Micro-LED Epitaxial Wafer, Its Preparation Method, and Micro-LED

Abstract

The present invention discloses a Micro-LED epitaxial wafer, a preparation method thereof, and a Micro-LED, relating to the field of semiconductor optoelectronic devices. Among them, the Micro-LED epitaxial wafer sequentially includes a substrate, a buffer layer, a first warpage control layer, an undoped 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; the first warpage control layer is a three-dimensional GaN layer, the second warpage control layer includes an alternately stacked first Si-doped GaN layer and a Si-doped AlGaN layer, the third warpage control layer includes a Si-doped AlInGaN layer and a superlattice layer sequentially stacked on the N-type GaN layer, and the superlattice layer includes an alternately stacked second Si-doped GaN layer and an InGaN layer. Implementing the present invention can improve the light-emitting efficiency and wavelength uniformity of the Micro-LED.

Description

Technical Field

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

[0002] Micro-LED is a new generation of display technology solution following LCD, OLED, and Mini-LED. It has many advantages such as high brightness, high display density, high color gamut, and low power consumption, and is a current frontier research direction of 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. The large lattice mismatch will cause dislocations with a density of about 10 8 cm -3 to be generated in the GaN-based epitaxial material. These dislocations can act as non-radiative recombination centers, causing carriers to be trapped by defects and reducing the light emission efficiency of Micro-LED. The large thermal mismatch causes huge stress in the epitaxial layer during the cooling process of the epitaxial wafer, resulting in very poor WD std (wavelength uniformity) of the epitaxial wafer. In severe cases, a large number of cracks will even be generated in the epitaxial wafer, leading to fragmentation of the epitaxial wafer. 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 light emission efficiency and wavelength uniformity of Micro-LED.

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

[0005] To solve the above problems, the present invention discloses a Micro-LED epitaxial wafer, which includes a substrate, a buffer layer, a first warpage control layer, an undoped 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 that are sequentially stacked on the substrate; the first warpage control layer is a three-dimensional GaN layer, the second warpage control layer includes an alternately stacked first Si-doped GaN layer and a Si-doped AlGaN layer, the third warpage control layer includes a Si-doped AlInGaN layer and a superlattice layer that are sequentially stacked 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 control layer is 3 to 20, and its thickness is 10 nm to 200 nm;

[0007] The ratio of the thickness of the first Si-doped GaN layer to the thickness of the Si-doped AlGaN layer is 1:1 to 10:1; the proportion of the Al component in the Si-doped AlGaN layer is less than or equal to 0.2.

[0008] As an improvement to the above technical solution, the growth temperature of the second warpage control layer is 50 °C to 200 °C lower than the growth temperature of the undoped GaN layer.

[0009] As an improvement to the above technical solution, the proportion of the Al component in the Si-doped AlInGaN layer is ≤0.2, and the proportion of the In component is ≤0.1;

[0010] The proportion of the In component in the InGaN layer is ≤0.15;

[0011] 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 less than the lattice constant of the InGaN layer.

[0012] As an improvement to the above technical solution, the growth temperature of the third warpage control layer is 50 °C to 200 °C lower than the growth temperature of the N-type GaN layer.

[0013] As an improvement to the above technical solution, the thickness of the first warpage control layer is 10 nm to 100 nm;

[0014] The number of periods of the second warpage control layer is 5 to 20, and its thickness is 100 nm to 200 nm; 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 , and the proportion of its Al component is 0.1 to 0.15;

[0015] The proportion of the Al component in the Si-doped AlInGaN layer is 0.01 to 0.2, the proportion of the In component is 0.01 to 0.1, its thickness is 10 nm to 100 nm, and the Si doping concentration is 1×10 17 cm -3 ~1×10 19 cm -3 ;

[0016] The number of periods of the superlattice layer is 3 to 15, the thickness of the second Si-doped GaN layer is 5 nm to 15 nm, and its Si doping concentration is 1×10 17 cm-3 ~1×10 19 cm -3 ; The thickness of the InGaN layer is 1 nm to 8 nm, and the In component ratio is 0.01 to 0.1.

