A Micro-LED Epitaxial Structure Suitable for Low Operating Current Density and Its Fabrication Method

Abstract

This invention discloses a Micro-LED epitaxial structure suitable for low operating current density and its fabrication method, relating to the field of semiconductor device technology. The Micro-LED epitaxial structure includes a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well (MFU) emitting layer, and a P-type semiconductor layer. The MFU emitting layer comprises a first short-wavelength MFU layer, a second long-wavelength MFU layer, and a third short-wavelength MFU layer arranged sequentially from bottom to top. The In content in the first and third short-wavelength MFU layers is lower than that in the second long-wavelength MFU layer. The Micro-LED epitaxial structure of this invention significantly improves the quality of the MFU emitting layer, improves the matching degree of electron-hole concentration in the emitting quantum well region, and increases the radiative recombination efficiency in the emitting quantum well region, thereby improving the luminous efficacy of the Micro-LED chip at low operating current density and solving the problem of low luminous efficacy of traditional visible light LED epitaxial structures at low operating current densities.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a Micro-LED epitaxial structure suitable for low operating current density and its fabrication method. Background Technology

[0002] With the rapid development of emerging wearable and portable technologies, micron-sized LED chips (Micro LED) have garnered significant attention and research from scientific institutions and enterprises due to their promising applications in displays, visible light communication, and biomedicine. Furthermore, Micro LED displays possess nanosecond (ns) level high-speed response performance, the stability of inorganic materials, and excellent properties such as high luminous efficiency, high reliability, high color purity, high contrast, and transparency—combinations of characteristics that are difficult to achieve with liquid crystal displays (LCDs) and organic LEDs (OLEDs).

[0003] While Micro LEDs possess many superior characteristics, they also face challenges in manufacturing technology and material / device physics. For example, the issue of decreasing peak EQE and correspondingly increasing current density as chip size decreases has not been fully resolved, with operating current densities remaining between 0.01 and 0.5 A / cm². 2 The efficiency of Micro LEDs in this range remains significantly insufficient. In fact, even standard-sized chips used in general lighting and backlighting applications exhibit relatively low efficiency at this current density. This is because standard-sized chips typically operate at a current density of 20 A / cm² to balance efficiency and cost. 2 Up to 40A / cm 2 The corresponding epitaxial structure design and material growth aim to improve efficiency at high current densities, with peak EQE typically ranging from 1 to 4 A / cm². 2 The study focused on the current density range, neglecting to consider device efficiency at low current densities. The dominant factors in the light-emitting mechanism of LED devices differ at different current densities, and the corresponding epitaxial layer structure should also vary. For example, in the Micro LED operating range of 0.01–0.5 A / cm²... 2 At low current densities, the carrier concentration in the quantum well is relatively low, resulting in a smaller Auger recombination rate and a corresponding reduction in the quantum well recombination volume. This reduces the number of quantum wells and defects, thereby improving the EQE (equivalent quantum efficiency) of the device at low current densities. Simultaneously, at low current densities, electron leakage has not yet occurred or is very low. The electron blocking layer structure not only fails to block electrons but also blocks hole injection, reducing the device's quantum efficiency. Therefore, in-depth mechanistic research, design, and growth of epitaxial layer structures under low current density operating conditions for Micro LEDs are essential key technologies for developing high-efficiency Micro LED devices driven by low operating current densities.

[0004] Traditional visible light LED epitaxial structure designs are primarily based on conventional applications requiring large chips, high current, and high power. However, Micro LED display applications demand small size, low current, and low power, making traditional epitaxial structure designs insufficient for their requirements. Therefore, redesigning epitaxial structures suitable for small-size, low-current, and low-power Micro LEDs, and improving their electro-optical conversion efficiency, is a significant challenge currently facing both academia and industry. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to propose a Micro-LED epitaxial structure suitable for low operating current density, which can significantly improve the quality of the multi-quantum-well light-emitting layer, improve the matching degree of electron-hole concentration in the light-emitting quantum well region, and improve the radiative recombination efficiency in the light-emitting quantum well region, thereby improving the luminous efficacy of the Micro-LED chip at low operating current density, and solving the problem of low luminous efficacy of traditional visible light LED epitaxial structures at low operating current density.

