is N2 and NH3 with a volume ratio of 1:(1~10).

[0075] This invention controls the deposition temperature of the third strain control layer 6 at 800℃~900℃. Due to the low deposition temperature, the thermal stress generated by the difference in thermal expansion coefficients between the substrate and the epitaxial layer can be effectively released. Specifically, the third strain control layer 6 is a superlattice layer composed of a C / Si co-doped AlInGaN layer 61 and an InGaN layer 62 that are periodically alternating. By introducing periodic compressive stress, it can offset part of the tensile stress from the substrate to the epitaxial layer, thereby suppressing cracks, reducing dislocation density, improving the integrity of the epitaxial layer, and improving luminescence efficiency.

[0076] In some embodiments, the Si doping concentration of the C / Si co-doped AlInGaN layer 61 of the third strain control layer 6 is 1x10⁻⁶. 17 atoms / cm 3 ~1x1019 atoms / cm 3 The C doping concentration is 1x10 16 atoms / cm 3 ~1x10 17 atoms / cm 3 .

[0077] It should be noted that the C doping of the C / Si co-doped AlInGaN layer 61 enables the defects generated during the epitaxial growth of the third strain control layer 6 to converge, thereby reducing the dislocation density and effectively releasing the stress of the epitaxial layer.

[0078] S7. Deposit a multi-quantum-well layer 7 in the third strain control layer 6; In some embodiments, MOCVD is used to deposit a multi-quantum well layer 7 on the third strain control layer 6. The multi-quantum well layer 7 is formed by periodically alternating InGaN quantum well layers and AlGaN quantum barrier layers. The deposition temperature of the InGaN quantum well layer is 790℃~810℃ and the deposition pressure is 50 torr~300 torr. The deposition temperature of the AlGaN quantum barrier layer is 800℃~900℃ and the deposition pressure is 50 torr~300 torr. The introduced gas is N2, H2, NH3, and their volume ratio is 1:(1~20):(1~10).

[0079] S8. Deposit an electron blocking layer 10 in the multi-quantum well layer 7; In some embodiments, an electron blocking layer 10 is deposited on the multi-quantum well layer 7 using MOCVD. The deposition temperature of the electron blocking layer 10 is 900°C to 1000°C, the deposition pressure is 50 torr to 500 torr, and the introduced gas is N2, H2, NH3 in a volume ratio of 1:(1 to 20):(1 to 10).

[0080] Specifically, the electron blocking layer 10 includes a Si-doped AlGaN layer 8 and an AlGaN / Al layer. x In y Ga 1-x-y N-composite superlattice layer 9, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer 9 is composed of the second AlGaN layer 91 and Al x In y Ga 1-x-y The N layers are composed of 92 periodic alternations.

[0081] In some embodiments, the Si-doped AlGaN layer 8 of the electron blocking layer 10 has a Si doping concentration of 1 x 10⁻⁶. 16 atoms / cm3 ~1x10 17 atoms / cm 3 .

[0082] Specifically, the Si doping of the Si-doped AlGaN layer 8 can change the hole injection path from C-plane injection to V-shaped pit injection, thereby increasing the hole injection ratio, reducing the operating voltage, and improving the luminous efficiency.

[0083] S9. Deposit a P-type GaN layer 11 on the electron blocking layer 10.

[0084] In some embodiments, a P-type GaN layer 11 is deposited on the electron blocking layer 10 using MOCVD. The deposition temperature of the P-type GaN layer 11 is 900°C to 1050°C, the deposition pressure is 100 torr to 600 torr, and the introduced gas is N2, H2, NH3, with a volume ratio of 1:(1 to 20):(1 to 10).

[0085] In some embodiments, the Mg doping concentration of the p-type GaN layer 11 is 1 x 10⁻⁶. 19 atoms / cm 3 ~1x10 21 atoms / cm 3 .

[0086] The p-type GaN layer 11 of the present invention provides holes through magnesium doping to achieve p-type conductivity. Within the above-mentioned Mg doping concentration range, it can provide low-resistance channels for holes, thereby improving injection efficiency and luminescence efficiency.

