LED epitaxial wafer, growth method of graphene layer and LED chip

Abstract

The invention relates to an LED epitaxial wafer, a growth method of a graphene layer and an LED chip, and belongs to the technical field of LEDs. The LED epitaxial wafer comprises a substrate, and a graphene layer, a buffer layer, an undoped GaN layer, an n-type GaN layer, a stress release layer, a multi-quantum well layer, an electron barrier layer and a p-type GaN layer which are sequentially epitaxially grown on the substrate, wherein the thickness of the single graphene layer is 0.5-1.5 nm, and the number of the graphene layers is at least two. According to the LED epitaxial wafer provided by the invention, the defect density in the GaN template layer is reduced through deposition of the graphene interlayer. Therefore, the recombination efficiency of electrons and holes is improved, so that the luminous efficiency of the LED is enhanced. Due to the existence of the graphene layer, the compressive strain of the chip is reduced, the influence of a polarization field is reduced, and the emission wavelength of electroluminescence (EL) is more stable.

Description

Technical Field

[0001] The present application relates to the field of LED technology, and in particular to an LED epitaxial wafer, a method for growing a graphene layer, and an LED chip. Background Art

[0002] LED chips are widely used in display terminals such as computers, mobile phones, and large event venues such as shopping malls and exhibition halls due to their high brightness, wide viewing angle, and energy-saving and environmentally friendly characteristics. Among them, the introduction of Mini LED technology has further improved the display effect and has been favored by more and more consumers. However, although LED chips perform well in many aspects, their heat dissipation problem is still a key factor restricting their performance and application.

[0003] As the power of LED chips continues to increase, especially when high-power current passes through, the heating phenomenon of the chip becomes more and more obvious. This overheating will not only lead to a decrease in luminous efficiency, but also affect the stability of color temperature, thereby affecting the display effect and user experience. Specifically, the increase in temperature will cause the following problems: 1. Insufficient heat dissipation performance: Traditional heat dissipation design cannot effectively meet the heat dissipation requirements of high-power LED chips, causing the temperature of the chip to rise during long-term operation, thereby affecting its normal operation; 2. Impaired luminous performance: When high-power current passes through the chip, the heat generated will reduce the luminous efficiency of the LED, causing energy waste and reducing the overall brightness; 3. Unstable color temperature: In a high-temperature environment, the color temperature of the LED will shift, resulting in poor display effects and affecting the visual experience.

[0004] Therefore, it is particularly necessary to develop an LED epitaxial wafer with improved heat dissipation performance. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the embodiments of the present application includes providing an LED epitaxial wafer, a method for growing a graphene layer, and an LED chip to solve the technical problem of poor heat dissipation performance of the LED chip when high-power current passes through.

[0006] In a first aspect, an embodiment of the present application provides an LED epitaxial wafer, comprising: a substrate, and a graphene layer, a buffer layer, an undoped GaN layer, an n-type GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a p-type GaN layer epitaxially grown in sequence on the substrate; wherein the thickness of a single graphene layer is 0.5-1.5 nm, and the number of graphene layers is at least 2.

[0007] The LED epitaxial wafer provided by the present application deposits a graphene interlayer on a substrate and continues to grow a high-crystalline quality GaN film on several layers of graphene; wherein the graphene interlayer provides carbon doping as a surfactant, which can reduce the defect density in the GaN template layer. In addition, the combined strain compensation layer significantly reduces the compressive strain in the n-GaN template, so that the In component in the InGaN quantum well increases, resulting in a significant red shift in the emission wavelength of the light-emitting diode. Therefore, the growth of graphene will significantly reduce the compressive strain of its LED chip, and the low-compression strain and piezoelectric field will reduce the influence of the polarization field on the screen, thereby causing the emission wavelength of the electroluminescence (EL) to be more stable. Furthermore, when the epitaxial wafer is used under high current and high power conditions, it has an excellent heat dissipation effect.

[0008] In some embodiments of the present application, the substrate includes a Si substrate or a sapphire substrate.

