High hole injection efficiency LED epitaxial structure and preparation method thereof

Abstract

The application discloses a high-hole-injection-efficiency LED epitaxial structure and a preparation method thereof, and relates to the technical field of semiconductor devices. The high-hole-injection-efficiency LED epitaxial structure comprises a substrate and an N-type semiconductor layer, a low-temperature stress release layer, a first confinement layer, a multi-quantum-well light-emitting layer, a second confinement layer, a low-temperature P-type semiconductor layer, an electron blocking layer and a high-temperature P-type semiconductor layer which are sequentially stacked on the substrate; the first confinement layer comprises periodically and alternately stacked first AlGaN layers and first GaN layers, and the Al component content of the first AlGaN layers changes in an increasing manner along an epitaxial direction; and the second confinement layer comprises periodically and alternately stacked second AlGaN layers and second InGaN layers, and the Al component content of the second AlGaN layers changes in a decreasing manner along the epitaxial direction. By adopting the application, the hole injection efficiency of the P-type semiconductor material can be improved, and the matching degree of the electron-hole concentration in the multi-quantum-well light-emitting layer can be improved, so that the light-emitting efficiency of the LED device is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a high hole injection efficiency LED epitaxial structure and its fabrication method. Background Technology

[0002] Light-emitting diodes (LEDs), as a new type of energy-saving and environmentally friendly light source, have received considerable attention in recent years, with many countries regarding LED-related semiconductor lighting as a strategic technology. Through extensive research and experimentation, semiconductor lighting technology has made rapid progress, truly realizing the commercialization of semiconductor lighting. Various types of LEDs are widely used in indication, display, backlighting, and projection fields. These achievements in semiconductor lighting are mainly attributed to advancements in GaN-based LED technology. Compared to other material systems, GaN-based LEDs have significant advantages in both efficiency and reliability.

[0003] For the AlGaInN material system, electrons have higher mobility and lower effective mass compared to holes. Electrons are also easier to activate and have a higher concentration, leading to a significant mismatch between electron and hole concentrations injected into the active region. Quantum wells near the N-type semiconductor layer emit almost no light, while electrons can easily be injected into the active region and even into the P-type semiconductor layer, causing electron leakage. Furthermore, obtaining high hole concentrations in P-type materials for LEDs is very difficult because the ionization rate of Mg in the AlGaInN system is low, resulting in generally low hole concentrations in P-type semiconductor materials. In addition, the electron blocking layer, as the main functional layer of the LED, not only blocks electron injection into the P-type layer but also blocks hole injection into the active region, further reducing the hole concentration in the active region and exacerbating the electron-hole concentration mismatch problem. Therefore, to improve the luminous efficiency of GaN-based LEDs, it is essential to improve the hole injection efficiency of the P-type material and improve the electron-hole matching degree in the active region. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high hole injection efficiency LED epitaxial structure and its preparation method, which can improve the hole injection efficiency of P-type semiconductor materials and improve the matching degree of electron-hole concentration in multi-quantum-well light-emitting layers, thereby improving the luminous efficiency of LED devices.

[0005] To achieve this objective, the present invention adopts the following technical solution: A high hole injection efficiency LED epitaxial structure includes a substrate and N-type semiconductor layer, low temperature stress relief layer, first confinement layer, multi-quantum well light-emitting layer, second confinement layer, low temperature P-type semiconductor layer, electron blocking layer and high temperature P-type semiconductor layer sequentially stacked on the substrate. The first confinement layer comprises a first AlGaN layer and a first GaN layer stacked alternately in a periodic manner, wherein the Al composition content of the first AlGaN layer increases along the epitaxial direction; The second confinement layer comprises a periodically alternating layer of a second AlGaN layer and a second InGaN layer, wherein the Al content of the second AlGaN layer decreases along the epitaxial direction.

[0006] As an improvement to the above technical solution, the Al component content of the first AlGaN layer is greater than that of the second AlGaN layer.

[0007] As an improvement to the above technical solution, along the epitaxial direction, the Al composition content of the first AlGaN layer increases from X11 to X12, where 0≤X11≤0.08 and 0.08≤X12≤0.39. The Al content of the second AlGaN layer decreases from X21 to X22, where 0.06≤X21≤0.35 and 0≤X22≤0.06. X12≥X21, and X11≥X22.

[0008] As an improvement to the above technical solution, the first GaN layer is doped with Si element, and the second InGaN layer is doped with Mg element; The doping concentration of Mg in the second InGaN layer is greater than the doping concentration of Si in the first GaN layer.

[0009] As an improvement to the above technical solution, the Si doping concentration in the first GaN layer is 1.12 × 10⁻⁶. 17 / cm 3 ~8.96×10 17 / cm 3 ; The Mg doping concentration in the second InGaN layer is 3.16 × 10⁻⁶. 17 / cm 3 ~7.98×10 19 / cm 3 ; The In content of the second InGaN layer is 0.01~0.11.