[0087] Therefore, this invention provides a green GaN epitaxial wafer and its fabrication method. The green GaN epitaxial wafer includes a substrate 1 and a buffer layer 2, a first strain control layer 3, an undoped GaN layer 4, a second strain control layer 5, a third strain control layer 6, a multi-quantum well layer 7, an electron blocking layer 10, and a p-type GaN layer 11 sequentially deposited on the substrate 1. This fabrication method inserts the first strain control layer 3 and the second strain control layer 5 before and after the undoped GaN layer 4, respectively, and inserts the third strain control layer 6 and the electron blocking layer 10 before and after the multi-quantum well layer 7, respectively. This effectively releases the stress in the epitaxial layer, improves the crystal quality of the epitaxial layer, and enhances the luminescence efficiency.

[0088] The following will provide further details with reference to specific embodiments.

[0089] 1. Preparation Example 1 Embodiment 1 of the present invention provides a green GaN epitaxial wafer, the epitaxial wafer comprising a substrate, and a buffer layer, a first strain control layer, an undoped GaN layer, a second strain control layer, a third strain control layer, a multiple quantum well layer, an electron blocking layer and a P-type GaN layer sequentially deposited on the substrate; The first strain control layer is a superlattice layer composed of alternating first AlGaN layers and GaN layers; The second strain control layer is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers; The third strain control layer is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers and InGaN layers. The electron blocking layer includes a Si-doped AlGaN layer and an AlGaN / Al layer. x In y Ga 1-x-y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The structure consists of N layers arranged in a periodic alternation.

[0090] Embodiment 1 of the present invention also provides a method for preparing a green GaN epitaxial wafer, comprising the following steps: (1) Deposit a buffer layer on the substrate; Using Applied Materials' PVD equipment, a 15nm thick AlN layer was deposited on a sapphire substrate as a buffer layer.

[0091] (2) Introduce gas to heat-treat the buffer layer; The substrate with the deposited buffer layer was placed in an A7 MOCVD apparatus, and high-purity N2, high-purity H2, and high-purity NH3 were introduced. The buffer layer was then heat-treated at 1000°C.

[0092] (3) Deposit a first strain control layer on the buffer layer; High-purity N2 and high-purity H2 were used as carrier gases, and high-purity NH3 was used as the N source, with a volume ratio of N2:H2:NH3 of 1:20:10. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources, and trimethylaluminum (TMAI) was used as the aluminum source. At a temperature of 900°C and a pressure of 500 torr, a first strain control layer was deposited on the buffer layer. The first strain control layer was a superlattice layer composed of a first AlGaN layer and a GaN layer with periodic alternations, with a period number of 3. The thickness of the first AlGaN layer was 100 nm, and the Al content was 0.01–0.2%, with the Al content decreasing along the epitaxial growth direction. The thickness of the GaN layer was 8 nm.

[0093] (4) Deposit an undoped GaN layer on the first strain control layer; High-purity N2 and high-purity H2 were used as carrier gases, and high-purity NH3 was used as the N source, with a volume ratio of N2:H2:NH3 of 1:10:10. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources. An undoped GaN layer was deposited on the first strain-controlled layer at a temperature of 1100°C and a pressure of 150 torr. The thickness of the undoped GaN layer was 2 μm.

[0094] (5) Deposit a second strain control layer on the undoped GaN layer; High-purity N2 and high-purity H2 were used as carrier gases, and high-purity NH3 was used as the N source, with a volume ratio of N2:H2:NH3 of 1:20:10. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources, and trimethylaluminum (TMAI) was used as the aluminum source. A second strain-modulated layer was deposited on the undoped GaN layer at a temperature of 1150°C and a pressure of 100 torr. The second strain-modulated layer was a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers, with a period number of 10. The thickness of the N-type GaN layer was 300 nm, and the dopant was silane (SiH4) with a Si doping concentration of 1 x 10⁻⁶. 19 atoms / cm 3 The thickness of the AlN layer is 15 nm.

