High-light-efficiency Micro-LED epitaxial wafer and preparation method thereof, Micro-LED

Abstract

The present invention discloses a high-light-efficiency Micro-LED epitaxial wafer and a preparation method thereof, and Micro-LED, and relates to the field of semiconductor optoelectronic devices. The Micro-LED epitaxial wafer comprises a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, a hole expansion layer, a hole storage layer, and a hole layer in sequence; the hole expansion layer is a periodic structure, and each period comprises a BN layer and a Mg lightly doped GaN layer stacked in sequence; the hole storage layer is a periodic structure, and each period comprises a GaN layer, an InGaN layer, and a Mg-doped AlGaN layer stacked in sequence; the hole layer is a periodic structure, and each period comprises a P-type BInGaN layer, a Mg3N2 layer, and a P-type GaN layer stacked in sequence; the doping concentration of the P-type GaN layer is ≥1×10 19 cm ‑3 The implementation of the present invention can improve the luminous efficiency.

Description

Technical Field

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

[0002] Micro-LED technology 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. Micro-LED generally refers to chips with a size of less than 100μm. Its application current density is very small and the luminous efficiency is low. An important reason for the low luminous efficiency of Micro-LED is that the injection efficiency of holes into the active layer is very low under low current density. First of all, the traditional P-type GaN layer has a low hole efficiency due to the high activation energy of Mg atoms, which is often less than 1×10 20 cm -3 Only 3×10 17 cm -3 ~7×10 17 cm -3 The hole concentration results in a relatively small amount of holes. Further increasing the Mg doping concentration means that the crystal quality of the P-type GaN layer will drop significantly, which will increase light absorption and reduce the luminous efficiency. Secondly, due to the large effective mass and low mobility of holes, the holes are mainly concentrated in a few quantum wells close to the P-type GaN layer. The electrons have a small effective mass and high mobility, and are distributed in multiple quantum wells, resulting in a low degree of hole-electron matching and low luminous efficiency. Finally, in traditional LEDs, an electron blocking layer is generally introduced between the P-type GaN layer and the multi-quantum well layer to reduce electron leakage, but the electron blocking layer will also block some holes, especially at low current density, where the blocking of holes is more obvious. Summary of the invention

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

[0004] Another technical problem to be solved by the present invention is to provide a Micro-LED.

[0005] In order to solve the above problems, the present invention provides a high-light-efficiency Micro-LED epitaxial wafer, which includes a substrate, a buffer layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer, a hole expansion layer, a hole storage layer and a hole layer stacked on the substrate in sequence;

[0006] The hole expansion layer is a periodic structure, each period includes a BN layer and a Mg lightly doped GaN layer stacked in sequence, and the Mg doping concentration in the Mg lightly doped GaN layer is ≤1×10 18 cm -3 ;

[0007] The hole storage layer is a periodic structure, each period includes a GaN layer, an InGaN layer and a Mg-doped AlGaN layer stacked in sequence, and the Mg doping concentration in the Mg-doped AlGaN layer is ≤1×10 20 cm -3 ;

[0008] The hole layer is a periodic structure, and each period includes a P-type BInGaN layer, a Mg3N2 layer and a P-type GaN layer stacked in sequence, and the doping concentration of the P-type BInGaN layer is ≥1×10 20 cm -3 ; The doping concentration of the P-type GaN layer is ≥1×10 19 cm -3 .

[0009] As an improvement of the above technical solution, the thickness of the BN layer is ≤5nm.

[0010] As an improvement of the above technical solution, the number of periods of the hole expansion layer is 2 to 20; and / or

[0011] The thickness of the BN layer is 0.5 nm to 5 nm; and / or

[0012] The thickness of the Mg lightly doped GaN layer is 1 nm to 10 nm, and the Mg doping concentration is 1×10 17 cm -3 ~1×10 18 cm -3 ; and / or

[0013] The number of periods of the hole storage layer is 3 to 15; and / or

[0014] The thickness of the GaN layer is 5nm to 15nm; and / or

[0015] The thickness of the InGaN layer is 2nm-8nm, and the In component ratio is 0.01-0.2; and / or

[0016] The thickness of the Mg-doped AlGaN layer is 2nm~10nm, the Al component ratio is 0.01~0.2, and the Mg doping concentration is 1×10 19 cm -3 ~1×10 20 cm -3 ; and / or

[0017] The period number of the hole layer is 2 to 20; and / or

[0018] The thickness of the P-type BInGaN layer is 2nm~10nm, the In component accounts for 0.05~0.2, the B component accounts for 0.01~0.2, and the Mg doping concentration is 1×10 20 cm -3 ~5×10 21 cm -3 ; and / or

[0019] The thickness of the Mg3N2 layer is 1nm~8nm; and / or

[0020] The thickness of the P-type GaN layer is 10 nm to 20 nm, and the Mg doping concentration is 5×10 19 cm -3 ~5×10 20 cm -3 .

[0021] As an improvement of the above technical solution, the band gap width of the P-type BInGaN layer is greater than the band gap width of the Mg-doped AlGaN layer.

[0022] Correspondingly, the present invention also discloses a method for preparing a high-light-efficiency Micro-LED epitaxial wafer, which is used to prepare the above-mentioned high-light-efficiency Micro-LED epitaxial wafer, and comprises:

[0023] Providing a substrate, and sequentially growing a buffer layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer, a hole expansion layer, a hole storage layer, and a hole layer on the substrate;

[0024] The hole expansion layer is a periodic structure, each period includes a BN layer and a Mg lightly doped GaN layer stacked in sequence, and the Mg doping concentration in the Mg lightly doped GaN layer is ≤1×10 18 cm -3 ;

[0025] The hole storage layer is a periodic structure, each period includes a GaN layer, an InGaN layer and a Mg-doped AlGaN layer stacked in sequence, and the Mg doping concentration in the Mg-doped AlGaN layer is ≤1×10 20 cm -3 ;

[0026] The hole layer is a periodic structure, and each period includes a P-type BInGaN layer, a Mg3N2 layer and a P-type GaN layer stacked in sequence, and the doping concentration of the P-type BInGaN layer is ≥1×10 20 cm -3 ; The doping concentration of the P-type GaN layer is ≥1×10 19 cm-3 .