[0010] As an improvement to the above technical solution, the low-temperature P-type semiconductor layer is Al. a In bGa 1-a-b N layers, where a≤0.6, b≤0.16; The Al a In b Ga 1-a-b The N-layer is doped with Mg, and the Mg doping concentration is 1.12 × 10⁻⁶. 19 / cm 3 ~3.05×10 20 / cm 3 ; The Al a In b Ga 1-a-b The thickness of the N layer ranges from 3 nm to 210 nm.

[0011] As an improvement to the above technical solution, the high-temperature P-type semiconductor layer is Al. c In d Ga 1-c-d N layers, where c≤0.3, d≤0.3; The Al c In d Ga 1-c-d The N-layer is doped with Mg, and the Mg doping concentration is 1.06 × 10⁻⁶. 19 / cm 3 ~8.52×10 20 / cm 3 ; The Al c In d Ga 1-c-d The thickness of the N layer ranges from 0.3 nm to 19 nm.

[0012] As an improvement to the above technical solution, the multi-quantum-well light-emitting layer includes periodically alternating InGaN quantum well layers and GaN barrier layers, with a period number of 3 to 16. The InGaN quantum well layer has an In content of 0.05~0.48 and a thickness of 2.1nm~4.8nm; The GaN barrier layer is doped with Si, and the Si doping concentration is 1.12 × 10⁻⁶. 17 / cm 3 ~8.96×10 17 / cm 3 The thickness of the GaN barrier layer is 5nm~15nm.

[0013] As an improvement to the above technical solution, the number of periods in which the first binding layer and the second binding layer are periodically stacked alternately is 2 to 30. The thicknesses of the first AlGaN layer, the first GaN layer, the second AlGaN layer, and the second InGaN layer are 0.1 nm to 2.5 nm, respectively.

[0014] Accordingly, a method for fabricating a high hole injection efficiency LED epitaxial structure is also provided, which includes the following steps: (1) Selecting a substrate; (2) An N-type semiconductor layer is grown on the substrate; (3) A low-temperature stress relief layer is grown on the N-type semiconductor layer; (4) A first binding layer is grown on the low-temperature stress relief layer; (5) A multi-quantum-well light-emitting layer is grown on the first confinement layer; (6) A second binding layer is grown on the multi-quantum-well light-emitting layer; (7) A low-temperature P-type semiconductor layer is grown on the second binding layer; (8) An electron blocking layer is grown on a low-temperature P-type semiconductor layer; (9) A high-temperature P-type semiconductor layer is grown on the electron blocking layer; The first confinement layer comprises a first AlGaN layer and a first GaN layer stacked alternately in a periodic manner, wherein the Al composition content of the first AlGaN layer increases along the epitaxial direction; The second confinement layer comprises a periodically alternating layer of a second AlGaN layer and a second InGaN layer, wherein the Al content of the second AlGaN layer decreases along the epitaxial direction; The growth temperatures of the first AlGaN layer, the first GaN layer, the second AlGaN layer, and the second InGaN layer are 780℃~930℃, and the pressures are 30 torr~380 torr, respectively. The growth temperature of the low-temperature P-type semiconductor layer is 700℃~880℃, and the pressure is 30 torr~680 torr. The growth temperature of the high-temperature P-type semiconductor layer is 820℃~1080℃, and the pressure is 30 torr~680 torr.

[0015] Implementing this invention has the following beneficial effects: 1. By redesigning the LED epitaxial structure, a first confinement layer 4 is designed before the multi-quantum-well light-emitting layer 5, and a second confinement layer 6 is designed after the multi-quantum-well light-emitting layer 5. This prevents holes from overflowing into the N-type semiconductor layer 3, confining the holes within the multi-quantum-well light-emitting layer 5 to achieve radiative recombination luminescence, thus improving the hole injection efficiency of the P-type semiconductor material. Simultaneously, it prevents electrons from overflowing into the P-type semiconductor layer, causing electron leakage, and confines the electrons within the multi-quantum-well light-emitting layer to achieve radiative recombination luminescence. Through the structural design of the first confinement layer 4 and the second confinement layer 6, the hole injection efficiency of the P-type semiconductor material can be improved, and the matching degree of electron-hole concentration in the multi-quantum-well light-emitting layer can be enhanced, thereby improving the luminous efficiency of the LED device.

