Micro-LED epitaxial wafer and preparation method thereof

Abstract

The invention discloses a Micro-LED epitaxial wafer and a preparation method thereof, and relates to the technical field of semiconductors. The Micro-LED epitaxial wafer comprises a substrate, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer. The barrier height of the first hole injection enhancement layer is greater than that of the second hole injection enhancement layer; the first hole injection enhancement layer comprises a first sub-layer, a second sub-layer and a third sub-layer which are stacked in sequence; and the second hole injection enhancement layer comprises a fourth sub-layer, a fifth sub-layer and a sixth sub-layer which are stacked in sequence. By implementing the invention, the lighting effect of the Micro-LED chip under low working current density can be improved.

Description

Technical Field

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

[0002] Micron-sized LED chips (Micro-LED) have excellent properties such as nanosecond-level high-speed response performance, stable characteristics of inorganic materials, high light efficiency, high reliability, high color purity, high contrast, and transparency. They have great application prospects in display, visible light communication, and biomedicine. However, under different current densities, the dominant reasons for the luminescence mechanism of LED devices are different, and the corresponding epitaxial layer structure also changes. For example, in the 0.01A / cm working range of Micro-LED, 2 ~0.5A / cm 2 At low current density, the carrier concentration in the quantum well is relatively low, the proportion of Auger recombination is small, and the corresponding quantum well recombination volume is reduced, which can reduce the number of quantum wells, reduce the number of defects, and improve the EQE of the device at low current density; at the same time, electron leakage has not occurred or the proportion is very low at low current density. The electron blocking layer structure not only has no effect of blocking electrons, but will block the injection of holes, reducing the quantum efficiency of the device. The current goal of epitaxial layer structure design and material growth is to improve the efficiency at high current density, and its peak EQE is usually at 1A / cm 2 ~4A / cm² current density range, without paying attention to the device efficiency at low current density, LEDs designed using traditional epitaxial structures can no longer meet the application requirements of Micro-LEDs. 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 significantly improve the hole injection efficiency and improve the matching degree of the electron-hole concentration of the multi-quantum well light-emitting layer, thereby improving the luminous efficiency of the Micro-LED chip at low operating current density.

[0004] In order to solve the above problems, the present invention discloses a Micro-LED epitaxial wafer, comprising a substrate, and an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer sequentially stacked on the substrate; The barrier height of the first hole injection enhancement layer is greater than the barrier height of the second hole injection enhancement layer; The first hole injection enhancement layer includes a first sublayer, a second sublayer and a third sublayer stacked in sequence; the first sublayer includes an AlN layer and a first InGaN layer stacked alternately periodically; the second sublayer includes a first AlGaN layer and a second InGaN layer stacked alternately periodically; the third sublayer includes a second AlGaN layer and a third InGaN layer stacked alternately periodically; The second hole injection enhancement layer includes a fourth sublayer, a fifth sublayer and a sixth sublayer stacked in sequence; the fourth sublayer includes a third AlGaN layer and a fourth InGaN layer periodically and alternately stacked; the fifth sublayer includes a fourth AlGaN layer, a fifth InGaN layer and a sixth InGaN layer periodically and alternately stacked; the sixth sublayer includes a fifth AlGaN layer, a seventh InGaN layer and an eighth InGaN layer periodically and alternately stacked.

[0005] As an improvement of the above technical solution, the In component ratio of the first InGaN layer is equal to the In component ratio of the second InGaN layer, and is equal to the In component ratio of the third InGaN layer; The In component ratio of the fourth InGaN layer is smaller than the In component ratio of the fifth InGaN layer, smaller than the In component ratio of the seventh InGaN layer, smaller than the In component ratio of the sixth InGaN layer, and smaller than the In component ratio of the eighth InGaN layer.

[0006] As an improvement of the above technical solution, the Al component ratio of the first AlGaN layer is greater than the Al component ratio of the second AlGaN layer, and greater than the Al component ratio of the third AlGaN layer, and greater than the Al component ratio of the fourth AlGaN layer, and greater than the Al component ratio of the fifth AlGaN layer.

[0007] As an improvement of the above technical solution, the number of cycles of the alternating growth of the first sub-layer is 1-3; the thickness of the AlN layer is 0.5nm-5nm; the In component ratio of the first InGaN layer is 0.01-0.09, and the thickness is 0.5nm-5nm; The number of cycles of the alternating growth of the second sub-layer is 2-5; the Al component ratio of the first AlGaN layer is 0.5-0.88, and the thickness is 0.5nm-5nm; the In component ratio of the second InGaN layer is 0.01-0.09, and the thickness is 0.5nm-5nm; The number of cycles of the alternating growth of the third sublayer is 2 to 6; the Al component ratio of the second AlGaN layer is 0.38 to 0.8, and the thickness is 0.5 nm to 5 nm; the third InGaN layer is a Mg-doped InGaN layer, the In component ratio is 0.01 to 0.09, the thickness is 0.5 nm to 5 nm, and the Mg doping concentration is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 .

[0008] As an improvement of the above technical solution, the number of cycles of the alternating growth of the fourth sublayer is 2 to 5; the Al component ratio of the third AlGaN layer is 0.3 to 0.7, and the thickness is 0.36 nm to 2.8 nm; the fourth InGaN layer is a Mg-doped InGaN layer, the In component is 0.01 to 0.07, the thickness is 0.36 nm to 2.8 nm, and the Mg doping concentration is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 ; The fifth sublayer has an alternating growth period of 3 to 7; the fourth AlGaN layer has an Al component ratio of 0.2 to 0.6 and a thickness of 0.36 nm to 2.8 nm; the fifth InGaN layer is a Mg-doped InGaN layer, with an In component ratio of 0.02 to 0.08, a thickness of 0.36 nm to 2.8 nm, and a Mg doping concentration of 2.08×10 18 cm -3 ~2.56×10 19 cm -3 The sixth InGaN layer is a Mg-doped InGaN layer, the In component ratio is 0.03-0.12, the thickness is 0.36 nm-2.8 nm, and the Mg doping concentration is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 ; The sixth sublayer has an alternating growth period of 3 to 10; the fifth AlGaN layer has an Al component ratio of 0.1 to 0.5 and a thickness of 0.36 nm to 2.8 nm; the seventh InGaN layer is a Mg-doped InGaN layer, with an In component ratio of 0.02 to 0.1, a thickness of 0.36 nm to 2.8 nm, and a Mg doping concentration of 2.08×10 18 cm -3 ~2.56×10 19 cm -3The eighth InGaN layer is a Mg-doped InGaN layer, the In component ratio is 0.03-0.15, the thickness is 0.36 nm-2.8 nm, and the Mg doping concentration is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 .

[0009] As an improvement of the above technical solution, the first P-type semiconductor layer is a Mg-doped AlInGaN layer, the Al component accounts for 0.01-0.27, the In component accounts for 0.01-0.08, the thickness is 6nm-258nm, and the Mg doping concentration is 1.35×10 19 cm -3 ~5.62×10 20 cm -3 ; Along the epitaxial growth direction, the Al component ratio and Mg doping concentration of the first P-type semiconductor layer decrease; The second P-type semiconductor layer is a Mg-doped GaN layer with a thickness of 5 nm to 210 nm and a Mg doping concentration of 1.12×10 19 cm -3 ~3.57×10 20 cm -3 ; Along the epitaxial growth direction, the Mg doping concentration of the second P-type semiconductor layer decreases; The P-type ohmic contact layer is a Mg-doped AlInGaN layer, the Al component accounts for 0.01-0.19, the In component accounts for 0.01-0.28, the thickness is 0.8nm-32nm, and the Mg doping concentration is 3.12×10 19 cm -3 ~8.75×10 20 cm -3 ; Along the epitaxial growth direction, the In component proportion of the P-type ohmic contact layer increases.

