Micro-LED epitaxial wafer, preparation method thereof and Micro-LED

Abstract

The invention discloses a Micro-LED epitaxial wafer, a preparation method of the Micro-LED epitaxial wafer and a Micro-LED, and relates to the field of semiconductor photoelectric devices. The Micro-LED epitaxial wafer sequentially comprises a substrate, a buffer layer, a first warping regulation and control layer, a non-doped GaN layer, a second warping regulation and control layer, an N-type GaN layer, a third warping regulation and control layer, a multi-quantum well layer and a P-type GaN layer. The first warping regulation and control layer is a three-dimensional GaN layer, the second warping regulation and control layer comprises a first Si-doped GaN layer and a Si-doped AlGaN layer which are alternately stacked, the third warping regulation and control layer comprises a Si-doped AlInGaN layer and a superlattice layer which are sequentially stacked on the N-type GaN layer, and the superlattice layer comprises a second Si-doped GaN layer and an InGaN layer which are alternately stacked. By implementing the invention, the luminous efficiency and wavelength uniformity of the Micro-LED can be improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic devices, and in particular to a Micro-LED epitaxial wafer and a preparation method thereof, and a Micro-LED. Background Art

[0002] Micro-LED is a new generation of display technology solution after LCD, OLED, and Mini-LED. It has many advantages such as high brightness, high display density, high color gamut, and low power consumption. It is the cutting-edge research direction of current display technology. Currently, Micro-LED generally uses sapphire as the substrate material and GaN material as the epitaxial layer. There is a lattice mismatch of up to 13.3% and a thermal mismatch of 25.5% between sapphire and GaN. Large lattice mismatch will cause a density of about 10 8 cm -3 These dislocations can act as non-radiative recombination centers, causing carriers to be captured by defects, reducing the luminous efficiency of Micro-LEDs. The large thermal mismatch causes huge stress in the epitaxial layer during the cooling process of the epitaxial wafer, resulting in poor WD std (wavelength uniformity) of the epitaxial wafer. In severe cases, a large number of cracks may even be generated in the epitaxial wafer, resulting in epitaxial wafer fragmentation. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a Micro-LED epitaxial wafer and a preparation method thereof, which can improve the luminous efficiency and wavelength uniformity of the Micro-LED.

[0004] Another technical problem to be solved by the present invention is to provide a Micro-LED with high luminous efficiency and good wavelength uniformity.

[0005] In order to solve the above problems, the present invention discloses a Micro-LED epitaxial wafer, which includes a substrate, a buffer layer, a first warp regulation layer, an undoped GaN layer, a second warp regulation layer, an N-type GaN layer, a third warp regulation layer, a multi-quantum well layer and a P-type GaN layer stacked in sequence on the substrate; the first warp regulation layer is a three-dimensional GaN layer, the second warp regulation layer includes an alternately stacked first Si-doped GaN layer and a Si-doped AlGaN layer, the third warp regulation layer includes a Si-doped AlInGaN layer and a superlattice layer stacked in sequence on the N-type GaN layer, and the superlattice layer includes an alternately stacked second Si-doped GaN layer and an InGaN layer.

[0006] As an improvement of the above technical solution, the number of periods of the second warpage regulating layer is 3 to 20, and the thickness thereof is 10 nm to 200 nm; The ratio of the thickness of the first Si-doped GaN layer to the thickness of the Si-doped AlGaN layer is 1:1-10:1; and the proportion of Al component in the Si-doped AlGaN layer is less than or equal to 0.2.

[0007] As an improvement of the above technical solution, the growth temperature of the second warp regulation layer is 50° C. to 200° C. lower than the growth temperature of the non-doped GaN layer.

[0008] As an improvement of the above technical solution, the Al component ratio in the Si-doped AlInGaN layer is ≤0.2, and the In component ratio is ≤0.1; The In component ratio in the InGaN layer is ≤0.15; The lattice constant of the Si-doped AlInGaN layer is greater than the lattice constant of the N-type GaN layer, and the lattice constant of the Si-doped AlInGaN layer is smaller than the lattice constant of the InGaN layer.

[0009] As an improvement of the above technical solution, the growth temperature of the third warpage regulating layer is 50° C. to 200° C. lower than the growth temperature of the N-type GaN layer.

[0010] As an improvement of the above technical solution, the thickness of the first warpage regulating layer is 10nm~100nm; The number of periods of the second warpage control layer is 5-20, and the thickness thereof is 100nm-200nm; the Si doping concentration of the first Si-doped GaN layer is 1×10 17 cm -3 ~1×10 19 cm -3 The Si doping concentration of the Si-doped AlGaN layer is 1×10 17 cm -3 ~1×10 19 cm -3 , the Al component accounts for 0.1~0.15; The Si-doped AlInGaN layer has an Al component ratio of 0.01-0.2, an In component ratio of 0.01-0.1, a thickness of 10 nm-100 nm, and a Si doping concentration of 1×10 17 cm -3 ~1×10 19 cm -3 ; The period number of the superlattice layer is 3 to 15, the thickness of the second Si-doped GaN layer is 5 nm to 15 nm, and the Si doping concentration is 1×10 17 cm -3 ~1×10 19 cm -3; The thickness of the InGaN layer is 1nm~8nm, and its In component ratio is 0.01~0.1.