[0009] Choosing Si substrate or sapphire substrate as the basis of LED epitaxial wafer can not only reduce production costs, but also improve the performance and reliability of LED. The two substrates have their own characteristics, which can provide good support for the efficient light emission and heat dissipation of LED, and promote the development and application of LED technology.

[0010] In some embodiments of the present application, the material of the buffer layer includes AlN.

[0011] Using AlN as a buffer layer can inhibit the longitudinal extension of the substrate, strengthen the lateral (2D) growth, and help cut off the extension of dislocations, reduce dislocation density, improve crystal quality, reduce reverse voltage and improve ESD yield. At the same time, it can improve brightness and reduce costs.

[0012] In some embodiments of the present application, the thickness of the buffer layer is 20-30 nm.

[0013] Controlling the thickness of the buffer layer within the range of 20-30nm can effectively release stress, optimize growth conditions, and enable good contact between layers while reducing material costs.

[0014] In some embodiments of the present application, the thickness of the n-type GaN layer is 5-7 μm.

[0015] Controlling the thickness of the n-type GaN layer within the range of 5-7μm helps to improve conductivity, reduce contact resistance, enhance light output, improve thermal management, and ensure good compatibility with other layers. This is conducive to improving the performance and reliability of LEDs and better meeting the needs of high-power and high-brightness applications.

[0016] In a second aspect, an embodiment of the present application provides a method for growing a graphene layer, which is used to prepare any of the above-mentioned graphene layers. The method for growing a graphene layer includes: growing a layer of Cu film on a substrate, and then growing a graphene layer on the surface of the Cu film; and removing the Cu film after the growth of the graphene layer is completed.

[0017] The present application, by growing graphene on a Cu film, the presence of the Cu film provides an excellent catalytic effect for the growth of graphene, which can effectively promote the crystal growth of graphene, reduce defects and inhomogeneity, and improve the quality and integrity of graphene. Moreover, by growing graphene on a Cu film, high-quality growth of graphene can be achieved at relatively low temperatures. During the growth of the graphene layer, the Cu film acts as a nanomask to control the growth morphology of graphene. This masking property can provide more uniform growth conditions and reduce impurities and defects between layers. At the same time, the Cu film provides good adhesion for graphene. This helps the growth of subsequent layers (such as AlN buffer layers), ensures good interlayer bonding, and improves overall device performance. The Cu film can be easily removed after the graphene layer growth is completed. After removing the Cu film, the graphene layer can directly contact the subsequent layer without affecting its performance, ensuring the integrity of the final structure.

[0018] In some embodiments of the present application, the thickness of the Cu film is 400-500 nm.

[0019] Controlling the thickness of the Cu film within the range of 400-500nm helps to improve the quality of the graphene layer, facilitate its removal, effectively catalyze growth, and reduce costs, while maintaining good mechanical strength and thermal conductivity.

[0020] In some embodiments of the present application, the method for removing the Cu film includes: immersing the substrate with the Cu film in an NH4S2O8 solution; wherein the mass concentration of the NH4S2O8 solution is 60-80%.

[0021] NH4S2O8 is a strong oxidant that can effectively oxidize and etch copper thin films. It can improve the efficiency of Cu film removal, shorten etching time, and save production cycles. Moreover, NH4S2O8 is relatively mild and will not cause excessive chemical damage to the graphene layer. At the same time, NH4S2O8 has strong selectivity for Cu and can effectively remove the Cu film without affecting the underlying material.

[0022] Controlling its mass concentration at 60-80% can optimize the etching rate, improve uniformity, reduce side reactions, and extend the service life of the solution.

[0023] In some embodiments of the present application, the soaking time is 1-2 minutes.

[0024] Controlling the immersion time to 1-2 minutes helps prevent over-etching, improve etching uniformity, save time and cost, while optimizing reaction kinetics, reducing side reactions, and ensuring operational safety.

[0025] In some embodiments of the present application, the preparation method further includes: using CH4 and H2 as precursor gases for growing a graphene layer, growing at 900-950°C for 10-15 minutes; the volume ratio of CH4 and H2 is (3-5):1.