[0027] As an improvement of the above technical solution, the growth temperature of the Mg3N2 layer is lower than the growth temperature of the P-type BInGaN layer;

[0028] The growth temperature of the Mg3N2 layer is lower than the growth temperature of the P-type GaN layer; and / or

[0029] The growth pressure of the Mg3N2 layer is greater than the growth pressure of the P-type BInGaN layer;

[0030] The growth pressure of the Mg3N2 layer is greater than the growth pressure of the P-type GaN layer.

[0031] As an improvement of the above technical solution, during the growth process of the P-type BInGaN layer, the B source, In source, Ga source, and N source are first introduced for 3s to 5s, and then the Mg source and N source are introduced for 1s to 3s, and this process is repeated periodically until the P-type BInGaN layer is obtained.

[0032] As an improvement of the above technical solution, the growth temperature of the BN layer is 800° C. to 1000° C., and the growth pressure is 50 torr to 500 torr; and / or

[0033] The growth temperature of the Mg lightly doped GaN layer is 800° C. to 900° C., and the growth pressure is 50 torr to 500 torr; and / or

[0034] The growth temperature of the GaN layer is 800° C. to 900° C., and the growth pressure is 50 torr to 500 torr; and / or

[0035] The growth temperature of the InGaN layer is 750° C. to 850° C., and the growth pressure is 50 torr to 500 torr; and / or

[0036] The growth temperature of the Mg-doped AlGaN layer is 850° C. to 1000° C., and the growth pressure is 50 torr to 500 torr; and / or

[0037] The growth temperature of the P-type BInGaN layer is 750° C. to 850° C., and the growth pressure is 50 torr to 200 torr; and / or

[0038] The growth temperature of the Mg3N2 layer is 700°C to 850°C, and the growth pressure is 300torr to 500torr; and / or

[0039] The growth temperature of the P-type GaN layer is 900° C. to 1000° C., and the growth pressure is 50 torr to 200 torr.

[0040] As an improvement of the above technical solution, the hole concentration of the hole layer is 1×10 18 cm -3 ~5×10 19 cm -3 .

[0041] Correspondingly, the present invention also discloses a Micro-LED, which includes the above-mentioned high-light-efficiency Micro-LED epitaxial wafer.

[0042] The implementation of the present invention has the following beneficial effects:

[0043] 1. In the high-efficiency Micro-LED epitaxial wafer in one embodiment of the present invention, a hole expansion layer, a hole storage layer and a hole layer are arranged after the multi-quantum well layer. Among them, the hole expansion layer is a periodic structure, and each period includes a BN layer and a Mg-lightly doped GaN layer stacked in sequence, which can make the hole distribution more uniform and improve the efficiency of hole injection into the multi-quantum well layer. The hole storage layer is a periodic structure, and each period includes a GaN layer, an InGaN layer and a Mg-doped AlGaN layer stacked in sequence. Through the change of the bandgap width of the three, a barrier / potential well / potential barrier structure can be formed, so that part of the holes are stored in the potential well-InGaN layer, thereby improving the hole concentration and hole injection efficiency. The hole layer is a periodic structure, and each period includes a P-type BInGaN layer, a Mg3N2 layer, and a P-type GaN layer stacked in sequence. The In introduced into the P-type BInGaN layer can reduce the activation energy of Mg and increase the hole concentration, and the introduction of B can effectively improve the crystal quality of the layer, block the extension of dislocations, and optimize the activation of Mg in the later P-type GaN layer; at the same time, the structure of sandwiching the Mg3N2 layer between the P-type BInGaN layer and the P-type GaN layer can promote the diffusion of Mg into the P-type BInGaN layer and the P-type GaN layer on both sides during the preparation of the periodic structure, further increasing the hole concentration. In summary, the high-efficiency Micro-LED epitaxial wafer in this embodiment can effectively improve the hole concentration, the hole expansion capability, and the injection efficiency of the hole injection into the multi-quantum well layer, thereby effectively improving the radiation recombination efficiency of electrons and holes in the multi-quantum well layer and improving the luminous efficiency.

[0044] 2. In the high-light-efficiency Micro-LED in one embodiment of the present invention, during the growth of the P-type BInGaN layer, the B source, In source, Ga source, and N source are first introduced for 3s to 5s, and then the Mg source and N source are introduced for 1s to 3s, that is, the growth is performed in a Mg source interruption mode. With this growth mode, firstly, stacking dislocations are not easily formed; secondly, even if stacking dislocations are formed, they can be filled by the subsequent Ga source and B source to prevent them from spreading, thereby reducing the dislocation density as a whole. Combining the above two, the crystal quality of the layer can be effectively improved and the hole concentration can be increased.

[0045] 3. In the high-efficiency Micro-LED epitaxial wafer in one embodiment of the present invention, the growth temperature of the Mg3N2 layer is lower than the growth temperature of the P-type BInGaN layer and the growth temperature of the P-type GaN layer, that is, after the growth of the Mg3N2 layer is completed, it is subjected to high-temperature annealing. During this process, Mg will diffuse into the adjacent P-type BInGaN layer and P-type GaN layer, increasing the doping concentration of both, thereby increasing the hole concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 1 is a schematic diagram of the structure of a high-light-efficiency Micro-LED epitaxial wafer in one embodiment of the present invention;

[0047] Figure 2 It is a flow chart of a method for preparing a high-light-efficiency Micro-LED epitaxial wafer in one embodiment of the present invention.

