A method for epitaxial growth of a molybdenum-based composite substrate

Abstract

The application discloses an epitaxial growth method of a molybdenum-based composite substrate, a graphene layer is evaporated on a molybdenum substrate to obtain a molybdenum-graphene composite substrate, since the graphene surface does not contain chemical dangling bonds, defects caused by lattice adaptation can be avoided, and the problem of heteroepitaxial growth caused by substrate lattice mismatch defects is solved, therefore, the molybdenum-graphene composite substrate can be used as a substrate to reduce material defects, improve the quality of epitaxial crystals, and thus improve the photoelectric performance of an LED. An aluminum nitride layer and a buffer layer are prepared on the molybdenum-graphene composite substrate in sequence, and the laser peeling of the substrate can be more easily carried out subsequently, and then a mini LED chip and a Micro vertical structure LED chip can be manufactured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a method for epitaxial growth of a molybdenum-based composite substrate. BACKGROUND

[0002] Gallium nitride (GaN) is the representative of the third generation of semiconductor materials due to its stable chemical properties, thermal stability, high temperature resistance and other advantages. Since the forbidden band width covers the entire wave band from ultraviolet to infrared, it is widely used in solid-state lighting field and full-color display area. There are various substrate materials for preparing light-emitting diodes, such as silicon carbide (SiC), gallium nitride (GaN), gallium arsenide (GaAs), etc. Although these materials have excellent performance, the manufacturing cost is high. Sapphire substrate is the earliest and most widely used substrate in the preparation of light-emitting diodes. However, the sapphire substrate material also has some weaknesses. The most obvious one is that there is a large lattice mismatch and thermal mismatch between sapphire and GaN. The large lattice mismatch and thermal mismatch will cause the GaN thin film material grown on the sapphire substrate to have a high dislocation density, and will also make the epitaxial layer more prone to warping and cracking, making the subsequent processing process difficult. Moreover, sapphire has high hardness, high cost of cutting and grinding processing, and poor heat dissipation, which seriously affects the performance of LED devices.

[0003] In the patent literature CN202189826U, a blue light LED epitaxial chip structure using molybdenum substrate to replace sapphire substrate is disclosed, which comprises molybdenum substrate, indium or molybdenum alloy layer, P+GaN contact layer, PAlGaN transition layer, InGaN / GaN light-emitting layer and N-GaN contact layer arranged in sequence. The molybdenum substrate is prepared by cutting the molybdenum substrate into the same size as the epitaxial wafer. Under certain conditions, the indium or molybdenum alloy is plated on the molybdenum substrate to form an indium or molybdenum alloy layer. Then the P+GaN contact layer of the sapphire substrate epitaxial wafer which has been prepared in advance is firmly bonded to the molybdenum substrate through the indium or molybdenum alloy layer. Finally, the sapphire substrate and the low-temperature GaN buffer layer are removed by laser stripping equipment, leaving the molybdenum substrate, i.e. the blue light LED epitaxial chip structure of the molybdenum substrate. Although this method improves the heat dissipation, it is complex to use laser cutting technology, and is only suitable for blue light LED epitaxial chip structure, with small application range. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method for epitaxial growth of a molybdenum-based composite substrate, which can facilitate laser stripping of the substrate and the epitaxial layer.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is:

[0006] A method for epitaxial growth of a molybdenum-based composite substrate, comprising the steps of:

[0007] evaporating a graphene layer on a molybdenum substrate to obtain a molybdenum-graphene composite substrate;

[0008] sequentially preparing an aluminum nitride layer and a buffer layer on the molybdenum-graphene composite substrate;

[0009] growing an epitaxial layer on the buffer layer, the epitaxial layer comprising a roughening layer, an N-type gallium nitride layer, a multiple quantum well layer, and a P-type gallium nitride layer stacked in sequence.