[0026] At high temperatures of 900-950°C, atomic mobility increases, which helps the formation of the crystal structure of graphene. The volume ratio of CH4 and H2 is controlled at (3-5):1, and at this carbon source concentration, uniform growth can be promoted. In other words, growing graphene layers at 900-950°C and controlling the volume ratio of CH4 and H2 at (3-5):1 helps optimize growth quality, increase growth rate, improve uniformity, and reduce defects and waste.

[0027] In a third aspect, an embodiment of the present application provides an LED chip, comprising any of the above-mentioned LED epitaxial wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 This is a diagram of the LED chip structure provided in Example 1 of the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0031] The following is a detailed description of an LED epitaxial wafer, a graphene layer growth method and an LED chip according to an embodiment of the present application.

[0032] An embodiment of the present application provides an LED epitaxial wafer, which includes a substrate, and a graphene layer, a buffer layer, an undoped GaN layer, an n-type GaN layer, a stress release layer (SRL), a multi-quantum well layer (MQW), an electron blocking layer (EBL) and a p-type GaN layer epitaxially grown in sequence on the substrate; wherein the thickness of a single graphene layer is 0.5-1.5 nm, and the number of graphene layers is at least 2.

[0033] The LED epitaxial wafer provided by the present application reduces the defect density in the GaN template layer through the deposition of the graphene interlayer. This improves the recombination efficiency of electrons and holes, thereby enhancing the luminous efficiency of the LED. The presence of the graphene layer reduces the compressive strain of the chip, reduces the influence of the polarization field, and makes the emission wavelength of the electroluminescence (EL) more stable. This stability is crucial for the application of high-performance LEDs, especially under high current conditions. Moreover, graphene has extremely high thermal conductivity, which can effectively conduct heat and improve the heat dissipation performance of the LED when working at high currents. This helps to prevent overheating and maintain the long-term stability of the chip. At the same time, the graphene interlayer provides carbon doping as a surfactant, which promotes the growth of GaN while suppressing dislocations and other crystal defects. This further improves the reliability and service life of the LED. In addition, the combined strain compensation layer significantly reduces the compressive strain in the n-GaN template, increases the In component in the InGaN quantum well, and causes the emission wavelength of the light-emitting diode to be significantly red-shifted. Therefore, when the high current increases, the heat dissipation obtained is better, which also drives the LED chip to be used in high current occasions.

[0034] The number of graphene layers includes but is not limited to 2, 3, 4, 5, 6, 7, and 8 layers.

[0035] In the present application, the substrate includes a Si substrate or a sapphire substrate. The cost of silicon material is low and suitable for large-scale production; moreover, silicon has good thermal conductivity, which helps to dissipate heat. Sapphire has good stability in high temperature environment and is suitable for the growth process of LED. Moreover, sapphire, as a transparent material, can effectively transmit the light emitted by the LED and reduce light loss. At the same time, the lattice structure of sapphire can provide a good epitaxial growth basis and promote the formation of high-quality GaN layer.

[0036] In the present application, the material of the buffer layer includes AlN, and the thickness of the buffer layer is 20-30nm. The lattice constant of AlN is relatively close to that of GaN, which helps to reduce the stress caused by lattice mismatch during the growth process. This matching can reduce the generation of dislocations and improve the crystal quality of the epitaxial growth layer. At the same time, the deposition of the AlN layer can effectively inhibit the upward transfer of dislocations on the substrate, which helps to reduce the defect density in the GaN layer and improve the luminous performance of the LED. In addition, AlN has good thermal conductivity, which helps to improve the heat dissipation performance of the LED and improve the stability under high-power operation.

[0037] Controlling the thickness of the buffer layer within the range of 20-30nm can effectively release the stress during the growth process, help improve the growth quality of the underlying GaN layer, and reduce the propagation of defects. It can also form a good interface between the buffer layer and the GaN layer, enhance the contact quality, and reduce material costs.

[0038] In the present application, the thickness of the n-type GaN layer is 5-7 μm.

[0039] A method for preparing an LED epitaxial wafer provided in an embodiment of the present application is described below.

[0040] Step S1. Substrate cleaning

[0041] The substrate (Si, sapphire substrate, etc.) is cleaned using the standard RCA cleaning method, and a patterned sapphire substrate (PSS substrate) is selected. The sapphire substrate has good stability at high temperatures and is inexpensive, making it suitable for large-scale production. It also prepares conditions for subsequent growth.