[0010] Correspondingly, the present invention also discloses a method for preparing a Micro-LED epitaxial wafer, which is used to prepare the above-mentioned Micro-LED epitaxial wafer, comprising the following steps: A substrate is provided, and an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer are sequentially grown on the substrate; The first hole injection enhancement layer includes a first sublayer, a second sublayer and a third sublayer stacked in sequence; the first sublayer includes an AlN layer and a first InGaN layer stacked periodically and alternately, the second sublayer includes a first AlGaN layer and a second InGaN layer stacked periodically and alternately, and the third sublayer includes a second AlGaN layer and a third InGaN layer stacked periodically and alternately; The second hole injection enhancement layer includes a fourth sublayer, a fifth sublayer and a sixth sublayer stacked in sequence; the fourth sublayer includes a third AlGaN layer and a fourth InGaN layer periodically and alternately stacked, the fifth sublayer includes a fourth AlGaN layer, a fifth InGaN layer and a sixth InGaN layer periodically and alternately stacked, and the sixth sublayer includes a fifth AlGaN layer, a seventh InGaN layer and an eighth InGaN layer periodically and alternately stacked; The barrier height of the first hole injection enhancement layer is greater than the barrier height of the second hole injection enhancement layer.

[0011] As an improvement of the above technical solution, the growth temperature of the AlN layer is 860°C~1080°C, and the growth pressure is 50torr~390torr; the growth temperature of the first InGaN layer is 820°C~1050°C, and the growth pressure is 50torr~390torr; The growth temperature of the first AlGaN layer is 860° C. to 1080° C., and the growth pressure is 50 torr to 390 torr; the growth temperature of the second InGaN layer is 820° C. to 1050° C., and the growth pressure is 50 torr to 390 torr; The growth temperature of the second AlGaN layer is 860°C to 1080°C, and the growth pressure is 50torr to 390torr; the growth temperature of the third InGaN layer is 820°C to 1050°C, and the growth pressure is 50torr to 390torr; The growth temperature of the third AlGaN layer is 860° C. to 1080° C., and the growth pressure is 50 torr to 390 torr; the growth temperature of the fourth InGaN layer is 820° C. to 1050° C., and the growth pressure is 50 torr to 390 torr; The growth temperature of the fourth AlGaN layer is 860°C to 1080°C, and the growth pressure is 50torr to 390torr; the growth temperature of the fifth InGaN layer is 820°C to 1050°C, and the growth pressure is 50torr to 390torr; the growth temperature of the sixth InGaN layer is 820°C to 1050°C, and the growth pressure is 50torr to 390torr; The growth temperature of the fifth AlGaN layer is 860°C~1080°C, and the growth pressure is 50torr~390torr; the growth temperature of the seventh InGaN layer is 820°C~1050°C, and the growth pressure is 50torr~390torr; the growth temperature of the eighth InGaN layer is 820°C~1050°C, and the growth pressure is 50torr~390torr.

[0012] As an improvement of the above technical solution, after the deposition of the fifth InGaN layer, the sixth InGaN layer, the seventh InGaN layer and the eighth InGaN layer, annealing treatment is performed at a temperature of 820° C. to 1080° C. and a pressure of 50 torr to 390 torr.

[0013] As an improvement of the above technical solution, the growth temperature of the second P-type semiconductor layer is greater than the growth temperature of the first P-type semiconductor layer; The growth temperature of the first P-type semiconductor layer is 716° C. to 858° C., and the growth pressure is 30 torr to 500 torr; The growth temperature of the second P-type semiconductor layer is 890° C. to 1060° C., and the growth pressure is 30 torr to 500 torr; The growth temperature of the P-type ohmic contact layer is 836° C. to 952° C., and the growth pressure is 30 torr to 500 torr.

[0014] The implementation of the present invention has the following beneficial effects: 1. The multi-quantum well light-emitting layer of the present invention is not provided with an electron blocking layer, but a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer and a second P-type semiconductor layer are stacked in sequence, which can eliminate the blocking effect of the electron blocking layer on hole injection, improve the hole injection efficiency of the P-type semiconductor material and improve the matching degree of the electron hole concentration in the multi-quantum well light-emitting layer. In addition, the barrier height of the first hole injection enhancement layer is greater than the barrier height of the second hole injection enhancement layer, which can weaken the blocking effect of the high barrier material on holes.

[0015] 2. The wide bandgap AlN and AlGaN materials in the first hole injection enhancement layer and the second hole injection enhancement layer of the present invention mainly play the role of reducing the electron mobility rate and preventing electrons from being injected into the P-type semiconductor material to cause electron leakage, while the low bandgap InGaN material in the first hole injection enhancement layer and the second hole injection enhancement layer can store some holes and at the same time weaken the blocking effect on hole injection of the P-type semiconductor material, so as to improve the hole injection efficiency of the P-type semiconductor material and improve the matching degree of the electron hole concentration in the multi-quantum well light-emitting layer, thereby improving the luminous efficiency of the Micro-LED. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of a Micro-LED epitaxial wafer in one embodiment of the present invention; Figure 2 is a schematic structural diagram of a first hole injection enhancement layer of a Micro-LED epitaxial wafer in one embodiment of the present invention; Figure 3 is a schematic structural diagram of a second hole injection enhancement layer of a Micro-LED epitaxial wafer in one embodiment of the present invention; Figure 4 It is a flow chart of a method for preparing a Micro-LED epitaxial wafer in one embodiment of the present invention. DETAILED DESCRIPTION

[0017] 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.

[0018] like Figure 1 As shown, the present invention provides a Micro-LED epitaxial wafer, including a substrate 100, and an N-type semiconductor layer 200, a low-temperature stress release layer 300, a multi-quantum well light-emitting layer 400, a first hole injection enhancement layer 500, a first P-type semiconductor layer 600, a second hole injection enhancement layer 700, a second P-type semiconductor layer 800 and a P-type ohmic contact layer 900 stacked in sequence on the substrate 100.

[0019] Under low operating current density, the electron leakage of Micro-LED has not occurred or the electron leakage ratio is very low. The traditional electron blocking layer structure not only has no effect of blocking electrons, but will block the injection of holes, reducing the quantum efficiency of the device. The multi-quantum well light-emitting layer 400 of the present invention does not have an electron blocking layer, but the first hole injection enhancement layer 500, the first P-type semiconductor layer 600, the second hole injection enhancement layer 700 and the second P-type semiconductor layer 800 are sequentially stacked and grown, which can eliminate the blocking effect of the electron blocking layer on hole injection, improve the hole injection efficiency of the P-type semiconductor material and improve the matching degree of the electron hole concentration in the multi-quantum well light-emitting layer. Among them, the barrier height of the first hole injection enhancement layer 500 is greater than the barrier height of the second hole injection enhancement layer 700, which can weaken the blocking effect of the high barrier material on holes.

[0020] Specifically, Figure 2As shown, the first hole injection enhancement layer 500 includes a first sublayer 510, a second sublayer 520 and a third sublayer 530 stacked in sequence; the first sublayer 510 includes an AlN layer 511 and a first InGaN layer 512 periodically alternately stacked; the second sublayer 520 includes a first AlGaN layer 521 and a second InGaN layer 522 periodically alternately stacked; the third sublayer 530 includes a second AlGaN layer 531 and a third InGaN layer 532 periodically alternately stacked.