[0016] 2. The low-temperature P-type semiconductor layer 7 is designed between the second confinement layer 6 and the electron blocking layer 8, that is, the low-temperature P-type semiconductor layer 7 is in front of the electron blocking layer 8, so that the electron blocking layer 8 will not block the hole injection from the low-temperature P-type semiconductor layer 7 to the multi-quantum well light-emitting layer 5. The low-temperature P-type semiconductor layer 7 is the main functional layer that provides holes, which can effectively improve the hole injection efficiency of the P-type semiconductor material, further increase the hole concentration in the multi-quantum well light-emitting layer 5, and improve the matching degree of electron-hole concentration in the multi-quantum well light-emitting layer 5, thereby further improving the luminous efficiency of the LED device. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a high hole injection efficiency LED epitaxial structure according to an embodiment of the present invention; Figure 2 yes Figure 1 A schematic diagram of the first binding layer in the high hole injection efficiency LED epitaxial structure of the embodiment shown; Figure 3 yes Figure 1 A schematic diagram of the second confinement layer in the high hole injection efficiency LED epitaxial structure of the embodiment shown; In the figure: Substrate 1, N-type semiconductor layer 2, low-temperature stress relief layer 3, first confinement layer 4, multi-quantum well light-emitting layer 5, second confinement layer 6, low-temperature P-type semiconductor layer 7, electron blocking layer 8, high-temperature P-type semiconductor layer 9, first AlGaN layer 41, first GaN layer 42, second AlGaN layer 61, second InGaN layer 62. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0019] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Raw materials whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0020] See Figure 1 As shown, this embodiment provides a high hole injection efficiency LED epitaxial structure, including a substrate 1 and N-type semiconductor layer 2, low temperature stress relief layer 3, first confinement layer 4, multi-quantum well light-emitting layer 5, second confinement layer 6, low temperature P-type semiconductor layer 7, electron blocking layer 8 and high temperature P-type semiconductor layer 9 sequentially stacked on the substrate 1. The first binding layer 4 includes a first AlGaN layer 41 and a first GaN layer 42 that are periodically and alternately stacked, and the Al composition content of the first AlGaN layer 41 increases along the epitaxial direction. The second binding layer 6 includes a periodically alternating second AlGaN layer 61 and a second InGaN layer 62, wherein the Al content of the second AlGaN layer 61 decreases along the epitaxial direction. The Al content of the first AlGaN layer 41 is greater than the Al content of the second AlGaN layer 61.

[0021] For GaN-based LEDs, the electron-hole concentration and its mismatch in the active region are significant issues. Quantum wells near the N-type semiconductor layer emit almost no light. Furthermore, obtaining P-type materials with high hole concentrations is extremely difficult for LEDs, as P-type materials generally have low hole concentrations. In addition, the electron blocking layer further hinders hole injection into the active region, exacerbating the electron-hole concentration mismatch problem. To address these issues, this embodiment improves the hole injection efficiency of the P-type semiconductor material and enhances the electron-hole matching in the multi-quantum-well emitting layer 5 by structural design and optimization of the LED epitaxial structure, thereby improving the luminous efficiency of the LED device.

[0022] Firstly, in this embodiment, a first confinement layer 4 is designed before the multi-quantum-well light-emitting layer 5, and a second confinement layer 6 is designed after the multi-quantum-well light-emitting layer 5. Based on the increasing Al content of the first AlGaN layer 41 in the first confinement layer 4 along the epitaxial direction, the material of the first AlGaN layer 41 is designed to be a high-Al material with a high bandgap near the multi-quantum-well light-emitting layer 5. This effectively prevents holes from overflowing to the N-type semiconductor layer 3 and confines the holes within the multi-quantum-well light-emitting layer 5, resulting in radiative recombination light emission. This improves the luminous efficacy of the LED device by reducing the hole injection efficiency of the P-type semiconductor material. Similarly, based on the decreasing Al content of the second AlGaN layer 61 along the epitaxial direction, the AlGaN material of the second AlGaN layer 61 is designed to be a high-Al material with a high bandgap near the multi-quantum-well light-emitting layer 5. This effectively prevents electrons from overflowing to the P-type semiconductor layer and causing electron leakage, and confines the electrons within the multi-quantum-well light-emitting layer, resulting in radiative recombination light emission.

[0023] Secondly, in this embodiment, the low-temperature P-type semiconductor layer 7 is designed between the second confinement layer 6 and the electron blocking layer 8, i.e., the low-temperature P-type semiconductor layer 7 is before the electron blocking layer 8. The low-temperature P-type semiconductor layer 7 is the main functional layer for providing holes in the LED epitaxial structure of this embodiment. Since the electron blocking layer 8 is stacked after the low-temperature P-type semiconductor layer 7, it does not block the injection of holes from the low-temperature P-type semiconductor layer 7 into the multi-quantum well light-emitting layer 5. This effectively improves the hole injection efficiency of the P-type semiconductor material, further increases the hole concentration in the multi-quantum well light-emitting layer 5, and improves the electron-hole matching degree in the multi-quantum well light-emitting layer 5, thereby further improving the luminous efficiency of the LED device. Furthermore, a high-temperature P-type semiconductor layer is provided above the electron blocking layer 8. The high-temperature P-type semiconductor layer can also provide holes, further improving the hole injection efficiency and thus the luminous efficiency of the LED device.