[0006] Another objective of this invention is to provide a method for fabricating Micro-LED epitaxial structures suitable for low operating current densities, for use in fabricating the aforementioned Micro-LED epitaxial structures suitable for low operating current densities.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] A Micro-LED epitaxial structure suitable for low operating current density includes a substrate, and further includes a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer and a P-type semiconductor layer sequentially stacked on the substrate;

[0009] The multi-quantum-well light-emitting layer comprises a first short-wavelength multi-quantum-well layer, a second long-wavelength multi-quantum-well layer, and a third short-wavelength multi-quantum-well layer, which are stacked sequentially from bottom to top; the In composition in the first short-wavelength multi-quantum-well layer and the In composition in the third short-wavelength multi-quantum-well layer are both smaller than the In composition in the second long-wavelength multi-quantum-well layer.

[0010] The first short-wavelength multi-quantum well layer includes a first short-wavelength multi-quantum well InGaN layer and a first short-wavelength multi-quantum well high barrier layer that are periodically and alternately grown from bottom to top.

[0011] The second long-wavelength multi-quantum-well layer includes a second long-wavelength multi-quantum-well InGaN layer and a second long-wavelength multi-quantum-well low-barrier layer that are periodically alternating from bottom to top.

[0012] The third short-wavelength multi-quantum well layer comprises a third short-wavelength multi-quantum well InGaN layer and a third short-wavelength multi-quantum well high barrier layer that are periodically and alternately grown from bottom to top.

[0013] Preferably, the first short-wavelength multi-quantum-well high barrier layer includes a first high barrier GaN-1 layer, a first high barrier AlGaN-2 layer and a first high barrier GaN-3 layer stacked sequentially from bottom to top.

[0014] Both the first high-barrier GaN-1 layer and the first high-barrier GaN-3 layer are doped with Si.

[0015] The third short-wavelength multi-quantum-well high barrier layer includes a third high barrier GaN-1 layer, a third high barrier AlGaInN-2 layer, a third high barrier AlGaN-3 layer and a third high barrier GaN-4 layer, which are stacked sequentially from bottom to top.

[0016] Both the third high-barrier AlGaInN-2 layer and the third high-barrier GaN-4 layer are doped with Mg.

[0017] Preferably, the proportion of In component in the first short-wavelength multi-quantum well InGaN layer is 0.02 to 0.4, the thickness is 2.05 nm to 3.95 nm, the growth temperature is 716 °C to 920 °C, and the pressure is 50 torr to 360 torr.

[0018] Preferably, the thickness of the first high-barrier GaN-1 layer is 2 nm to 6 nm, and the Si doping concentration is 1.2 × 10⁻⁶. 17 ~7.6×10 18 atoms / cm3, growth temperature 820℃~935℃, pressure 50torr~360torr;

[0019] The first high-barrier AlGaN-2 layer has an Al content of 0.02–0.3%, a thickness of 1.2 nm–5 nm, a growth temperature of 820 °C–935 °C, and a pressure of 50 torr–360 torr.

[0020] The thickness of the first high-barrier GaN-3 layer is 2nm to 6nm, and the Si doping concentration is 1.2×10⁻⁶. 17 ~7.6×10 18 atoms / cm3, growth temperature 820℃-935℃, pressure 50torr-360torr.

[0021] Preferably, the proportion of In component in the second long-wavelength multi-quantum-well InGaN layer is 0.08 to 0.46, the thickness is 2.25 nm to 4.65 nm, the growth temperature is 680 °C to 920 °C, and the pressure is 50 torr to 360 torr.

[0022] Preferably, the second long-wavelength multi-quantum well low barrier layer is a GaN single-layer or multi-layer structure with a growth thickness of 7.5 nm to 16.5 nm, a growth temperature of 820 °C to 935 °C, and a pressure of 50 torr to 360 torr.

[0023] Preferably, the proportion of In component in the third short-wavelength multi-quantum-well InGaN layer is 0.02 to 0.4, the thickness is 2.05 nm to 3.95 nm, the growth temperature is 716 °C to 920 °C, and the pressure is 50 torr to 360 torr.