[0011] Correspondingly, the present invention also discloses a method for preparing a Micro-LED epitaxial wafer, which is used to prepare the above-mentioned Micro-LED epitaxial wafer, and comprises: Providing a substrate, and sequentially growing a buffer layer, a first warp regulation layer, a non-doped GaN layer, a second warp regulation layer, an N-type GaN layer, a third warp regulation layer, a multi-quantum well layer, and a P-type GaN layer on the substrate; Among them, the first warp regulation layer is a three-dimensional GaN layer, the second warp regulation layer includes a first Si-doped GaN layer and a Si-doped AlGaN layer alternately stacked, the third warp regulation layer includes a Si-doped AlInGaN layer and a superlattice layer sequentially stacked on the N-type GaN layer, and the superlattice layer includes a second Si-doped GaN layer and an InGaN layer alternately stacked.

[0012] As an improvement of the above technical solution, after the growth of the buffer layer is completed, heat treatment is performed at 1000° C. to 1100° C. in an atmosphere of the first mixed gas; The first mixed gas is a mixed gas of N2, H2 and NH3, and the volume ratio of N2, H2 and NH3 is 1:(1-20):(1-10).

[0013] As an improvement of the above technical solution, the growth temperature of the first warpage regulating layer is 800° C. to 900° C., the growth atmosphere is a second mixed gas, the second mixed gas is a mixed gas of N2, H2 and NH3, and the volume ratio of N2, H2 and NH3 is 1: (1-20): (1-10); The growth temperature of the second warpage regulating layer is 950° C. to 1050° C., and the growth atmosphere is a third mixed gas, wherein the third mixed gas is a mixed gas of N2, H2, and NH3, and the volume ratio of N2, H2, and NH3 is 1:(1-20):(1-10); The growth temperature of the third warp regulation layer is 800° C. to 1000° C., the growth atmosphere is a fourth mixed gas, the fourth mixed gas is a mixed gas of N2 and NH3, and the volume ratio of N2 to NH3 is 1:1 to 1:10.

[0014] Correspondingly, the present invention also discloses a Micro-LED, which includes the above-mentioned Micro-LED epitaxial wafer.

[0015] The implementation of the present invention has the following beneficial effects: The Micro-LED epitaxial wafer in one embodiment of the present invention includes a substrate, a buffer layer, a first warp regulation layer, an undoped GaN layer, a second warp regulation layer, an N-type GaN layer, a third warp regulation layer, a multi-quantum well layer and a P-type GaN layer stacked on the substrate in sequence; the first warp regulation layer is a three-dimensional GaN layer, and the dislocation can be released through the three-dimensional structure to reduce the dislocation density. The second warp regulation layer includes an alternately stacked first Si-doped GaN layer and a Si-doped AlGaN layer, which can introduce compressive stress, balance the tensile stress caused by the cooling process, reduce the amount of wafer warpage, and improve the luminous efficiency and wavelength uniformity. At the same time, since the dislocation density is greatly reduced by the first warp regulation layer and the undoped GaN layer, the compressive stress in the second warp regulation layer is not relaxed by the dislocation and can be accumulated, thereby playing the effect of balancing the tensile stress in the subsequent cooling process. The third warp regulation layer includes a Si-doped AlInGaN layer and a superlattice layer stacked in sequence on the N-type GaN layer, and the superlattice layer includes an alternately stacked second Si-doped GaN layer and an InGaN layer. Among them, the Si-doped AlInGaN layer can not only further reduce the dislocation density, but also raise the energy band, allowing electrons to enter the multi-quantum well layer more evenly and recombine with holes, improving the wavelength uniformity and luminous efficiency. The superlattice layer realizes the transition between the previous layers and the multi-quantum well layer, further reducing the dislocation density entering the multi-quantum well layer, improving its crystal quality, and improving the wavelength uniformity and luminous efficiency of Micro-LED. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of a Micro-LED epitaxial wafer in one embodiment of the present invention; Figure 2 It is a flow chart of a method for preparing a Micro-LED epitaxial wafer in one embodiment of the present invention. DETAILED DESCRIPTION

[0017] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation or embodiment, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0019] See also Figure 1 As a first aspect, the present invention discloses a Micro-LED epitaxial wafer, which includes a substrate 100, a buffer layer 200, a first warp regulation layer 300, an undoped GaN layer 400, a second warp regulation layer 500, an N-type GaN layer 600, a third warp regulation layer 700, a multi-quantum well layer 800 and a P-type GaN layer 900 stacked in sequence on the substrate.