[0048] Among them, 100 is a substrate, 200 is a buffer layer, 300 is an undoped GaN layer, 400 is an N-type GaN layer, 500 is a multiple quantum well layer, 600 is a hole expansion layer, 610 is a BN layer, 620 is a Mg lightly doped GaN layer, 700 is a hole storage layer, 710 is a GaN layer, 720 is an InGaN layer, 730 is a Mg-doped AlGaN layer, 800 is a hole layer, 810 is a P-type BInGaN layer, 820 is a Mg3N2 layer, and 830 is a P-type GaN layer. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0050] See also Figure 1 The present invention discloses a high-light-efficiency Micro-LED epitaxial wafer, which includes a substrate 100, a buffer layer 200, a non-doped GaN layer 300, an N-type GaN layer 400, a multi-quantum well layer 500, a hole expansion layer 600, a hole storage layer 700 and a hole layer 800 sequentially stacked on the substrate 100.

[0051] The hole expansion layer 600 is a periodic structure, and each period includes a sequentially stacked BN layer 610 and a Mg lightly doped GaN layer 620. The BN layer 610 has a large bandgap, so it is compounded with the Mg lightly doped GaN layer 620 to adopt a periodic stacking structure, which can make the holes evenly distributed, improve the hole expansion, and improve the injection efficiency of holes into the multi-quantum well. In addition, the BN layer 610 can also prevent the overflow of a small amount of electrons and reduce the non-radiative recombination of holes and electrons.

[0052] Specifically, the number of periods of the hole expansion layer 600 is 2 to 20. An increase in the number of periods can make the expansion of holes more uniform and improve the luminous efficiency; however, when the number of periods is too large, the blocking effect on holes will be too large, reducing the movement rate of holes when injected into the multi-quantum well layer, which will reduce the luminous efficiency. Exemplarily, the number of periods of the hole expansion layer 600 is 3, 5, 9, 12, 15 or 18, but is not limited thereto. Preferably, it is 5 to 10.

[0053] Specifically, the thickness of the BN layer 610 is ≤5nm. If the thickness is too large, the blocking effect on holes is too strong, and it is difficult to effectively improve the hole injection efficiency. Preferably, the thickness of the BN layer 610 is 0.5nm~5nm, and exemplary thickness is 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm or 4.5nm, but not limited thereto. More preferably, it is 1nm~3nm.

[0054] Specifically, the Mg doping concentration in the Mg lightly doped GaN layer 620 is ≤ 1×10 18 cm -3 If the Mg doping concentration is too high, the hole expansion effect is poor. Preferably, in one embodiment, the Mg doping concentration in the Mg lightly doped GaN layer 620 is 1×10 17 cm -3 ~1×10 18 cm -3 ; An exemplary value is 1.5×10 17 cm -3 , 3×10 17 cm -3 , 4.5×10 17 cm -3 , 6×10 17 cm -3 or 8×10 17 cm -3 , but not limited thereto. More preferably, 1×10 17 cm -3 ~6×10 17 cm -3 .

[0055] The thickness of the Mg lightly doped GaN layer 620 is 0.5 nm to 12 nm, exemplarily 0.8 nm, 3 nm, 5.5 nm, 7 nm, 7.8 nm, 9.2 nm, 10 nm or 11.5 nm, but not limited thereto, preferably 1 nm to 10 nm, more preferably 5 nm to 10 nm.

[0056] The hole storage layer 700 is a periodic structure, and each period includes a GaN layer 710, an InGaN layer 720, and a Mg-doped AlGaN layer 730 stacked in sequence, wherein the bandgap widths of the GaN layer 710 and the Mg-doped AlGaN layer 730 are relatively large, and the bandgap width of the InGaN layer 720 is relatively small, so a barrier / potential well / potential barrier composite structure can be formed to temporarily store holes in the InGaN layer 720. The introduction of Mg doping into the Mg-doped AlGaN layer 730 allows the holes in the hole layer 800 to enter the hole storage layer 700 with higher efficiency, and the GaN layer 710 prevents the Mg in the Mg-lightly doped GaN layer 620 from penetrating into the InGaN layer 720, reducing its crystal quality, and ensuring that the InGaN layer 720 can store more holes. That is, based on the hole storage layer 700 , the holes in the hole layer 800 can be injected into the hole storage layer 700 with higher efficiency and stored temporarily, thereby increasing the hole concentration and improving the luminous efficiency.

[0057] Specifically, the number of periods of the hole storage layer 700 is 2-15, exemplarily 3, 5, 8, 10 or 12, but not limited thereto, preferably 3-15.

[0058] Specifically, the thickness of the GaN layer 710 is 3 nm to 15 nm, and is exemplarily 4 nm, 6 nm, 8 nm, 10 nm or 12 nm, but is not limited thereto, and is preferably 5 nm to 15 nm.

[0059] Specifically, the thickness of the InGaN layer 720 is 1 nm to 10 nm, exemplarily 2 nm, 4 nm, 6 nm, 8 nm or 9 nm, but not limited thereto, preferably 2 nm to 8 nm.

[0060] The proportion of In component in the InGaN layer 720 is 0.01~0.22. If the proportion of In component is less than 0.01, the bandgap is large and it is difficult to effectively store holes. If the In component is greater than 0.22, the crystal quality of this layer is poor, which will greatly reduce the mobility of holes. Exemplarily, the proportion of In component in the InGaN layer 720 is 0.05, 0.08, 0.12, 0.14, 0.16, 0.18 or 0.21, but not limited to this. Preferably, it is 0.01~0.2, and more preferably, it is 0.05~0.15.