[0042] The substrate is cleaned using a standard RCA cleaning method to remove surface dirt and impurities, improve the cleanliness of the substrate surface, and reduce defects; this provides a good growth environment for subsequent growth and improves the quality of the epitaxial layer.

[0043] Step S2. Cu film growth

[0044] Deposition of Cu film: A 400-500nm thick Cu film is grown on the substrate to avoid the degradation of graphene stacking quality at the interface.

[0045] As an intermediate layer, the Cu film can improve the quality of graphene, enhance the migration ability of the graphene layer, and promote the deposition of subsequent materials.

[0046] Step S3. Graphene layer growth

[0047] CH4 and H2 are used as precursor gases for growing graphene layers at 900-950°C for 10-15 minutes; the volume ratio of CH4 and H2 is (3-5):1, and the working pressure is 0.2 torr.

[0048] The graphene layer reduces the surface migration barrier and promotes the subsequent migration of Al atoms. At the same time, it acts as a nanomask to improve the nucleation quality of subsequent thin films.

[0049] In this application, the Cu film needs to be removed after the graphene layer is grown, and the residual Cu film is removed by wet etching with NH4S2O8 solution. Removing the Cu film after the graphene layer is grown can effectively protect the quality of the graphene layer, reduce the defect density, promote the growth of subsequent layers, and optimize the interface quality.

[0050] Step S4. AlN buffer layer growth

[0051] Deposition conditions: 20-30 nm thick AlN was deposited at 600-650°C using a sputtering system.

[0052] The growth of the AlN layer is more intense at the bottom, which inhibits the longitudinal extension of the substrate (3D) and strengthens the lateral growth (2D), which will help cut off the stretching of dislocations and improve crystal quality. Due to the relative reduction of crystal defects, the reverse voltage will be reduced and the ESD yield will be improved, which will greatly improve the brightness while reducing costs.

[0053] Step S5. GaN thin film growth

[0054] The GaN thin film is prepared by MOCVD method. The specific implementation method is:

[0055] A mixed gas of high purity (99.99%) H2 and N2 is used as a carrier gas, high purity (99.99%) NH3 is used as a nitrogen source, and trimethyl gallium (TMGa) is used as a gallium source. The substrate with the AlN buffer layer plated in the above step S4 is transferred to MOCVD, pretreated at 1000-1100°C for 3-5 minutes under H2 atmosphere, and then nitrided to achieve the purpose of improving the crystal quality of the AlN layer.

[0056] Step S6. Deposition of undoped GaN layer

[0057] An undoped GaN layer is deposited on the AlN layer. Growth conditions: the undoped GaN layer is deposited at 1000-1200° C. and a pressure of 100-200 torr.

[0058] Due to the weakening of the diffusion and migration ability of the reaction species during low-temperature and high-pressure growth, there are not enough Ga atoms diffusing to the step surfaces of layered growth, so that the growth mode of the crystal surface tends to be island growth. Therefore, when choosing high-temperature and low-pressure growth, the growth mode of the crystal surface tends to be layered growth.

[0059] Step S7. n-type GaN layer growth

[0060] An n-type GaN layer (Si doped) is deposited on the non-doped GaN layer, wherein the growth temperature is 1000-1100° C., the pressure is 100-200 torr, the growth thickness is 5-7 μm, and the growth time is 3-5 minutes.

[0061] Si replaces the equilibrium position of Ga atoms, high-cost replaces low-cost, and one more electron is added, which belongs to n-type doping. n-GaN provides electrons for the composite light emission of LEDs. At the same time, it grows in a high-temperature and low-pressure environment, with more uniform gas phase diffusion, smoother growth, and better crystal quality. In other words, Si doping provides additional electrons to form n-type semiconductors, enhancing the composite light emission ability of LEDs. It can also increase the concentration of electrons and improve the light output of LEDs.