[0020] Among them, the first warp control layer 300 is a three-dimensional GaN layer, the second warp control layer 500 includes a first Si-doped GaN layer 510 and a Si-doped AlGaN layer 520 alternately stacked, and the third warp control layer includes a Si-doped AlInGaN layer 710 and a superlattice layer 720 sequentially stacked on the N-type GaN layer 600, and the superlattice layer 720 includes a second Si-doped GaN layer 721 and an InGaN layer 722 alternately stacked.

[0021] Among them, the first warpage control layer 300 is a three-dimensional GaN layer, which can release dislocations and reduce dislocation density through a three-dimensional structure. The second warpage control layer 500 can introduce compressive stress to balance the tensile stress caused by the cooling process, reduce the amount of wafer warpage, and improve the luminous efficiency and wavelength uniformity. At the same time, since the dislocation density is greatly reduced by the first warpage control layer 300 and the undoped GaN layer 400, the compressive stress in the second warpage control layer 500 is not relaxed by dislocations and can be accumulated, thereby balancing the tensile stress in the subsequent cooling process. The Si-doped AlInGaN layer 710 can not only further reduce the dislocation density, but also pull up the energy band, so that electrons can more evenly enter the multi-quantum well layer 800 to recombine with holes, thereby improving the wavelength uniformity and luminous efficiency. The superlattice layer 720 realizes the transition between the previous layers and the multi-quantum well layer 800, further reduces the dislocation density entering the multi-quantum well layer 800, improves its crystal quality, and improves the luminous efficiency and wavelength uniformity of the Micro-LED.

[0022] Specifically, in some embodiments, the thickness of the first warpage regulating layer 300 is 10 nm to 200 nm, exemplarily 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 120 nm, 140 nm, 160 nm or 180 nm, but not limited thereto, preferably 10 nm to 100 nm.

[0023] Specifically, in some embodiments, the number of periods of the second warpage regulating layer 500 is 2 to 20, exemplarily 4, 6, 8, 10, 12, 14, 16 or 18, but not limited thereto. Preferably, it is 3 to 20, and more preferably, it is 5 to 20. The thickness of the second warpage regulating layer 500 is 10 nm to 500 nm, exemplarily 80 nm, 150 nm, 220 nm, 290 nm, 360 nm or 430 nm, but not limited thereto.

[0024] Specifically, in some embodiments, the thickness of the first Si-doped GaN layer 510 is greater than or equal to the thickness of the Si-doped AlGaN layer 520 to accumulate more compressive stress. More specifically, the ratio of the thickness of the first Si-doped GaN layer 510 to the thickness of the Si-doped AlGaN layer 520 is 1:1 to 12:1, exemplarily 2:1, 4:1, 6:1, 8:1 or 11:1, but not limited thereto.

[0025] Specifically, in some embodiments, the Al component ratio in the Si-doped AlGaN layer 520 is ≤0.3. Based on the control of the Al component, the generation of dislocations can be reduced while increasing the accumulation of compressive stress. It should be noted that the compressive stress accumulated in the second warpage control layer 500 mainly comes from the lattice mismatch between the Si-doped AlGaN layer 520 and the first Si-doped GaN layer 510. However, when the lattice mismatch is too large, new dislocations are easily formed, which will reduce the luminous efficiency.

[0026] Specifically, the Si doping concentration in the first Si-doped GaN layer 510 is 1×10 17 cm -3 ~5×10 19 cm -3 ; exemplarily 3×10 17 cm -3 ,7×10 17 cm -3 , 1×10 18 cm -3 , 5×10 18 cm -3 ,9×10 18 cm -3 or 3×10 19 cm -3 , but not limited thereto. Preferably 1×10 17 cm -3~1×10 19 cm -3 .

[0027] Specifically, in some embodiments, the Si doping concentration in the Si-doped AlGaN layer 520 is 1×10 17 cm -3 ~5×10 19 cm -3 ; exemplarily 3×10 17 cm -3 ,7×10 17 cm -3 , 1×10 18 cm -3 , 5×10 18 cm -3 ,9×10 18 cm -3 or 3×10 19 cm -3 , but not limited thereto. Preferably 1×10 17 cm -3 ~1×10 19 cm -3 .

[0028] Preferably, in some embodiments of the present invention, the number of cycles of the second warpage control layer 500 is 3 to 20, and its thickness is 10 nm to 200 nm; the ratio of the thickness of the first Si-doped GaN layer 510 to the thickness of the Si-doped AlGaN layer 520 is 1:1 to 10:1; the Al component ratio in the Si-doped AlGaN layer 520 is ≤ 0.2. Based on this technical solution, the accumulation of compressive stress can be greatly improved, the amount of wafer warpage can be reduced, and the luminous efficiency and wavelength uniformity can be improved.

[0029] Specifically, in some embodiments, the Al component ratio in the Si-doped AlInGaN layer 710 is ≤0.2, and the In component ratio is ≤0.15, so that the lattice constant of the Si-doped AlInGaN layer 710 is greater than the lattice constant of the N-type GaN layer 600, thereby reducing the lattice mismatch between the N-type GaN layer 600 and the multi-quantum well layer 800. Preferably, the Al component ratio in the Si-doped AlInGaN layer 710 is 0.01-0.2, exemplarily 0.02, 0.08, 0.14 or 0.2, but not limited thereto, and more preferably 0.05-0.2. Preferably, the In component ratio in the Si-doped AlInGaN layer 710 is 0.01-0.15, exemplarily 0.03, 0.08, 0.12 or 0.13, but not limited thereto. Preferably 0.01-0.1.