[0010] The method has the advantages that: the graphene layer is evaporated on the molybdenum substrate to obtain the molybdenum-graphene composite substrate, the graphene surface does not contain chemical dangling bonds, defects caused by lattice adaptation can be avoided, and the problem of heteroepitaxial growth of defects induced by lattice mismatch of the substrate is solved, so that the molybdenum-graphene composite substrate as the substrate can reduce material defects, improve the quality of the epitaxial crystal, and thus improve the photoelectric performance of the LED. The aluminum nitride layer and the buffer layer are sequentially prepared on the molybdenum-graphene composite substrate, and the laser peeling of the substrate can be more easily performed subsequently, and then the mini LED chip and the Micro vertical structure LED chip are manufactured. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 A flowchart of a method for epitaxial growth of a molybdenum-based composite substrate according to an embodiment of the present application;

[0012] Figure 2 An epitaxial diagram prepared by a method for epitaxial growth of a molybdenum-based composite substrate according to an embodiment of the present application;

[0013] REFERENCE NUMERALS:

[0014] 1, molybdenum-graphene composite substrate; 2, aluminum nitride layer; 3, buffer layer; 4, U-type gallium nitride layer; 5, N-type gallium nitride layer; 6, multiple quantum well layer; 7, low-temperature P-type gallium nitride layer; 8, superlattice layer; 9, high-temperature P-type gallium nitride layer. DETAILED DESCRIPTION

[0015] To make the technical contents, purposes and effects of the present application clear, the following will be described in detail in conjunction with the embodiments and the accompanying drawings.

[0016] Please refer to Figure 1 The embodiment of the present application provides a method for epitaxial growth of a molybdenum-based composite substrate, comprising the steps of:

[0017] evaporating a graphene layer on a molybdenum substrate to obtain a molybdenum-graphene composite substrate;

[0018] sequentially preparing an aluminum nitride layer and a buffer layer on the molybdenum-graphene composite substrate;

[0019] An epitaxial layer is grown on the buffer layer, and the epitaxial layer comprises a roughening layer, an N-type gallium nitride layer, a multi-quantum well layer, and a P-type gallium nitride layer which are sequentially stacked.

[0020] As can be seen from the above description, the beneficial effects of the present application are that a graphene layer is evaporated on a molybdenum substrate to obtain a molybdenum-graphene composite substrate, since the graphene surface does not contain chemical dangling bonds, defects caused by lattice adaptation can be avoided, and the problem of heteroepitaxial growth induced by lattice mismatch of the substrate is solved, so that using the molybdenum-graphene composite substrate as a substrate can reduce material defects, improve the quality of epitaxial crystals, and thus improve the photoelectric performance of the LED. An aluminum nitride layer and a buffer layer are prepared on the molybdenum-graphene composite substrate in sequence, and subsequent laser peeling of the substrate can be more easily performed, and then a mini LED chip and a Micro vertical structure LED chip are manufactured.

[0021] Further, the preparation of the aluminum nitride layer on the molybdenum-graphene composite substrate comprises:

[0022] An aluminum nitride layer with a thickness of 10-60nm is prepared on the molybdenum-graphene composite substrate.

[0023] As can be seen from the above description, the aluminum nitride layer is prepared on the molybdenum-graphene composite substrate, and subsequent laser peeling of the substrate can be more easily performed.

[0024] Further, the preparation of the buffer layer on the molybdenum-graphene composite substrate comprises:

[0025] The molybdenum-graphene composite substrate is placed in a reaction cavity of a metal organic chemical vapor deposition device, and a buffer layer containing AlN / AlGaN / GaN is grown on the molybdenum-graphene composite substrate.

[0026] As can be seen from the above description, the preparation of the buffer layer can improve the thermal conductivity and increase the service life of the device.

[0027] Further, the growth of the buffer layer containing AlN / AlGaN / GaN on the molybdenum-graphene composite substrate comprises:

[0028] The temperature of the reaction cavity is set to 780-880℃, the pressure is set to 100-200mbar, ammonia gas, nitrogen gas, 100-300sccm of TmGa2 and 25-200sccm of TmAl are introduced, and the buffer layer of AlN / AlGaN / GaN is grown on the molybdenum-graphene composite substrate for 2-4min.

[0029] As can be seen from the above description, during the epitaxial growth on the molybdenum-graphene composite substrate, the special buffer layer is set to improve the generation quality and efficiency of the buffer layer.

[0030] Further, the growing the roughened layer and the N-type gallium nitride layer on the buffer layer comprises:

[0031] Setting the temperature of the reaction cavity to 1100-1300℃, the pressure to 250-350mbar, and introducing nitrogen, hydrogen, ammonia and TmGa2, and maintaining for 15-20 minutes, so that the roughened layer is formed on the buffer layer, and the roughened layer is a U-shaped gallium nitride layer;

[0032] Setting the temperature of the reaction cavity to 1000-1100℃, the pressure to 500-1000mbar, and growing the N-type gallium nitride layer with a thickness of 2-3μm on the roughened layer.

