Light emitting diode epitaxial structure and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor devices, in particular to a light-emitting diode epitaxial structure which comprises a substrate, and a graphene composite nano layer, an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer are sequentially stacked on the substrate. The graphene composite nano layer comprises a modified graphene layer and a ZnO sub-layer which are stacked in sequence, the modified graphene layer is arranged on the substrate, and the ZnO sub-layer is arranged on the modified graphene layer; the modified graphene layer is subjected to nitrogen plasma treatment, and the thickness of the modified graphene layer is 10-100 nm; and the thickness of the ZnO sub layer is 20 nm to 200 nm. According to the invention, lattice mismatch dislocation, residual stress and thermal mismatch of the epitaxial material grown on the heterogeneous substrate can be effectively modulated, the scattering efficiency under high current is improved, the probability of radiation recombination of the heterogeneous epitaxial material is improved, and the requirement of heterogeneous epitaxy is relaxed at the same time.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to an epitaxial structure of a light-emitting diode and its fabrication method. Background Technology

[0002] Existing third-generation GaN semiconductors lack commercially available GaN homopolymer substrates, typically using heteropolymer substrates such as Si, SiC, or sapphire. These heteropolymer substrates suffer from lattice mismatch and thermal mismatch due to differences in thermal expansion coefficients, resulting in high residual stress in the GaN epitaxial material. This residual stress generates high-density through-dislocation (TD) defects, cracks, and wafer warping, significantly impacting the performance of GaN-based devices. In GaN optoelectronic devices, stress induces piezoelectric polarization in the quantum well (QW), which, along with spontaneous polarization, leads to non-overlapping electron and hole wave functions, resulting in charge separation and reducing the probability of radiative recombination, significantly decreasing the internal quantum efficiency of optoelectronic devices. Current methods incorporating AlN and AlGaN buffer layers still suffer from high lattice mismatch and introduce new heteropolymer interfaces, generating numerous dislocations and causing a decrease in breakdown voltage. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides a light-emitting diode epitaxial structure and its preparation method, which can effectively modulate the lattice mismatch dislocations, residual stress and thermal mismatch of the epitaxial material grown on the heterogeneous substrate, improve the scattering efficiency under high current, increase the probability of radiative recombination of the heteroepitaxial material, and relax the requirements of heteroepitaxialization.

[0004] To address the aforementioned issues, this invention proposes a light-emitting diode epitaxial structure comprising a substrate, wherein a graphene composite nanolayer, an N-type semiconductor layer, a multiple quantum well layer, and a P-type semiconductor layer are sequentially stacked on the substrate. The graphene composite nanolayer comprises a modified graphene layer and a ZnO sublayer stacked sequentially, wherein the modified graphene layer is disposed on the substrate and the ZnO sublayer is disposed on the modified graphene layer. The modified graphene layer is treated with nitrogen plasma and has a thickness of 10 nm to 100 nm. The thickness of the ZnO sublayer is 20nm~200nm.

[0005] As an improvement to the above technical solution, the modified graphene layer is prepared by the following method: The substrate is placed in a reaction chamber, CH4 and carrier gas are introduced, and a graphene sublayer is deposited on the substrate. N2 or a N2-H2 mixture is introduced into the reaction chamber and ionized into nitrogen plasma. The nitrogen plasma bombards the surface of the graphene sublayer, causing dense nucleation sites to form on its surface.

[0006] As an improvement to the above technical solution, the number of atomic layers of the graphene sublayer is >2, the reaction chamber temperature is 600℃~1100℃, the reaction chamber pressure is 0.5 torr~1 torr, the radio frequency power is 20W~70W, the CH4 inlet flow rate is 800sccm~1800sccm, the carrier gas is H2 gas and Ar2 gas, and the carrier gas inlet flow rate is 1000sccm~2500sccm; The nitrogen plasma treatment has a processing power of 50W~100W, an N2 flow rate of 10sccm~25sccm, a processing pressure of 1atm~5atm, a processing temperature of 450℃~700℃, and a processing time of 30min~300min. In the N2-H2 mixed gas, N2 accounts for 5% to 20%, and the H2 flow rate is 1000 sccm to 2500 sccm.

[0007] As an improvement to the above technical solution, the ZnO sublayer is prepared by the following method: Zn powder is heated in a reaction chamber and evaporates into Zn vapor. Ar2 and O2 are then introduced, forming a ZnO sublayer on the surface of the modified graphene layer. The growth temperature of the ZnO sublayer is 500℃~900℃, and the evaporation rate of the Zn powder is 1×10⁻⁶. -4 g·cm -2 ·s -1 ~1×10 -2 g·cm -2 ·s -1 The flow rate of Ar2 gas is 50 sccm to 500 sccm, and the flow rate of O2 is 20 sccm to 300 sccm.