[0030] Specifically, in some embodiments, the thickness of the Si-doped AlInGaN layer 710 is 10 nm to 120 nm, exemplarily 20 nm, 40 nm, 60 nm, 80 nm, 100 nm or 110 nm, but not limited thereto, preferably 10 nm to 100 nm.

[0031] Specifically, in some embodiments, the Si doping concentration in the Si-doped AlInGaN layer 710 is 1×10 17 cm -3 ~5×10 19 cm -3 ; exemplarily 3×10 17 cm -3 ,7×10 17 cm -3 , 1×10 18 cm -3 , 5×10 18 cm -3 ,9×10 18 cm -3 or 3×10 19 cm -3 , but not limited thereto. Preferably 1×10 17 cm -3 ~1×10 19 cm -3 .

[0032] Specifically, in some embodiments, the number of periods of the superlattice layer 720 is 3-20, exemplarily 4, 6, 8, 10, 12, 14, 16 or 18, but not limited thereto, preferably 3-15.

[0033] Specifically, in some embodiments, the thickness of the second Si-doped GaN layer 721 is 3 nm to 15 nm, exemplarily 4 nm, 7 nm, 10 nm, 12 nm or 14 nm, but not limited thereto, preferably 5 nm to 15 nm.

[0034] Specifically, in some embodiments, the Si doping concentration in the second Si-doped GaN layer 721 is 1×10 17 cm -3 ~5×10 19 cm -3 ; exemplarily 3×10 17 cm -3 ,7×10 17 cm -3 , 1×10 18 cm -3 , 5×10 18 cm -3 ,9×10 18 cm-3 or 3×10 19 cm -3 , but not limited thereto. Preferably 1×10 17 cm -3 ~1×10 19 cm -3 .

[0035] Specifically, in some embodiments, the thickness of the InGaN layer 722 is 1 nm to 10 nm, exemplarily 3 nm, 5 nm, 7 nm or 9 nm, but not limited thereto, preferably 1 nm to 8 nm, and more preferably 2 nm to 5 nm.

[0036] Specifically, the In component ratio in the InGaN layer 722 is 0.01-0.15, exemplarily 0.03, 0.05, 0.07, 0.09, 0.11 or 0.13, but not limited thereto, preferably 0.01-0.1.

[0037] Preferably, in some embodiments, the Al component ratio in the Si-doped AlInGaN layer 710 is ≤0.2, and the In component ratio is ≤0.1; the In component ratio in the InGaN layer 722 is ≤0.15; based on the above-mentioned component control, the lattice constant of the Si-doped AlInGaN layer 710 can be made greater than the lattice constant of the N-type GaN layer 600, and smaller than the lattice constant of the InGaN layer 722, thereby further reducing the dislocation density in the multi-quantum well layer 800 and improving the luminescence efficiency.

[0038] Specifically, in some embodiments, the substrate 100 may be a sapphire substrate or a silicon substrate, but is not limited thereto. Preferably, it is a sapphire substrate.

[0039] Specifically, in some embodiments, the buffer layer 200 is an AlN layer, a GaN layer or an AlGaN layer, but is not limited thereto. Preferably, it is an AlN layer. The thickness of the buffer layer 200 is 10nm to 50nm, preferably 20nm to 50nm. It should be noted that the thickness of the buffer layer 200 in the present invention refers to the thickness of the buffer layer 200 after high temperature annealing.

[0040] Specifically, in some embodiments, the thickness of the undoped GaN layer 400 is 1 μm to 3 μm.

[0041] Specifically, in some embodiments, the thickness of the N-type GaN layer 600 is 1 μm to 5 μm, and the Si doping concentration is 5×10 18 cm -3 ~5×10 19 cm -3 .

[0042] Specifically, in some embodiments, the multi-quantum well layer 800 includes alternately stacked InGaN quantum well layers and GaN quantum barrier layers, the thickness of the InGaN quantum well layer is 3nm~5nm, the In component ratio is 0.15~0.45, and the thickness of the GaN quantum barrier layer is 8nm~20nm.

[0043] Specifically, in some embodiments, the thickness of the P-type GaN layer 900 is 50 nm to 200 nm, and the Mg doping concentration is 1×10 19 cm -3 ~5×10 20 cm -3 .