[0024] Preferably, the thickness of the third high-barrier GaN-1 layer is 0.5 nm to 3 nm, the growth temperature is 820 °C to 935 °C, and the pressure is 50 torr to 360 torr;

[0025] The third high-barrier AlGaInN-2 layer has an Al content of 0.02–0.3%, an In content of 0.01–0.08%, a thickness of 0.8 nm–5 nm, and a Mg doping concentration of 3.6 × 10⁻⁶. 18 ~7.8×10 19 atoms / cm 3 The growth temperature is 820℃~935℃, and the pressure is 50 torr~360 torr;

[0026] The third high-barrier AlGaN-3 layer has an Al content of 0.02–0.3%, a thickness of 0.5 nm–3 nm, a growth temperature of 820 °C–935 °C, and a pressure of 50 torr–360 torr.

[0027] The thickness of the third high-barrier GaN-4 layer is 0.8 nm to 5 nm, and the Mg doping concentration is 3.6 × 10⁻⁶. 18 ~7.8×10 19 atoms / cm 3 The growth temperature is 820℃~935℃, and the pressure is 50 torr~360 torr.

[0028] Preferably, the number of cycles in which the first short-wavelength multi-quantum well layer is alternately grown is 2 to 6;

[0029] The number of alternating growth cycles of the second long-wavelength multi-quantum-well layer is 2 to 9;

[0030] The number of cycles for the alternating growth of the third short-wavelength multi-quantum well layer is 1 to 5.

[0031] A method for fabricating a Micro-LED epitaxial structure suitable for low operating current density, comprising the following steps:

[0032] (1) Selecting a substrate;

[0033] (2) A buffer layer is grown on the substrate;

[0034] (3) Introduce a Si doping source to grow an N-type semiconductor layer on the buffer layer;

[0035] (4) A low-temperature stress relief layer is grown on the N-type semiconductor layer;

[0036] (5) A multi-quantum well light-emitting layer is grown on the low-temperature stress relief layer;

[0037] (6) A P-type semiconductor layer on a multi-quantum-well light-emitting layer.

[0038] Implementing this invention offers the following advantages: This technical solution redesigns the epitaxial structure suitable for small-size, low-current, and low-power Micro-LEDs. Firstly, it innovatively designs the structure of the multi-quantum-well (MFU) emitting layer. The MFU emitting layer of this technical solution comprises three sub-layers stacked sequentially from bottom to top: a first short-wavelength MFU layer, a second long-wavelength MFU layer, and a third short-wavelength MFU layer. The second long-wavelength MFU layer has a higher In content and a longer emission wavelength than the first and third short-wavelength MFU layers. Furthermore, the second long-wavelength MFU layer serves as the emitting unit for the Micro-LED at low operating current densities. Compared to the structural and process designs of MFU emitting layers with the same emission wavelength, the Micro-LED chip fabricated using the epitaxial structure of this technical solution significantly improves the quality of the MFU emitting layer and enhances the matching degree of electron-hole concentration in the emitting quantum well region, thereby increasing the radiative recombination efficiency of the emitting quantum well region and ultimately improving the luminous efficacy of the Micro-LED chip at low operating current densities. Furthermore, this technical solution does not employ a conventional electron blocking layer above the multi-quantum-well light-emitting layer. Since electron leakage is minimal or nonexistent at the low operating current density of Micro-LEDs, the electron blocking layer structure not only fails to block electrons but also hinders hole injection, reducing the device's radiative recombination efficiency. Therefore, by omitting the electron blocking layer above the multi-quantum-well light-emitting layer, this technical solution eliminates the blocking effect of the electron blocking layer on hole injection, significantly improving the hole injection efficiency of the P-type semiconductor layer and further enhancing the matching degree of electron-hole concentration in the multi-quantum-well light-emitting layer region. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the Micro-LED epitaxial structure of Embodiment 1 of the present invention;

[0040] Figure 2 This is a schematic diagram of the multi-quantum-well light-emitting layer in the Micro-LED epitaxial structure of Embodiment 1 of the present invention;