[0008] As an improvement to the above technical solution, the Si doping concentration in the N-type semiconductor layer is 5 × 10⁻⁶. 17 atoms / cm 3 ~1×10 19 atoms / cm 3 The growth thickness is 1.0 μm to 3.0 μm; The number of stacking periods of the quantum barrier layer and the quantum well layer in the multi-quantum well layer is ≥8, and the growth thickness of the quantum well layer is 2nm~4nm; the growth thickness of the quantum barrier layer is 8nm~12nm. The p-type semiconductor layer is a Mg-doped GaN layer with a growth thickness of 15nm~20nm and a Mg doping concentration of 5×10⁻⁶. 18 atoms / cm 3 ~5×10 21 atoms / cm3 .

[0009] Accordingly, the present invention also provides a method for fabricating the aforementioned light-emitting diode epitaxial structure, comprising the following steps: Provide substrate; A graphene sublayer is deposited on the substrate, and then the surface of the graphene sublayer is treated with nitrogen plasma to form the modified graphene layer. A ZnO sublayer is deposited on the modified graphene layers to form a graphene composite nanolayer. An N-type semiconductor layer is deposited on the graphene composite nanolayer; A multi-quantum-well layer is deposited on the N-type semiconductor layer; A P-type semiconductor layer is deposited on the multi-quantum-well layer.

[0010] As an improvement to the above technical solution, in the step of depositing the graphene sublayer, the substrate is placed in a reaction chamber, CH4 is used as the carbon source, and the flow rate of the CH4 is 800 sccm~1800 sccm; H2 and Ar2 are introduced as carrier gases, and the flow rate of the carrier gases is 1000 sccm~2500 sccm; the reaction chamber temperature is 600℃~1100℃, the reaction chamber pressure is 0.5 torr~1 torr, and the radio frequency power is 20W~70W; In the nitrogen plasma treatment step, N2 or a N2-H2 mixed gas is introduced into the reaction chamber and ionized into nitrogen plasma. The treatment power is 50W~100W, the N2 flow rate is 10sccm~25sccm, the treatment pressure is 1atm~5atm, the treatment temperature is 450℃~700℃, and the treatment time is 30min~300min. In the N2-H2 mixed gas, N2 accounts for 5% to 20%, and the H2 flow rate is 1000 sccm to 2500 sccm.

[0011] As an improvement to the above technical solution, in the step of depositing the ZnO sublayer, Zn powder is heated in the reaction chamber, and the Zn powder evaporates into Zn vapor. The evaporation rate of the Zn powder is 1×10⁻⁶. -4 g·cm -2 ·s -1 ~1×10 -2 g·cm -2 ·s -1 Ar2 and O2 are introduced, with an Ar2 flow rate of 50 sccm to 500 sccm and an O2 flow rate of 20 sccm to 300 sccm; the growth temperature of the ZnO sublayer is 500℃ to 900℃.

[0012] As an improvement to the above technical solution, in the deposition of the N-type semiconductor layer, NH3 and TMGa are used as raw materials, SiH4 is used as an N-type dopant, and the growth temperature is 1000℃~1200℃. In the deposition of the P-type semiconductor layer, NH3 and TEGa are used as raw materials, CP2Mg is used as a P-type dopant, and deposition is carried out in an H2 atmosphere; wherein the growth temperature is 980°C~1050°C.

[0013] As an improvement to the above technical solution, in the deposition of multiple quantum well layers, the multiple quantum well layers are formed by periodically alternating growth of quantum barrier layers and quantum well layers, with a stacking period number ≥ 8; When depositing the quantum well layer, NH3, TEGa and TMIn are used as raw materials, the growth temperature is 760℃~800℃, and the growth pressure is 150 torr~250 torr. When depositing the quantum barrier layer, NH3 and TEGa are used as raw materials, the growth temperature is 860°C~900°C, and the growth pressure is 150 torr~250 torr.

[0014] The implementation of this invention has the following beneficial effects: This invention inserts a graphene composite nanolayer between a heterogeneous substrate and an N-type semiconductor layer. The graphene composite nanolayer comprises a modified graphene layer and a ZnO sublayer stacked sequentially. The modified graphene layer is formed by nitrogen plasma treatment of the graphene sublayer and is disposed on the substrate. The graphene sublayer is composed of carbon atoms arranged in sp... 2 The alternating hybrid arrangement forms a six-membered ring network 2D structure with a smooth, unsuspended surface. Weak van der Waals bonds between layers reduce stress caused by lattice and thermal mismatches, and minimize substrate-related defects. The graphene sublayer surface is treated with nitrogen plasma to increase the density of nucleation sites, upon which a ZnO sublayer composed of wurtzite-type ZnO is grown. Because the ZnO sublayer's crystal planes grow along the C-axis, coinciding with the C-axis lattice of GaN, it induces preferential growth of GaN along the C-axis, forming a highly oriented epitaxial layer with a smooth, flat surface and improved thermal conductivity.

[0015] Furthermore, N doping works synergistically with interface charge transfer to improve the conductivity of ZnO while suppressing nonradiative recombination, making it suitable for applications such as photodetectors and light-emitting devices.