[0044] See also Figure 2 As a second aspect, the present invention discloses a method for preparing a Micro-LED epitaxial wafer, which is used to prepare the above-mentioned Micro-LED epitaxial wafer, and specifically includes: S1: providing a substrate; S2: sequentially growing a buffer layer, a first warpage control layer, a non-doped GaN layer, a second warpage control layer, an N-type GaN layer, a third warpage control layer, a multi-quantum well layer and a P-type GaN layer on the substrate; Specifically, the first warp control layer is a three-dimensional GaN layer, which can release dislocations and reduce dislocation density through a three-dimensional structure. The second warp control layer includes an alternately stacked first Si-doped GaN layer and a Si-doped AlGaN layer, which can introduce compressive stress, balance the tensile stress caused by the cooling process, reduce the amount of wafer warpage, and improve luminous efficiency and wavelength uniformity. At the same time, since the dislocation density is greatly reduced by the first warp control layer and the undoped GaN layer, the compressive stress in the second warp control layer is not relaxed by the dislocation and can be accumulated, thereby balancing the tensile stress in the subsequent cooling process. The third warp control layer includes a Si-doped AlInGaN layer and a superlattice layer stacked sequentially on the N-type GaN layer, and the superlattice layer includes an alternately stacked second Si-doped GaN layer and an InGaN layer. Among them, the Si-doped AlInGaN layer can not only further reduce the dislocation density, but also pull up the energy band, so that electrons enter the multi-quantum well layer more evenly and recombine with holes, thereby improving wavelength uniformity and luminous efficiency. The superlattice layer realizes the transition between the previous layers and the multi-quantum well layer, further reducing the dislocation density entering the multi-quantum well layer, improving its crystal quality, and enhancing the luminous efficiency and wavelength uniformity of the Micro-LED.

[0045] Specifically, in some embodiments, step S2 includes the following steps: S21: growing a buffer layer on the substrate; Specifically, in some embodiments, one or more of an AlN layer, a GaN layer, and an AlGaN layer may be grown by PVD, MOCVD, or MBE as a buffer layer, but is not limited thereto.

[0046] Preferably, in one embodiment, an AlN layer is grown by PVD as a buffer layer.

[0047] More preferably, in one embodiment, after the growth of the buffer layer is completed, heat treatment is performed at 1000°C~1100°C in an atmosphere of a first mixed gas; wherein the first mixed gas is a mixed gas of N2, H2 and NH3, and the volume ratio of N2, H2 and NH3 is 1:(1~20):(1~10). Since the crystal quality of the buffer layer itself is poor, usually in a polycrystalline or amorphous state, the crystal quality can be improved through the above-mentioned first mixed gas atmosphere and high temperature treatment, and the buffer layer can also be partially decomposed to reduce the stress on the substrate.

[0048] S22: growing a first warpage regulating layer on the buffer layer; Specifically, in some embodiments, a three-dimensional GaN layer is grown by MOCVD as the first warp control layer, and its growth temperature is 800°C to 900°C, and the growth atmosphere is a second mixed gas, which is a mixed gas of N2, H2 and NH3, and the volume ratio of N2, H2 and NH3 is 1: (1 to 20): (1 to 10). Based on the above-mentioned lower growth temperature and growth atmosphere, the first warp control layer tends to grow in a three-dimensional form, thereby achieving the purpose of reducing the dislocation density.

[0049] S23: growing a non-doped GaN layer on the first warpage regulating layer; Specifically, in some embodiments, the undoped GaN layer is grown by MOCVD, and the growth temperature is 950° C. to 1100° C. and the growth pressure is 50 torr to 500 torr.

[0050] S24: growing a second warpage regulating layer on the non-doped GaN layer; Specifically, in some embodiments, a first Si-doped GaN layer and a Si-doped AlGaN layer are periodically grown by MOCVD until a second warpage control layer is obtained. The growth temperature of the second warpage control layer is 950°C to 1050°C, and the growth atmosphere is a third mixed gas, which is a mixed gas of N2, H2, and NH3, and the volume ratio of N2, H2, and NH3 is 1: (1-20): (1-10).

[0051] Preferably, in some embodiments, the growth temperature of the second warp regulation layer is 50° C. to 200° C. lower than the growth temperature of the undoped GaN layer, which can effectively reduce the accumulation of thermal stress and improve the luminous efficiency and wavelength uniformity.

[0052] S25: growing an N-type GaN layer on the second warpage regulating layer; Specifically, in some embodiments, the N-type GaN layer is grown by MOCVD, and the growth temperature is 980° C. to 1150° C. and the growth pressure is 100 torr to 500 torr.

[0053] S26: growing a third warpage regulating layer on the N-type GaN layer; Specifically, in some embodiments, a Si-doped AlInGaN layer and a superlattice layer are sequentially grown by MOCVD to obtain a third warp control layer. The growth temperature of the third warp control layer is 800°C to 1000°C, and the growth atmosphere is a fourth mixed gas, which is a mixed gas of N2 and NH3, and the volume ratio of N2 to NH3 is 1: (1 to 10).

[0054] Preferably, in some embodiments, the growth temperature of the third warpage regulating layer is 50° C. to 200° C. lower than the growth temperature of the N-type GaN layer. Growing the third warpage regulating layer at a lower temperature is beneficial to further release thermal stress and improve luminous efficiency and wavelength uniformity.