[0017] Correspondingly, the present invention also discloses a method for preparing a Micro-LED epitaxial wafer for preparing the above-mentioned Micro-LED epitaxial wafer, which includes:

[0018] Providing a substrate, and sequentially growing a buffer layer, a first warpage control layer, an undoped 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;

[0019] Among them, the first warpage control layer is a three-dimensional GaN layer, the second warpage control layer includes an alternately stacked first Si-doped GaN layer and a Si-doped AlGaN layer, the third warpage control layer includes a Si-doped AlInGaN layer and a superlattice layer sequentially stacked on the N-type GaN layer, and the superlattice layer includes an alternately stacked second Si-doped GaN layer and an InGaN layer.

[0020] As an improvement of the above technical solution, after the growth of the buffer layer, heat treatment is performed at 1000 °C to 1100 °C in an atmosphere of a first mixed gas;

[0021] Among them, the first mixed gas is a mixed gas of N 2 , H 2 , and NH 3 , and the volume ratio of N 2 , H 2 , and NH 3 is 1:(1 to 20):(1 to 10).

[0022] As an improvement of the above technical solution, the growth temperature of the first warpage control layer is 800 °C to 900 °C, and the growth atmosphere is a second mixed gas. The second mixed gas is a mixed gas of N 2 , H 2 , and NH 3 , and the volume ratio of N 2 , H 2 , and NH 3 is 1:(1 to 20):(1 to 10);

[0023] The growth temperature of the second warpage control layer is 950 °C to 1050 °C, and the growth atmosphere is a third mixed gas. The third mixed gas is a mixed gas of N 2 , H 2 , and NH 3 , and the volume ratio of N 2 , H 2and NH 3 The volume ratio thereof is 1:(1 - 20):(1 - 10);

[0024] The growth temperature of the third warpage control layer is 800°C - 1000°C, and the growth atmosphere is a fourth mixed gas, and the fourth mixed gas is N 2 and NH 3 mixed gas, and the volume ratio of N 2 and NH 3 is 1:1 - 1:10.

[0025] Correspondingly, the present invention also discloses a Micro-LED, which includes the above-mentioned Micro-LED epitaxial wafer.

[0026] Implementing the present invention has the following beneficial effects:

[0027] The Micro-LED epitaxial wafer in an embodiment of the present invention includes a substrate, a buffer layer, a first warpage control layer, an undoped 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 that are sequentially stacked on the substrate; the first warpage control layer is a three-dimensional GaN layer, and dislocations can be released through the three-dimensional structure to reduce the dislocation density. The second warpage control layer includes alternately stacked first Si-doped GaN layers and Si-doped AlGaN layers, which can introduce compressive stress to balance the tensile stress brought by the cooling process, reduce the wafer warpage amount, and improve the light emission efficiency and wavelength uniformity. At the same time, since the dislocation density is greatly reduced by the first warpage control layer and the undoped GaN layer, the compressive stress in the second warpage control layer is not relaxed by dislocations and can be accumulated, thereby playing a role in balancing the tensile stress during the subsequent cooling process. The third warpage control layer includes a Si-doped AlInGaN layer and a superlattice layer that are sequentially stacked on the N-type GaN layer, and the superlattice layer includes alternately stacked second Si-doped GaN layers and InGaN layers. 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 uniformly to recombine with holes, improving the wavelength uniformity and light emission 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 wavelength uniformity and light emission efficiency of the Micro-LED. Description of the Drawings

[0028] Figure 1 is a schematic structural diagram of a Micro-LED epitaxial wafer in an embodiment of the present invention;

[0029] Figure 2 is a flowchart of a preparation method of a Micro-LED epitaxial wafer in an embodiment of the present invention. Detailed Embodiments

[0030] For ease of understanding 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, these embodiments or examples are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments or examples 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 the related listed items, and the any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items.