[0095] (6) Deposit a third strain control layer on the second strain control layer; High-purity N2 was used as the carrier gas, and high-purity NH3 as the N source, with a N2:NH3 volume ratio of 1:10. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources, trimethylaluminum (TMAI) as the aluminum source, and trimethylindium (TMIn) as the indium source. A third strain control layer was deposited on the second strain control layer at a temperature of 800°C and a pressure of 600 torr. The third strain control layer was a superlattice layer composed of periodically alternating C / Si co-doped AlInGaN layers and InGaN layers, with a period number of 20. The thickness of the C / Si co-doped AlInGaN layers was 10 nm, with an Al content of 0.01–0.2%, increasing along the epitaxial growth direction; the In content was 0.01–0.1%, decreasing along the epitaxial growth direction; and the Si doping concentration was 1 x 10⁻⁶. 17 atoms / cm 3 The C doping concentration is 1x10 16 atoms / cm 3 The InGaN layer has a thickness of 1 nm and an In content of 0.01–0.1%.

[0096] (7) Deposit a multi-quantum-well layer in the third strain control layer; High-purity N2 and high-purity H2 were used as carrier gases, and high-purity NH3 was used as the N source, with a volume ratio of N2:H2:NH3 of 1:1:10. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources, trimethylaluminum (TMAI) as the aluminum source, and trimethylindium (TMIn) as the indium source. A multi-quantum well layer was deposited in the third strain-controlled layer. The multi-quantum well layer consisted of alternating stacked InGaN quantum well layers and AlGaN quantum barrier layers with a period of 10. The InGaN quantum well layer was deposited at a deposition temperature of 790°C, a deposition pressure of 200 torr, a thickness of 3.5 nm, and an In content of 0.23%. The AlGaN quantum barrier layer was deposited at a deposition temperature of 855°C, a deposition pressure of 200 torr, a thickness of 12 nm, and an Al content of 0.05%.

[0097] (8) Deposit an electron blocking layer in the multi-quantum well layer; High-purity N2 and high-purity H2 were used as carrier gases, and high-purity NH3 was used as the N source, with a volume ratio of N2:H2:NH3 of 1:1:10. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources, trimethylaluminum (TMAI) as the aluminum source, and trimethylindium (TMIn) as the indium source. An electron blocking layer was deposited on the multi-quantum well layer at a temperature of 900°C and a pressure of 500 torr. The electron blocking layer included a Si-doped AlGaN layer and an AlGaN / Al layer. x In y Ga 1-x-yN-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The N-layers are periodically alternating, wherein the thickness of the Si-doped AlGaN layer is 5 nm, the Al content is 0.01–0.5%, and the Si doping concentration is 1 x 10⁻⁶. 16 atoms / cm 3 AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer has 2 periods, the second AlGaN layer has a thickness of 15 nm, and the Al content is 0.01–0.5%. x In y Ga 1-x-y The thickness of the N layer is 5 nm, the Al content is 0.01–0.5% decreasing along the epitaxial growth direction, and the In content is 0.01–0.2% increasing along the epitaxial growth direction.

[0098] (9) Deposit a P-type GaN layer in the electron blocking layer.

[0099] High-purity N2 and high-purity H2 were used as carrier gases, and high-purity NH3 was used as the N source, with an N2:H2:NH3 ratio of 1:1:10. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources. A p-type GaN layer with a thickness of 15 nm was deposited in the electron blocking layer at a temperature of 985 °C and a pressure of 200 torr. The dopant was magnesia-dicenocene (CP2Mg), and the Mg doping concentration was 2 x 10⁻⁶. 20 atoms / cm 3 .