[0055] S27: growing a multi-quantum well layer on the third warpage control layer; Specifically, in some embodiments, InGaN quantum well layers and GaN quantum barrier layers are periodically grown by MOCVD until a multi-quantum well layer is obtained, wherein the growth temperature of the InGaN quantum well layer is 730°C to 820°C, the growth pressure is 100 torr to 300 torr, and the growth temperature of the GaN quantum barrier layer is 850°C to 950°C, and the growth pressure is 100 torr to 300 torr.

[0056] S28: growing a P-type GaN layer on the multi-quantum well layer; Specifically, in some embodiments, the P-type GaN layer is grown by MOCVD, and the growth temperature is 900° C. to 1050° C. and the growth pressure is 100 torr to 500 torr.

[0057] As the third aspect of the present invention, the present invention also discloses a Micro-LED, which includes the above-mentioned Micro-LED epitaxial wafer, which also includes a transparent conductive layer, a passivation layer, an electrode, a reflective layer, etc. commonly used in the art, but is not limited thereto. The Micro-LED epitaxial wafer in the present invention includes a substrate, a buffer layer, a first warp regulation layer, an undoped GaN layer, a second warp regulation layer, an N-type GaN layer, a third warp regulation layer, a multi-quantum well layer, and a P-type GaN layer stacked on the substrate in sequence; the first warp regulation layer is a three-dimensional GaN layer, and the dislocation can be released through the three-dimensional structure to reduce the dislocation density. The second warp regulation layer includes an alternately stacked first Si-doped GaN layer and a Si-doped AlGaN layer, which can introduce compressive stress, balance the tensile stress caused by the cooling process, reduce the amount of wafer warpage, and improve the luminous efficiency and wavelength uniformity of the Micro-LED. At the same time, since the dislocation density is greatly reduced by the first warp regulation layer and the undoped GaN layer, the compressive stress in the second warp regulation layer is not relaxed by the dislocation, and can be accumulated, thereby playing the role of balancing the tensile stress in the subsequent cooling process. The third warp control layer includes a Si-doped AlInGaN layer and a superlattice layer stacked on the N-type GaN layer in sequence, and the superlattice layer includes a second Si-doped GaN layer and an InGaN layer stacked alternately. Among them, the Si-doped AlInGaN layer can not only further reduce the dislocation density, but also pull up the energy band, so that electrons can enter the multi-quantum well layer more evenly and recombine with holes, thereby improving the wavelength uniformity and luminous efficiency of the Micro-LED. The superlattice layer realizes the transition between the previous layers and the multi-quantum well layer, further reduces the dislocation density entering the multi-quantum well layer, improves its crystal quality, and improves the luminous efficiency and wavelength uniformity of the Micro-LED.

[0058] The present invention will be further described below with specific embodiments: Example 1 The present embodiment provides a Micro-LED epitaxial wafer, which includes a substrate, a buffer layer stacked sequentially on the substrate, a first warp regulation layer, an undoped GaN layer, a second warp regulation layer, an N-type GaN layer, a third warp regulation layer, a multi-quantum well layer and a P-type GaN layer.

[0059] The substrate is a sapphire substrate, the buffer layer is an AlN layer with a thickness of 25 nm, the first warpage control layer is a three-dimensional GaN layer with a thickness of 50 nm, and the thickness of the non-doped GaN layer is 2 μm.

[0060] The second warpage control layer is a periodic structure with 10 periods and a thickness of 240 nm. Each period includes a first Si-doped GaN layer and a Si-doped AlGaN layer stacked in sequence. The ratio of the thickness of the first Si-doped GaN layer to the thickness of the Si-doped AlGaN layer is 11:1. The Si doping concentration of the first Si-doped GaN layer is 3×1017 cm -3 The Si doping concentration of the Si-doped AlGaN layer is 3×10 17 cm -3 , and its Al component accounts for 0.25.

[0061] The thickness of the N-type GaN layer is 2 μm, and its Si doping concentration is 8.5×10 18 cm -3 .

[0062] The third warpage control layer includes a Si-doped AlInGaN layer and a superlattice layer stacked on the N-type GaN layer in sequence, and the superlattice layer includes a second Si-doped GaN layer and an InGaN layer stacked alternately. The In component ratio in the Si-doped AlInGaN layer is 0.14, the Al component ratio is 0.1, and the Si doping concentration is 3×10 18 cm -3 The number of periods of the superlattice layer is 10, and each period includes a second Si-doped GaN layer and an InGaN layer stacked in sequence, wherein the thickness of the second Si-doped GaN layer is 10 nm and the Si doping concentration is 5×10 18 cm -3 The thickness of the InGaN layer is 2nm, and the In component ratio is 0.04.

[0063] The multi-quantum well layer includes alternately stacked InGaN quantum well layers and GaN quantum barrier layers, with a period number of 10, a thickness of 3nm for the InGaN quantum well layer, a ratio of 0.18 for In component, and a thickness of 10nm for the GaN quantum barrier layer. The thickness of the P-type GaN layer is 80nm, and the Mg doping concentration is 1.5×10 20 cm -3 .