[0032] See 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 warpage control layer 300, an undoped GaN layer 400, a second warpage control layer 500, an N-type GaN layer 600, a third warpage control layer 700, a multi-quantum well layer 800, and a P-type GaN layer 900, which are sequentially stacked on the substrate.

[0033] Among them, the first warpage control layer 300 is a three-dimensional GaN layer, the second warpage control layer 500 includes an alternately stacked first Si-doped GaN layer 510 and a Si-doped AlGaN layer 520, the third warpage 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 an alternately stacked second Si-doped GaN layer 721 and an InGaN layer 722.

[0034] Among them, the first warpage control layer 300 is a three-dimensional GaN layer, and the three-dimensional structure can release dislocations and reduce the dislocation density. The second warpage control layer 500 can introduce compressive stress to balance the tensile stress brought by the cooling process, reduce the wafer warpage amount, and improve the light emission 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, thus playing the role of balancing the tensile stress during 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, enabling electrons to enter the multi-quantum well layer 800 more uniformly to recombine with holes, improving the wavelength uniformity and light emission efficiency. The superlattice layer 720 realizes the transition between the previous layers and the multi-quantum well layer 800, further reducing the dislocation density entering the multi-quantum well layer 800, improving its crystal quality, and enhancing the light emission efficiency and wavelength uniformity of the Micro-LED.

[0035] Specifically, in some embodiments, the thickness of the first warpage control 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, it is 10 nm to 100 nm.

[0036] Specifically, in some embodiments, the number of periods of the second warpage control 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 5 to 20. The thickness of the second warpage control 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.

[0037] Specifically, in some embodiments, the thickness of the first Si-doped GaN layer 510 ≥ 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.

[0038] 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.

[0039] 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 .

[0040] 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 .

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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。

[0045] Specifically, in some embodiments, the number of periods of the superlattice layer 720 is 3 to 20, exemplarily 4, 6, 8, 10, 12, 14, 16, or 18, but not limited thereto. Preferably, it is 3 to 15.

[0046] 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, it is 5 nm to 15 nm.

[0047] 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, it is 1×10 17 cm -3 ~1×10 19 cm -3 。

[0048] 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, it is 1 nm to 8 nm, and more preferably 2 nm to 5 nm.

[0049] Specifically, the In component ratio in the InGaN layer 722 is 0.01 to 0.15, exemplarily 0.03, 0.05, 0.07, 0.09, 0.11, or 0.13, but not limited thereto. Preferably, it is 0.01 to 0.1.

[0050] Preferably, in some embodiments, the proportion of Al component in the Si-doped AlInGaN layer 710 is ≤0.2, and the proportion of In component is ≤0.1; the proportion of In component in the InGaN layer 722 is ≤0.15; based on the above component control, the lattice constant of the Si-doped AlInGaN layer 710 can be made larger than that of the N-type GaN layer 600 and smaller than that of the InGaN layer 722, so as to further reduce the dislocation density in the multi-quantum well layer 800 and improve the light-emitting efficiency.

[0051] Specifically, in some embodiments, the substrate 100 can be a sapphire substrate or a silicon substrate, but is not limited thereto. Preferably, it is a sapphire substrate.

[0052] 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 10 nm to 50 nm, preferably 20 nm to 50 nm. 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.

[0053] Specifically, in some embodiments, the thickness of the undoped GaN layer 400 is 1 μm to 3 μm.

[0054] Specifically, in some embodiments, the thickness of the N-type GaN layer 600 is 1 μm to 5 μm, and its Si doping concentration is 5×10 18 cm -3 ~5×10 19 cm -3 。

[0055] 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 3 nm to 5 nm, the proportion of In component is 0.15 to 0.45, and the thickness of the GaN quantum barrier layer is 8 nm to 20 nm.