[0024] Thirdly, the first confinement layer 4 is an AlGaN / GaN superlattice structure material, and the Al composition of the AlGaN material increases from bottom to top. The second confinement layer 6 is an AlGaN / InGaN superlattice structure material, and the Al composition of the AlGaN material decreases from bottom to top. That is, in the structure and process design of the confinement layer, the AlGaN material is designed to be a low-Al material with a low bandgap near the N-type semiconductor layer 2 and the low-temperature P-type semiconductor layer 7, and a high-Al material with a high bandgap near the multi-quantum-well light-emitting layer 5. This structure design can effectively reduce the blocking effect of the wide-bandgap semiconductor AlGaN material on the carrier injection of the N-type semiconductor layer 2 and the low-temperature P-type semiconductor layer 7 into the multi-quantum-well light-emitting layer 5, and increase the electron / hole concentration injected into the active region from the N-type semiconductor layer 2 and the low-temperature P-type semiconductor layer 7, thereby improving the radiative recombination efficiency of electrons and holes in the region of the multi-quantum-well light-emitting layer 5 and the luminous efficacy of the LED device.

[0025] In one embodiment, the Al component content of the first AlGaN layer 41 is greater than the Al component content of the second AlGaN layer 61.

[0026] For the AlGaInN material system, electrons have higher mobility and lower effective mass compared to holes. Electrons are also more easily activated and have a higher concentration, leading to a mismatch between electron and hole concentrations injected into the active region. This embodiment controls the Al content of the first AlGaN layer 41 to be greater than that of the second AlGaN layer 61, thereby regulating the electron mobility rate and reducing it. This further improves the electron-hole concentration matching in the active region and effectively prevents electron overflow and injection into the P-type semiconductor layer, thus improving the luminous efficacy and yield of the LED device.

[0027] In one embodiment, along the epitaxial direction, the Al component content of the first AlGaN layer 41 increases from X11 to X12, wherein 0≤X11≤0.08, 0.08≤X12≤0.39, and X12 and X11 are not equal; The Al content of the second AlGaN layer 61 decreases from X21 to X22, wherein 0.06≤X21≤0.35, 0≤X22≤0.06, and X21 and X22 are not equal; X12≥X21, and X11≥X22.

[0028] Specifically, X11 is exemplarily 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, or 0.08, and X12 is exemplarily 0.08, 0.9, 0.1, 0.13, 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, or 0.39, but is not limited thereto.

[0029] Specifically, X21 is exemplarily 0.06, 0.07, 0.9, 0.1, 0.12, 0.15, 0.17, 0.2, 0.22, 0.25, 0.27, 0.3, 0.32, or 0.35, and X22 is exemplarily 0, 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06, but is not limited thereto.

[0030] In one embodiment, the first GaN layer 42 is doped with Si, and the second InGaN layer 62 is doped with Mg. The doping concentration of Mg in the second InGaN layer 62 is greater than the doping concentration of Si in the first GaN layer 42.

[0031] The first confinement layer 4 is doped with Si, while the second confinement layer 6 is doped with Mg. This allows the first confinement layer 4 to provide electrons to the multi-quantum-well light-emitting layer 5 for radiative recombination, and the second confinement layer 6 to provide holes to the multi-quantum-well light-emitting layer 5 for radiative recombination. This further increases the electron and hole concentrations in the multi-quantum-well light-emitting layer 5. Simultaneously, by controlling the Mg doping concentration in the second InGaN layer 62 to be greater than the Si doping concentration in the first GaN layer 42, the matching degree of electron and hole concentrations in the multi-quantum-well light-emitting layer 5 can be further improved, thereby enhancing the luminous efficacy of the LED device.

[0032] In one embodiment, the Si doping concentration in the first GaN layer 42 is 1.12 × 10⁻⁶. 17 / cm 3 ~8.96×10 17 / cm 3 For example, it is 1.12 × 10 17 / cm 3 1.5×10 17 / cm 3 2.0×10 17 / cm 3 2.5×10 17 / cm 3 3×10 17 / cm 3 3.5×1017 / cm 3 4×10 17 / cm 3 4.5×10 17 / cm 3 5×10 17 / cm 3 5.5×10 17 / cm 3 6×10 17 / cm 3 6.5×10 17 / cm 3 7×10 17 / cm 3 7.5×10 17 / cm 3 Or 8.96×10 17 / cm 3 However, it is not limited to this.

[0033] In one embodiment, the Mg doping concentration in the second InGaN layer 62 is 3.16 × 10⁻⁶. 17 / cm 3 ~7.98×10 19 / cm 3 For example, it is 3.16 × 10 17 / cm 3 4×10 17 / cm 3 5×10 17 / cm 3 6×10 17 / cm 3 7×10 17 / cm 3 8×10 17 / cm 3 9×10 17 / cm 3 1×10 18 / cm 3 2×10 18 / cm 3 3×10 18 / cm 3 4×10 18 / cm 3 5×10 18 / cm 3 6×10 18 / cm 3 7×10 18 / cm 3 8×10 18 / cm 39×10 18 / cm 3 1×10 19 / cm 3 2×10 19 / cm 3 3×10 19 / cm 3 4×10 19 / cm 3 5×10 19 / cm 3 6×10 19 / cm 3 7×10 19 / cm 3 Or 7.98×10 19 / cm 3 However, it is not limited to this.