[0016] In addition, the chemical bonds treated with nitrogen plasma can hinder the oxidation of graphene sublayers and enhance the corrosion resistance of ZnO sublayers.

[0017] This invention can effectively modulate lattice mismatch dislocations, residual stress, and thermal mismatch in epitaxial materials grown on heterogeneous substrates, improve scattering efficiency under high current, increase the probability of radiative recombination in heteroepitaxial materials, and relax the requirements for heteroepitaxial growth. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the epitaxial structure of a light-emitting diode according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a quantum well layer according to an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0020] See Figure 1 As shown, an embodiment of the present invention provides a light-emitting diode epitaxial structure, including a substrate 1, on which a graphene composite nanolayer 2, an N-type semiconductor layer 3, a multiple quantum well layer 4 and a P-type semiconductor layer 5 are sequentially stacked.

[0021] Substrate 1 can be made of sapphire, which is currently the most commonly used substrate material. Sapphire substrates have advantages such as mature fabrication processes, low cost, ease of cleaning and processing, and good stability at high temperatures. The N-type semiconductor layer 3 is typically a Si-doped N-type GaN layer. The multiple quantum well layer 4 is formed by periodically alternating quantum barrier layers 42 and quantum well layers 41. The P-type semiconductor layer 5 is typically a Mg-doped GaN layer.

[0022] Specifically, the graphene composite nanolayer includes a modified graphene layer 21 and a ZnO sublayer 22 stacked sequentially, wherein the modified graphene layer 21 is disposed on the substrate 1 and the ZnO sublayer 22 is disposed on the modified graphene layer 21. The modified graphene layer 21 is treated with nitrogen plasma and has a thickness of 10nm to 100nm. The thickness of the modified graphene layer 21 is exemplarily 10nm, 20nm, 30nm, 40nm, 50nm, 70nm, or 80nm, but is not limited thereto. The thickness of the ZnO sublayer 22 is 20nm to 200nm. Examples of the thickness of the ZnO sublayer 22 are 20nm, 50nm, 80nm, 120nm, 150nm, 180nm, and 200nm, but it is not limited to these.

[0023] This invention inserts a graphene composite nanolayer 2 between a heterogeneous substrate 1 and an N-type semiconductor layer 3. The graphene composite nanolayer 2 comprises a modified graphene layer 21 and a ZnO sublayer 22 stacked sequentially. The modified graphene layer 21 is formed by nitrogen plasma treatment of the graphene sublayer and is disposed on the substrate 1. The graphene sublayer is composed of carbon atoms arranged in sp... 2The alternating hybrid arrangement forms a six-membered ring network 2D structure with a smooth, unsuspended surface. Weak van der Waals bonding between layers reduces stress caused by lattice and thermal mismatches, and minimizes substrate-related defects. The graphene sublayer surface is treated with nitrogen plasma to increase the density of nucleation sites, upon which a ZnO sublayer 22, composed of wurtzite-type ZnO, is grown. Because the crystal plane of ZnO sublayer 22 grows along the C-axis, coinciding with the C-axis lattice of GaN, it induces preferential growth of GaN along the C-axis, forming a highly oriented epitaxial layer with a smooth, flat surface and improved thermal conductivity.

[0024] Furthermore, N doping works synergistically with interface charge transfer to improve the conductivity of ZnO while suppressing nonradiative recombination, making it suitable for applications such as photodetectors and light-emitting devices.

[0025] In addition, the chemical bonds treated with nitrogen plasma can hinder the oxidation of graphene sublayers and enhance the corrosion resistance of ZnO sublayer 22.

[0026] This invention can effectively modulate lattice mismatch dislocations, residual stress, and thermal mismatch in epitaxial materials grown on heterogeneous substrates, improve scattering efficiency under high current, increase the probability of radiative recombination in heteroepitaxial materials, and relax the requirements for heteroepitaxial growth.

[0027] Preferably, the modified graphene layer 21 is prepared by the following method: The substrate 1 is placed in the reaction chamber, CH4 and carrier gas are introduced, and a graphene sublayer is deposited on the substrate 1.

[0028] Specifically, the substrate 1 is placed in a reaction chamber at a temperature of 600℃ to 1100℃, a reaction pressure of 0.5 torr to 1 torr, and a radio frequency power of 20W to 70W. CH4 is used as the carbon source, and H2 and Ar2 are introduced as carrier gases. The flow rate of CH4 is 800 sccm to 1800 sccm, and the flow rate of the carrier gases is 1000 sccm to 2500 sccm. The flow rate ratio of H2 to Ar2 can be (1 to 2):(1 to 2), but is not limited to this.