[0064] The method for preparing the Micro-LED epitaxial wafer in this embodiment includes the following steps: (1) Providing a substrate; (2) growing a buffer layer on the substrate; Specifically, an AlN layer is grown by PVD as a buffer layer.

[0065] (3) growing a first warpage control layer on the buffer layer; Specifically, a three-dimensional GaN layer is grown by MOCVD as the first warp control layer. The growth temperature is 850°C, the growth atmosphere is a second mixed gas, and the second mixed gas is a mixed gas of N2, H2 and NH3, and the volume ratio of N2, H2 and NH3 is 1:15:5.

[0066] (4) growing a non-doped GaN layer on the first warp control layer; Specifically, in some embodiments, the undoped GaN layer is grown by MOCVD at a growth temperature of 1020° C. and a growth pressure of 400 torr.

[0067] (5) growing a second warp control layer on the undoped GaN layer; Specifically, a first Si-doped GaN layer and a Si-doped AlGaN layer are periodically grown by MOCVD until a second warpage control layer is obtained. The growth temperature of the second warpage control layer is 1020°C, and the growth atmosphere is a third mixed gas, which is a mixed gas of N2, H2 and NH3, and the volume ratio of N2, H2 and NH3 is 1:10:8.

[0068] (6) growing an N-type GaN layer on the second warp control layer; Specifically, the N-type GaN layer is grown by MOCVD at a growth temperature of 1000° C. and a growth pressure of 300 torr.

[0069] (7) growing a third warp control layer on the N-type GaN layer; Specifically, a Si-doped AlInGaN layer and a superlattice layer are grown in sequence by MOCVD to obtain a third warp control layer. The growth temperature of the third warp control layer is 980°C, and the growth atmosphere is a fourth mixed gas, which is a mixed gas of N2 and NH3, and the volume ratio of N2 to NH3 is 1:5.

[0070] (8) growing a multi-quantum well layer on the third warp control layer; Specifically, InGaN quantum well layers and GaN quantum barrier layers are periodically grown by MOCVD until a multi-quantum well layer is obtained, wherein the growth temperature of the InGaN quantum well layer is 790°C and the growth pressure is 200 torr, and the growth temperature of the GaN quantum barrier layer is 920°C and the growth pressure is 200 torr.

[0071] (9) Growing a P-type GaN layer on the multi-quantum well layer; Specifically, the P-type GaN layer is grown by MOCVD at a growth temperature of 1030° C. and a growth pressure of 200 torr.

[0072] Example 2 This embodiment provides a Micro-LED epitaxial wafer, which is different from the embodiment 1 in that: The thickness of the second warp control layer is 150nm, the ratio of the thickness of the first Si-doped GaN layer to the thickness of the Si-doped AlGaN layer is 5:1; the proportion of Al component in the Si-doped AlGaN layer is 0.12.

[0073] The rest are the same as in Example 1.

[0074] Example 3 This embodiment provides a Micro-LED epitaxial wafer, which is different from Embodiment 2 in that: The In component ratio in the Si-doped AlInGaN layer is 0.08, and the Al component ratio is 0.12. The In component ratio in the InGaN layer is 0.08.

[0075] The rest is the same as Example 2.

[0076] Example 4 This embodiment provides a Micro-LED epitaxial wafer, which is different from the embodiment 3 in that: After the growth of the buffer layer is completed, a heat treatment is performed at 1050° C. for 3 minutes in an atmosphere of a first mixed gas, wherein the first mixed gas is a mixed gas of N2, H2, and NH3, and the volume ratio of N2, H2, and NH3 is 1:6:8.

[0077] The rest is the same as Example 3.

[0078] Example 5 This embodiment provides a Micro-LED epitaxial wafer, which is different from the embodiment 4 in that: The growth temperature of the second warpage regulating layer is 960°C.

[0079] The rest are the same as in Example 4.

[0080] Example 6 This embodiment provides a Micro-LED epitaxial wafer, which is different from Embodiment 5 in that: The growth temperature of the third warpage regulating layer is 880°C.

[0081] The rest are the same as in Example 5.

[0082] Comparative Example 1 This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that: The first warp regulating layer, the second warp regulating layer and the third warp regulating layer are not included.

[0083] The rest are the same as in Example 1.

[0084] Comparative Example 2 This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that: The first warpage regulating layer is not included, and the rest is the same as in Example 1.

[0085] Comparative Example 3 This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that: The first warpage regulating layer and the second warpage regulating layer are not included, and the rest are the same as in Example 1.

[0086] Comparative Example 4 This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that: The third warpage regulating layer is not included, and the rest is the same as in Example 1.

[0087] The Micro-LED epitaxial wafers obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were prepared into 3mil×5mil chips, and the luminous brightness and wavelength uniformity (PL-WD std) were measured at 2mA. The specific data are shown in the following table:

[0088] It can be seen from the table that the Micro-LED epitaxial wafer in the embodiment of the present invention effectively improves the luminous efficiency and wavelength uniformity of the light-emitting diode.