[0021] like Figure 3 As shown, the second hole injection enhancement layer 700 includes a fourth sublayer 710, a fifth sublayer 720 and a sixth sublayer 730 stacked in sequence; the fourth sublayer 710 includes a third AlGaN layer 711 and a fourth InGaN layer 712 periodically alternately stacked; the fifth sublayer 720 includes a fourth AlGaN layer 721, a fifth InGaN layer 722 and a sixth InGaN layer 723 periodically alternately stacked; the sixth sublayer 730 includes a fifth AlGaN layer 731, a seventh InGaN layer 732 and an eighth InGaN layer 733 periodically alternately stacked.

[0022] The wide bandgap AlN and AlGaN materials in the first hole injection enhancement layer and the second hole injection enhancement layer of the present invention mainly play the role of reducing the electron mobility rate, preventing electrons from being injected into the P-type semiconductor material to cause electron leakage, while the low bandgap InGaN material in the first hole injection enhancement layer and the second hole injection enhancement layer can store some holes and also weaken the blocking effect on hole injection of the P-type semiconductor material, so as to improve the hole injection efficiency of the P-type semiconductor material.

[0023] In a preferred embodiment, the In component ratio of the first InGaN layer 512 is equal to the In component ratio of the second InGaN layer 522 , and is equal to the In component ratio of the third InGaN layer 532 .

[0024] The In component ratio of the fourth InGaN layer 712 is less than the In component ratio of the fifth InGaN layer 722, and less than the In component ratio of the seventh InGaN layer 732, and less than the In component ratio of the sixth InGaN layer 723, and less than the In component ratio of the eighth InGaN layer 733. In one embodiment, the In component ratios of the fourth InGaN layer 712, the fifth InGaN layer 722, the seventh InGaN layer 732, the sixth InGaN layer 723, and the eighth InGaN layer 733 increase. The size of In atoms is relatively large, and they react with NH3 to generate In-N with a narrow energy band gap, which has a weak effect on electron holes. Therefore, the In component of the InGaN material in the fourth sublayer, the fifth sublayer, and the sixth sublayer increases along the epitaxial growth direction, enhancing the blocking effect of the hole injection enhancement layer close to the multi-quantum well light-emitting layer on electrons, and weakening the blocking effect of the hole injection enhancement layer close to the P-type ohmic contact layer on hole injection.

[0025] In a preferred embodiment, the Al component ratio of the first AlGaN layer 521 is greater than the Al component ratio of the second AlGaN layer 531, and greater than the Al component ratio of the third AlGaN layer 711, and greater than the Al component ratio of the fourth AlGaN layer 721, and greater than the Al component ratio of the fifth AlGaN layer 731. In one embodiment, the Al component ratios of the first AlGaN layer 521, the second AlGaN layer 531, the third AlGaN layer 711, the fourth AlGaN layer 721, and the fifth AlGaN layer 731 decrease. The Al atom size is relatively small, and the Al-N generated by the reaction with NH3 has a wide energy band gap, and has a significant blocking effect on electron holes. Therefore, along the epitaxial growth direction, the Al component ratio decreases, which enhances the blocking of electrons by the hole injection enhancement layer close to the multi-quantum well light-emitting layer, and weakens the blocking of hole injection by the hole injection enhancement layer close to the P-type ohmic contact layer.

[0026] Specifically, in one embodiment, the number of cycles of the alternating growth of the first sublayer 510 is 1 to 3. The AlN layer 511 is an unintentionally doped AlN layer, and the thickness is 0.5 nm to 5 nm, and is exemplarily 0.8 nm, 1 nm, 2 nm, 3 nm or 4 nm, but is not limited thereto. The first InGaN layer 512 is an unintentionally doped InGaN layer, and the In component ratio is 0.01 to 0.09, and is exemplarily 0.02, 0.04, 0.05, 0.07 or 0.08, but is not limited thereto. The thickness of the first InGaN layer is 0.5 nm to 5 nm, and is exemplarily 0.8 nm, 1 nm, 2 nm, 3 nm or 4 nm, but is not limited thereto.

[0027] The number of cycles of the alternating growth of the second sublayer 520 is 2 to 5. The first AlGaN layer 521 is an unintentionally doped AlGaN layer, the Al component ratio is 0.5 to 0.88, and is 0.55, 0.6, 0.7, 0.8 or 0.85, but not limited thereto. The thickness of the first AlGaN layer is 0.5 nm to 5 nm, and is 0.8 nm, 1 nm, 2 nm, 3 nm or 4 nm, but not limited thereto. The second InGaN layer 522 is an unintentionally doped InGaN layer, the In component ratio is 0.01 to 0.09, and is 0.02, 0.04, 0.05, 0.07 or 0.08, but not limited thereto. The thickness of the second InGaN layer is 0.5 nm to 5 nm, and is 0.8 nm, 1 nm, 2 nm, 3 nm or 4 nm, but not limited thereto.

[0028] The number of cycles of alternating growth of the third sublayer 530 is 2 to 6. The second AlGaN layer 531 is an AlGaN layer that is not intentionally doped, and the Al component ratio is 0.38 to 0.8, and is 0.4, 0.5, 0.55, 0.6 or 0.7, but not limited to this. The thickness of the second AlGaN layer is 0.5nm to 5nm, and is 0.8nm, 1nm, 2nm, 3nm or 4nm, but not limited to this. The In component ratio of the third InGaN layer 532 is 0.01 to 0.09, and is 0.02, 0.04, 0.05, 0.07 or 0.08, but not limited to this. The thickness of the third InGaN layer is 0.5nm to 5nm, and is 0.8nm, 1nm, 2nm, 3nm or 4nm, but not limited to this. The Mg doping concentration of the third InGaN layer is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 , an exemplary value is 2.5×10 18 cm -3 , 5×10 18 cm -3 , 8×10 18 cm -3 , 1×10 19 cm -3 or 2×10 19 cm -3 , but not limited to this.

[0029] The number of cycles of alternating growth of the fourth sublayer 710 is 2 to 5. The third AlGaN layer 711 is an AlGaN layer that is not intentionally doped, and the Al component ratio is 0.3 to 0.7, and is 0.4, 0.45, 0.5, 0.55 or 0.6, but not limited thereto. The thickness of the third AlGaN layer is 0.36 nm to 2.8 nm, and is 0.5 nm, 0.8 nm, 1 nm, 1.5 nm or 2 nm, but not limited thereto. The In component of the fourth InGaN layer 712 is 0.01 to 0.07, and is 0.02, 0.03, 0.04, 0.05 or 0.06, but not limited thereto. The thickness of the fourth InGaN layer is 0.36 nm to 2.8 nm, and is 0.5 nm, 0.8 nm, 1 nm, 1.5 nm or 2 nm, but not limited thereto. The Mg doping concentration of the fourth InGaN layer is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 , an exemplary value is 2.5×10 18 cm -3 , 5×10 18 cm -3 , 8×10 18 cm -3 , 1×10 19 cm -3 or 2×10 19 cm -3 , but not limited to this.