[0041] Figure 3 yes Figure 2 A schematic diagram of the structure of the first short-wavelength multi-quantum well high barrier layer in the multi-quantum well light-emitting layer;

[0042] Figure 4 yes Figure 2 A schematic diagram of the structure of the third short-wavelength multi-quantum well high barrier layer 532 in the multi-quantum well light-emitting layer;

[0043] Among them, 100-substrate, 200-buffer layer, 300-N-type semiconductor layer, 400-low temperature stress relief layer, 500-multiple quantum well light-emitting layer, 600-P-type semiconductor layer, 510-first short-wavelength multiple quantum well layer, 511-first short-wavelength multiple quantum well InGaN material, 512-first short-wavelength multiple quantum well high barrier layer, 520-second long-wavelength multiple quantum well layer, 521-second long-wavelength multiple quantum well InGaN material, 522-second long-wavelength multiple quantum well low barrier layer, 530-the... Three short-wavelength multi-quantum-well layers, 531-Third short-wavelength multi-quantum-well InGaN material, 532-Third short-wavelength multi-quantum-well high-barrier layer, 5121-First high-barrier GaN-1 layer, 5122-First high-barrier AlGaN-2 layer, 5123-First high-barrier GaN-3 layer, 5321-Third high-barrier GaN-1 layer, 5322-Third high-barrier AlGaInN-2 layer, 5323-Third high-barrier AlGaN-3 layer, 5324-Third high-barrier GaN-4 layer. Detailed Implementation

[0044] 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.

[0045] 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.

[0046] like Figures 1 to 4As shown, this technical solution provides a Micro-LED epitaxial structure suitable for low operating current density, including a substrate 100, and further including a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress relief layer 400, a multi-quantum well light-emitting layer 500 and a P-type semiconductor layer 600 sequentially stacked on the substrate 100.

[0047] The multi-quantum-well light-emitting layer 500 includes a first short-wavelength multi-quantum-well layer 510, a second long-wavelength multi-quantum-well layer 520, and a third short-wavelength multi-quantum-well layer 530, which are stacked sequentially from bottom to top; the In component in the first short-wavelength multi-quantum-well layer 510 and the In component in the third short-wavelength multi-quantum-well layer 530 are both smaller than the In component in the second long-wavelength multi-quantum-well layer 520.

[0048] The first short-wavelength multi-quantum well layer 510 includes a first short-wavelength multi-quantum well InGaN layer 511 and a first short-wavelength multi-quantum well high barrier layer 512 that are periodically and alternately grown from bottom to top.

[0049] The second long-wavelength multi-quantum well layer 520 includes a second long-wavelength multi-quantum well InGaN layer 521 and a second long-wavelength multi-quantum well low barrier layer 522 that are periodically alternating from bottom to top.

[0050] The third short-wavelength multi-quantum well layer 530 includes a third short-wavelength multi-quantum well InGaN layer 531 and a third short-wavelength multi-quantum well high barrier layer 532 that are periodically and alternately grown from bottom to top.

[0051] It is worth noting that this technical solution redesigns the epitaxial structure suitable for small-size, low-current, and low-power Micro-LEDs. First, the structure of the multi-quantum-well light-emitting layer 500 is innovatively designed. The multi-quantum-well light-emitting layer 500 of this technical solution includes three sub-layers stacked from bottom to top, namely the first short-wavelength multi-quantum-well layer 510, the second long-wavelength multi-quantum-well layer 520, and the third short-wavelength multi-quantum-well layer 530. The In content of the second long-wavelength multi-quantum-well layer 520 is higher and the emission wavelength is longer than that of the first short-wavelength multi-quantum-well layer 510 and the third short-wavelength multi-quantum-well layer 530. Moreover, the second long-wavelength multi-quantum-well layer 520 is the light-emitting unit of the Micro-LED of this technical solution under low operating current density. Compared to the structure and fabrication design of multi-quantum-well emissive layers with the same emission wavelength, the Micro-LED chip fabricated using the epitaxial structure of this technical solution can significantly improve the quality of the multi-quantum-well emissive layer 500 and improve the matching degree of electron-hole concentration in the emissive quantum well region, thereby increasing the radiative recombination efficiency of the emissive quantum well region and improving the luminous efficacy of the Micro-LED chip at low operating current density. Furthermore, this technical solution does not place a conventional electron blocking layer on top of the multi-quantum-well emissive layer 500. Since electron leakage has not yet occurred or is very low at the low operating current density of Micro-LEDs, the electron blocking layer structure not only fails to block electrons but also blocks hole injection, reducing the radiative recombination efficiency of the device. Therefore, this technical solution does not place an electron blocking layer on top of the multi-quantum-well emissive layer 500, which can eliminate the blocking effect of the electron blocking layer structure on hole injection, significantly improve the hole injection efficiency of the P-type semiconductor layer 600, and further improve the matching degree of electron-hole concentration in the multi-quantum-well emissive layer region.