[0100] Example 2 Embodiment 2 of the present invention provides a green GaN epitaxial wafer and its preparation method, which are basically the same as those in Embodiment 1, except that: In step (1), the thickness of the buffer layer is 50 nm; In step (2), the temperature at which the buffer layer is heat-treated is 1100℃; In step (3), the deposition temperature of the first strain-controlled layer is 1000℃ and the deposition pressure is 100 torr; the first strain-controlled layer is a superlattice layer composed of a first AlGaN layer and a GaN layer that alternate periodically, with a period number of 5, wherein the thickness of the first AlGaN layer is 50nm, the Al content is 0.01~0.2, the Al content decreases along the epitaxial growth direction, and the thickness of the GaN layer is 2nm; In step (4), the deposition temperature of the undoped GaN layer is 1200℃, the deposition pressure is 600 torr, and the thickness of the undoped GaN layer is 3μm. In step (5), the deposition temperature of the second strain-controlled layer is 1150℃, and the deposition pressure is 100 torr; the second strain-controlled layer is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers, with a period number of 20, wherein the thickness of the N-type GaN layer is 100nm, and the Si doping concentration is 1x10⁻⁶. 17 atoms / cm 3 The thickness of the AlN layer is 10 nm; In step (6), the deposition temperature of the third strain control layer is 900℃, and the deposition pressure is 100 torr. The third strain control layer is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers and InGaN layers, with a period number of 3. The thickness of the C / Si co-doped AlInGaN layer is 100 nm, the Al content is 0.01–0.2%, increasing along the epitaxial growth direction, the In content is 0.01–0.1%, decreasing along the epitaxial growth direction, and the Si doping concentration is 1 x 10⁻⁶. 19 atoms / cm 3 The C doping concentration is 1x10 17 atoms / cm 3 The InGaN layer has a thickness of 10 nm and an In content of 0.01–0.1%. In step (7), the multiple quantum well layer consists of alternating stacked InGaN quantum well layers and AlGaN quantum barrier layers with a period of 18. The InGaN quantum well layer has a deposition temperature of 810°C, a deposition pressure of 50 torr, a thickness of 5 nm, and an In content of 0.15%. The AlGaN quantum barrier layer has a deposition temperature of 900°C, a deposition pressure of 50 torr, a thickness of 5 nm, and an Al content of 0.04%.

[0101] In step (8), the deposition temperature of the electron blocking layer is 1000℃ and the deposition pressure is 50 torr; the electron blocking layer includes a Si-doped AlGaN layer and an AlGaN / Al layer. x Iny Ga 1-x-y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The N-layers are periodically alternating, wherein the thickness of the Si-doped AlGaN layer is 50 nm, the Al content is 0.01–0.5%, and the Si doping concentration is 1 x 10⁻⁶. 17 atoms / cm 3 AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer has 3 periods, the second AlGaN layer has a thickness of 5 nm, and the Al content is 0.01–0.5%. x In y Ga 1-x-y The thickness of the N layer is 15 nm, the Al content is 0.01–0.5% decreasing along the epitaxial growth direction, and the In content is 0.01–0.2% increasing along the epitaxial growth direction.

[0102] In step (9), the deposition temperature of the P-type GaN layer is 1050℃, and the deposition pressure is 600 torr; the thickness of the P-type GaN layer is 35 nm, and the Mg doping concentration is 1 x 10⁻⁶. 19 atoms / cm 3 .

[0103] Example 3 Embodiment 3 of the present invention provides a green GaN epitaxial wafer and its preparation method, which are basically the same as those in Embodiment 1, except that: In step (1), the thickness of the buffer layer is 35 nm; In step (2), the temperature at which the buffer layer is heat-treated is 1050°C; In step (3), the deposition temperature of the first strain-controlled layer is 950℃ and the deposition pressure is 350 torr; the first strain-controlled layer is a superlattice layer composed of a first AlGaN layer and a GaN layer that alternate periodically, with a period number of 4, wherein the thickness of the first AlGaN layer is 10nm, the Al content is 0.01~0.2, the Al content decreases along the epitaxial growth direction, and the thickness of the GaN layer is 6nm; In step (4), the deposition temperature of the undoped GaN layer is 1150℃, the deposition pressure is 300 torr, and the thickness of the undoped GaN layer is 2.5 μm. In step (5), the deposition temperature of the second strain-controlled layer is 1000℃, and the deposition pressure is 250 torr; the second strain-controlled layer is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers, with a period number of 15, wherein the thickness of the N-type GaN layer is 200nm, and the Si doping concentration is 1x10⁻⁶. 17 atoms / cm 3 The thickness of the AlN layer is 12 nm; In step (6), the deposition temperature of the third strain control layer is 850℃, and the deposition pressure is 150 torr. The third strain control layer is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers and InGaN layers, with a period number of 10. The thickness of the C / Si co-doped AlInGaN layer is 60 nm, the Al content is 0.01-0.2, increasing along the epitaxial growth direction, the In content is 0.01-0.1, decreasing along the epitaxial growth direction, and the Si doping concentration is 1 x 10⁻⁶. 19 atoms / cm 3 The C doping concentration is 1x10 17 atoms / cm 3 The InGaN layer has a thickness of 8 nm and an In content of 0.01–0.1%. In step (7), the multiple quantum well layer consists of alternating stacked InGaN quantum well layers and AlGaN quantum barrier layers with a period of 6. The InGaN quantum well layer has a deposition temperature of 800°C, a deposition pressure of 150 torr, a thickness of 2 nm, and an In content of 0.3%. The AlGaN quantum barrier layer has a deposition temperature of 850°C, a deposition pressure of 200 torr, a thickness of 15 nm, and an Al content of 0.08%.