[0029] Examples of reaction temperatures include 600℃, 700℃, 800℃, 900℃, 1000℃, and 1100℃, but are not limited to these. Examples of reaction pressures include 0.5 torr, 0.7 torr, 0.8 torr, 0.9 torr, and 1.0 torr. Examples of radio frequency power include 20W, 30W, 40W, 50W, 60W, and 70W, but are not limited to these. Examples of CH4 flow rates include 800 sccm, 900 sccm, 1000 sccm, 1100 sccm, 1200 sccm, 1300 sccm, 1400 sccm, 1500 sccm, 1600 sccm, 1700 sccm, and 1800 sccm, but are not limited to these. Examples of carrier gas flow rates are 1000 sccm, 1100 sccm, 1500 sccm, 1700 sccm, 1900 sccm, 2100 sccm, and 2500 sccm, but are not limited to these.

[0030] The above-mentioned graphene sublayers are composed of carbon atoms arranged in sp... 2 The six-membered ring network 2D structure formed by the alternating arrangement of hybrid layers has a smooth, unsuspended surface and more than 2 atomic layers. The weak van der Waals bonding between graphene sublayers can reduce stress caused by lattice and thermal mismatches and reduce defects introduced by the substrate.

[0031] In the reaction chamber, a mixture of N2 or N2-H2 gas ionizes nitrogen into free nitrogen atoms. These nitrogen atoms mix with nitrogen molecules and other nitrogen molecules to form a plasma. This nitrogen plasma bombards the surface of the graphene sublayer, creating dense nucleation sites. The nitrogen plasma treatment has a processing power of 50W~100W, an N2 flow rate of 10sccm~25sccm, a processing pressure of 1atm~5atm, a processing temperature of 450℃~700℃, and a processing time of 30min~300min. Examples of nitrogen plasma treatment power include 50W, 60W, 70W, 80W, and 100W, but are not limited to these. Examples of nitrogen flow rate include 10sccm, 13sccm, 15sccm, 18sccm, 20sccm, and 25sccm, but are not limited to these. Examples of treatment pressure include 1atm, 2atm, 3atm, 4atm, and 5atm, but are not limited to these. Examples of treatment temperature include 450℃, 500℃, 550℃, 600℃, 650℃, and 700℃, but are not limited to these.

[0032] In the N2-H2 mixed gas, N2 accounts for 5% to 20%, and the H2 flow rate is 1000 sccm to 2500 sccm. Examples of H2 flow rates are 1000 sccm, 1100 sccm, 1500 sccm, 1700 sccm, 2000 sccm, 2200 sccm, 2300 sccm, and 2500 sccm, but the flow rate is not limited to these.

[0033] Specifically, the method for depositing a ZnO sublayer 22 on the modified graphene layer 21 includes the following steps: Zn powder is superheated in the reaction chamber to evaporate it into Zn vapor. Ar2 is used as a carrier gas, and O2 is introduced into the reaction chamber to deposit a ZnO sublayer 22 on the modified graphene layer 21. The growth temperature of the ZnO sublayer 22 is 500℃~900℃, and the evaporation rate of the Zn powder is 1×10⁻⁶. -4 g·cm -2 ·s -1 ~1×10 -2 g·cm -2 ·s -1 The flow rate of Ar2 gas is 50 sccm to 500 sccm, and the flow rate of O2 is 20 sccm to 300 sccm.

[0034] It should be noted that Zn powder needs to be overheated to 910~1000℃ to evaporate it into Zn vapor. The evaporation rate of the Zn powder is then controlled. By precisely controlling the evaporation rate, the nucleation density and growth rate of ZnO grains can be adjusted, resulting in a uniformly distributed nanowall structure and avoiding defects caused by grains that are too large or too small. A stable evaporation rate is beneficial for the preferential growth of the ZnO sublayer 22 along the C-axis, ensuring lattice matching with the subsequent GaN epitaxial layer.

[0035] The growth temperature of the ZnO sublayer 22 is exemplarily 500℃, 700℃, 800℃, or 900℃, but is not limited to these. The Ar2 gas flow rate is exemplarily 50 sccm, 100 sccm, 200 sccm, 300 sccm, 400 sccm, or 500 sccm, but is not limited to these. The O2 flow rate is exemplarily 20 sccm, 50 sccm, 100 sccm, 150 sccm, 200 sccm, 250 sccm, or 300 sccm, but is not limited to these. The evaporation rate of the Zn powder is exemplarily 1×10⁻⁶. -4 g·cm -2 ·s -1 5.7×10 -4 g·cm -2 ·s -1 9.6×10 -4 g·cm -2·s -1 1.7×10 -3 g·cm -2 ·s -1 2.8×10 - 3 g·cm -2 ·s -1 However, it is not limited to this.

[0036] The deposited ZnO sublayer 22 grows along the C-axis, coinciding with the C-axis lattice of GaN. This induces preferential growth of GaN along the C-axis, forming a highly oriented epitaxial layer, thereby achieving high consistency in grain orientation with the N-type semiconductor layer 3. The ZnO sublayer 22 formed on the modified graphene layer 21 has a smooth and flat surface, providing an ideal substrate for the subsequent growth of the N-type semiconductor layer 3, reducing defect density, minimizing defects introduced by the substrate 1, and lowering the density of through-hole dislocations (TD).