[0030] The number of cycles of alternating growth of the fifth sublayer 720 is 3 to 7. The fourth AlGaN layer 721 is an AlGaN layer that is not intentionally doped, and the Al component ratio is 0.2 to 0.6, and is 0.3, 0.35, 0.4, 0.45 or 0.5, but not limited to this. The thickness of the fourth AlGaN layer is 0.36nm to 2.8nm, and is 0.5nm, 0.8nm, 1nm, 1.5nm or 2nm, but not limited to this. The In component ratio of the fifth InGaN layer 722 is 0.02 to 0.08, and is 0.03, 0.04, 0.05, 0.06 or 0.07, but not limited to this. The thickness of the fifth InGaN layer is 0.36nm to 2.8nm, and is 0.5nm, 0.8nm, 1nm, 1.5nm or 2nm, but not limited to this. The Mg doping concentration of the fifth InGaN layer is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 , an exemplary value is 2.5×10 18 cm -3 , 5×10 18 cm-3 , 8×10 18 cm -3 , 1×10 19 cm -3 or 2×10 19 cm -3 The In component ratio of the sixth InGaN layer 723 is 0.03-0.12, and is 0.04, 0.05, 0.07, 0.09 or 0.1, but is not limited thereto. The thickness of the sixth InGaN layer is 0.36nm-2.8nm, and is 0.5nm, 0.8nm, 1nm, 1.5nm or 2nm, but is not limited thereto. The Mg doping concentration of the sixth InGaN layer is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 , an exemplary value is 2.5×10 18 cm -3 , 5×10 18 cm -3 , 8×10 18 cm -3 , 1×10 19 cm -3 or 2×10 19 cm -3 , but not limited to this.

[0031] The number of cycles of alternating growth of the sixth sublayer 730 is 3 to 10. The fifth AlGaN layer 731 is an AlGaN layer that is not intentionally doped, and the Al component ratio is 0.1 to 0.5, and is 0.15, 0.2, 0.25, 0.3 or 0.4, but not limited thereto. The thickness of the fifth AlGaN layer is 0.36 nm to 2.8 nm, and is 0.5 nm, 0.8 nm, 1 nm, 1.5 nm or 2 nm, but not limited thereto. The In component ratio of the seventh InGaN layer 732 is 0.02 to 0.1, and is 0.03, 0.04, 0.06, 0.07 or 0.08, but not limited thereto. The thickness of the seventh InGaN layer is 0.36 nm to 2.8 nm, and is 0.5 nm, 0.8 nm, 1 nm, 1.5 nm or 2 nm, but not limited thereto. The Mg doping concentration of the seventh InGaN layer is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 , an exemplary value is 2.5×10 18 cm -3 , 5×10 18 cm -3 , 8×10 18 cm-3 , 1×10 19 cm -3 or 2×10 19 cm -3 The In component ratio of the eighth InGaN layer 733 is 0.03-0.15, and is 0.05, 0.08, 0.1, 0.12 or 0.14, but not limited thereto. The thickness of the eighth InGaN layer is 0.36nm-2.8nm, and is 0.5nm, 0.8nm, 1nm, 1.5nm or 2nm, but not limited thereto. The Mg doping concentration of the eighth InGaN layer is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 , an exemplary value is 2.5×10 18 cm -3 , 5×10 18 cm -3 , 8×10 18 cm -3 , 1×10 19 cm -3 or 2×10 19 cm -3 , but not limited to this.

[0032] In the third sublayer of the first hole injection enhancement layer and the second hole injection enhancement layer, the InGaN material is doped with Mg element, which can provide some holes to the multi-quantum well light-emitting layer to participate in luminescence, further improve the hole injection efficiency, and improve the electron-hole matching in the multi-quantum well light-emitting layer, thereby improving the luminescence efficiency of Micro-LED.

[0033] In one embodiment, the first P-type semiconductor layer 600 is a Mg-doped AlInGaN layer, the Al component ratio is 0.01-0.27, exemplarily 0.05, 0.08, 0.1, 0.15 or 0.2, but not limited thereto, the In component ratio is 0.01-0.08, exemplarily 0.02, 0.04, 0.05, 0.06 or 0.07, but not limited thereto, and the Mg doping concentration is 1.35×10 19 cm -3 ~5.62×10 20 cm -3 , an exemplary value is 2.5×10 19 cm -3 , 5×10 19 cm -3 , 8×10 19 cm -3 , 1×10 20 cm -3or 2.5 × 10 20 cm -3 , but not limited to this, the thickness of the first P-type semiconductor layer is 6nm~258nm, exemplarily 10nm, 50nm, 100nm, 150nm or 200nm, but not limited to this. The first P-type semiconductor layer is a main functional layer that provides holes, which can improve the hole injection efficiency of the P-type semiconductor material. In a preferred embodiment, along the epitaxial growth direction, the Al component ratio and Mg doping concentration of the first P-type semiconductor layer decrease, the band gap of the first P-type semiconductor layer close to the multi-quantum well light-emitting layer is wider, and the blocking of electrons is enhanced. The band gap of the first P-type semiconductor layer close to the P-type ohmic contact layer is narrower, which weakens the blocking of hole injection.

[0034] In one embodiment, the second P-type semiconductor layer 800 is a Mg-doped GaN layer, and the Mg doping concentration is 1.12×10 19 cm -3 ~3.57×10 20 cm -3 , an exemplary value is 2.5×10 19 cm -3 , 5×10 19 cm -3 , 8×10 19 cm -3 , 1×10 20 cm -3 or 2.5 × 10 20 cm -3 , but not limited thereto, the thickness of the second P-type semiconductor layer is 5nm~210nm, exemplarily 10nm, 50nm, 100nm, 150nm or 200nm, but not limited thereto. In a preferred embodiment, along the epitaxial growth direction, the Mg doping concentration of the second P-type semiconductor layer decreases, the band gap of the second P-type semiconductor layer close to the multi-quantum well light-emitting layer is wider, enhancing the blocking of electrons, and the band gap of the second P-type semiconductor layer close to the P-type ohmic contact layer is narrower, weakening the blocking of hole injection.

[0035] In one embodiment, the P-type ohmic contact layer 900 is a Mg-doped AlInGaN layer, the Al component ratio is 0.01-0.19, exemplarily 0.02, 0.05, 0.08, 0.1 or 0.15, but not limited thereto, the In component ratio is 0.01-0.28, exemplarily 0.05, 0.08, 0.1, 0.15 or 0.2, but not limited thereto, and the Mg doping concentration is 3.12×10 19 cm -3 ~8.75×10 20 cm -3 , exemplarily 5×1019 cm -3 , 8×10 19 cm -3 , 1×10 20 cm -3 , 2.5×10 20 cm -3 or 5×10 20 cm -3 , but not limited thereto, the thickness of the P-type ohmic contact layer is 0.8nm~32nm, exemplarily 1nm, 5nm, 10nm, 20nm or 30nm, but not limited thereto. In a preferred embodiment, along the epitaxial growth direction, the proportion of the In component of the P-type ohmic contact layer increases, further reducing the activation energy of the Mg element, thereby increasing the hole concentration and improving the ohmic contact performance.

[0036] In addition to the above structure, other layered structures of the present invention are characterized as follows: The substrate 100 may be one of a sapphire substrate, a SiO2 sapphire composite substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, and a zinc oxide substrate.

[0037] The N-type semiconductor layer 200 includes an undoped GaN layer and an N-type GaN layer. The thickness of the undoped GaN layer is 1 μm to 5 μm, the thickness of the N-type GaN layer is 2 μm to 3 μm, and the Si doping concentration is 1×10 19 cm -3 ~5×10 19 cm -3 .