[0104] In step (8), the deposition temperature of the electron blocking layer is 950°C, and the deposition pressure is 350 torr; the electron blocking layer includes a Si-doped AlGaN layer and an AlGaN / Al layer. x In y Ga 1-x-y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The N-layers are periodically alternating, wherein the thickness of the Si-doped AlGaN layer is 35 nm, the Al content is 0.01–0.5%, and the Si doping concentration is 1 x 10⁻⁶. 17 atoms / cm 3AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer has 5 periods, the second AlGaN layer has a thickness of 10 nm, and the Al content is 0.01–0.5%. x In y Ga 1-x-y The thickness of the N layer is 1 nm, the Al content is 0.01–0.5, decreasing along the epitaxial growth direction, and the In content is 0.01–0.2, increasing along the epitaxial growth direction.

[0105] In step (9), the deposition temperature of the P-type GaN layer is 1000℃, and the deposition pressure is 300 torr; the thickness of the P-type GaN layer is 50 nm, and the Mg doping concentration is 1 x 10⁻⁶. 21 atoms / cm 3 .

[0106] Example 4 Example 4 of this invention provides a green GaN epitaxial wafer and its preparation method, which are basically the same as those in Example 1, except that: In step (1), the thickness of the buffer layer is 20 nm; In step (2), the temperature at which the buffer layer is heat-treated is 1050°C; In step (3), the deposition temperature of the first strain-controlled layer is 950℃ and the deposition pressure is 350 torr; the first strain-controlled layer is a superlattice layer composed of a first AlGaN layer and a GaN layer that alternate periodically, with a period number of 4, wherein the thickness of the first AlGaN layer is 30nm, the Al content is 0.01~0.2, the Al content decreases along the epitaxial growth direction, and the thickness of the GaN layer is 4nm; In step (4), the deposition temperature of the undoped GaN layer is 1150℃, the deposition pressure is 300 torr, and the thickness of the undoped GaN layer is 5μm. In step (5), the deposition temperature of the second strain-controlled layer is 1000℃, and the deposition pressure is 250 torr; the second strain-controlled layer is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers, with a period number of 12, wherein the thickness of the N-type GaN layer is 250 nm, and the Si doping concentration is 1 x 10⁻⁶. 17 atoms / cm 3 The thickness of the AlN layer is 13 nm; In step (6), the deposition temperature of the third strain control layer is 850℃, and the deposition pressure is 150 torr. The third strain control layer is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers and InGaN layers, with a period number of 10. The thickness of the C / Si co-doped AlInGaN layer is 50nm, the Al content is 0.01-0.2%, increasing along the epitaxial growth direction, the In content is 0.01-0.1%, decreasing along the epitaxial growth direction, and the Si doping concentration is 1x10⁻¹⁰. 19 atoms / cm 3 The C doping concentration is 1x10 17 atoms / cm 3 The InGaN layer has a thickness of 5 nm and an In content of 0.01–0.1%. In step (7), the multiple quantum well layer consists of alternating stacked InGaN quantum well layers and AlGaN quantum barrier layers with a period of 6. The InGaN quantum well layer has a deposition temperature of 800°C, a deposition pressure of 150 torr, a thickness of 2 nm, and an In content of 0.3%. The AlGaN quantum barrier layer has a deposition temperature of 850°C, a deposition pressure of 200 torr, a thickness of 15 nm, and an Al content of 0.08%.