[0061] Specifically, the Mg doping concentration in the Mg-doped AlGaN layer 730 is ≤1×10 20 cm -3 Preferably, in one embodiment, the Mg doping concentration in the Mg-doped AlGaN layer 730 is 1×10 19 cm -3 ~1×10 20 cm-3 , exemplarily 3×10 19 cm -3 , 5×10 19 cm -3 ,7×10 19 cm -3 or 9×10 19 cm -3 , but not limited thereto. Preferably 1×10 19 cm -3 ~5×10 19 cm -3 .

[0062] Specifically, the proportion of Al in the Mg-doped AlGaN layer 730 is ≤ 0.25 to prevent it from blocking holes. Preferably, in one embodiment, the proportion of Al in the Mg-doped AlGaN layer 730 is 0.01-0.2, exemplarily 0.05, 0.1, 0.15 or 0.18, but not limited thereto. Preferably, it is 0.03-0.08.

[0063] The thickness of the Mg-doped AlGaN layer 730 is 2 nm to 15 nm, exemplarily 4 nm, 6 nm, 8 nm, 10 nm, 12 nm or 14 nm, but not limited thereto, preferably 2 nm to 10 nm.

[0064] Among them, the hole layer 800 is a periodic structure, and each period includes a P-type BInGaN layer 810, a Mg3N2 layer 820 and a P-type GaN layer 830 stacked in sequence. The In introduced into the P-type BInGaN layer 810 can reduce the activation energy of Mg and increase the hole concentration, and the introduction of B can effectively improve the crystal quality of the layer, block the extension of dislocations, and optimize the activation of Mg in the later P-type GaN layer 830. At the same time, the structure in which the Mg3N2 layer 820 is sandwiched between the P-type BInGaN layer 810 and the P-type GaN layer 830 can promote Mg to diffuse into the P-type BInGaN layer 810 and the P-type GaN layer 830 on both sides during the preparation of the periodic structure, thereby further increasing the hole concentration.

[0065] Specifically, the number of periods of the hole layer 800 is 2 to 20, and exemplarily is 3, 5, 7, 9, 11, 13 or 17, but is not limited thereto.

[0066] Specifically, the proportion of In component in the P-type BInGaN layer 810 is 0.01-0.25. In can help improve the activation of Mg. If its content is small, it is difficult to effectively activate Mg. If its proportion is too large, it will reduce the crystal quality of the overall P-type BInGaN layer 810, which is not conducive to the diffusion of Mg in the later Mg3N2 layer 820 into the P-type BInGaN layer 810, and it is difficult to effectively increase the hole concentration. Exemplarily, the proportion of In component in the P-type BInGaN layer 810 is 0.03, 0.08, 0.14, 0.19, 0.23 or 0.24, but not limited to this. Preferably, it is 0.05-0.2, and more preferably, it is 0.05-0.1.

[0067] The proportion of B component in the P-type BInGaN layer 810 is 0.01-0.25. The B atomic radius is small, which can fill defects well and improve the crystal quality of the layer. If its content is small, the crystal quality of the layer is poor and the hole concentration is low. If its content is too high, the barrier height is high, which is not conducive to the injection of holes from the hole layer 800 into the hole storage layer 700 and the hole expansion layer 600. Exemplarily, the proportion of B component in the P-type BInGaN layer 810 is 0.03, 0.08, 0.1, 0.14, 0.2 or 0.23, but not limited thereto. Preferably, it is 0.01-0.2, and more preferably, it is 0.05-0.15.

[0068] The P-type doping element in the P-type BInGaN layer 810 is Mg, and its doping concentration is ≥ 1×10 20 cm -3 , to increase the hole concentration. Preferably, the Mg doping concentration in the P-type BInGaN layer 810 is 1×10 20 cm -3 ~5×10 21 cm -3 ; Exemplary is 2×10 20 cm -3 , 6×10 20 cm -3 ,9×10 20 cm -3 , 1×10 21 cm -3 , 3×10 21 cm -3 or 4×10 21 cm -3 , but not limited thereto. Preferably 5×10 20 cm -3 ~3×10 21 cm -3 .

[0069] The thickness of the P-type BInGaN layer 810 is 1 nm to 10 nm, exemplarily 2.5 nm, 4 nm, 5.5 nm, 7 nm or 8.5 nm, but not limited thereto, preferably 2 nm to 10 nm.

[0070] Specifically, the thickness of the Mg3N2 layer 820 is 1 nm to 10 nm, exemplarily 2 nm, 4 nm, 6 nm or 8 nm, but not limited thereto, preferably 1 nm to 8 nm.

[0071] Specifically, the P-type doping element in the P-type GaN layer 830 is Mg, and its doping concentration is ≥ 1×10 19 cm -3 In this embodiment, Mg is diffused and doped by forming a Mg3N2 layer 820 before the P-type GaN layer 830, so that the P-type GaN layer 830 adopts a relatively low Mg doping concentration, which is beneficial to improve its lattice quality and thus also improve the hole concentration. Preferably, the Mg doping concentration in the P-type GaN layer 830 is 5×10 19 cm -3 ~5×10 20 cm -3 , exemplarily 6×10 19 cm -3 ,9×10 19 cm -3 , 2×10 20 cm -3 or 4×10 20 cm -3 , but not limited thereto. More preferably, 5×10 19 cm -3 ~1×10 20 cm -3 .

[0072] The thickness of the P-type GaN layer 830 is 8 nm to 20 nm, exemplarily 9 nm, 12 nm, 15 nm or 18 nm, but not limited thereto, preferably 10 nm to 20 nm.

[0073] The substrate 100 is a sapphire substrate or a silicon substrate, but is not limited thereto.

[0074] The buffer layer 200 is an AlN layer or an AlGaN layer, but is not limited thereto. The buffer layer 200 has a thickness of 10 nm to 50 nm.