[0034] In one embodiment, the In content of the second InGaN layer 62 is 0.01 to 0.11, exemplarily 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10 or 0.11, but not limited thereto.

[0035] In one embodiment, the number of periods in which the first binding layer 4 and the second binding layer 6 are periodically stacked alternately is 2 to 30, with examples being 2, 5, 8, 10, 12, 15, 18, 22, 25, 28, or 30, but not limited to these. Specifically, the number of periods in which the first binding layer 4 and the second binding layer 6 are periodically stacked alternately can be the same or different.

[0036] In one embodiment, the thicknesses of the first AlGaN layer 41, the first GaN layer 42, the second AlGaN layer 61, and the second InGaN layer 62 are respectively 0.1 nm to 2.5 nm. Specifically, the thickness of the first AlGaN layer 41 is exemplarily 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, or 2.5 nm, the thickness of the first GaN layer 42 is exemplarily 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, or 2.5 nm, the thickness of the second AlGaN layer 61 is exemplarily 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, or 2.5 nm, and the thickness of the second InGaN layer 62 is exemplarily 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, or 2.5 nm, but is not limited to these. By rationally setting the thickness of each layer, the performance of the LED epitaxial structure can be further optimized, the hole injection efficiency of the P-type semiconductor material can be better improved, and the matching degree of electron-hole concentration in the multi-quantum-well light-emitting layer can be enhanced, thereby improving the luminous efficiency of the LED device. In the actual fabrication process, the thickness of each layer can be precisely controlled according to specific needs and experimental conditions to achieve the best luminous effect.

[0037] In one embodiment, the low-temperature P-type semiconductor layer 7 is Al. a In b Ga 1-a-b N layers, where a≤0.6, b≤0.16; preferably, a is 0.2~0.6, b is 0.03~0.16; The Al a In b Ga 1-a-b The N-layer is doped with Mg, and the Mg doping concentration is 1.12 × 10⁻⁶. 19 / cm 3 ~3.05×10 20 / cm 3 The Al a In b Ga 1-a-b The N layer is an AlInGaN material heavily doped with Mg, serving as the main functional layer for providing holes in the LED. The Al a In b Ga 1-a-b The thickness of the N layer ranges from 3 nm to 210 nm.

[0038] In one embodiment, the high-temperature P-type semiconductor layer 9 is Al. c In d Ga 1-c-dN layers, where c≤0.3, d≤0.3; preferably, c is 0.05~0.3, d is 0.05~0.3; The Al c In d Ga 1-c-d The N-layer is doped with Mg, and the Mg doping concentration is 1.06 × 10⁻⁶. 19 / cm 3 ~8.52×10 20 / cm 3 Al c In d Ga 1-c-d The N-layer is heavily doped with Mg, which can provide holes to the multi-quantum-well light-emitting layer 5 to improve the matching degree of electron-hole concentration in the active region. The Al c In d Ga 1-c-d The thickness of the N layer ranges from 0.3 nm to 19 nm.

[0039] In one embodiment, the multi-quantum-well light-emitting layer 5 includes periodically alternating layers of InGaN quantum wells and GaN barrier layers, with a period number of 3 to 16. The InGaN quantum well layer has an In content of 0.05~0.48 and a thickness of 2.1nm~4.8nm; The GaN barrier layer is doped with Si, and the Si doping concentration is 1.12 × 10⁻⁶. 17 / cm 3 ~8.96×10 17 / cm 3 The thickness of the GaN barrier layer is 5nm~15nm.

[0040] Accordingly, a method for fabricating a high hole injection efficiency LED epitaxial structure is also provided, which includes the following steps: (1) Select substrate 1; (2) An N-type semiconductor layer 2 is grown on the substrate; (3) A low-temperature stress relief layer 3 is grown on the N-type semiconductor layer 2; (4) A first binding layer 4 is grown on the low-temperature stress relief layer 3; The first confinement layer 4 is an AlGaN / GaN superlattice structure material, comprising a periodically alternating first AlGaN layer 41 and a first GaN layer 42. The Al content of the first AlGaN layer 41 increases along the epitaxial direction, and the first GaN layer 42 is doped with Si. Specifically, the number of alternating growth cycles of the first confinement layer 4 is 2 to 30. The first AlGaN layer 41 is a gradient AlGaN material with an increasing Al content along the epitaxial direction, and no intentional doping is performed on the AlGaN material. Preferably, the Al content of the first AlGaN layer 41 increases from 0 ≤ x11 ≤ 0.08 to 0.08 ≤ x12 ≤ 0.39, the growth thickness is 0.1 nm to 2.5 nm, the growth temperature is 780 °C to 930 °C, and the pressure is 30 torr to 380 torr. The first GaN layer 42 is a GaN material with low Si doping, a thickness of 0.1 nm to 2.5 nm, and a Si doping concentration of 1.12 × 10⁻⁶. 17 / cm 3 ~8.96×10 17 / cm 3 The growth temperature is 780℃~930℃, and the pressure is 30 torr~380 torr.