[0107] In step (8), the deposition temperature of the electron blocking layer is 950°C, and the deposition pressure is 350 torr; the electron blocking layer includes a Si-doped AlGaN layer and an AlGaN / Al layer. x In y Ga 1-x-y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The N-layers are periodically alternating, wherein the thickness of the Si-doped AlGaN layer is 20 nm, the Al content is 0.01–0.5%, and the Si doping concentration is 1 x 10⁻⁶. 17 atoms / cm 3 AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer has 3 periods, the second AlGaN layer has a thickness of 10 nm, and the Al content is 0.01–0.5%. x In y Ga 1-x-yThe thickness of the N layer is 11 nm, the Al content is 0.01–0.5, decreasing along the epitaxial growth direction, and the In content is 0.01–0.2, increasing along the epitaxial growth direction.

[0108] In step (9), the deposition temperature of the P-type GaN layer is 1000℃, and the deposition pressure is 300 torr; the thickness of the P-type GaN layer is 40 nm, and the Mg doping concentration is 1 x 10⁻⁶. 21 atoms / cm 3 .

[0109] Comparative Example 1 Comparative Example 1 of the present invention provides a green GaN epitaxial wafer, comprising a substrate, and a buffer 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 deposited on the substrate.

[0110] Comparative Example 1 of the present invention also provides a method for preparing a green GaN epitaxial wafer, wherein the preparation steps of the buffer layer, the undoped GaN layer, the multiple quantum well layer, and the P-type GaN layer are the same as those in Example 1; The method for preparing the N-type GaN layer includes the following steps: High-purity N2 and high-purity H2 were used as carrier gases, and high-purity NH3 was used as the N source, with an N2:H2:NH3 ratio of 1:20:10. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources, and trimethylaluminum (TMAI) was used as the aluminum source. An N-type GaN layer with a thickness of 3 μm was deposited on the undoped GaN layer at a temperature of 1150 °C and a pressure of 100 torr. The dopant was silane (SiH4), and the Si doping concentration was 1 x 10⁻⁶. 19 atoms / cm 3 ; The method for preparing the electron blocking layer includes the following steps: High-purity N2 and high-purity H2 were used as carrier gases, and high-purity NH3 was used as the N source, with N2:H2:NH3 = 1:1:10. Trimethylgallium (TMGa) and triethylgallium (TEGa) were used as Ga sources, and trimethylaluminum (TMAI) was used as the aluminum source. An electron blocking layer was deposited in the multi-quantum well layer at a temperature of 900°C and a pressure of 500 torr. The electron blocking layer was an AlGaN layer with a thickness of 30 nm and an Al content of 0.01–0.5%.

[0111] 2. Detection (1) Detection method The green GaN epitaxial wafers obtained in Examples 1 to 4 and Comparative Example 1 were fabricated into 3 mil*5 mil chips using the same chip process conditions. 300 LED chips were extracted from each chip, and the improvement in ESD yield and photoelectric efficiency were tested at a current of 2mA. The calculations were based on Comparative Example 1.

[0112] (2) Test results Table 1 Test Results

[0113] As shown in Table 1, compared with Comparative Example 1, the green GaN epitaxial wafers provided in Examples 1 to 4 of the present invention, when used to make LED chips, can improve the photoelectric efficiency by 3.5% to 6% and the ESD yield by 2.2% to 3.5%.

[0114] Therefore, the green GaN epitaxial wafer and its preparation method provided by the present invention, by inserting a first strain control layer and a second strain control layer before and after the undoped GaN layer, and inserting a third strain control layer and an electron blocking layer before and after the multi-quantum well layer, can effectively release the stress of the epitaxial layer, improve the crystal quality of the epitaxial layer, and enhance the luminescence efficiency.