[0038] The low temperature stress release layer 300 may include periodically alternately stacked InGaN stress release layers and GaN stress release layers, and the number of alternately grown cycles is 2 to 10. The thickness of the InGaN stress release layer is 1 nm to 3 nm, and the thickness of the GaN stress release layer is 15 nm to 30 nm.

[0039] The multi-quantum well light-emitting layer 400 includes periodically alternately stacked InGaN quantum well layers and AlGaN quantum barrier layers, and the number of alternating growth periods is 3 to 15. Among them, the In component in the InGaN quantum well layer accounts for 0.1 to 0.3, and the thickness is 2nm to 5nm, and the Al component in the AlGaN quantum barrier layer accounts for 0.01 to 0.1, and the thickness is 5nm to 15nm.

[0040] like Figure 4 As shown, the present invention also discloses a method for preparing a Micro-LED epitaxial wafer, which is used to prepare the above-mentioned Micro-LED epitaxial wafer, comprising the following steps: S1. Provide a substrate.

[0041] S2. Growing an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer in sequence on the substrate.

[0042] Specifically, the preparation of the first hole injection enhancement layer includes sequentially growing a first sublayer, a second sublayer and a third sublayer on the multi-quantum well light-emitting layer.

[0043] In one embodiment, the preparation of the first sublayer includes the following steps: controlling the growth temperature to 860°C~1080°C, the growth pressure to 50torr~390torr, introducing Al source and N source to grow an AlN layer; controlling the growth temperature to 820°C~1050°C, the growth pressure to 50torr~390torr, introducing In source, Ga source and N source to grow a first InGaN layer; repeatedly stacking and periodically growing the AlN layer and the first InGaN layer.

[0044] In one embodiment, the preparation of the second sublayer includes the following steps: controlling the growth temperature to 860°C~1080°C, the growth pressure to 50torr~390torr, introducing Al source, Ga source and N source, and growing a first AlGaN layer; controlling the growth temperature to 820°C~1050°C, the growth pressure to 50torr~390torr, introducing In source, Ga source and N source, and growing a second InGaN layer; repeating the periodic growth of the first AlGaN layer and the second InGaN layer by stacking.

[0045] In one embodiment, the preparation of the third sublayer includes the following steps: controlling the growth temperature to 860°C~1080°C, the growth pressure to 50torr~390torr, introducing Al source, Ga source and N source to grow a second AlGaN layer; controlling the growth temperature to 820°C~1050°C, the growth pressure to 50torr~390torr, introducing In source, Ga source, N source and Mg source to grow a third InGaN layer; repeating the stacking periodically to grow the second AlGaN layer and the third InGaN layer.

[0046] In one embodiment, the preparation of the first P-type semiconductor layer includes the following steps: controlling the growth temperature to 716°C~858°C, the growth pressure to 30torr~500torr, introducing Al source, In source, Ga source, N source and Mg source to grow the first P-type semiconductor layer.

[0047] Specifically, the preparation of the second hole injection enhancement layer includes sequentially growing a fourth sublayer, a fifth sublayer and a sixth sublayer on the first P-type semiconductor layer.

[0048] In one embodiment, the preparation of the fourth sublayer includes the following steps: controlling the growth temperature to 860°C~1080°C, the growth pressure to 50torr~390torr, introducing Al source, Ga source and N source, and growing a third AlGaN layer; controlling the growth temperature to 820°C~1050°C, the growth pressure to 50torr~390torr, introducing In source, Ga source, N source and Mg source, and growing a fourth InGaN layer; repeating the stacking periodically to grow the third AlGaN layer and the fourth InGaN layer.

[0049] In one embodiment, the preparation of the fifth sublayer includes the following steps: controlling the growth temperature to 860°C~1080°C, the growth pressure to 50torr~390torr, introducing Al source, Ga source and N source, and growing a fourth AlGaN layer; controlling the growth temperature to 820°C~1050°C, the growth pressure to 50torr~390torr, introducing In source, Ga source, N source and Mg source, and growing a fifth InGaN layer; controlling the growth temperature to 820°C~1050°C, the growth pressure to 50torr~390torr, introducing In source, Ga source, N source and Mg source, and growing a sixth InGaN layer; repeating the stacking periodically to grow the fourth AlGaN layer, the fifth InGaN layer and the sixth InGaN layer.

[0050] In one embodiment, the preparation of the sixth sublayer includes the following steps: controlling the growth temperature to 860°C~1080°C, the growth pressure to 50torr~390torr, introducing Al source, Ga source and N source, and growing the fifth AlGaN layer; controlling the growth temperature to 820°C~1050°C, the growth pressure to 50torr~390torr, introducing In source, Ga source, N source and Mg source, and growing the seventh InGaN layer; controlling the growth temperature to 820°C~1050°C, the growth pressure to 50torr~390torr, introducing In source, Ga source, N source and Mg source, and growing the eighth InGaN layer; repeating the stacking periodically to grow the fifth AlGaN layer, the seventh InGaN layer and the eighth InGaN layer.

[0051] In a preferred embodiment, after the deposition of the fifth InGaN layer, the sixth InGaN layer, the seventh InGaN layer, and the eighth InGaN layer, annealing treatment is performed. After the growth of the fifth InGaN layer, the sixth InGaN layer, the seventh InGaN layer, and the eighth InGaN layer, the temperature of the annealing treatment is controlled to be 820°C to 1080°C, and the pressure is 50torr to 390torr. The H2 and N2 mixed gas is intermittently and cyclically introduced into the reaction chamber and stabilized for 5s to 60s. After the annealing treatment, defects such as materials with poor surface crystallization quality and In clusters with high In components will be decomposed, which is beneficial to improving the crystal quality of the material, while forming a slightly rough material surface, reducing the in-plane total reflection and light absorption loss of photons, and improving the light extraction efficiency.

[0052] In one embodiment, the preparation of the second P-type semiconductor layer includes the following steps: controlling the growth temperature to 890°C to 1060°C, the growth pressure to 30torr to 500torr, introducing Ga source, N source and Mg source, and growing the second P-type semiconductor layer. In a preferred embodiment, the growth temperature of the second P-type semiconductor layer is greater than the growth temperature of the first P-type semiconductor layer, and the first P-type semiconductor layer close to the multi-quantum well light-emitting layer preferably has a relatively low growth temperature to prevent high-temperature growth from damaging the material quality of the multi-quantum well light-emitting layer, while the second P-type semiconductor layer far from the multi-quantum well light-emitting layer adopts a high-temperature growth mode, and the high-temperature growth has high atomic mobility and is more inclined to the growth of two-dimensional materials, which is conducive to the merging of V-shaped pits in semiconductor materials and obtaining high-quality epitaxial layer materials to improve the brightness and yield of Micro-LED chips.

[0053] In one embodiment, the preparation of the P-type ohmic contact layer includes the following steps: controlling the growth temperature to 836°C~952°C, the growth pressure to 30torr~500torr, introducing Al source, In source, Ga source, N source and Mg source to grow the P-type ohmic contact layer.

[0054] The present invention will be further described below with specific embodiments: Example 1 The present embodiment provides a Micro-LED epitaxial wafer, including a substrate, and an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer stacked in sequence on the substrate.

[0055] The barrier height of the first hole injection enhancement layer is greater than the barrier height of the second hole injection enhancement layer.