[0041] (5) A multi-quantum-well light-emitting layer 5 is grown on the first binding layer 4; Specifically, the multi-quantum-well light-emitting layer 5 comprises periodically alternating InGaN quantum well layers and GaN barrier layers, with the number of alternating growth periods of the multi-quantum-well light-emitting layer 5 being 3 to 16. The InGaN quantum well layers are undoped InGaN single-layer or multi-layer structures with an In content of 0.05 to 0.48% and a thickness of 2.1 nm to 4.8 nm. The growth temperature is 600℃ to 920℃, and the pressure is 30 torr to 380 torr. The GaN barrier layer is doped with Si element, with a Si doping concentration of 1.12 × 10⁻⁶. 17 / cm 3 ~8.96×10 17 / cm 3 The GaN barrier layer has a thickness of 5nm to 15nm, a growth temperature of 800℃ to 950℃, and a pressure of 30 torr to 380 torr.

[0042] (6) A second binding layer 6 is grown on the multi-quantum-well light-emitting layer 5; The second confinement layer is an AlGaN / InGaN superlattice structure material, comprising a periodically alternating second AlGaN layer 61 and a second InGaN layer 62. The Al content of the second AlGaN layer 61 decreases along the epitaxial direction, and the second InGaN layer 62 is doped with Mg. Specifically, the second confining layer has 2 to 30 alternating growth cycles; the second AlGaN layer 61 is a gradient AlGaN material with decreasing Al content along the epitaxial direction, and no intentional doping is performed on the AlGaN material. Its Al content decreases from 0.06 ≤ x21 ≤ 0.35 to 0 ≤ x22 ≤ 0.06, with a growth thickness of 0.1 nm to 2.5 nm, a growth temperature of 780 °C to 930 °C, and a pressure of 30 torr to 380 torr; the second InGaN layer 62 is a lightly doped InGaN material with an In content of 0.01 to 0.11, a thickness of 0.1 nm to 2.5 nm, and a Mg doping concentration of 3.16 × 10⁻⁶. 17 / cm 3 ~7.98×10 19 / cm 3 The growth temperature is 780℃~930℃, and the pressure is 30 torr~380 torr.

[0043] (7) A low-temperature P-type semiconductor layer 7 is grown on the second binding layer 6. The low-temperature P-type semiconductor layer 7 is a low-temperature grown AlInGaN single-layer or multi-layer structure, which serves as the main functional layer for providing holes for the LED. The growth temperature of the low-temperature P-type semiconductor layer 7 is 700℃~880℃ and the pressure is 30 torr~680 torr. (8) An electron blocking layer 8 is grown on a low-temperature P-type semiconductor layer 7; In some embodiments, the electron blocking layer 8 is an AlGaN and / or AlN single-layer or multi-layer structure, and the material of the electron blocking layer is not intentionally doped, wherein the Al content is 0.2~1, the thickness is 1.6nm~120nm, the growth temperature is 860℃~1080℃, and the pressure is 30torr~500torr.

[0044] (9) A high-temperature P-type semiconductor layer 9 is grown on the electron blocking layer 8; The high-temperature P-type semiconductor layer 9 is a single-layer or multi-layer AlInGaN structure grown at high temperature. Preferably, the growth temperature of the high-temperature P-type semiconductor layer 9 is 820℃~1080℃, and the pressure is 30 torr~680 torr. It should be noted that the growth temperature of the high-temperature P-type semiconductor layer 9 is higher than the growth temperature of the low-temperature P-type semiconductor layer 7.

[0045] The technical solution of the present invention will be further described below through embodiments and comparative examples.

[0046] Example 1 This embodiment provides a high hole injection efficiency LED epitaxial structure, including a substrate and an N-type semiconductor layer, a low-temperature stress relief layer, a first confinement layer, a multi-quantum well light-emitting layer, a second confinement layer, a low-temperature P-type semiconductor layer, an electron blocking layer and a high-temperature P-type semiconductor layer sequentially stacked on the substrate. The first confinement layer comprises periodically alternating layers of AlGaN and GaN, with 20 periods. The Al content of the first AlGaN layer increases along the epitaxial direction; specifically, along the epitaxial direction, the Al content of the first AlGaN layer increases from X11 to X12, where X11 is 0.02 and X12 is 0.1. The first GaN layer is doped with Si, and the Si doping concentration in the first GaN layer is 1.12 × 10⁻⁶. 17 / cm 3 ; The second confinement layer comprises a periodically alternating stack of a second AlGaN layer and a second InGaN layer. The Al content of the second AlGaN layer decreases along the epitaxial direction; specifically, the Al content of the second AlGaN layer decreases from X21 to X22, where X21 is 0.07 and X22 is 0. The second InGaN layer is doped with Mg, and the Mg doping concentration in the second InGaN layer is 3.16 × 10⁻⁶. 17 / cm 3 The In content of the second InGaN layer is 0.06. The thicknesses of the first AlGaN layer, the first GaN layer, the second AlGaN layer, and the second InGaN layer are all 1.5 nm.