[0037] The lattice mismatch dislocations of the epitaxial material grown on the heteroepitaxial substrate 1 are effectively modulated, the stress of the GaN layer heteroepitaxial material is reduced, and the thermal conductivity of the electronic device is improved, thereby increasing the probability of radiative recombination, significantly improving the internal quantum efficiency of the high optoelectronic device, improving the crystal quality of the prepared epitaxial film, and improving the device performance.

[0038] Preferably, the Si doping concentration in the N-type semiconductor layer 3 is 5 × 10⁻⁶. 17 atoms / cm 3 ~1×10 19 atoms / cm 3 The growth thickness is 1.0 μm to 3.0 μm; The exemplary doping concentration of Si is 5.1 × 10⁻⁶. 17 atoms / cm 3 6.3×10 17 atoms / cm 3 7.8×10 17 atoms / cm 3 8.8×10 17 atoms / cm 3 9.1×10 17 atoms / cm 3 1.8×10 18 atoms / cm 3 5.6×10 18 atoms / cm 3 5.8×10 18 atoms / cm 3However, it is not limited to this. Exemplary growth thicknesses of the N-type semiconductor layer are 1.0 μm, 1.5 μm, 1.8 μm, 2.1 μm, 2.5 μm, 2.7 μm, and 3.0 μm, but are not limited to this.

[0039] See Figure 2 As shown, the number of stacking cycles of the quantum barrier layer 42 and the quantum well layer 41 in the multi-quantum well layer 4 is ≥8, the growth thickness of the quantum well layer 41 is 2nm~4nm, and the growth thickness of the quantum barrier layer 42 is 8nm~12nm. The number of stacking cycles is exemplarily 8, 9, 10, 11, 12, or 13, but is not limited to these. The growth thickness of the quantum well layer 41 is exemplarily 2.2 nm, 2.5 nm, 2.8 nm, 3.4 nm, 3.7 nm, or 3.9 nm, but is not limited to these. The growth thickness of the quantum barrier layer 42 is exemplarily 8.5 nm, 8.7 nm, 8.9 nm, 10.1 nm, 10.5 nm, 11.2 nm, 12.5 nm, or 12.9 nm, but is not limited to these.

[0040] The p-type semiconductor layer 5 is a Mg-doped GaN layer with a growth thickness of 15nm~20nm and a Mg doping concentration of 5×10⁻⁶. 18 atoms / cm 3 ~5×10 21 atoms / cm 3 .

[0041] The exemplary thickness of the P-type semiconductor layer 5 is 15nm, 16nm, 18nm, or 20nm, but it is not limited to these. The doping concentration of Mg is 5.3 × 10⁻⁶. 18 atoms / cm 3 6.8×10 18 atoms / cm 3 7.7×10 18 atoms / cm 3 8.6×10 18 atoms / cm 3 8.3×10 19 atoms / cm 3 5.6×10 20 atoms / cm 3 5.9×10 20 atoms / cm 3 3.7×10 21 atoms / cm 3 4.9×10 21 atoms / cm 3 However, it is not limited to this.

[0042] This invention also provides a method for fabricating a light-emitting diode epitaxial structure, comprising the following steps: Substrate 1 is provided; A graphene sublayer is deposited on the substrate 1, and then the surface of the graphene sublayer is treated with nitrogen plasma to form the modified graphene layer 21. A ZnO sublayer 22 is deposited on the modified graphene layer 21 to form a graphene composite nanolayer 2; An N-type semiconductor layer 3 is deposited on the graphene composite nanolayer 2; A multi-quantum well layer 4 is deposited on the N-type semiconductor layer 3; A P-type semiconductor layer 5 is deposited on the multi-quantum-well layer 4.

[0043] Preferably, in the step of depositing the graphene sublayer, the substrate 1 is placed in a reaction chamber, CH4 is used as the carbon source, and the flow rate of the CH4 is 800 sccm to 1800 sccm; H2 and Ar2 are introduced as carrier gases, and the flow rate of the carrier gases is 1000 sccm to 2500 sccm; the reaction chamber temperature is 600℃ to 1100℃, the reaction chamber pressure is 0.5 torr to 1 torr, and the radio frequency power is 20W to 70W. In the nitrogen plasma treatment step, N2 or a N2-H2 mixed gas is introduced into the reaction chamber and ionized into nitrogen plasma. The treatment power is 50W~100W, the N2 flow rate is 10sccm~25sccm, the treatment pressure is 1atm~5atm, the treatment temperature is 450℃~700℃, and the treatment time is 30min~300min. In the N2-H2 mixed gas, N2 accounts for 5% to 20%, and the H2 flow rate is 1000 sccm to 2500 sccm.