[0033] As can be seen from the above description, the method for growing the U-shaped gallium nitride can change the three-dimensional growth method to two-dimensional growth, and reduce dislocation defects; the N-type gallium nitride layer is grown by setting the temperature and pressure of the reaction cavity, which can improve the quality and growth efficiency of the N-type gallium nitride layer, and facilitate subsequent evaporation of electrodes on the N-type gallium nitride layer.

[0034] Further, the growing the multi-quantum well layer comprises:

[0035] Setting the temperature of the reaction cavity to 850-950℃, the well-barrier temperature difference to 100-150℃, the reaction chamber pressure to 500-1000mbar, the rotation speed to 550-650rpm, and growing the multi-quantum well layer in an H2 carrier gas environment;

[0036] The number of periods of the multi-quantum well layer is 8-12.

[0037] As can be seen from the above description, the multi-quantum well layer is grown by setting the temperature and pressure of the reaction cavity, which can improve the quality and growth efficiency of the multi-quantum well layer, and facilitate subsequent growth of the P-type gallium nitride layer on the multi-quantum well layer.

[0038] Further, the P-type gallium nitride layer comprises:

[0039] Growing a low-temperature P-type gallium nitride layer on the multi-quantum well layer;

[0040] Introducing NH3, TmGa2, Cp2Mg and TmAl into the reaction cavity, so that a periodic AlGaN / GaN superlattice layer is grown on the low-temperature P-type gallium nitride layer;

[0041] Forming a doped high-temperature P-type gallium nitride layer on the superlattice layer;

[0042] As can be seen from the above description, it is beneficial to reduce the Droop effect of the LED chip under a large current density, improve the injection efficiency of the carriers, and improve the light-emitting efficiency of the device.

[0043] Further, the low-temperature P-type gallium nitride layer is grown on the multi-quantum well layer by setting the temperature and pressure of the reaction cavity.

[0044] The temperature of the reaction cavity is set to 600-700℃, the pressure is set to 300-800mbar, 55000-65000sccm of NH3 and 25-50sccm of TmGa2 are introduced, and the low-temperature P-type gallium nitride layer with a thickness of 60-90nm is formed on the multi-quantum well layer.

[0045] As can be seen from the above description, the quality and growth efficiency of the low-temperature P-type gallium nitride layer can be improved by setting the temperature and pressure of the reaction cavity to grow the low-temperature P-type gallium nitride layer, which facilitates the subsequent growth of the superlattice layer on the low-temperature P-type gallium nitride layer.

[0046] Further, the low-temperature P-type gallium nitride layer is grown on the multi-quantum well layer by setting the temperature and pressure of the reaction cavity.

[0047] The temperature of the reaction cavity is set to 700-950℃, the pressure is set to 300-800mbar, 30000-60000sccm of NH3, 30-50sccm of TmGa2, 1500-2000sccm of Cp2Mg, 150-200sccm of TmAl, and 100-500sccm of TmIN are introduced, and the periodic AlInGaN / AlGaN superlattice layer is grown on the low-temperature P-type gallium nitride layer.

[0048] The period of the AlInGaN / AlGaN is 5-10, the single-layer thickness of the AlGaN is 4-6nm, and the thickness ratio of the AlInGaN and AlGaN layers in a single period is 1:1-3:1.

[0049] The thickness of the superlattice layer is 50-70nm, the doping concentration of Mg is 1E+18-1E+19atom / cm 3 , the doping concentration of Al is 1E+17-1E+18atom / cm 3 , and the doping concentration of In is 1E+17-2E+18atom / cm 3 .

[0050] As can be seen from the above description, the quality and growth efficiency of the superlattice layer can be improved by setting the temperature and pressure of the reaction cavity to grow the superlattice layer, which facilitates the subsequent growth of the high-temperature P-type gallium nitride layer on the superlattice layer.

[0051] Further, the doped high-temperature P-type gallium nitride layer is formed on the superlattice layer.