[0056] Specifically, in some embodiments, the thickness of the P-type GaN layer 900 is 50 nm to 200 nm, and its Mg doping concentration is 1×10 19 cm -3 ~5×10 20 cm -3 。

[0057] See Figure 2 As a second aspect, the present invention discloses a method for preparing a Micro-LED epitaxial wafer for preparing the above-mentioned Micro-LED epitaxial wafer, which specifically includes:

[0058] S1: Provide a substrate;

[0059] S2: Grow a buffer layer, a first warpage control layer, an undoped 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 in sequence;

[0060] Specifically, the first warpage control layer is a three-dimensional GaN layer, and the three-dimensional structure can release dislocations and reduce the dislocation density. The second warpage control layer includes alternately stacked first Si-doped GaN layers and Si-doped AlGaN layers, which can introduce compressive stress, balance the tensile stress brought by the cooling process, reduce the wafer warpage amount, and improve the light emission efficiency and wavelength uniformity. At the same time, since the dislocation density is greatly reduced by the first warpage control layer and the undoped GaN layer, the compressive stress in the second warpage control layer is not relaxed by dislocations and can be accumulated, thereby balancing the tensile stress during the subsequent cooling process. The third warpage control layer includes an Si-doped AlInGaN layer and a superlattice layer stacked in sequence on the N-type GaN layer, and the superlattice layer includes alternately stacked second Si-doped GaN layers and InGaN layers. Among them, the Si-doped AlInGaN layer can not only further reduce the dislocation density, but also pull up the energy band, making electrons enter the multi-quantum well layer more uniformly to recombine with holes, improving the wavelength uniformity and light emission 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 light emission efficiency and wavelength uniformity of the Micro-LED.

[0061] Specifically, in some embodiments, step S2 includes the following steps:

[0062] S21: Grow a buffer layer on the substrate;

[0063] Specifically, in some embodiments, one or more of an AlN layer, a GaN layer, and an AlGaN layer can be grown by PVD, MOCVD, or MBE as the buffer layer, but not limited thereto.

[0064] Preferably, in one embodiment, an AlN layer is grown by PVD as the buffer layer.

[0065] More preferably, in one embodiment, after the growth of the buffer layer, heat treatment is performed at 1000 °C to 1100 °C in an atmosphere of a first mixed gas; wherein the first mixed gas is a mixed gas of N 2 , H 2 and NH 3 , and N 2 , H 2 , NH 3The volume ratio is 1:(1~20):(1~10). Since the crystal quality of the buffer layer itself is poor, usually in a polycrystalline or amorphous state, through the above-mentioned first mixed gas atmosphere and high-temperature treatment, the crystal quality can be improved, and the buffer layer can also be partially decomposed to reduce the stress on the substrate.

[0066] S22: Grow the first warpage control layer on the buffer layer;

[0067] Specifically, in some embodiments, a three-dimensional GaN layer is grown by MOCVD as the first warpage control layer, with a growth temperature of 800°C to 900°C and a growth atmosphere of a second mixed gas, and the second mixed gas is a mixed gas of N 2 、H 2 and NH 3 The volume ratio of N 2 、H 2 、NH 3 is 1:(1~20):(1~10). Based on the above-mentioned lower growth temperature and growth atmosphere, the first warpage control layer tends to grow in a three-dimensional form, so as to achieve the purpose of reducing the dislocation density.

[0068] S23: Grow an undoped GaN layer on the first warpage control layer;

[0069] Specifically, in some embodiments, an undoped GaN layer is grown by MOCVD, with a growth temperature of 950°C to 1100°C and a growth pressure of 50 torr to 500 torr.

[0070] S24: Grow the second warpage control layer on the undoped GaN layer;

[0071] Specifically, in some embodiments, a first Si-doped GaN layer and a Si-doped AlGaN layer are grown periodically by MOCVD until the 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, and the third mixed gas is a mixed gas of N 2 、H 2 and NH 3 The volume ratio of N 2 、H 2 、NH 3 is 1:(1~20):(1~10).