[0044] Preferably, in the step of depositing the ZnO sublayer 22, Zn powder is heated in the reaction chamber, and the Zn powder evaporates into Zn vapor at an evaporation rate of 1×10⁻⁶. -4 g·cm -2 ·s -1 ~1×10 -2 g·cm -2 ·s -1 Ar2 gas and O2 are introduced, with the flow rate of Ar2 gas being 50 sccm to 500 sccm and the flow rate of O2 being 20 sccm to 300 sccm; the growth temperature of the ZnO sublayer is 500℃ to 900℃.

[0045] Preferably, an N-type semiconductor layer 3 is deposited on the graphene composite nanoparticles 2. Specifically, the reaction chamber temperature is lowered to 1000℃~1200℃, using NH3 as the nitrogen source, TMGa as the gallium source, and SiH4 as the N-type dopant. Exemplary reaction chamber temperatures for depositing the N-type semiconductor layer 3 are 1000℃, 1100℃, and 1200℃, but are not limited to these.

[0046] Preferably, a multi-quantum-well layer 4 is deposited on the N-type semiconductor layer 3. The multi-quantum-well layer 4 is formed by periodically alternating quantum barrier layers 42 and quantum well layers 41, with a growth period of ≥8.

[0047] When depositing the quantum well layer 41, NH3, TEGa and TMIn are used as raw materials, the growth temperature is 760℃~800℃, and the growth pressure is 150 torr~250 torr. When depositing the quantum barrier layer 42, NH3 and TEGa were used as raw materials, the growth temperature was 860°C~900°C, and the growth pressure was 150 torr~250 torr.

[0048] A P-type semiconductor layer 5 is deposited on the multi-quantum-well layer 4, with the reaction chamber temperature controlled at 980°C to 1050°C. NH3 and TEGa are used as raw materials, and CP2Mg is used as the P-type dopant. The deposition is carried out in an H2 atmosphere. The reaction chamber temperature of the P-type semiconductor layer 5 is exemplarily 980°C, 1000°C, or 1050°C, but is not limited to these.

[0049] The technical solution of the present invention will be further described below with reference to specific embodiments and comparative examples.

[0050] Example 1 A method for fabricating a light-emitting diode epitaxial structure includes the following steps: Provide a substrate, which is sapphire; A graphene composite nanolayer is formed on the substrate; The preparation method of graphene composite nanolayers includes the following steps: The substrate was placed in a PECVD reaction chamber at a temperature of 850°C, a pressure of 0.75 torr, and an RF power of 45 W. CH4 was introduced at a flow rate of 1300 sccm, with H2 and Ar2 gases used as carrier gases at a flow rate of 1750 sccm, forming a graphene sublayer on the substrate. Then, N2 was introduced and ionized into nitrogen plasma at a power of 75 W, a flow rate of 20 sccm, a pressure of 3.5 atm, a temperature of 575°C, and a processing time of 150 min, yielding a modified graphene layer with a thickness of 50 nm.

[0051] Zn powder is superheated in the reaction chamber, causing it to evaporate into Zn vapor. The evaporation rate of the Zn powder is 1 × 10⁻⁶. -4 g·cm -2 ·s -1 ~1×10 -2 g·cm -2 ·s -1 Ar2 gas and O2 were introduced, with Ar2 gas as the carrier gas at a flow rate of 250 sccm and O2 at a flow rate of 150 sccm. The growth temperature was 700℃, and a ZnO sublayer with a thickness of 100 nm was deposited on the modified graphene layer.

[0052] Depositing an N-type semiconductor layer on a graphene composite nanolayer; Specifically, the deposition process is as follows: the reaction chamber temperature is lowered to 1100℃, NH3 is used as the N (nitrogen) source, TMGa is used as the Ga (gallium) source, and SiH4 is used as the N-type dopant to deposit a Si-doped N-type GaN layer with a Si doping concentration of 5×10⁻⁶. 18 atoms / cm 3 The thickness of the deposited N-type GaN layer is controlled to be approximately 2 μm.

[0053] Deposit a multi-quantum-well layer on an N-type semiconductor layer; The specific deposition process is as follows: When growing the quantum well layer, the N (nitrogen) source is NH3, the Ga (gallium) source is TEGa, and the In (indium) source is TMIn. The temperature of the reaction chamber is controlled at 780℃, the pressure at 200 torr, and the thickness of the deposited InGaN quantum well layer is controlled to be approximately 3 nm. When growing the quantum barrier layer, the N (nitrogen) source is NH3, the Ga (gallium) source is TEGa, the temperature of the reaction chamber is controlled at 880℃, the pressure at 200 torr, and the thickness of the deposited GaN quantum barrier layer is controlled to be 10 nm. The quantum well layer and the quantum barrier layer are alternately deposited and stacked 10 times to obtain a multi-quantum well layer.

[0054] Deposit a P-type semiconductor layer on a multi-quantum-well layer; The specific deposition process was as follows: NH3 was used as the N (nitrogen) source, TEGa as the Ga (gallium) source, and CP2Mg as the P-type dopant. The reaction chamber temperature was controlled at 1000℃, and the deposition thickness was controlled under an H2 atmosphere. The deposited P-type low-Mg-doped GaN layer had a thickness of 17 nm, and the Mg doping concentration was 5 × 10⁻⁶. 20 atoms / cm 3 .