[0052] The temperature of the reaction cavity is set to 900-1050 DEG C, the pressure is 600-1000 mbar, 60000-75000 sccm of NH3, 25-50 sccm of TmGa2 and 2000-3000 sccm of Cp2Mg are introduced, and a doped high-temperature P-type gallium nitride layer is formed on the superlattice layer;

[0053] The total thickness of the high-temperature P-type gallium nitride layer is 60-90 nm, and the doping concentration of Mg is 1E+20-3E+20 atom / cm 3 The thickness ratio of the U-shaped gallium nitride layer and the P-type gallium nitride layer is 1:3-1:5.

[0054] As can be seen from the above description, by setting the temperature and pressure of the reaction cavity to grow the high-temperature P-type gallium nitride layer, the quality and growth efficiency of the high-temperature P-type gallium nitride layer can be improved.

[0055] The above-mentioned epitaxial growth method of a molybdenum-based composite substrate can facilitate substrate laser peeling after being manufactured, and the following specific embodiments are described:

[0056] Embodiment one

[0057] Please refer to Figure 1 An epitaxial growth method of a molybdenum-based composite substrate includes the following steps:

[0058] S1, evaporating a graphene layer on a molybdenum substrate to obtain a molybdenum-graphene composite substrate.

[0059] Specifically, the molybdenum substrate is placed in an evaporation furnace under normal pressure, the temperature is raised to 950-1050 DEG C, 100-150 sccm of methane, 10-30 sccm of hydrogen and 100-150 sccm of argon are introduced, and a graphene layer is evaporated to obtain a molybdenum-graphene composite substrate.

[0060] S2, an aluminum nitride layer and a buffer layer are sequentially prepared on the molybdenum-graphene composite substrate.

[0061] S21, an aluminum nitride layer with a thickness of 10-60 nm is prepared on the molybdenum-graphene composite substrate, and the thickness of the aluminum nitride layer in this embodiment is 18 nm.

[0062] S22, the molybdenum-graphene composite substrate is placed in the reaction cavity of a metal organic chemical vapor deposition device, and a buffer layer containing AlN / AlGaN / GaN is grown on the molybdenum-graphene composite substrate.

[0063] Specifically, the temperature of the reaction cavity is set to 780-880℃, the pressure is set to 100-200mbar, ammonia, nitrogen, 100-300sccm of TmGa2 and 25-200sccm of TmAl are introduced, and the growth lasts for 2-4min, so as to grow the buffer layer of AlN / AlGaN / GaN on the molybdenum-graphene composite substrate.

[0064] In this embodiment, the temperature of the reaction cavity is 810℃, and the growth lasts for 2min, so as to grow the buffer layer of 0.1μm.

[0065] S3, growing an epitaxial layer on the buffer layer, the epitaxial layer comprising a roughening layer, an N-type gallium nitride layer, a multi-quantum well layer and a P-type gallium nitride layer which are sequentially stacked.

[0066] S31, setting the temperature of the reaction cavity to 1100-1300℃, the pressure to 250-350mbar, introducing nitrogen, hydrogen, ammonia and TmGa2, and the growth lasting for 15-20min, preferably 15min, so as to form a roughening layer on the buffer layer, the roughening layer being a U-shaped gallium nitride layer.

[0067] S32, setting the temperature of the reaction cavity to 1000-1100℃, the pressure to 500-1000mbar, and growing an N-type gallium nitride layer with a thickness of 2-3μm on the roughening layer.

[0068] S33, setting the temperature of the reaction cavity to 850-950℃, the temperature difference between the well and the barrier to 100-150℃, the pressure of the reaction cavity to 500-1000mbar, the rotation speed to 550-650rpm, preferably 600rpm, and growing a multi-period quantum well layer in an environment of H2 carrier gas. The number of periods of the multi-period quantum well layer is 8-12.

[0069] In some embodiments, the method for preparing the multi-period quantum well layer can also be:

[0070] Setting the pressure of the reaction cavity to 500-1000mbar and the temperature to 700-800℃, while introducing ammonia, hydrogen, nitrogen and 25-40sccm of TmGa2, and intermittently introducing 1200-1500sccm of TmIn, so as to grow a periodic InGaN / GaN multi-quantum well active region layer on the N-type GaN layer, the number of periods of InGaN / GaN being 10-16; the thickness of the multi-quantum well active region layer is 0.15-0.2μm, and the doping concentration of In is 1E+20-2E+20atom / cm 3 .