[0072] Preferably, in some embodiments, the growth temperature of the second warpage control layer is 50°C to 200°C lower than that of the undoped GaN layer, which can effectively reduce the accumulation of thermal stress and improve the luminous efficiency and wavelength uniformity.

[0073] S25: Grow an N-type GaN layer on the second warpage control layer;

[0074] Specifically, in some embodiments, the N-type GaN layer is grown by MOCVD at a growth temperature of 980°C to 1150°C and a growth pressure of 100 torr to 500 torr.

[0075] S26: Grow a third warpage control layer on the N-type GaN layer;

[0076] Specifically, in some embodiments, an Si-doped AlInGaN layer and a superlattice layer are sequentially grown by MOCVD to obtain the third warpage control layer. The growth temperature of the third warpage control layer is 800°C to 1000°C, and the growth atmosphere is a fourth mixed gas, which is a mixed gas of N 2 and NH 3 The volume ratio of N 2 and NH 3 is 1:(1 to 10).

[0077] Preferably, in some embodiments, the growth temperature of the third warpage control layer is 50°C to 200°C lower than that of the N-type GaN layer. Growing the third warpage control layer at a lower temperature is beneficial to further release thermal stress and improve the light emission efficiency and wavelength uniformity.

[0078] S27: Grow a multi-quantum well layer on the third warpage control layer;

[0079] Specifically, in some embodiments, an InGaN quantum well layer and a GaN quantum barrier layer are periodically grown by MOCVD until a multi-quantum well layer is obtained. Among them, the growth temperature of the InGaN quantum well layer is 730°C to 820°C, the growth pressure is 100 torr to 300 torr, 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.

[0080] S28: Grow a P-type GaN layer on the multi-quantum well layer;

[0081] Specifically, in some embodiments, the P-type GaN layer is grown by MOCVD at a growth temperature of 900°C to 1050°C and a growth pressure of 100 torr to 500 torr.

[0082] 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, and also includes a transparent conductive layer, a passivation layer, electrodes, a reflective layer, etc. commonly used in the art, but not limited thereto. The Micro-LED epitaxial wafer in the present invention includes a substrate, a buffer layer, a first warpage control layer, an undoped 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 sequentially stacked on the substrate; the first warpage control layer is a three-dimensional GaN layer, and dislocations can be released through the three-dimensional structure to reduce the dislocation density. The second warpage control layer includes an alternately stacked first Si-doped GaN layer and a Si-doped AlGaN layer, which can introduce compressive stress to balance the tensile stress brought by the cooling process, reduce the wafer warpage amount, and improve the light emission efficiency and wavelength uniformity of the Micro-LED. At the same time, since the dislocation density is greatly reduced by the first warpage control layer and the undoped GaN layer, the compressive stress in the second warpage control layer is not relaxed by dislocations and can be accumulated, thereby playing an effect of balancing the tensile stress in the subsequent cooling process. The third warpage control layer includes a Si-doped AlInGaN layer and a superlattice layer sequentially stacked 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 uniformly to recombine with holes, improving the wavelength uniformity and light emission efficiency of the Micro-LED. 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 light emission efficiency and wavelength uniformity of the Micro-LED.

[0083] The following further illustrates the present invention with specific embodiments:

[0084] Example 1

[0085] This example provides a Micro-LED epitaxial wafer, which includes a substrate, a buffer layer, a first warpage control layer, an undoped 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 sequentially stacked on the substrate.

[0086] Among them, the substrate is a sapphire substrate, the buffer layer is an AlN layer, and its thickness is 25 nm. The first warpage control layer is a three-dimensional GaN layer, and its thickness is 50 nm. The thickness of the undoped GaN layer is 2 μm.

[0087] 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 thickness ratio of the first Si-doped GaN layer to the Si-doped AlGaN layer is 11:1, and the Si doping concentration of the first Si-doped GaN layer is 3×10 17 cm -3 , and the Si doping concentration of the Si-doped AlGaN layer is 3×10 17 cm -3 , and its Al component ratio is 0.25.