[0075] The thickness of the non-doped GaN layer 300 is 1 μm-5 μm.

[0076] The doping element of the N-type GaN layer 400 is Si, but not limited thereto. The doping concentration of Si in the N-type GaN layer 400 is 1×10 19cm -3 ~5×10 19 cm -3 , and its thickness is 1μm~3μm.

[0077] The multi-quantum well layer 500 is a periodic structure with a period number of 3 to 15, and each period includes sequentially stacked InGaN quantum well layers and AlGaN quantum barrier layers. The In component in the InGaN quantum well layer accounts for 0.1 to 0.3, and its thickness is 2 nm to 5 nm. The Al component in the AlGaN quantum barrier layer accounts for 0.01 to 0.1, and its thickness is 5 nm to 15 nm.

[0078] Preferably, in one embodiment of the present invention, the band gap width of the P-type BInGaN layer 810 is greater than the band gap width of the Mg-doped AlGaN layer 730, which can make it easier for holes in the hole layer 800 to be injected into the hole storage layer 700 and the hole expansion layer 600, further improving the luminous efficiency.

[0079] Preferably, in one embodiment of the present invention, the growth temperature of the Mg3N2 layer 820 is lower than the growth temperature of the P-type BInGaN layer 810; the growth temperature of the Mg3N2 layer 820 is lower than the growth temperature of the P-type GaN layer 830; that is, after the growth of the Mg3N2 layer 820 is completed, it is subjected to high-temperature annealing. During this process, Mg will diffuse into the adjacent P-type BInGaN layer 810 and P-type GaN layer 830, thereby increasing the doping concentration of both, thereby increasing the hole concentration.

[0080] More preferably, in one embodiment of the present invention, the growth temperature of the Mg3N2 layer 820 is lower than the growth temperature of the P-type BInGaN layer 810 and the P-type GaN layer 830, but the growth pressure of the Mg3N2 layer 820 is higher than the growth pressure of the P-type BInGaN layer 810 and the P-type GaN layer 830, so that the Mg3N2 layer 820 grows more in a three-dimensional manner, and the P-type BInGaN layer 810 and the P-type GaN layer 830 grow more in a two-dimensional manner, thereby increasing the contact area between the Mg3N2 layer 820 and the adjacent P-type BInGaN layer 810 and the P-type GaN layer 830, making it easier for Mg to diffuse into the adjacent layer during high-temperature annealing, thereby increasing the hole concentration. Specifically, based on the control of the growth temperature and the growth pressure, the hole concentration of the hole layer 800 can be increased to 1×10 18 cm -3 ~1×10 19 cm -3 .

[0081] Preferably, in one embodiment of the present invention, during the growth of the P-type BInGaN layer 810, its P-type doping source (i.e., Mg source CP2Mg) is intermittently introduced into the reaction chamber, and the Ga source (TMGa or TEGa), In source (TMIn), and B source (TMB or B2H6) are also intermittently introduced into the reaction chamber. With this growth mode, on the one hand, stacking dislocations are not easily formed; on the other hand, even if stacking dislocations are formed, they can be filled by the subsequent Ga source and B source to prevent them from spreading, thereby reducing the dislocation density as a whole. Combining the above two, the crystal quality of the layer can be effectively improved and the hole concentration can be increased. More specifically, during the growth of the P-type BInGaN layer 810, the B source, In source, Ga source, and N source are first introduced for 3s to 5s, and then the Mg source and N source are introduced for 1s to 3s, and the cycle is repeated until the P-type BInGaN layer 810 is obtained. Specifically, based on the control of the above MO source (N source, Mg source, B source, Ga source, In source, etc.), the hole concentration of the hole layer 800 can be increased to 1×10 18 cm -3 ~1×10 19 cm -3 .

[0082] More preferably, based on the intermittent introduction of MO source and the control of growth temperature and growth pressure, the hole concentration of the hole layer 800 can be increased to 1×10 19 cm -3 ~5×10 19 cm -3 .

[0083] Accordingly, see Figure 2 The present invention also provides a method for preparing a high-light-efficiency Micro-LED epitaxial wafer, which is used to prepare the above-mentioned high-light-efficiency Micro-LED epitaxial wafer, and specifically comprises the following steps:

[0084] S1: providing a substrate;

[0085] S2: sequentially growing a buffer layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer, a hole expansion layer, a hole storage layer and a hole layer on the substrate;

[0086] Specifically, in some embodiments of the present invention, step S2 includes:

[0087] S21: growing a buffer layer on the substrate;

[0088] Specifically, in one embodiment of the present invention, an AlN layer is grown by PVD as a buffer layer.

[0089] S22: growing a non-doped GaN layer on the buffer layer;

[0090] Specifically, in one embodiment of the present invention, the non-doped GaN layer is grown by MOCVD, the growth temperature is 1000° C. to 1200° C., and the growth pressure is 100 torr to 500 torr.

[0091] S23: growing an N-type GaN layer on the non-doped GaN layer;

[0092] Specifically, in one embodiment of the present invention, an N-type GaN layer is grown by MOCVD, and the growth temperature is 1100° C. to 1200° C. and the growth pressure is 100 torr to 500 torr.

[0093] S24: growing a multi-quantum well layer on the N-type GaN layer;

[0094] Specifically, in one embodiment, an InGaN quantum well layer and an AlGaN quantum barrier layer are periodically grown on an N-type GaN layer by MOCVD until a multi-quantum well layer is obtained.

[0095] The growth temperature of the InGaN quantum well layer is 760°C to 820°C, and the growth pressure is 50 torr to 300 torr. The growth temperature of the AlGaN quantum barrier layer is 850°C to 950°C, and the growth pressure is 50 torr to 300 torr.