[0056] The first hole injection enhancement layer includes a first sublayer, a second sublayer and a third sublayer stacked in sequence. The first sublayer includes an AlN layer and a first InGaN layer that are periodically alternately stacked, the number of periods is 2, the thickness of the AlN layer is 2nm, the In component ratio of the first InGaN layer is 0.06, and the thickness is 2nm. The second sublayer includes a first AlGaN layer and a second InGaN layer that are periodically alternately stacked, the number of periods is 3, the Al component ratio of the first AlGaN layer is 0.5, the thickness is 2nm, the In component ratio of the second InGaN layer is 0.06, and the thickness is 2nm. The third sublayer includes a second AlGaN layer and a third InGaN layer that are periodically alternately stacked, the number of periods is 4, the Al component ratio of the second AlGaN layer is 0.5, the thickness is 2nm, and the In component ratio of the third InGaN layer is 0.06, and the thickness is 2nm.

[0057] The second hole injection enhancement layer includes a fourth sublayer, a fifth sublayer and a sixth sublayer stacked in sequence. The fourth sublayer includes a third AlGaN layer and a fourth InGaN layer stacked periodically and alternately, with a period number of 3, an Al component ratio of 0.5 in the third AlGaN layer, a thickness of 2nm, and an In component ratio of 0.06 in the fourth InGaN layer, and a thickness of 2nm. The fifth sublayer includes a fourth AlGaN layer, a fifth InGaN layer and a sixth InGaN layer stacked periodically and alternately, with a period number of 5, an Al component ratio of 0.5 in the fourth AlGaN layer, a thickness of 2nm, an In component ratio of 0.06 in the fifth InGaN layer, a thickness of 2nm, and an In component ratio of 0.06 in the sixth InGaN layer, and a thickness of 2nm. The sixth sublayer includes a fifth AlGaN layer, a seventh InGaN layer and an eighth InGaN layer that are periodically alternately stacked, with a period number of 8. The Al component ratio of the fifth AlGaN layer is 0.5 and the thickness is 2nm. The In component ratio of the seventh InGaN layer is 0.06 and the thickness is 2nm. The In component ratio of the eighth InGaN layer is 0.06 and the thickness is 2nm.

[0058] The first P-type semiconductor layer is a Mg-doped AlInGaN layer with an Al component ratio of 0.15, an In component ratio of 0.4, a thickness of 150 nm, and a Mg doping concentration of 5×10 19 cm -3 .

[0059] The second P-type semiconductor layer is a Mg-doped GaN layer with a thickness of 150 nm and a Mg doping concentration of 8×10 19 cm -3 .

[0060] The P-type ohmic contact layer is a Mg-doped AlInGaN layer with an Al component ratio of 0.1, an In component ratio of 0.12, a thickness of 10 nm, and a Mg doping concentration of 8.5×10 19 cm -3 .

[0061] The method for preparing the above-mentioned Micro-LED epitaxial wafer comprises the following steps: S1. Provide a substrate.

[0062] S2. Growing an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer in sequence on the substrate.

[0063] Specifically, the preparation of the first hole injection enhancement layer includes sequentially growing a first sublayer, a second sublayer and a third sublayer on the multi-quantum well light-emitting layer.

[0064] The preparation of the first sublayer includes the following steps: controlling the growth temperature to 900°C and the growth pressure to 300 torr, introducing Al source and N source, and growing an AlN layer; controlling the growth temperature to 850°C and the growth pressure to 300 torr, introducing In source, Ga source and N source, and growing a first InGaN layer; and repeatedly stacking and periodically growing an AlN layer and a first InGaN layer.

[0065] The preparation of the second sublayer includes the following steps: controlling the growth temperature to 900°C and the growth pressure to 300 torr, introducing Al source, Ga source and N source, and growing the first AlGaN layer; controlling the growth temperature to 850°C and the growth pressure to 300 torr, introducing In source, Ga source and N source, and growing the second InGaN layer; repeating the stacking to periodically grow the first AlGaN layer and the second InGaN layer.

[0066] The preparation of the third sublayer includes the following steps: controlling the growth temperature to 900°C and the growth pressure to 300 torr, introducing Al source, Ga source and N source, and growing a second AlGaN layer; controlling the growth temperature to 850°C and the growth pressure to 300 torr, introducing In source, Ga source and N source, and growing a third InGaN layer; repeating the stacking to periodically grow the second AlGaN layer and the third InGaN layer.

[0067] The preparation of the first P-type semiconductor layer includes the following steps: controlling the growth temperature to 780° C., the growth pressure to 300 torr, introducing Al source, In source, Ga source, N source and Mg source, and growing the first P-type semiconductor layer.

[0068] The preparation of the second hole injection enhancement layer includes sequentially growing a fourth sublayer, a fifth sublayer and a sixth sublayer on the first P-type semiconductor layer.

[0069] The preparation of the fourth sublayer includes the following steps: controlling the growth temperature to 900°C and the growth pressure to 300 torr, introducing Al source, Ga source and N source, and growing the third AlGaN layer; controlling the growth temperature to 850°C and the growth pressure to 300 torr, introducing In source, Ga source and N source, and growing the fourth InGaN layer; repeating the stacking periodically to grow the third AlGaN layer and the fourth InGaN layer.

[0070] The preparation of the fifth sublayer includes the following steps: controlling the growth temperature to 900°C, the growth pressure to 300 torr, introducing Al source, Ga source and N source, and growing the fourth AlGaN layer; controlling the growth temperature to 850°C, the growth pressure to 300 torr, introducing In source, Ga source and N source, and growing the fifth InGaN layer; controlling the growth temperature to 900°C, the growth pressure to 300 torr, introducing In source, Ga source and N source, and growing the sixth InGaN layer; repeating the stacking to periodically grow the fourth AlGaN layer, the fifth InGaN layer and the sixth InGaN layer.

[0071] The preparation of the sixth sublayer includes the following steps: controlling the growth temperature to 900°C, the growth pressure to 300 torr, introducing Al source, Ga source and N source, and growing the fifth AlGaN layer; controlling the growth temperature to 850°C, the growth pressure to 300 torr, introducing In source, Ga source and N source, and growing the seventh InGaN layer; controlling the growth temperature to 900°C, the growth pressure to 300 torr, introducing In source, Ga source and N source, and growing the eighth InGaN layer; repeating the stacking to periodically grow the fifth AlGaN layer, the seventh InGaN layer and the eighth InGaN layer.

[0072] The preparation of the second P-type semiconductor layer includes the following steps: controlling the growth temperature to 950° C., the growth pressure to 300 torr, introducing Ga source, N source and Mg source, and growing the second P-type semiconductor layer.

[0073] The preparation of the P-type ohmic contact layer includes the following steps: controlling the growth temperature to 920° C., the growth pressure to 300 torr, introducing Al source, In source, Ga source, N source and Mg source, and growing the P-type ohmic contact layer.

[0074] Example 2 This embodiment provides a Micro-LED epitaxial wafer, which is different from the embodiment 1 in that the third InGaN layer is a Mg-doped InGaN layer, and the Mg doping concentration is 8×10 18 cm -3 The fourth InGaN layer is a Mg-doped InGaN layer with a Mg doping concentration of 8×10 18 cm -3The fifth InGaN layer is a Mg-doped InGaN layer with a Mg doping concentration of 8×10 18 cm -3 The sixth InGaN layer is a Mg-doped InGaN layer with a Mg doping concentration of 8×10 18 cm -3 The seventh InGaN layer is a Mg-doped InGaN layer with a Mg doping concentration of 8×10 18 cm -3 The eighth InGaN layer is a Mg-doped InGaN layer, and the Mg doping concentration is 8×10 18 cm -3 Correspondingly, in the preparation method, the third InGaN layer, the fourth InGaN layer, the fifth InGaN layer, the sixth InGaN layer, the seventh InGaN layer and the eighth InGaN layer are prepared by introducing an In source, a Ga source, a N source and a Mg source.