[0088] The thickness of the N-type GaN layer is 2 μm, and its Si doping concentration is 8.5×10 18 cm -3 .

[0089] The third warpage control layer includes a Si-doped AlInGaN layer and a superlattice layer stacked in sequence on the N-type GaN layer. The superlattice layer includes an alternating stack of a second Si-doped GaN layer and an InGaN layer. In the Si-doped AlInGaN layer, the In component ratio is 0.14, the Al component ratio is 0.1, and the Si doping concentration is 3×10 18 cm -3 , and the thickness is 50 nm. The superlattice layer has 10 periods, and each period includes a second Si-doped GaN layer and an InGaN layer stacked in sequence. Among them, the thickness of the second Si-doped GaN layer is 10 nm, and the Si doping concentration is 5×10 18 cm -3 , and the thickness of the InGaN layer is 2 nm, and the In component ratio is 0.04.

[0090] The multiple quantum well layer includes an alternating stack of InGaN quantum well layers and GaN quantum barrier layers. It has 10 periods. The thickness of the InGaN quantum well layer is 3 nm, and the In component ratio is 0.18. The thickness of the GaN quantum barrier layer is 10 nm. The thickness of the P-type GaN layer is 80 nm, and the Mg doping concentration is 1.5×10 20 cm -3 .

[0091] The method for preparing the Micro-LED epitaxial wafer in this embodiment includes the following steps:

[0092] (1) Provide a substrate;

[0093] (2) Grow a buffer layer on the substrate;

[0094] Specifically, grow an AlN layer by PVD as the buffer layer.

[0095] (3) Grow the first warpage control layer on the buffer layer;

[0096] Specifically, a three-dimensional GaN layer is grown by MOCVD as the first warpage control layer. Its growth temperature is 850 °C, and the growth atmosphere is a second mixed gas, which is a mixed gas of N 2 , H 2 , and NH 3 . The volume ratio of N 2 , H 2 , and NH 3 is 1:15:5.

[0097] (4) A non-doped GaN layer is grown on the first warpage control layer;

[0098] Specifically, in some embodiments, a non-doped GaN layer is grown by MOCVD. Its growth temperature is 1020 °C, and the growth pressure is 400 torr.

[0099] (5) A second warpage control layer is grown on the non-doped GaN layer;

[0100] Specifically, a first Si-doped GaN layer and a Si-doped AlGaN layer are periodically grown by MOCVD until the 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 N 2 , H 2 , and NH 3 . The volume ratio of N 2 , H 2 , and NH 3 is 1:10:8.

[0101] (6) An N-type GaN layer is grown on the second warpage control layer;

[0102] Specifically, an N-type GaN layer is grown by MOCVD. Its growth temperature is 1000 °C, and the growth pressure is 300 torr.

[0103] (7) A third warpage control layer is grown on the N-type GaN layer;

[0104] Specifically, a Si-doped AlInGaN layer and a superlattice layer are sequentially grown by MOCVD to obtain the third warpage control layer. The growth temperature of the third warpage control layer is 980 °C, and the growth atmosphere is a fourth mixed gas, which is a mixed gas of N 2 and NH 3 . The volume ratio of N 2 and NH 3 is 1:5.

[0105] (8) A multi-quantum well layer is grown on the third warpage control layer;

[0106] Specifically, the InGaN quantum well layer and the GaN quantum barrier layer are periodically grown by MOCVD until a multi-quantum well layer is obtained. Among them, the growth temperature of the InGaN quantum well layer is 790 °C, the growth pressure is 200 torr, the growth temperature of the GaN quantum barrier layer is 920 °C, and the growth pressure is 200 torr.

[0107] (9)Grow a P-type GaN layer on the multi-quantum well layer;

[0108] Specifically, a P-type GaN layer is grown by MOCVD, and its growth temperature is 1030 °C and the growth pressure is 200 torr.