[0096] S25: growing a hole expansion layer on the multi-quantum well layer;

[0097] Specifically, in one embodiment of the present invention, a BN layer and a Mg lightly doped GaN layer are periodically grown by MOCVD until a hole expansion layer is obtained. Specifically, the growth temperature of the BN layer is 800°C to 1000°C, and the growth pressure is 50 torr to 500 torr; the growth temperature of the Mg lightly doped GaN layer is 800°C to 900°C, and the growth pressure is 50 torr to 500 torr.

[0098] S26: growing a hole storage layer on the hole expansion layer;

[0099] Specifically, in one embodiment of the present invention, a GaN layer, an InGaN layer and a Mg-doped AlGaN layer are periodically grown by MOCVD until a hole storage layer is obtained. The growth temperature of the GaN layer is 800°C to 900°C, and the growth pressure is 50 torr to 500 torr; the growth temperature of the InGaN layer is 750°C to 850°C, and the growth pressure is 50 torr to 500 torr; the growth temperature of the Mg-doped AlGaN layer is 850°C to 1000°C, and the growth pressure is 50 torr to 500 torr.

[0100] S27: growing a hole layer on the hole storage layer;

[0101] Specifically, in one embodiment of the present invention, a P-type BInGaN layer, a Mg3N2 layer and a P-type GaN layer are periodically grown by MOCVD. Specifically, the growth temperature of the P-type BInGaN layer is 750°C to 850°C, and the growth pressure is 50torr to 200torr; the growth temperature of the Mg3N2 layer is 700°C to 850°C, and the growth pressure is 300torr to 500torr; the growth temperature of the P-type GaN layer is 900°C to 1000°C, and the growth pressure is 50torr to 200torr.

[0102] Preferably, in one embodiment of the present invention, the growth temperature of the Mg3N2 layer is lower than the growth temperature of the P-type BInGaN layer; the growth temperature of the Mg3N2 layer is lower than the growth temperature of the P-type GaN layer; the growth pressure of the Mg3N2 layer is higher than the growth pressure of the P-type BInGaN layer; the growth pressure of the Mg3N2 layer is higher than the growth pressure of the P-type GaN layer.

[0103] Preferably, in one embodiment of the present invention, during the growth of the P-type BInGaN layer, the B source, In source, Ga source, and N source are first introduced for 3s to 5s, and then the Mg source and N source are introduced for 1s to 3s, and this process is repeated periodically until the P-type BInGaN layer is obtained.

[0104] The present invention will be further described below with specific embodiments:

[0105] Example 1

[0106] This embodiment provides a high-light-efficiency Micro-LED epitaxial wafer, which includes a substrate, a buffer layer, an undoped GaN layer, an N-type GaN layer, a multi-quantum well layer, a hole expansion layer, a hole storage layer and a hole layer stacked in sequence on the substrate.

[0107] The substrate is a sapphire substrate, the buffer layer is an AlN layer with a thickness of 40 nm, and the thickness of the undoped GaN layer is 2.5 μm. The Si doping concentration in the N-type GaN layer is 1.2×10 19 cm -3 , and its thickness is 2μm. The multi-quantum well layer includes alternately stacked InGaN quantum well layers and AlGaN quantum barrier layers, and its period number is 10. Among them, the In component in the InGaN quantum well layer accounts for 0.15, and its thickness is 3nm, and the Al component in the AlGaN quantum barrier layer accounts for 0.05, and its thickness is 12nm.

[0108] The hole expansion layer is a periodic structure with 8 periods. Each period includes a BN layer and a Mg lightly doped GaN layer stacked in sequence. The thickness of the BN layer is 2nm, the thickness of the Mg lightly doped GaN layer is 8nm, and the Mg doping concentration is 3×1017 cm -3 .

[0109] The hole storage layer is a periodic structure with 10 periods. Each period includes a GaN layer, an InGaN layer and a Mg-doped AlGaN layer stacked in sequence. The thickness of the GaN layer is 10 nm, the thickness of the InGaN layer is 6 nm, and the In component accounts for 0.08. The thickness of the Mg-doped AlGaN layer is 5 nm, and the Al component accounts for 0.08. The Mg doping concentration is 4.5×10 19 cm -3 .

[0110] The hole layer is a periodic structure with 15 periods. Each period includes a P-type BInGaN layer, a Mg3N2 layer and a P-type GaN layer stacked in sequence. The In component in the P-type BInGaN layer accounts for 0.1, the B component accounts for 0.03, and the Mg doping concentration is 8.3×10 20 cm -3 , its thickness is 8nm. The thickness of Mg3N2 layer is 5nm. The Mg doping concentration in P-type GaN layer is 7.5×10 19 cm -3 , and its thickness is 15nm.

[0111] The band gap width of the P-type BInGaN layer is smaller than that of the Mg-doped AlGaN layer.

[0112] The method for preparing a high-light-efficiency Micro-LED epitaxial wafer in this embodiment includes the following steps:

[0113] (1) Providing a substrate;

[0114] (2) growing a buffer layer on the substrate;

[0115] Specifically, an AlN layer is grown by PVD to serve as a buffer layer.

[0116] (3) growing a non-doped GaN layer on the buffer layer;

[0117] Specifically, the non-doped GaN layer is grown by MOCVD, with a growth temperature of 1100° C. and a growth pressure of 300 torr.

[0118] (4) growing an N-type GaN layer on the undoped GaN layer;

[0119] Specifically, the N-type GaN layer is grown by MOCVD, with a growth temperature of 1150° C. and a growth pressure of 300 torr.

[0120] (5) Growing a multi-quantum well layer on the N-type GaN layer;

[0121] Specifically, InGaN quantum well layers and AlGaN quantum barrier layers are alternately grown on the N-type GaN layer by MOCVD until a multi-quantum well layer is obtained. The growth temperature of the InGaN quantum well layer is 800°C and the growth pressure is 200 torr. The growth temperature of the AlGaN quantum barrier layer is 920°C and the growth pressure is 200 torr.