[0089] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A Micro-LED epitaxial wafer, characterized in that: The invention comprises a substrate, a buffer layer, a first warp regulation layer, an undoped GaN layer, a second warp regulation layer, an N-type GaN layer, a third warp regulation layer, a multi-quantum well layer and a P-type GaN layer sequentially stacked on the substrate; the first warp regulation layer is a three-dimensional GaN layer, the second warp regulation layer comprises a first Si-doped GaN layer and a Si-doped AlGaN layer alternately stacked, the third warp regulation layer comprises a Si-doped AlInGaN layer and a superlattice layer sequentially stacked on the N-type GaN layer, and the superlattice layer comprises a second Si-doped GaN layer and an InGaN layer alternately stacked.

2. The Micro-LED epitaxial wafer according to claim 1, characterized in that: The second warpage regulating layer has a period number of 3 to 20 and a thickness of 10 nm to 200 nm; The ratio of the thickness of the first Si-doped GaN layer to the thickness of the Si-doped AlGaN layer is 1:1-10:1; and the proportion of Al component in the Si-doped AlGaN layer is less than or equal to 0.

2.

3. The Micro-LED epitaxial wafer according to claim 1, characterized in that: The growth temperature of the second warpage regulating layer is 50° C. to 200° C. lower than the growth temperature of the undoped GaN layer.

4. The Micro-LED epitaxial wafer according to claim 1, wherein: The Al component ratio in the Si-doped AlInGaN layer is ≤0.2, and the In component ratio is ≤0.1; The In component ratio in the InGaN layer is ≤0.15; The lattice constant of the Si-doped AlInGaN layer is greater than the lattice constant of the N-type GaN layer, and the lattice constant of the Si-doped AlInGaN layer is smaller than the lattice constant of the InGaN layer.

5. The Micro-LED epitaxial wafer according to claim 1, wherein: The growth temperature of the third warpage regulating layer is 50° C. to 200° C. lower than the growth temperature of the N-type GaN layer.

6. The Micro-LED epitaxial wafer according to any one of claims 1 to 5, characterized in that: The thickness of the first warpage regulating layer is 10nm~100nm; The number of periods of the second warpage control layer is 5-20, and the thickness thereof is 100nm-200nm; the Si doping concentration of the first Si-doped GaN layer is 1×10 17 cm -3 ~1×10 19 cm -3 The Si doping concentration of the Si-doped AlGaN layer is 1×10 17 cm -3 ~1×10 19 cm -3 , the Al component accounts for 0.1~0.15; The Si-doped AlInGaN layer has an Al component ratio of 0.01-0.2, an In component ratio of 0.01-0.1, a thickness of 10 nm-100 nm, and a Si doping concentration of 1×10 17 cm -3 ~1×10 19 cm -3 ; The period number of the superlattice layer is 3 to 15, the thickness of the second Si-doped GaN layer is 5 nm to 15 nm, and the Si doping concentration is 1×10 17 cm -3 ~1×10 19 cm -3 ; The thickness of the InGaN layer is 1nm~8nm, and its In component ratio is 0.01~0.

1.

7. A method for preparing a Micro-LED epitaxial wafer, for preparing the Micro-LED epitaxial wafer according to any one of claims 1 to 6, characterized in that: include: Providing a substrate, and sequentially growing a buffer layer, a first warp regulation layer, a non-doped GaN layer, a second warp regulation layer, an N-type GaN layer, a third warp regulation layer, a multi-quantum well layer, and a P-type GaN layer on the substrate; Among them, the first warp regulation layer is a three-dimensional GaN layer, the second warp regulation layer includes a first Si-doped GaN layer and a Si-doped AlGaN layer alternately stacked, the third warp regulation layer includes a Si-doped AlInGaN layer and a superlattice layer sequentially stacked on the N-type GaN layer, and the superlattice layer includes a second Si-doped GaN layer and an InGaN layer alternately stacked.

8. The method for preparing a Micro-LED epitaxial wafer according to claim 7, wherein: After the growth of the buffer layer is completed, heat treatment is performed at 1000° C. to 1100° C. in an atmosphere of the first mixed gas; Wherein, the first mixed gas is a mixed gas of N2, H2 and NH3.

9. The method for preparing a Micro-LED epitaxial wafer according to claim 7, wherein: The growth temperature of the first warpage regulating layer is 800° C. to 900° C., and the growth atmosphere is a second mixed gas, which is a mixed gas of N2, H2 and NH3; The growth temperature of the second warpage regulating layer is 950° C. to 1050° C., and the growth atmosphere is a third mixed gas, and the third mixed gas is a mixed gas of N2, H2 and NH3; The growth temperature of the third warp regulation layer is 800° C. to 1000° C., the growth atmosphere is a fourth mixed gas, the fourth mixed gas is a mixed gas of N2 and NH3, and the volume ratio of N2 to NH3 is 1:1 to 1:

10.

10. A Micro-LED, characterized in that: Comprising the Micro-LED epitaxial wafer as described in any one of claims 1 to 6.

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