[0071] S341, growing a low-temperature P-type gallium nitride layer on the multi-quantum well layer.

[0072] Specifically, the temperature of the reaction cavity is set to 600-700℃, the pressure is set to 300-800mbar, 55000-65000sccm of NH3 and 25-50sccm of TmGa2 are introduced, and a low-temperature P-type gallium nitride layer with a thickness of 60-90nm is formed on the multi-quantum well layer.

[0073] S342, NH3, TmGa2, Cp2Mg and TmAl are introduced into the reaction cavity, and a periodic AlGaN / GaN superlattice layer is grown on the low-temperature P-type gallium nitride layer.

[0074] Specifically, the temperature of the reaction cavity is set to 700-950℃, the pressure is set to 300-800mbar, 30000-60000sccm of NH3, 30-50sccm of TmGa2, 1500-2000sccm of Cp2Mg and 150-200sccm of TmAl, and 100-500sccm of TmIN are introduced, and a periodic AlInGaN / AlGaN superlattice layer is grown on the low-temperature P-type gallium nitride layer.

[0075] The period of the AlInGaN / AlGaN is 5-10, the single-layer thickness of the AlGaN is 4-6nm, and the thickness ratio of the AlInGaN and AlGaN layers in a single period is 1:1-3:1.

[0076] The thickness of the superlattice layer is 50-70nm, the doping concentration of Mg is 1E+18-1E+19atom / cm 3 , the doping concentration of Al is 1E+17-1E+18atom / cm 3 , and the doping concentration of In is 1E+17-2E+18atom / cm 3 .

[0077] S343, a doped high-temperature P-type gallium nitride layer is formed on the superlattice layer.

[0078] Specifically, the temperature of the reaction cavity is set to 900-1050℃, the pressure is set to 600-1000mbar, 60000-75000sccm of NH3, 25-50sccm of TmGa2 and 2000-3000sccm of Cp2Mg are introduced, and a doped high-temperature P-type gallium nitride layer is formed on the superlattice layer.

[0079] The total thickness of the high-temperature P-type gallium nitride layer is 60-90nm, the doping concentration of Mg is 1E+20-3E+20atom / cm 3 , and the thickness ratio of the U-type gallium nitride layer and the P-type gallium nitride layer is 1:3-1:5, preferably 1:4.

[0080] Therefore, in the embodiment, the substrate is a molybdenum-graphene composite substrate, and a special buffer layer is arranged in the structure, so that the heat conductivity of the structure is improved, the service life of the device is improved, and the brightness of the prepared GaN-based epitaxial layer is improved by 2% to 5% compared with a conventional LED structure.

[0081] Embodiment two

[0082] The embodiment provides a specific embodiment of an epitaxial growth method based on a molybdenum composite substrate.

[0083] 11. A molybdenum (Mo)-graphene composite substrate is plated with 20 nm thick AlN.

[0084] 12. The molybdenum (Mo)-graphene composite substrate plated with AlN is placed into a reaction chamber of a metal organic chemical vapor deposition device.

[0085] 13. The temperature of the reaction chamber is set to 830°C, the pressure is set to 100-200 mbar, ammonia, nitrogen, 100-300 sccm of TmGa2 and 25-200 sccm of TmAl are introduced, a special buffer layer of AlN / AlGaN / GaN is grown on the substrate for 3 min, and a 0.15 μm buffer layer is grown on the substrate.

[0086] 14. The pressure of the reaction chamber is set to 250-350 mbar, the temperature is set to 1100-1300°C, nitrogen, hydrogen, ammonia and TmGa2 are introduced, and a U-shaped GaN layer is formed on the buffer layer for 12 min.

[0087] 15. The temperature of the reaction chamber is set to 1000°C, the pressure is set to 500 mbar, and a 2 μm N-type GaN layer is grown on the U-shaped GaN layer.

[0088] 16. The pressure of the reaction chamber is set to 500 mbar, the temperature is set to 700°C, ammonia, hydrogen, nitrogen and 25 sccm of TmGa2 are introduced, 1200 sccm of TmIn is intermittently introduced, a periodic InGaN / GaN multi-quantum well active region layer is grown on the N-type GaN layer, the period number of InGaN / GaN is 10, and the doping concentration of In is 1E+20 atom / cm2. 3 .