[0062] Step S8. Stress relief layer (SRL) growth

[0063] Using NH3, TMGa, TEMGa, and TMln as raw materials, the growth is carried out at 800-900℃ and 200torr pressure, the growth time is 5-10min, and the thickness is 65-75nm. The adaptation strain of GaN epitaxial growth mainly comes from the lattice mismatch between the sapphire substrate and the growth material, as well as the thermal mismatch caused by the different thermal expansion coefficients of the substrate and the growth material during the heating and cooling process. The growth of SRL can effectively adjust this mismatch strain, release the residual stress and growth stress accumulated in the epitaxial growth, reduce crystal defects, and improve the luminous efficiency of LEDs.

[0064] Step S9. Multi-quantum well layer (MQW) deposition

[0065] A multi-quantum well layer is deposited on the stress release layer. The multi-quantum well layer is formed by alternately stacked InGaN quantum well layers and AlGaN quantum barrier layers. The stacking period is 10-15. Since the effect of a single quantum well is limited, a multi-quantum well layer is set to confine the injected carriers as much as possible to increase the recombination probability.

[0066] Step S10. Growth of electron blocking layer (EBL)

[0067] The electron blocking layer (EBL) is grown on the MQW, using NH3, TMGa, TEMGa, TMAI and CP2Mg as raw materials, at a temperature of 900-930°C and a pressure of 200-250torr for 5-10 minutes. The electrons are confined in the quantum well area to reduce the Auger recombination of carriers, and overcome the problem of decreased luminous efficiency caused by electrons overflowing the quantum well under high current density injection conditions, thereby improving the luminous efficiency of the LED; the material of the final electron blocking layer is p-lnAlGaN.

[0068] Step S11. p-type GaN layer deposition

[0069] Finally, Mg-doped p-type GaN is deposited on the EBL, using NH3, TEGa, TMln, and CP2Mg as raw materials, and grown at a growth temperature of 900-1000°C, a growth pressure of 200-500torr, and a growth time of 3-5 minutes. The incorporation of Mg will form a p-type semiconductor, providing hole injection for the active area, ensuring that it has better luminescence performance.

[0070] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0071] Example 1

[0072] Figure 1 For the LED chip structure diagram provided in Example 1 of this application, please refer to Figure 1 .

[0073] This embodiment provides an LED chip, and the preparation method thereof comprises the following steps:

[0074] (1) Substrate cleaning: The patterned sapphire substrate (PSS substrate) was cleaned using a standard RCA cleaning method.

[0075] (2) Cu film growth: A 450 nm thick Cu film is grown on the patterned sapphire substrate in step (1) using an evaporation system.

[0076] (3) Growth of graphene layer: CH4 and H2 were used as precursor gases for growing graphene layers at 900°C for 12 min; the volume ratio of CH4 and H2 was 4:1, and the working pressure was 0.2 torr, to achieve the growth of graphene layers, and 3 layers were grown. After the growth of the graphene layer, the substrate with the Cu film was immersed in a 70% mass concentration NH4S2O8 solution to remove the Cu film.

[0077] (4) AlN buffer layer growth: A 23 nm thick AlN layer was deposited at 650°C using a sputtering system.

[0078] (5) GaN film growth: A mixed gas of high-purity H2 and N2 is used as a carrier gas, high-purity NH3 is used as a nitrogen source, and trimethylgallium (TMGa) is used as a gallium source. The substrate with the AlN buffer layer deposited in the above step (4) is transferred to the MOCVD, pretreated at 1100°C for 4 minutes under a H2 atmosphere, and then the substrate is nitrided.

[0079] (6) Deposition of undoped GaN layer: Depositing an undoped GaN layer on the AlN layer at 1200° C. and a pressure of 200 torr.

[0080] (7) Growth of n-type GaN layer: An n-type GaN layer (Si doped) is deposited on the non-doped GaN layer, wherein the growth temperature is 1000° C., the pressure is 200 torr, and the growth thickness is 6 μm.

[0081] (8) Stress release layer (SRL) growth: using NH3, TMGa, TEMGa, and TMln as raw materials, grown at 870°C and a pressure of 200 torr, with a thickness of 70 nm.