[0055] Example 2 The difference from Example 1 is that the thickness of the modified graphene layer is 100 nm.

[0056] Example 3 The difference from Example 1 is that the thickness of the modified graphene layer is 10 nm.

[0057] Example 4 The difference from Example 1 is that the growth thickness of the ZnO sublayer is 200 nm.

[0058] Example 5 The difference from Example 1 is that the growth thickness of the ZnO sublayer is 20 nm.

[0059] Example 6 The difference from Example 1 is that in the nitrogen plasma treatment step, the treatment power is 50W, the nitrogen flow rate is 10sccm, and the treatment pressure is 1atm.

[0060] Example 7 The difference from Example 1 is that in the nitrogen plasma treatment step, the treatment power is 100W, the nitrogen flow rate is 25sccm, and the treatment pressure is 5atm.

[0061] Example 8 The difference from Example 1 is that in the nitrogen plasma treatment step, a N2-H2 mixed gas is introduced, with N2 accounting for 10% and the H2 flow rate being 1750 sccm.

[0062] Example 9 The difference from Example 1 is that in the step of depositing the ZnO sublayer, the growth temperature of the ZnO sublayer is 500°C and the O2 flow rate is 20 sccm.

[0063] Example 10 The difference from Example 1 is that in the step of depositing the ZnO sublayer, the growth temperature of the ZnO sublayer is 900°C and the O2 flow rate is 300 sccm.

[0064] Comparative Example 1 The epitaxial structure and preparation method of this comparative example are basically the same as those of Example 1. The difference is that this comparative example 1 does not have a ZnO sublayer.

[0065] Comparative Example 2 The epitaxial structure and preparation method of this comparative example are basically the same as those of Example 1. The difference is that this comparative example 2 does not have a modified graphene layer and a ZnO sublayer.

[0066] Performance testing: (1) Stress test: Raman spectroscopy (RS) non-destructive testing technology was used to characterize the composition and crystal quality of the epitaxial structure. The stress δ of the GaN epitaxial structure was quantitatively calculated based on the shift of the E2-high peak on the Raman spectrum. aThe calculation formula is as follows: δ a =-Δω / K a Where Δω is the shift of the E2-high peak position relative to the stress-free state, and K a K is a constant. a =4.2cm -1 ·GPa.

[0067] (2) The epitaxial structures obtained in the examples and comparative examples were fabricated into 3mil×5mil chips using the same chip process conditions. The photoelectric performance of the chips was tested under a working current of 2mA using the same Micro LED spot tester. The improvement in luminous efficacy was calculated based on Comparative Example 2.

[0068] Specifically, the performance test results are shown in Table 1 below.

[0069] Table 1 Performance test results of each embodiment and comparative example

[0070] As can be seen from the above results, the graphene composite nanolayer set between the heterogeneous substrate and the N-type semiconductor layer in this invention can effectively modulate the lattice mismatch dislocations, residual stress and thermal mismatch of the epitaxial material grown on the heterogeneous substrate, improve the scattering efficiency under high current, increase the probability of radiative recombination of the heteroepitaxial material, and relax the requirements of heteroepitaxialization.

[0071] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A light-emitting diode epitaxial structure, characterized in that, The substrate includes a graphene composite nanolayer, an N-type semiconductor layer, a multiple quantum well layer, and a P-type semiconductor layer, which are sequentially stacked on the substrate. The graphene composite nanolayer comprises a modified graphene layer and a ZnO sublayer stacked sequentially, wherein the modified graphene layer is disposed on the substrate and the ZnO sublayer is disposed on the modified graphene layer. The modified graphene layer is treated with nitrogen plasma and has a thickness of 10 nm to 100 nm. The thickness of the ZnO sublayer is 20nm~200nm.

2. The light-emitting diode epitaxial structure as described in claim 1, characterized in that, The modified graphene layer was prepared by the following method: The substrate is placed in a reaction chamber, CH4 and carrier gas are introduced, and a graphene sublayer is deposited on the substrate. N2 or a N2-H2 mixture is introduced into the reaction chamber and ionized into nitrogen plasma. The nitrogen plasma bombards the surface of the graphene sublayer, causing dense nucleation sites to form on its surface.

3. The light-emitting diode epitaxial structure as described in claim 2, characterized in that, The number of atomic layers in the graphene sublayer is >2, the reaction chamber temperature is 600℃~1100℃, the reaction chamber pressure is 0.5 torr~1 torr, the radio frequency power is 20W~70W, the CH4 inlet flow rate is 800sccm~1800sccm, the carrier gas is H2 gas and Ar2 gas, and the carrier gas inlet flow rate is 1000sccm~2500sccm; The nitrogen plasma treatment has a processing power of 50W~100W, an N2 flow rate of 10sccm~25sccm, a processing pressure of 1atm~5atm, a processing temperature of 450℃~700℃, and a processing time of 30min~300min. In the N2-H2 mixed gas, N2 accounts for 5% to 20%, and the H2 flow rate is 1000 sccm to 2500 sccm.