[0122] (6) growing a hole expansion layer on the multi-quantum well layer;

[0123] Specifically, a BN layer and a Mg lightly doped GaN layer are periodically grown by MOCVD until a hole expansion layer is obtained. Specifically, the growth temperature of the BN layer is 920° C. and the growth pressure is 200 torr; the growth temperature of the Mg lightly doped GaN layer is 850° C. and the growth pressure is 200 torr.

[0124] (7) growing a hole storage layer on the hole extension layer;

[0125] Specifically, a GaN layer, an InGaN layer and a Mg-doped AlGaN layer are periodically grown by MOCVD until a hole storage layer is obtained. The growth temperature of the GaN layer is 820°C and the growth pressure is 200 torr; the growth temperature of the InGaN layer is 780°C and the growth pressure is 200 torr; the growth temperature of the Mg-doped AlGaN layer is 900°C and the growth pressure is 200 torr.

[0126] (8) growing a hole layer on the hole storage layer;

[0127] Specifically, in one embodiment of the present invention, a P-type BInGaN layer, a Mg3N2 layer and a P-type GaN layer are periodically grown by MOCVD. Specifically, the growth temperature of the P-type BInGaN layer is 800°C, and the growth pressure is 200torr; and during the growth of the P-type BInGaN layer, the MO source is continuously introduced. The growth temperature of the Mg3N2 layer is 800°C, and the growth pressure is 300torr; the growth temperature of the P-type GaN layer is 900°C, and the growth pressure is 200torr.

[0128] Example 2

[0129] This embodiment provides a high-light-efficiency Micro-LED epitaxial wafer, which differs from Embodiment 1 in that: the proportion of Al component in the Mg-doped AlGaN layer is 0.05; the proportion of In component in the P-type BInGaN layer is 0.05, and the proportion of B component is 0.12, and the band gap width of the P-type BInGaN layer is greater than the band gap width of the Mg-doped AlGaN layer.

[0130] The rest are the same as in Example 1.

[0131] Example 3

[0132] This embodiment provides a high-light-efficiency Micro-LED epitaxial wafer, which differs from Embodiment 2 in that:

[0133] The growth temperature of the P-type BInGaN layer is 820°C, the growth pressure is 100 torr, and the MO source is continuously introduced during the growth of the P-type BInGaN layer. The growth temperature of the Mg3N2 layer is 720°C, the growth pressure is 500 torr; the growth temperature of the P-type GaN layer is 900°C, and the growth pressure is 100 torr.

[0134] The rest are the same as in Example 2.

[0135] Example 4

[0136] This embodiment provides a high-light-efficiency Micro-LED epitaxial wafer, which differs from Embodiment 3 in that:

[0137] The preparation method of the P-type BInGaN layer is as follows: firstly introduce B source, In source, Ga source and N source for 5 seconds, then introduce Mg source and N source for 2 seconds, and repeat periodically until the P-type BInGaN layer is obtained.

[0138] The rest is the same as Example 3.

[0139] Comparative Example 1

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

[0141] The epitaxial wafer does not include a hole expansion layer, a hole storage layer, and a hole layer; an electron blocking layer and a P-GaN layer are sequentially arranged on the multi-quantum well layer. Specifically, the electron blocking layer is Al 0.4 Ga 0.6 N layer, with a thickness of 30nm; its growth temperature is 1120℃ and the growth pressure is 300torr.

[0142] The thickness of the P-GaN layer is 200 nm and its doping concentration is 3×10 20 cm -3 , the growth temperature is 950℃ and the growth pressure is 300torr.

[0143] The rest are the same as in Example 1.

[0144] Comparative Example 2

[0145] This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that:

[0146] The hole layer is a P-GaN layer with a thickness of 200 nm and a doping concentration of 3×10 20cm -3 , the growth temperature is 950℃ and the growth pressure is 300torr.

[0147] The rest are the same as in Example 1.

[0148] Comparative Example 3

[0149] This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that:

[0150] The hole storage layer is not included, and the rest is the same as in Example 1.

[0151] Comparative Example 4

[0152] This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that:

[0153] The hole expansion layer is not included, and the rest is the same as in Example 1.

[0154] Comparative Example 5

[0155] This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that:

[0156] The hole extension layer is replaced by a BN layer having a thickness of 20 nm and a growth condition consistent with that of the BN layer in Example 1.

[0157] The rest are the same as in Example 1.

[0158] Comparative Example 6

[0159] This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that:

[0160] The hole layer does not include the Mg3N2 layer, and the rest is the same as in Example 1.

[0161] The epitaxial wafers obtained in Examples 1 to 4 and Comparative Examples 1 to 6 were prepared into Micro-LEDs with a size of 50 μm×50 μm and a horizontal structure, and the 2 The brightness was tested at a current density of , and the brightness improvement rate was calculated based on the data of comparative example 1. The specific results are shown in the following table:

[0162]

[0163] It can be seen from the table that the high-efficiency Micro-LED epitaxial wafer in the present invention can effectively improve the luminous efficiency.