[0109] Example 2

[0110] This example provides a Micro-LED epitaxial wafer, and the difference from Example 1 is that:

[0111] The thickness of the second warpage control layer is 150 nm, and 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 Al component ratio in the Si-doped AlGaN layer is 0.12.

[0112] The rest are the same as in Example 1.

[0113] Example 3

[0114] This example provides a Micro-LED epitaxial wafer, and the difference from Example 2 is that:

[0115] 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.

[0116] The rest are the same as in Example 2.

[0117] Example 4

[0118] This example provides a Micro-LED epitaxial wafer, and the difference from Example 3 is that:

[0119] After the growth of the buffer layer is completed, heat treatment is performed at 1050 °C in the atmosphere of the first mixed gas for 3 min; among them, the first mixed gas is a mixed gas of N 2 、H 2 and NH 3 And the volume ratio of N 2 、H 2 、NH 3 is 1:6:8.

[0120] The rest are the same as in Example 3.

[0121] Example 5

[0122] This embodiment provides a Micro-LED epitaxial wafer, which is different from that of Embodiment 4 in that:

[0123] The growth temperature of the second warpage control layer is 960 °C.

[0124] The rest are the same as those of Embodiment 4.

[0125] Embodiment 6

[0126] This embodiment provides a Micro-LED epitaxial wafer, which is different from that of Embodiment 5 in that:

[0127] The growth temperature of the third warpage control layer is 880 °C.

[0128] The rest are the same as those of Embodiment 5.

[0129] Comparative Example 1

[0130] This comparative example provides a Micro-LED epitaxial wafer, which is different from that of Embodiment 1 in that:

[0131] It does not include the first warpage control layer, the second warpage control layer, and the third warpage control layer.

[0132] The rest are the same as those of Embodiment 1.

[0133] Comparative Example 2

[0134] This comparative example provides a Micro-LED epitaxial wafer, which is different from that of Embodiment 1 in that:

[0135] It does not include the first warpage control layer, and the rest are the same as those of Embodiment 1.

[0136] Comparative Example 3

[0137] This comparative example provides a Micro-LED epitaxial wafer, which is different from that of Embodiment 1 in that:

[0138] It does not include the first warpage control layer and the second warpage control layer, and the rest are the same as those of Embodiment 1.

[0139] Comparative Example 4

[0140] This comparative example provides a Micro-LED epitaxial wafer, which is different from that of Embodiment 1 in that:

[0141] It does not include the third warpage control layer, and the rest are the same as those of Embodiment 1.

[0142] The Micro-LED epitaxial wafers obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were fabricated into chips of 3 mil × 5 mil, and the luminous intensity and wavelength uniformity (PL-WD std) were measured at 2 mA. The specific data are shown in the following table:

[0143]

[0144] As can be seen from the table, the Micro-LED epitaxial wafers in the examples of the present invention effectively improve the luminous efficiency and wavelength uniformity of light-emitting diodes.

[0145] The above are the preferred embodiments of the invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A Micro-LED epitaxial wafer, characterized in that: It 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; The Al component ratio in the Si-doped AlGaN layer is 0.1-0.15, and the ratio of the thickness of the first Si-doped GaN layer to the thickness of the Si-doped AlGaN layer is 4:1-10:1; 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.

2. The Micro-LED epitaxial wafer according to claim 1, characterized in that: The period number of the second warp regulation layer is 3-20, and the thickness thereof is 10nm-200nm.

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 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.

5. The Micro-LED epitaxial wafer according to any one of claims 1 to 4, 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 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.

6. A method for preparing a Micro-LED epitaxial wafer, for preparing the Micro-LED epitaxial wafer as claimed in any one of claims 1 to 5, 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.

7. The method for preparing a Micro-LED epitaxial wafer according to claim 6, characterized in that: 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.

8. The method for preparing a Micro-LED epitaxial wafer according to claim 6, 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.

9. A Micro-LED, characterized in that: Comprising the Micro-LED epitaxial wafer as described in any one of claims 1 to 5.

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