4. The light-emitting diode epitaxial structure as described in claim 1, characterized in that, The ZnO sublayer is prepared by the following method: Zn powder is heated in a reaction chamber and evaporates into Zn vapor. Ar2 and O2 are then introduced, forming a ZnO sublayer on the surface of the modified graphene layer. The growth temperature of the ZnO sublayer is 500℃~900℃, and the evaporation rate of the Zn powder is 1×10⁻⁶. -4 g·cm -2 ·s -1 ~1×10 -2 g·cm -2 ·s -1 The flow rate of Ar2 gas is 50 sccm to 500 sccm, and the flow rate of O2 gas is 20 sccm to 300 sccm.

5. The light-emitting diode epitaxial structure as described in claim 1, characterized in that, The Si doping concentration in the N-type semiconductor layer is 5 × 10⁻⁶. 17 atoms / cm 3 ~1×10 19 atoms / cm 3 The growth thickness is 1.0 μm to 3.0 μm; The number of stacking periods of the quantum barrier layer and the quantum well layer in the multi-quantum well layer is ≥8, and the growth thickness of the quantum well layer is 2nm~4nm; the growth thickness of the quantum barrier layer is 8nm~12nm. The p-type semiconductor layer is a Mg-doped GaN layer with a growth thickness of 15nm~20nm and a Mg doping concentration of 5×10⁻⁶. 18 atoms / cm 3 ~5×10 21 atoms / cm 3 .

6. A method for fabricating a light-emitting diode epitaxial structure as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Provide substrate; A graphene sublayer is deposited on the substrate, and then the surface of the graphene sublayer is treated with nitrogen plasma to form the modified graphene layer. A ZnO sublayer is deposited on the modified graphene layers to form a graphene composite nanolayer; An N-type semiconductor layer is deposited on the graphene composite nanolayer; A multi-quantum-well layer is deposited on the N-type semiconductor layer; A P-type semiconductor layer is deposited on the multi-quantum-well layer.

7. The method for fabricating a light-emitting diode epitaxial structure as described in claim 6, characterized in that, In the step of depositing the graphene sublayer, the substrate is placed in a reaction chamber, CH4 is used as the carbon source, and the flow rate of the CH4 is 800 sccm to 1800 sccm; H2 and Ar2 are introduced as carrier gases, and the flow rate of the carrier gases is 1000 sccm to 2500 sccm; the reaction chamber temperature is 600℃ to 1100℃, the reaction chamber pressure is 0.5 torr to 1 torr, and the radio frequency power is 20W to 70W. In the nitrogen plasma treatment step, N2 or a N2-H2 mixed gas is introduced into the reaction chamber and ionized into nitrogen plasma. The treatment power is 50W~100W, the N2 flow rate is 10sccm~25sccm, the treatment pressure is 1atm~5atm, the treatment temperature is 450℃~700℃, and the treatment time is 30min~300min. In the N2-H2 mixed gas, N2 accounts for 5% to 20%, and the H2 flow rate is 1000 sccm to 2500 sccm.

8. The method for fabricating a light-emitting diode epitaxial structure as described in claim 6, characterized in that, In the step of depositing the ZnO sublayer, Zn powder is heated in the reaction chamber and evaporates into Zn vapor at an evaporation rate of 1 × 10⁻⁶. -4 g·cm -2 ·s -1 ~1×10 -2 g·cm -2 ·s -1 Ar2 and O2 are introduced, with an Ar2 flow rate of 50 sccm to 500 sccm and an O2 flow rate of 20 sccm to 300 sccm; the growth temperature of the ZnO sublayer is 500℃ to 900℃.

9. The method for fabricating a light-emitting diode epitaxial structure as described in claim 6, characterized in that, In the deposition of the N-type semiconductor layer, NH3 and TMGa are used as raw materials, SiH4 is used as N-type dopant, and the growth temperature is 1000℃~1200℃. In the deposition of the P-type semiconductor layer, NH3 and TEGa are used as raw materials, CP2Mg is used as a P-type dopant, and deposition is carried out in an H2 atmosphere; wherein the growth temperature is 980°C~1050°C.

10. The method for fabricating a light-emitting diode epitaxial structure as described in claim 6, characterized in that, In the deposition of multiple quantum well layers, the multiple quantum well layers are formed by periodically alternating quantum barrier layers and quantum well layers, with a stacking period number ≥ 8; When depositing the quantum well layer, NH3, TEGa and TMIn are used as raw materials, the growth temperature is 760℃~800℃, and the growth pressure is 150 torr~250 torr. When depositing the quantum barrier layer, NH3 and TEGa are used as raw materials, the growth temperature is 860°C~900°C, and the growth pressure is 150 torr~250 torr.

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