[0089] 17. The temperature of the reaction chamber is set to 600°C, the pressure is set to 300-800 mbar, 55000 sccm of NH3 and 25 sccm of TmGa2 are introduced, and a low-temperature P-type GaN layer with a thickness of 60 nm is formed on the multi-quantum well active region layer.

[0090] 18. Set the temperature of the reaction chamber to 700 °C, the pressure to 300 mbar, and introduce 30000 seem of NH3, 30 seem of TmGa2, 1500 seem of Cp2Mg, and 150 seem of TmAl, and grow a periodic AlGaN / GaN superlattice layer on the low-temperature P-type GaN layer; the period of the AlGaN / GaN is 5, the single-layer thickness of the AlGaN is 4 nm, the thickness ratio of the AlGaN and GaN layers in a single period is 1:1-3:1; the doping concentration of Mg is 1E+18 atom / cm 3 , and the doping concentration of Al is 1E+17 atom / cm 3 .

[0091] 19. Set the temperature of the reaction chamber to 900 °C, the pressure to 600 mbar, and introduce 60000 seem of NH3, 25 seem of TmGa2, and 2000 seem of Cp2Mg, and form a doped high-temperature P-type GaN layer on the superlattice layer; the doping concentration of Mg is 1E+20 atom / cm 3 .

[0092] In this way, the growth of the GaN-based epitaxial layer is completed.

[0093] Example Three

[0094] This example provides another specific embodiment of the method for epitaxial growth of a molybdenum-based composite substrate:

[0095] 21. Plate the molybdenum (Mo)-graphene composite substrate with 25 nm thickness of AlN.

[0096] 22. Place the molybdenum (Mo)-graphene composite substrate plated with AlN into the reaction chamber of a metal organic chemical vapor deposition device.

[0097] 23. Set the temperature of the reaction chamber to 850 °C, the pressure to 100-200 mbar, and introduce ammonia, nitrogen, 100-300 seem of TmGa2, and 25-200 seem of TmAl, and grow a special buffer layer of AlN / AlGaN / GaN on the substrate for 4 min, so that a 0.2 μm buffer layer is grown on the substrate.

[0098] 24. Set the pressure of the reaction chamber to 250-350 mbar, the temperature to 1100-1300 °C, and introduce nitrogen, hydrogen, ammonia, and TmGa2; and continue for 10 min, so that a U-shaped GaN layer is formed on the buffer layer.

[0099] 25. Set the temperature of the reaction chamber to 1050 °C, the pressure to 750 mbar, and grow a 2.5 μm N-type GaN layer on the U-shaped GaN layer.

[0100] 26. Set the pressure of the reaction chamber to 750 mbar and the temperature to 750°C, and grow a periodic InGaN / GaN multi-quantum well active layer on the N-type GaN layer by intermittently supplying 1350 seem of TmIn while supplying ammonia, hydrogen, nitrogen and 33 seem of TmGa2, the number of periods of InGaN / GaN being 13, and the doping concentration of In being 1.5E+20 atom / cm 3 .

[0101] 27. Set the temperature of the reaction chamber to 600-700°C and the pressure to 300-800 mbar, and form a low-temperature P-type GaN layer having a thickness of 60-90 nm on the multi-quantum well active layer by supplying 55000-65000 seem of NH3 and 25-50 seem of TmGa2.

[0102] 28. Set the temperature of the reaction chamber to 825°C and the pressure to 550 mbar, and grow a periodic AlGaN / GaN superlattice layer on the low-temperature P-type GaN layer by supplying 45000 seem of NH3, 30-50 seem of TmGa2, 1500-2000 seem of Cp2Mg and 150-200 seem of TmAl, the number of periods of AlGaN / GaN being 5-10, the thickness of a single layer of AlGaN being 4-6 nm, the thickness of the superlattice layer being 50-70 nm, the doping concentration of Mg being 1E+18-1E+19 atom / cm 3 , and the doping concentration of Al being 1E+17-1E+18 atom / cm 3 .

[0103] 29. Set the temperature of the reaction chamber to 975°C and the pressure to 800 mbar, and form a doped high-temperature P-type GaN layer on the superlattice layer by supplying 60000-75000 seem of NH3, 25-50 seem of TmGa2 and 2000-3000 seem of Cp2Mg, the thickness of the high-temperature P-type GaN layer being 60-90 nm, and the doping concentration of Mg being 1E+20-3E+20 atom / cm 3 .