[0164] 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 high-light-efficiency Micro-LED epitaxial wafer, characterized in that: It includes a substrate, a buffer layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer, a hole expansion layer, a hole storage layer and a hole layer stacked in sequence on the substrate; The hole expansion layer is a periodic structure, each period includes a BN layer and a Mg lightly doped GaN layer stacked in sequence, and the Mg doping concentration in the Mg lightly doped GaN layer is ≤1×10 18 cm -3 ; The hole storage layer is a periodic structure, each period includes a GaN layer, an InGaN layer and a Mg-doped AlGaN layer stacked in sequence, and the Mg doping concentration in the Mg-doped AlGaN layer is ≤1×10 20 cm -3 ; The hole layer is a periodic structure, and each period includes a P-type BInGaN layer, a Mg3N2 layer and a P-type GaN layer stacked in sequence, and the doping concentration of the P-type BInGaN layer is ≥1×10 20 cm -3 The band gap width of the P-type BInGaN layer is greater than the band gap width of the Mg-doped AlGaN layer; the doping concentration of the P-type GaN layer is ≥1×10 19 cm -3 .

2. The high-light-efficiency Micro-LED epitaxial wafer according to claim 1, wherein: The thickness of the BN layer is ≤5 nm.

3. The high-light-efficiency Micro-LED epitaxial wafer according to claim 1 or 2, characterized in that: The period number of the hole extension layer is 2 to 20; and / or The thickness of the BN layer is 0.5 nm to 5 nm; and / or The thickness of the Mg lightly doped GaN layer is 1 nm to 10 nm, and the Mg doping concentration is 1×10 17 cm -3 ~1×10 18 cm -3 ; and / or The number of periods of the hole storage layer is 3 to 15; and / or The thickness of the GaN layer is 5nm to 15nm; and / or The thickness of the InGaN layer is 2nm-8nm, and the In component ratio is 0.01-0.2; and / or The thickness of the Mg-doped AlGaN layer is 2nm~10nm, the Al component ratio is 0.01~0.2, and the Mg doping concentration is 1×10 19 cm -3 ~1×10 20 cm -3 ; and / or The period number of the hole layer is 2 to 20; and / or The thickness of the P-type BInGaN layer is 2nm~10nm, the In component accounts for 0.05~0.2, the B component accounts for 0.01~0.2, and the Mg doping concentration is 1×10 20 cm -3 ~5×10 21 cm -3 ; and / or The thickness of the Mg3N2 layer is 1nm~8nm; and / or The thickness of the P-type GaN layer is 10 nm to 20 nm, and the Mg doping concentration is 5×10 19 cm -3 ~5×10 20 cm -3 .

4. A method for preparing a high-light-efficiency Micro-LED epitaxial wafer, used to prepare the high-light-efficiency Micro-LED epitaxial wafer as claimed in any one of claims 1 to 3, characterized in that: include: Providing a substrate, and sequentially growing a buffer layer, a non-doped GaN layer, an N-type GaN layer, a multi-quantum well layer, a hole expansion layer, a hole storage layer, and a hole layer on the substrate; The hole expansion layer is a periodic structure, each period includes a BN layer and a Mg lightly doped GaN layer stacked in sequence, and the Mg doping concentration in the Mg lightly doped GaN layer is ≤1×10 18 cm -3 ; The hole storage layer is a periodic structure, each period includes a GaN layer, an InGaN layer and a Mg-doped AlGaN layer stacked in sequence, and the Mg doping concentration in the Mg-doped AlGaN layer is ≤1×10 20 cm -3 ; The hole layer is a periodic structure, and each period includes a P-type BInGaN layer, a Mg3N2 layer and a P-type GaN layer stacked in sequence, and the doping concentration of the P-type BInGaN layer is ≥1×10 20 cm -3 The band gap width of the P-type BInGaN layer is greater than the band gap width of the Mg-doped AlGaN layer; the doping concentration of the P-type GaN layer is ≥1×10 19 cm -3 .

5. The method for preparing a high-light-efficiency Micro-LED epitaxial wafer according to claim 4, characterized in that: The growth temperature of the Mg3N2 layer is lower than the growth temperature of the P-type BInGaN layer; The growth temperature of the Mg3N2 layer is lower than the growth temperature of the P-type GaN layer; and / or The growth pressure of the Mg3N2 layer is greater than the growth pressure of the P-type BInGaN layer; The growth pressure of the Mg3N2 layer is greater than the growth pressure of the P-type GaN layer.

6. The method for preparing a high-light-efficiency Micro-LED epitaxial wafer according to claim 4, characterized in that: During the growth of the P-type BInGaN layer, the B source, In source, Ga source and N source are first introduced for 3s to 5s, and then the Mg source and N source are introduced for 1s to 3s, and the process is repeated periodically until the P-type BInGaN layer is obtained.

7. The method for preparing a high-light-efficiency Micro-LED epitaxial wafer according to claim 4, characterized in that: The growth temperature of the BN layer is 800° C. to 1000° C., and the growth pressure is 50 torr to 500 torr; and / or The growth temperature of the Mg lightly doped GaN layer is 800° C. to 900° C., and the growth pressure is 50 torr to 500 torr; and / or The growth temperature of the GaN layer is 800° C. to 900° C., and the growth pressure is 50 torr to 500 torr; and / or The growth temperature of the InGaN layer is 750° C. to 850° C., and the growth pressure is 50 torr to 500 torr; and / or The growth temperature of the Mg-doped AlGaN layer is 850° C. to 1000° C., and the growth pressure is 50 torr to 500 torr; and / or The growth temperature of the P-type BInGaN layer is 750° C. to 850° C., and the growth pressure is 50 torr to 200 torr; and / or The growth temperature of the Mg3N2 layer is 700°C to 850°C, and the growth pressure is 300torr to 500torr; and / or The growth temperature of the P-type GaN layer is 900° C. to 1000° C., and the growth pressure is 50 torr to 200 torr.

8. The method for preparing a high-light-efficiency Micro-LED epitaxial wafer according to claim 5 or 6, characterized in that: The hole concentration of the hole layer is 1×10 18 cm -3 ~5×10 19 cm -3 .

9. A Micro-LED, characterized in that: Comprising the high-efficiency Micro-LED epitaxial wafer as described in any one of claims 1 to 3.

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