[0075] The rest are the same as in Example 1.

[0076] Example 3 This embodiment provides a Micro-LED epitaxial wafer, which differs from Embodiment 2 in that after the deposition of the fifth InGaN layer, the sixth InGaN layer, the seventh InGaN layer and the eighth InGaN layer, annealing treatment is performed at a temperature of 950°C and a pressure of 250 torr, and a mixed gas of H2 and N2 is intermittently and cyclically introduced into the reaction chamber and stabilized for 40 seconds.

[0077] The rest is the same as Example 2.

[0078] Example 4 This embodiment provides a Micro-LED epitaxial wafer, which differs from Embodiment 3 in that the Al component ratio of the first AlGaN layer is 0.85; the Al component ratio of the second AlGaN layer is 0.8; the Al component ratio of the third AlGaN layer is 0.7; the Al component ratio of the fourth AlGaN layer is 0.6; and the Al component ratio of the fifth AlGaN layer is 0.5.

[0079] The rest is the same as Example 3.

[0080] Example 5 This embodiment provides a Micro-LED epitaxial wafer, which differs from Embodiment 4 in that the In component ratio of the first InGaN layer is 0.06; the In component ratio of the second InGaN layer is 0.06; and the In component ratio of the third InGaN layer is 0.06.

[0081] The In component ratio of the fourth InGaN layer is 0.06; the In component ratio of the fifth InGaN layer is 0.08; the In component ratio of the sixth InGaN layer is 0.12; the In component ratio of the seventh InGaN layer is 0.1; and the In component ratio of the eighth InGaN layer is 0.15.

[0082] The rest is the same as Example 4.

[0083] Example 6 This embodiment provides a Micro-LED epitaxial wafer, which is different from the embodiment 5 in that, along the epitaxial growth direction, the Al component ratio of the first P-type semiconductor layer decreases from 0.25 to 0.05, and the Mg doping concentration decreases from 5×10 20 cm -3 Decrease to 5×10 19 cm -3 ; The Mg doping concentration of the second P-type semiconductor layer is 1×10 20 cm -3 Decrease to 5×10 19 cm -3 ; The In component ratio of the P-type ohmic contact layer increased from 0.05 to 0.22.

[0084] The rest are the same as in Example 5.

[0085] Comparative Example 1 This comparative example provides a Micro-LED epitaxial wafer, which is different from Example 1 in that the epitaxial wafer does not include a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer, a second P-type semiconductor layer, and a P-type ohmic contact layer, but an electron blocking layer and a P-type semiconductor layer are sequentially arranged on the multi-quantum well light-emitting layer. Specifically, the electron blocking layer is Al 0.02 In 0.1 Ga 0.88 The N layer has a thickness of 30 nm; the P-type semiconductor layer is a Mg-doped GaN layer with a Mg doping concentration of 5×10 20 cm -3 , thickness is 100nm.

[0086] Correspondingly, the preparation method does not include the preparation of the first hole injection enhancement layer, the first P-type semiconductor layer, the second hole injection enhancement layer, the second P-type semiconductor layer and the P-type ohmic contact layer. The preparation method of the electron blocking layer is: controlling the growth temperature to 1120°C, the growth pressure to 300 torr, and introducing Al source, In source, Ga source, N and Mg source; the preparation method of the P-type semiconductor layer is: controlling the growth temperature to 950°C, the growth pressure to 300 torr, and introducing Ga source, N and Mg source.

[0087] The rest are the same as in Example 1.

[0088] Comparative Example 2 This comparative example provides a Micro-LED epitaxial wafer, which differs from Example 1 in that the epitaxial wafer does not include a second hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer, that is, a first hole injection enhancement layer and a first P-type semiconductor layer are sequentially stacked on the multi-quantum well light-emitting layer.

[0089] Accordingly, the preparation method does not include the preparation of the second hole injection enhancement layer, the second P-type semiconductor layer and the P-type ohmic contact layer.

[0090] The rest are the same as in Example 1.

[0091] Comparative Example 3 This comparative example provides a Micro-LED epitaxial wafer, which differs from Example 1 in that the epitaxial wafer includes a second hole injection enhancement layer, a first P-type semiconductor layer, a first hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer stacked in sequence on the multi-quantum well light-emitting layer.

[0092] Accordingly, in the preparation method, the preparation order of the first hole injection enhancement layer and the second hole injection enhancement layer is adjusted.

[0093] The rest are the same as in Example 1.

[0094] The micro-LED epitaxial wafers prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were made into 20 μm×20 μm micro-LED chips. 2 The test was conducted under a current density of , and the light efficiency improvement of Examples 1 to 6, Comparative Example 2 and Comparative Example 3 compared with Comparative Example 1 was calculated. The test results are shown in the following table.

[0095]

[0096] It can be seen from the above table that the Micro-LED epitaxial wafer provided in the embodiment of the present invention can effectively improve the luminous efficiency of the chip.

[0097] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A Micro-LED epitaxial wafer, characterized in that: It includes a substrate, and an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer sequentially stacked on the substrate; The barrier height of the first hole injection enhancement layer is greater than the barrier height of the second hole injection enhancement layer; The first hole injection enhancement layer includes a first sublayer, a second sublayer and a third sublayer stacked in sequence; the first sublayer includes an AlN layer and a first InGaN layer stacked alternately periodically; the second sublayer includes a first AlGaN layer and a second InGaN layer stacked alternately periodically; the third sublayer includes a second AlGaN layer and a third InGaN layer stacked alternately periodically; The second hole injection enhancement layer includes a fourth sublayer, a fifth sublayer and a sixth sublayer stacked in sequence; the fourth sublayer includes a third AlGaN layer and a fourth InGaN layer periodically and alternately stacked; the fifth sublayer includes a fourth AlGaN layer, a fifth InGaN layer and a sixth InGaN layer periodically and alternately stacked; the sixth sublayer includes a fifth AlGaN layer, a seventh InGaN layer and an eighth InGaN layer periodically and alternately stacked.

2. The Micro-LED epitaxial wafer according to claim 1, characterized in that: The In component ratio of the first InGaN layer is equal to the In component ratio of the second InGaN layer, and is equal to the In component ratio of the third InGaN layer; The In component ratio of the fourth InGaN layer is smaller than that of the fifth InGaN layer, smaller than that of the seventh InGaN layer, smaller than that of the sixth InGaN layer, and smaller than that of the eighth InGaN layer.

3. The Micro-LED epitaxial wafer according to claim 1, characterized in that: The Al component ratio of the first AlGaN layer is greater than that of the second AlGaN layer, and greater than that of the third AlGaN layer, and greater than that of the fourth AlGaN layer, and greater than that of the fifth AlGaN layer.

4. The Micro-LED epitaxial wafer according to claim 1, wherein: The number of cycles of the alternating growth of the first sublayer is 1 to 3; the thickness of the AlN layer is 0.5 nm to 5 nm; the In component ratio of the first InGaN layer is 0.01 to 0.09, and the thickness is 0.5 nm to 5 nm; The number of cycles of the alternating growth of the second sub-layer is 2-5; the Al component ratio of the first AlGaN layer is 0.5-0.88, and the thickness is 0.5nm-5nm; the In component ratio of the second InGaN layer is 0.01-0.09, and the thickness is 0.5nm-5nm; The number of cycles of the alternating growth of the third sublayer is 2 to 6; the Al component ratio of the second AlGaN layer is 0.38 to 0.8, and the thickness is 0.5 nm to 5 nm; the third InGaN layer is a Mg-doped InGaN layer, the In component ratio is 0.01 to 0.09, the thickness is 0.5 nm to 5 nm, and the Mg doping concentration is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 .