[0104] In this way, the growth of the GaN-based epitaxial layer is completed.

[0105] The GaN-based epitaxial layer sample 1 produced in this example was compared with a conventional chip sample 2, as shown in Tables 1 and 2.

[0106] Table 1 Comparison of luminous flux of GaN-based epitaxial layer sample 1 and conventional chip sample 2

[0107]

[0108] Table 2 Aging condition comparison table of GaN-based epitaxial layer sample 1 and conventional chip sample 2

[0109]

[0110] It can be seen that the light flux of the LED chip produced by the embodiment is increased by about 5% compared with the light flux of the conventional chip in the prior art, and the heat conductivity and the service life of the LED chip are obviously improved.

[0111] Example Four

[0112] Please refer to Figure 2 , using the epitaxial structure prepared by example one or example two or example three, comprising:

[0113] The molybdenum-graphene composite substrate 1, the aluminum nitride layer 2, the buffer layer 3, the U-shaped gallium nitride layer 4, the N-type gallium nitride layer 5, the multi-quantum well layer 6, the low-temperature P-type gallium nitride layer 7, the superlattice layer 8 and the high-temperature P-type gallium nitride layer 9 are sequentially stacked.

[0114] The thickness of the aluminum nitride layer 2 is 10-60nm; the thickness of the buffer layer 3 is 0.1-0.2μm; the thickness of the U-shaped gallium nitride layer 4 is 2-3μm; the thickness of the N-type gallium nitride layer 5 is 2-3μm; the thickness of the multi-quantum well layer 6 is 0.15-0.2μm; the thickness of the low-temperature P-type gallium nitride layer 7 is 60-90nm; the thickness of the superlattice layer 8 is 50-70nm; and the thickness of the high-temperature P-type gallium nitride layer 9 is 60-90nm.

[0115] In summary, the epitaxial growth method of the molybdenum-based composite substrate provided by the application evaporates a graphene layer on a molybdenum substrate to obtain a molybdenum-graphene composite substrate. Since the graphene surface does not contain chemical dangling bonds, defects caused by lattice adaptation can be avoided, and the problem of heteroepitaxial growth induced by substrate lattice mismatch can be solved. Therefore, using the molybdenum-graphene composite substrate as a substrate can reduce material defects, improve the quality of epitaxial crystals, and thus improve the photoelectric performance of the LED. An aluminum nitride layer and a buffer layer are sequentially prepared on the molybdenum-graphene composite substrate, and subsequent laser peeling of the substrate can be more easily performed, thereby manufacturing mini LED chips and Micro vertical structure LED chips, and realizing the application of gallium nitride LED products in flexible display, intelligent wearable devices and the like.

[0116] The above only describes the embodiments of the application, and does not limit the patent scope of the application. Any equivalent transformation or direct or indirect application in the related technical field based on the content of the specification and drawings of the application is also included in the patent protection scope of the application.

Claims

1. A method for epitaxial growth of a molybdenum-based composite substrate, characterized by, The method comprises the steps of: evaporating a graphene layer on a molybdenum substrate to obtain a molybdenum-graphene composite substrate; preparing an aluminum nitride layer and a buffer layer on the molybdenum-graphene composite substrate in sequence; growing an epitaxial layer on the buffer layer, the epitaxial layer comprising a roughening layer, an N-type gallium nitride layer, a multi-quantum well layer, and a P-type gallium nitride layer stacked in sequence; preparing the aluminum nitride layer on the molybdenum-graphene composite substrate comprises: preparing an aluminum nitride layer with a thickness of 10-60 nm on the molybdenum-graphene composite substrate; preparing the buffer layer on the molybdenum-graphene composite substrate comprises: placing the molybdenum-graphene composite substrate in a reaction chamber of a metal organic chemical vapor deposition device to grow a buffer layer containing AlN / AlGaN / GaN on the molybdenum-graphene composite substrate.