[0082] (9) Multi-quantum well layer (MQW) deposition: A multi-quantum well layer is deposited on the stress release layer. The multi-quantum well layer is formed by alternately stacked InGaN quantum well layers and AlGaN quantum barrier layers, with a stacking period of 12.

[0083] (10) Growth of electron blocking layer (EBL): using NH3, TMGa, TEMGa, TMAI and CP2Mg as raw materials, the growth was carried out at a temperature of 930°C and a pressure of 220 torr for 6 min.

[0084] (11) Deposition of p-type GaN layer: using NH3, TEGa, TMln, and CP2Mg as raw materials, the growth was carried out at a growth temperature of 1000°C and a growth pressure of 400 torr for a growth time of 5 minutes.

[0085] Example 2

[0086] This embodiment provides an LED chip, and the preparation method thereof comprises the following steps:

[0087] (1) Substrate cleaning: The patterned sapphire substrate (PSS substrate) was cleaned using a standard RCA cleaning method.

[0088] (2) Cu film growth: A 400 nm thick Cu film is grown on the patterned sapphire substrate in step (1) using an evaporation system.

[0089] (3) Growth of graphene layer: CH4 and H2 were used as precursor gases for growing graphene layers at 900°C for 12 min; the volume ratio of CH4 and H2 was 4:1, and the working pressure was 0.2 torr, to achieve the growth of graphene layers, and 3 layers were grown. After the growth of the graphene layer, the substrate with the Cu film was immersed in a 70% mass concentration NH4S2O8 solution to remove the Cu film.

[0090] (4) AlN buffer layer growth: A 28 nm thick AlN layer was deposited at 650°C using a sputtering system.

[0091] (5) GaN film growth: A mixed gas of high-purity H2 and N2 is used as a carrier gas, high-purity NH3 is used as a nitrogen source, and trimethylgallium (TMGa) is used as a gallium source. The substrate with the AlN buffer layer deposited in the above step (4) is transferred to the MOCVD, pretreated at 1100°C for 4 minutes under a H2 atmosphere, and then the substrate is nitrided.

[0092] (6) Deposition of undoped GaN layer: Depositing an undoped GaN layer on the AlN layer at 1200° C. and a pressure of 200 torr.

[0093] (7) Growth of n-type GaN layer: An n-type GaN layer (Si doped) is deposited on the non-doped GaN layer, wherein the growth temperature is 1000° C., the pressure is 200 torr, and the growth thickness is 7 μm.

[0094] (8) Stress release layer (SRL) growth: using NH3, TMGa, TEMGa, and TMln as raw materials, grown at 870°C and a pressure of 200 torr, with a thickness of 70 nm.

[0095] (9) Multi-quantum well layer (MQW) deposition: A multi-quantum well layer is deposited on the stress release layer. The multi-quantum well layer is formed by alternately stacked InGaN quantum well layers and AlGaN quantum barrier layers, with a stacking period of 12.

[0096] (10) Growth of electron blocking layer (EBL): using NH3, TMGa, TEMGa, TMAI and CP2Mg as raw materials, the growth was carried out at a temperature of 930°C and a pressure of 220 torr for a growth time of 5 min.

[0097] (11) Deposition of p-type GaN layer: using NH3, TEGa, TMln, and CP2Mg as raw materials, the growth was carried out at a growth temperature of 1000°C and a growth pressure of 400 torr for a growth time of 5 minutes.

[0098] Example 3

[0099] This embodiment provides an LED chip, and the preparation method thereof comprises the following steps:

[0100] (1) Substrate cleaning: The patterned sapphire substrate (PSS substrate) was cleaned using a standard RCA cleaning method.

[0101] (2) Cu film growth: A 500 nm thick Cu film is grown on the patterned sapphire substrate in step (1) using an evaporation system.

[0102] (3) Growth of graphene layer: CH4 and H2 are used as precursor gases for growing graphene layers at 900°C for 12 minutes; the volume ratio of CH4 and H2 is 4:1, and the working pressure is 0.2 torr, to achieve the growth of graphene layers, and grow 4 layers. After the growth of the graphene layer, the substrate with the Cu film is immersed in a 70% mass concentration NH4S2O8 solution to remove the Cu film.