5. The Micro-LED epitaxial wafer according to claim 1, wherein: The number of cycles of the alternating growth of the fourth sublayer is 2 to 5; the Al component ratio of the third AlGaN layer is 0.3 to 0.7, and the thickness is 0.36 nm to 2.8 nm; the fourth InGaN layer is a Mg-doped InGaN layer, the In component is 0.01 to 0.07, the thickness is 0.36 nm to 2.8 nm, and the Mg doping concentration is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 ; The fifth sublayer has an alternating growth period of 3 to 7; the fourth AlGaN layer has an Al component ratio of 0.2 to 0.6 and a thickness of 0.36 nm to 2.8 nm; the fifth InGaN layer is a Mg-doped InGaN layer, with an In component ratio of 0.02 to 0.08, a thickness of 0.36 nm to 2.8 nm, and a Mg doping concentration of 2.08×10 18 cm -3 ~2.56×10 19 cm -3 The sixth InGaN layer is a Mg-doped InGaN layer, the In component ratio is 0.03-0.12, the thickness is 0.36 nm-2.8 nm, and the Mg doping concentration is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 ; The sixth sublayer has an alternating growth period of 3 to 10; the fifth AlGaN layer has an Al component ratio of 0.1 to 0.5 and a thickness of 0.36 nm to 2.8 nm; the seventh InGaN layer is a Mg-doped InGaN layer, with an In component ratio of 0.02 to 0.1, a thickness of 0.36 nm to 2.8 nm, and a Mg doping concentration of 2.08×10 18 cm -3 ~2.56×10 19 cm -3 The eighth InGaN layer is a Mg-doped InGaN layer, the In component ratio is 0.03-0.15, the thickness is 0.36 nm-2.8 nm, and the Mg doping concentration is 2.08×10 18 cm -3 ~2.56×10 19 cm -3 .

6. The Micro-LED epitaxial wafer according to claim 1, characterized in that: The first P-type semiconductor layer is a Mg-doped AlInGaN layer, wherein the Al component accounts for 0.01-0.27, the In component accounts for 0.01-0.08, the thickness is 6nm-258nm, and the Mg doping concentration is 1.35×10 19 cm -3 ~5.62×10 20 cm -3 ; Along the epitaxial growth direction, the Al component ratio and Mg doping concentration of the first P-type semiconductor layer decrease; The second P-type semiconductor layer is a Mg-doped GaN layer with a thickness of 5 nm to 210 nm and a Mg doping concentration of 1.12×10 19 cm -3 ~3.57×10 20 cm -3 ; Along the epitaxial growth direction, the Mg doping concentration of the second P-type semiconductor layer decreases; The P-type ohmic contact layer is a Mg-doped AlInGaN layer, the Al component accounts for 0.01-0.19, the In component accounts for 0.01-0.28, the thickness is 0.8nm-32nm, and the Mg doping concentration is 3.12×10 19 cm -3 ~8.75×10 20 cm -3 ; Along the epitaxial growth direction, the In component proportion of the P-type ohmic contact layer increases.

7. A method for preparing a Micro-LED epitaxial wafer, for preparing the Micro-LED epitaxial wafer according to any one of claims 1 to 6, characterized in that: The following steps are involved: A substrate is provided, and an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, a first hole injection enhancement layer, a first P-type semiconductor layer, a second hole injection enhancement layer, a second P-type semiconductor layer and a P-type ohmic contact layer are sequentially grown on the substrate; The first hole injection enhancement layer includes a first sublayer, a second sublayer and a third sublayer stacked in sequence; the first sublayer includes an AlN layer and a first InGaN layer stacked periodically and alternately, the second sublayer includes a first AlGaN layer and a second InGaN layer stacked periodically and alternately, and the third sublayer includes a second AlGaN layer and a third InGaN layer stacked periodically and alternately; The second hole injection enhancement layer includes a fourth sublayer, a fifth sublayer and a sixth sublayer stacked in sequence; the fourth sublayer includes a third AlGaN layer and a fourth InGaN layer periodically and alternately stacked, the fifth sublayer includes a fourth AlGaN layer, a fifth InGaN layer and a sixth InGaN layer periodically and alternately stacked, and the sixth sublayer includes a fifth AlGaN layer, a seventh InGaN layer and an eighth InGaN layer periodically and alternately stacked; The barrier height of the first hole injection enhancement layer is greater than the barrier height of the second hole injection enhancement layer.

8. The method for preparing a Micro-LED epitaxial wafer according to claim 7, wherein: The growth temperature of the AlN layer is 860° C. to 1080° C., and the growth pressure is 50 torr to 390 torr; the growth temperature of the first InGaN layer is 820° C. to 1050° C., and the growth pressure is 50 torr to 390 torr; The growth temperature of the first AlGaN layer is 860° C. to 1080° C., and the growth pressure is 50 torr to 390 torr; the growth temperature of the second InGaN layer is 820° C. to 1050° C., and the growth pressure is 50 torr to 390 torr; The growth temperature of the second AlGaN layer is 860°C to 1080°C, and the growth pressure is 50torr to 390torr; the growth temperature of the third InGaN layer is 820°C to 1050°C, and the growth pressure is 50torr to 390torr; The growth temperature of the third AlGaN layer is 860° C. to 1080° C., and the growth pressure is 50 torr to 390 torr; the growth temperature of the fourth InGaN layer is 820° C. to 1050° C., and the growth pressure is 50 torr to 390 torr; The growth temperature of the fourth AlGaN layer is 860°C to 1080°C, and the growth pressure is 50torr to 390torr; the growth temperature of the fifth InGaN layer is 820°C to 1050°C, and the growth pressure is 50torr to 390torr; the growth temperature of the sixth InGaN layer is 820°C to 1050°C, and the growth pressure is 50torr to 390torr; The growth temperature of the fifth AlGaN layer is 860°C~1080°C, and the growth pressure is 50torr~390torr; the growth temperature of the seventh InGaN layer is 820°C~1050°C, and the growth pressure is 50torr~390torr; the growth temperature of the eighth InGaN layer is 820°C~1050°C, and the growth pressure is 50torr~390torr.

9. The method for preparing a Micro-LED epitaxial wafer according to claim 7, wherein: After the deposition of the fifth InGaN layer, the sixth InGaN layer, the seventh InGaN layer and the eighth InGaN layer, annealing treatment is performed at a temperature of 820° C. to 1080° C. and a pressure of 50 torr to 390 torr.

10. The method for preparing a Micro-LED epitaxial wafer according to claim 7, characterized in that: The growth temperature of the second P-type semiconductor layer is greater than the growth temperature of the first P-type semiconductor layer; The growth temperature of the first P-type semiconductor layer is 716° C. to 858° C., and the growth pressure is 30 torr to 500 torr; The growth temperature of the second P-type semiconductor layer is 890° C. to 1060° C., and the growth pressure is 30 torr to 500 torr; The growth temperature of the P-type ohmic contact layer is 836° C. to 952° C., and the growth pressure is 30 torr to 500 torr.

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