[0115] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A green GaN epitaxial wafer, characterized in that, It includes a substrate, and a buffer layer, a first strain control layer, an undoped GaN layer, a second strain control layer, a third strain control layer, a multiple quantum well layer, an electron blocking layer and a P-type GaN layer sequentially deposited on the substrate; The first strain control layer is a superlattice layer composed of alternating first AlGaN layers and GaN layers; The second strain control layer is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers; The third strain control layer is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers and InGaN layers. The electron blocking layer includes a Si-doped AlGaN layer and an AlGaN / Al layer. x In y Ga 1-x-y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The structure consists of N layers arranged in a periodic alternation.

2. The green GaN epitaxial wafer according to claim 1, characterized in that, The first strain control layer has 3 to 5 superlattice layers, the first AlGaN layer has a thickness of 10 nm to 100 nm, and the GaN layer has a thickness of 2 nm to 8 nm. The second strain control layer has a superlattice layer period number of 10 to 20, the thickness of the N-type GaN layer is 100 nm to 300 nm, and the thickness of the AlN layer is 10 nm to 15 nm. The number of superlattice layers in the third strain control layer is 3 to 20, and the thickness of the C / Si co-doped AlInGaN layer is 10 nm to 100 nm. The thickness of the Si-doped AlGaN layer in the electron blocking layer is 5 nm to 50 nm, and the AlGaN / Al x In y Ga 1-x-y The number of periods in the N-composite superlattice layer is 2–5, and the thickness of the second AlGaN layer is 5 nm–15 nm. x In y Ga 1-x-y The thickness of the N layer is 1 nm to 15 nm.

3. The green GaN epitaxial wafer according to claim 1, characterized in that, The thickness of the buffer layer is 10–50 nm; The thickness of the undoped GaN layer is 1 μm to 5 μm; The multiple quantum well layer is formed by periodically alternating InGaN quantum well layers and AlGaN quantum barrier layers, with a period number of 5 to 20. The thickness of the InGaN quantum well layer is 2 nm to 5 nm, and the thickness of the AlGaN quantum barrier layer is 5 nm to 15 nm. The thickness of the P-type GaN layer is 10 nm to 50 nm.

4. The green GaN epitaxial wafer according to claim 1, characterized in that, The second strain-controlled N-type GaN layer is a Si-doped N-type GaN layer with a Si doping concentration of 1 x 10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm 3 ; The third strain-tuning layer is a C / Si co-doped AlInGaN layer with a Si doping concentration of 1x10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm 3 The C doping concentration is 1x10 16 atoms / cm 3 ~1x10 17 atoms / cm 3 ; The Si-doped AlGaN layer of the electron blocking layer has a Si doping concentration of 1x10⁻⁶. 16 atoms / cm 3 ~1x10 17 atoms / cm 3 ; The p-type GaN layer is a Mg-doped p-type GaN layer with a Mg doping concentration of 1 x 10⁻⁶. 19 atoms / cm 3 ~1x10 21 atoms / cm 3 .

5. The green GaN epitaxial wafer according to claim 1, characterized in that, The first AlGaN layer of the first strain-controlled layer has an Al content of 0.01 to 0.2, and the Al content decreases along the epitaxial growth direction. The third strain-controlled layer, a C / Si co-doped AlInGaN layer, has an Al content of 0.01–0.2%, which increases along the epitaxial growth direction. The Si-doped AlGaN layer of the electron blocking layer has an Al content of 0.01 to 0.5%. The electron blocking layer AlGaN / Al x In y Ga 1-x-y N-composite superlattice layer, wherein the Al content of the second AlGaN layer is 0.01–0.5, Al x In y Ga 1-x-y The Al component content of the N layer is 0.01–0.5%, wherein the Al x In y Ga 1-x-y The Al content of the N layer decreases along the epitaxial growth direction; The AlGaN quantum barrier layer with multiple quantum wells has an Al content of 0.01 to 0.1%.

6. The green GaN epitaxial wafer according to claim 1, characterized in that, The third strain-controlled layer, the C / Si co-doped AlInGaN layer, has an In content of 0.01 to 0.1, which decreases along the epitaxial growth direction. The InGaN layer of the third strain control layer has an In content of 0.01 to 0.