[0047] The low-temperature P-type semiconductor layer is Al a In b Ga 1-a-b N layers, where a is 0.4, b is 0.12, and Al a In b Ga 1-a-b The N-layer is doped with Mg, and the Mg doping concentration is 8.5 × 10⁻⁶. 19 / cm 3 The thickness is 105nm.

[0048] The high-temperature P-type semiconductor layer is Al c In d Ga 1-c-d N layers, where c is 0.2, d is 0.2, and Al c In d Ga 1-c-d The N-layer is doped with Mg, and the Mg doping concentration is 2.36 × 10⁻⁶.19 / cm 3 The thickness is 15nm.

[0049] Example 2 This embodiment provides a high hole injection efficiency LED epitaxial structure, which is basically the same as that in Embodiment 1, except that: The Al content in the first AlGaN layer increases from X11 (0.05) to X12 (0.23), and the Si doping concentration in the first GaN layer is 5.5 × 10⁻⁶. 17 / cm 3 ; The Al content in the second AlGaN layer decreases from X21 (0.17) to X22 (0.03), and the Mg doping concentration in the second InGaN layer is 6 × 10⁻⁶. 18 / cm 33 .

[0050] Example 3 This embodiment provides a high hole injection efficiency LED epitaxial structure, which is basically the same as that in Embodiment 1, except that: The Al content in the first AlGaN layer increases from X11 (0.08) to X12 (0.39), and the Si doping concentration in the first GaN layer is 8.96 × 10⁻⁶. 17 / cm 3 ; The Al content in the second AlGaN layer decreases from X21 (0.25) to X22 (0.06), and the Mg doping concentration in the second InGaN layer is 7.98 × 10⁻⁶. 19 / cm 3 .

[0051] Comparative Example 1 This comparative example provides an LED epitaxial structure, including a substrate and N-type semiconductor layer, low-temperature stress relief layer, multi-quantum well light-emitting layer, electron blocking layer, low-temperature P-type semiconductor layer and high-temperature P-type semiconductor layer sequentially stacked on the substrate; the materials and structural composition of the N-type semiconductor layer, low-temperature stress relief layer, multi-quantum well light-emitting layer, electron blocking layer, low-temperature P-type semiconductor layer and high-temperature P-type semiconductor layer in Comparative Example 1 are the same as those in Example 1.

[0052] Comparative Example 2 This comparative example provides an LED epitaxial structure, including a substrate and N-type semiconductor layer, low-temperature stress relief layer, multi-quantum well light-emitting layer, low-temperature P-type semiconductor layer, electron blocking layer and high-temperature P-type semiconductor layer sequentially stacked on the substrate; the materials and structural composition of the N-type semiconductor layer, low-temperature stress relief layer, multi-quantum well light-emitting layer, electron blocking layer, low-temperature P-type semiconductor layer and high-temperature P-type semiconductor layer in Comparative Example 2 are the same as those in Example 1.

[0053] Comparative Example 3 This comparative example provides an LED epitaxial structure, including a substrate and N-type semiconductor layer, low-temperature stress relief layer, first confinement layer, multi-quantum well light-emitting layer, low-temperature P-type semiconductor layer, electron blocking layer and high-temperature P-type semiconductor layer stacked sequentially on the substrate; the materials and structural composition of the N-type semiconductor layer, low-temperature stress relief layer, first confinement layer, multi-quantum well light-emitting layer, low-temperature P-type semiconductor layer, electron blocking layer and high-temperature P-type semiconductor layer in Comparative Example 3 are the same as those in Example 1.

[0054] Performance testing: The LED epitaxial structures obtained in Examples 1-3 and Comparative Examples 1-3 were fabricated into LED chips using the same chip manufacturing process conditions. Their luminous efficiency was tested, and the luminous efficiency improvement rate in each example and comparative example was calculated based on Comparative Example 1. Light efficiency improvement rate = (Improved light efficiency - Original light efficiency) / Original light efficiency × 100%; In the above calculation formula: the original light effect is the same as the light effect of Comparative Example 1.

[0055] Specifically, the test results are shown in Table 1 below: Table 1 Performance Test Results

[0056] As can be seen from the experimental data in Table 1, the present invention can improve the hole injection efficiency of P-type semiconductor materials and improve the matching degree of electron-hole concentration in the multi-quantum well light-emitting layer by redesigning the LED epitaxial structure, thereby improving the luminous efficiency of LED devices.

[0057] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A high hole injection efficiency LED epitaxial structure, characterized in that, It includes a substrate and N-type semiconductor layer, low-temperature stress relief layer, first confinement layer, multi-quantum well light-emitting layer, second confinement layer, low-temperature P-type semiconductor layer, electron blocking layer and high-temperature P-type semiconductor layer sequentially stacked on the substrate; The first confinement layer comprises a first AlGaN layer and a first GaN layer stacked alternately in a periodic manner, wherein the Al composition content of the first AlGaN layer increases along the epitaxial direction; The second confinement layer comprises a periodically alternating layer of a second AlGaN layer and a second InGaN layer, wherein the Al content of the second AlGaN layer decreases along the epitaxial direction.