[0103] (4) AlN buffer layer growth: A 20 nm thick AlN layer was deposited at 650°C using a sputtering system.

[0104] (5) GaN film growth: A mixed gas of high-purity H2 and N2 is used as a carrier gas, high-purity NH3 is used as a nitrogen source, and trimethylgallium (TMGa) is used as a gallium source. The substrate with the AlN buffer layer deposited in the above step (4) is transferred to the MOCVD, pretreated at 1100°C for 4 minutes under a H2 atmosphere, and then the substrate is nitrided.

[0105] (6) Deposition of undoped GaN layer: Depositing an undoped GaN layer on the AlN layer at 1200° C. and a pressure of 200 torr.

[0106] (7) Growth of n-type GaN layer: An n-type GaN layer (Si doped) is deposited on the non-doped GaN layer, wherein the growth temperature is 1000° C., the pressure is 200 torr, and the growth thickness is 5 μm.

[0107] (8) Stress release layer (SRL) growth: using NH3, TMGa, TEMGa, and TMln as raw materials, grown at 870°C and a pressure of 200 torr, with a thickness of 70 nm.

[0108] (9) Multi-quantum well layer (MQW) deposition: A multi-quantum well layer is deposited on the stress release layer. The multi-quantum well layer is formed by alternately stacked InGaN quantum well layers and AlGaN quantum barrier layers, with a stacking period of 12.

[0109] (10) Growth of electron blocking layer (EBL): using NH3, TMGa, TEMGa, TMAI and CP2Mg as raw materials, the growth was carried out at a temperature of 930°C and a pressure of 220 torr for 6 min.

[0110] (11) Deposition of p-type GaN layer: using NH3, TEGa, TMln, and CP2Mg as raw materials, the growth was carried out at a growth temperature of 1000°C and a growth pressure of 400 torr for a growth time of 5 minutes.

[0111] The LED epitaxial wafer preparation method provided in this application can significantly reduce the dislocation density and compressive strain. The low compressive strain and piezoelectric field weaken the influence of the screen polarization field, thereby producing a stable EL emission wavelength, which is more beneficial for high current driving InGaN LEDs. Low chip temperature of InGaN LEDs has been achieved, indicating that graphene interlayer / PSS is a promising substrate for high-power semiconductor devices.

[0112] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

Claims

1. An LED epitaxial wafer, characterized in that: include: A substrate, and a graphene layer, a buffer layer, an undoped GaN layer, an n-type GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a p-type GaN layer epitaxially grown in sequence on the substrate; The thickness of a single graphene layer is 0.5-1.5 nm, and the number of graphene layers is at least 2.

2. The LED epitaxial wafer according to claim 1, characterized in that: The substrate includes a Si substrate or a sapphire substrate.

3. The LED epitaxial wafer according to claim 1, characterized in that: The material of the buffer layer includes AlN.

4. The LED epitaxial wafer according to claim 3, characterized in that: The thickness of the buffer layer is 20-30 nm; Optionally, the n-type GaN layer has a thickness of 5-7 μm.

5. A method for growing a graphene layer, characterized in that: For preparing the graphene layer according to any one of claims 1 to 4, the growth method of the graphene layer comprises: Growing a Cu film on the substrate, and then growing the graphene layer on the surface of the Cu film; The Cu film is removed after the graphene layer is grown.

6. The method for growing a graphene layer according to claim 5, characterized in that: The thickness of the Cu film is 400-500 nm.

7. The method for growing a graphene layer according to claim 5 or 6, characterized in that: The method for removing the Cu film comprises: The substrate with the Cu film is immersed in an NH4S2O8 solution; wherein the mass concentration of the NH4S2O8 solution is 60-80%.

8. The method for growing a graphene layer according to claim 7, characterized in that: The soaking time is 1-2 minutes.

9. The method for growing a graphene layer according to claim 5 or 6, characterized in that: Also includes: Using CH4 and H2 as precursor gases for growing the graphene layer at 900-950° C. for 10-15 min; The volume ratio of the CH4 and the H2 is (3-5):

1.

10. An LED chip, characterized in that: It comprises the LED epitaxial wafer as claimed in claim 1 or 2.

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