1. Al of the electron blocking layer x In y Ga 1-x-y The N-layer has an In content of 0.01 to 0.2, wherein the In content increases along the epitaxial growth direction. The InGaN quantum well layer with multiple quantum well layers has an In content of 0.01 to 0.3%.

7. A method for preparing a green GaN epitaxial wafer as described in any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Deposit a buffer layer on the substrate; (2) Introduce gas to heat-treat the buffer layer; (3) Deposit a first strain control layer on the buffer layer; (4) Deposit an undoped GaN layer on the first strain control layer; (5) Deposit a second strain control layer on the undoped GaN layer; (6) Deposit a third strain control layer on the second strain control layer; (7) Deposit a multi-quantum-well layer in the third strain control layer; (8) Deposit an electron blocking layer in the multi-quantum well layer; (9) Deposit a P-type GaN layer in the electron blocking layer; The first strain control layer is a superlattice layer composed of alternating first AlGaN layers and GaN layers. The second strain control layer is a superlattice layer composed of periodically alternating N-type GaN layers and AlN layers; The third strain control layer is a superlattice layer composed of alternating C / Si co-doped AlInGaN layers and InGaN layers. The electron blocking layer includes a Si-doped AlGaN layer and an AlGaN / Al layer. x In y Ga 1-x-y N-composite superlattice layer, wherein the AlGaN / Al x In y Ga 1-x-y The N-composite superlattice layer consists of a second AlGaN layer and Al x In y Ga 1-x-y The structure consists of N layers arranged in a periodic alternation.

8. The method for preparing a green GaN epitaxial wafer according to claim 7, characterized in that, The temperature for heat treatment of the buffer layer is 1000℃~1100℃; The deposition temperature of the first strain-controlled layer is 900℃~1000℃, and the deposition pressure is 100 torr~500 torr; The deposition temperature of the undoped GaN layer is 1050℃~1200℃, and the deposition pressure is 100 torr~600 torr. The deposition temperature of the second strain-controlled layer is 850℃~1150℃, and the deposition pressure is 100 torr~500 torr; The deposition temperature of the third strain control layer is 800℃~900℃, and the deposition pressure is 100torr~600torr; The multi-quantum well layer is formed by periodically alternating InGaN quantum well layers and AlGaN quantum barrier layers. The deposition temperature of the InGaN quantum well layer is 790℃~810℃ and the deposition pressure is 50 torr~300 torr. The deposition temperature of the AlGaN quantum barrier layer is 800℃~900℃ and the deposition pressure is 50 torr~300 torr. The electron blocking layer is deposited at a temperature of 900℃ to 1000℃ and at a pressure of 50 torr to 500 torr. The deposition temperature of the P-type GaN layer is 900℃~1050℃, and the deposition pressure is 100 torr~600 torr.

9. The method for preparing a green GaN epitaxial wafer according to claim 7, characterized in that, In steps (2) to (9), the gas introduced is a mixture of N2, H2, and NH3, or a mixture of N2 and NH3; When the introduced gas is a mixture of N2, H2, and NH3, its volume ratio is 1:(1-20):(1-10). When the gas introduced is a mixture of N2 and NH3, the volume ratio is 1:(1~10).

10. The method for preparing a green GaN epitaxial wafer according to claim 7, characterized in that, The second strain-controlled N-type GaN layer is a Si-doped N-type GaN layer with a Si doping concentration of 1 x 10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm 3 ; The third strain-tuning layer is a C / Si co-doped AlInGaN layer with a Si doping concentration of 1x10⁻⁶. 17 atoms / cm 3 ~1x10 19 atoms / cm 3 The C doping concentration is 1x10 16 atoms / cm 3 ~1x10 17 atoms / cm 3 ; The Si-doped AlGaN layer of the electron blocking layer has a Si doping concentration of 1x10⁻⁶. 16 atoms / cm 3 ~1x10 17 atoms / cm 3 ; The p-type GaN layer is a Mg-doped p-type GaN layer with a Mg doping concentration of 1 x 10⁻⁶. 19 atoms / cm 3 ~1x10 21 atoms / cm 3 .

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