2. The high hole injection efficiency LED epitaxial structure according to claim 1, characterized in that, The Al component content of the first AlGaN layer is greater than that of the second AlGaN layer.

3. The high hole injection efficiency LED epitaxial structure according to claim 1, characterized in that, Along the epitaxial direction, the Al composition content of the first AlGaN layer increases from X11 to X12, where 0≤X11≤0.08 and 0.08≤X12≤0.39; The Al content of the second AlGaN layer decreases from X21 to X22, where 0.06≤X21≤0.35 and 0≤X22≤0.

06. X12≥X21, and X11≥X22.

4. The high hole injection efficiency LED epitaxial structure according to claim 1, characterized in that, The first GaN layer is doped with Si, and the second InGaN layer is doped with Mg. The doping concentration of Mg in the second InGaN layer is greater than the doping concentration of Si in the first GaN layer.

5. The high hole injection efficiency LED epitaxial structure according to claim 4, characterized in that, The Si doping concentration in the first GaN layer is 1.12 × 10⁻⁶. 17 / cm 3 ~8.96×10 17 / cm 3 ; The Mg doping concentration in the second InGaN layer is 3.16 × 10⁻⁶. 17 / cm 3 ~7.98×10 19 / cm 3 ; The In content of the second InGaN layer is 0.01~0.

11.

6. The high hole injection efficiency LED epitaxial structure according to claim 1, characterized in that, The low-temperature P-type semiconductor layer is Al. a In b Ga 1-a-b N layers, where a≤0.6, b≤0.16; The Al a In b Ga 1-a-b The N-layer is doped with Mg, and the Mg doping concentration is 1.12 × 10⁻⁶. 19 / cm 3 ~3.05×10 20 / cm 3 ; The Al a In b Ga 1-a-b The thickness of the N layer ranges from 3 nm to 210 nm.

7. The high hole injection efficiency LED epitaxial structure according to claim 1, characterized in that, The high-temperature P-type semiconductor layer is Al. c In d Ga 1-c-d N layers, where c≤0.3, d≤0.3; The Al c In d Ga 1-c-d The N-layer is doped with Mg, and the Mg doping concentration is 1.06 × 10⁻⁶. 19 / cm 3 ~8.52×10 20 / cm 3 ; The Al c In d Ga 1-c-d The thickness of the N layer ranges from 0.3 nm to 19 nm.

8. The high hole injection efficiency LED epitaxial structure according to claim 1, characterized in that, The multi-quantum-well light-emitting layer comprises periodically alternating layers of InGaN quantum wells and GaN barrier layers, with a period number of 3 to 16. The InGaN quantum well layer has an In content of 0.05~0.48 and a thickness of 2.1nm~4.8nm; The GaN barrier layer is doped with Si, and the Si doping concentration is 1.12 × 10⁻⁶. 17 / cm 3 ~8.96×10 17 / cm 3 The thickness of the GaN barrier layer is 5nm~15nm.

9. The high hole injection efficiency LED epitaxial structure according to claim 1, characterized in that, The number of periods in which the first binding layer and the second binding layer are periodically stacked alternately is 2 to 30, respectively; The thicknesses of the first AlGaN layer, the first GaN layer, the second AlGaN layer, and the second InGaN layer are 0.1 nm to 2.5 nm, respectively.

10. A method for fabricating a high hole injection efficiency LED epitaxial structure, characterized in that, The method for preparing the high hole injection efficiency LED epitaxial structure according to any one of claims 1-9 comprises the following steps: (1) Selecting a substrate; (2) An N-type semiconductor layer is grown on the substrate; (3) A low-temperature stress relief layer is grown on the N-type semiconductor layer; (4) A first binding layer is grown on the low-temperature stress relief layer; (5) A multi-quantum-well light-emitting layer is grown on the first confinement layer; (6) A second binding layer is grown on the multi-quantum-well light-emitting layer; (7) A low-temperature P-type semiconductor layer is grown on the second binding layer; (8) An electron blocking layer is grown on a low-temperature P-type semiconductor layer; (9) A high-temperature P-type semiconductor layer is grown on the electron blocking layer; The first confinement layer comprises a first AlGaN layer and a first GaN layer stacked alternately in a periodic manner, wherein the Al composition content of the first AlGaN layer increases along the epitaxial direction; The second confinement layer comprises a periodically alternating layer of a second AlGaN layer and a second InGaN layer, wherein the Al content of the second AlGaN layer decreases along the epitaxial direction; The growth temperatures of the first AlGaN layer, the first GaN layer, the second AlGaN layer, and the second InGaN layer are 780℃~930℃, and the pressures are 30 torr~380 torr, respectively. The growth temperature of the low-temperature P-type semiconductor layer is 700℃~880℃, and the pressure is 30 torr~680 torr. The growth temperature of the high-temperature P-type semiconductor layer is 820℃~1080℃, and the pressure is 30 torr~680 torr.

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