2. The method of claim 1, wherein the molybdenum-based composite substrate is formed by a method comprising: growing the buffer layer containing AlN / AlGaN / GaN on the molybdenum-graphene composite substrate comprises: ​ setting the temperature of the reaction chamber to 780-880 ℃, the pressure to 100-200 mbar, and introducing ammonia, nitrogen, 100-300 sccm of TmGa2, and 25-200 sccm of TmAl, and growing the buffer layer of AlN / AlGaN / GaN on the molybdenum-graphene composite substrate for 2-4 min.

3. The epitaxial growth method for a molybdenum-based composite substrate according to claim 1, characterized in that, growing the roughening layer and the N-type gallium nitride layer on the buffer layer comprises: setting the temperature of the reaction chamber to 1100-1300 ℃, the pressure to 250-350 mbar, and introducing nitrogen, hydrogen, ammonia, and TmGa2, and growing the roughening layer on the buffer layer for 15-20 min, so that the roughening layer is a U-shaped gallium nitride layer; setting the temperature of the reaction chamber to 1000-1100 ℃, the pressure to 500-1000 mbar, and growing the N-type gallium nitride layer with a thickness of 2-3 μm on the roughening layer.

4. The epitaxial growth method for a molybdenum-based composite substrate according to claim 1, characterized in that, growing the multi-quantum well layer comprises: setting the temperature of the reaction chamber to 850-950 ℃, the well-barrier temperature difference to 100-150 ℃, the reaction chamber pressure to 500-1000 mbar, the rotation speed to 550-650 rpm, and growing the multi-quantum well layer in an H2 carrier gas environment; the multi-quantum well layer has a period number of 8-12.

5. The epitaxial growth method for a molybdenum-based composite substrate according to claim 1, characterized in that, the P-type gallium nitride layer comprises: growing a low-temperature P-type gallium nitride layer on the multi-quantum well layer; introducing NH3, TmGa2, Cp2Mg, and TmAl into the reaction chamber to grow a periodic AlGaN / GaN superlattice layer on the low-temperature P-type gallium nitride layer; forming a doped high-temperature P-type gallium nitride layer on the superlattice layer.

6. The method of claim 5, wherein the molybdenum-based composite substrate is formed by a method comprising: growing the low-temperature P-type gallium nitride layer on the multi-quantum well layer comprises: ​ setting the temperature of the reaction chamber to 600-700 ℃, the pressure to 300-800 mbar, and introducing 55000-65000 sccm of NH3 and 25-50 sccm of TmGa2 to form a low-temperature P-type gallium nitride layer with a thickness of 60-90 nm on the multi-quantum well layer.

7. The epitaxial growth method for a molybdenum-based composite substrate according to claim 5, characterized in that, introducing NH3, TmGa2, Cp2Mg, and TmAl into the reaction chamber to grow a periodic AlGaN / GaN superlattice layer on the low-temperature P-type gallium nitride layer comprises: The temperature of the reaction cavity is set to 700-950℃, the pressure is set to 300-800mbar, 30000-60000sccm of NH3, 30-50sccm of TmGa2, 1500-2000sccm of Cp2Mg and 150-200sccm of TmAl, and 100-500sccm of TmIN are introduced to grow a periodic AlInGaN / AlGaN superlattice layer on a low-temperature P-type gallium nitride layer; The period of the AlInGaN / AlGaN is 5-10, the single-layer thickness of the AlGaN is 4-6nm, and the thickness ratio of the AlInGaN and AlGaN layers in a single period is 1:1-3:1; The superlattice layer has a thickness of 50-70 nm, a doping concentration of Mg of 1E+18-1E+19 atom / cm 3 , a doping concentration of Al of 1E+17-1E+18 atom / cm 3 , and a doping concentration of In of 1E+17-2E+18 atom / cm 3 .

8. The epitaxial growth method for a molybdenum-based composite substrate according to claim 5, characterized in that, forming a doped high-temperature P-type gallium nitride layer on the superlattice layer comprises: The temperature of the reaction cavity is set to 900-1050℃, the pressure is set to 600-1000mbar, 60000-75000sccm of NH3, 25-50sccm of TmGa2 and 2000-3000sccm of Cp2Mg are introduced to form a doped high-temperature P-type gallium nitride layer on the superlattice layer; The total thickness of the high-temperature P-type gallium nitride layer is 60-90 nm, and the doping concentration of Mg is 1E+20-3E+20 atom / cm 3 The thickness ratio of the U-shaped gallium nitride layer and the P-type gallium nitride layer is 1:3-1:5.

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