[0052] Furthermore, based on the above-mentioned epitaxial structure and process design for low-current-density Micro-LEDs, firstly, the In composition in the first short-wavelength multi-quantum-well layer 510 and the third short-wavelength multi-quantum-well layer 530 of this technical solution are both less than the In composition in the second long-wavelength multi-quantum-well layer 520. This results in the InGaN material of the multi-quantum-well emitting layer 500 forming an InGaN / barrier superlattice structure with a change in In composition from increasing to decreasing. This structure and process design can effectively reduce the lattice mismatch stress between the second long-wavelength multi-quantum-well InGaN layer 521 and the first short-wavelength multi-quantum-well high-barrier layer 512, thereby improving the quality of the emitting quantum well region (i.e., the second long-wavelength multi-quantum-well layer 520) under low operating current density, and thus improving the radiative recombination efficiency of the active region. Secondly, in this technical solution, the In content of the second long-wavelength multi-quantum-well layer 520 is higher than that of the first short-wavelength multi-quantum-well layer 510 and the third short-wavelength multi-quantum-well layer 530, resulting in a longer emission wavelength. That is, the growth temperatures of the first short-wavelength multi-quantum-well layer 510 and the third short-wavelength multi-quantum-well layer 530 are both higher than those of the second long-wavelength multi-quantum-well layer 520. High-temperature growth of InGaN material leads to higher atomic mobility, favoring two-dimensional material growth. This significantly reduces defects in the InGaN material, making it easier to obtain high-quality InGaN material. The InGaN material in the first short-wavelength multi-quantum-well InGaN layer 511 and the third short-wavelength multi-quantum-well InGaN layer 531 has a lower In content than the InGaN material in the second long-wavelength multi-quantum-well InGaN layer 521. The lattice mismatch stress between the InGaN material and the GaN material in the multi-quantum-well layer is reduced, and the defects caused by the large mismatch stress are reduced. This can significantly improve the quality of the multi-quantum-well light-emitting layer 500. The reduction of defects in the multi-quantum-well light-emitting layer 500 is beneficial to improving the radiative recombination efficiency of the active region, thereby improving the luminous efficacy and yield of Micro-LED at low operating current densities. Thirdly, the barrier design of the multi-quantum well light-emitting layer 500 in this technical solution is a multi-layer structure of high barrier layer + low barrier layer + high barrier layer. This barrier design of structure and process can effectively confine charge carrier electrons and holes in the region of the second long-wavelength multi-quantum well layer 520, thereby improving the matching degree of electron and hole concentration in the light-emitting quantum well region (i.e. the region of the second long-wavelength multi-quantum well layer 520) and further improving the luminous efficiency of Micro-LED at low operating current density.

[0053] Specifically, the substrate 100 in this technical solution is selected from commonly used substrates in the art, such as sapphire substrates. The buffer layer 200, N-type semiconductor layer 300, low-temperature stress relief layer 400 and P-type semiconductor layer 600 in this technical solution are all prepared using existing processes and materials, and will not be further described in this technical solution.

[0054] Preferably, the total thickness of the first short-wavelength multi-quantum-well high barrier layer 512 is 7.8 nm to 17 nm.

[0055] Further explanation: the first short-wavelength multi-quantum well high barrier layer 512 includes a first high barrier GaN-1 layer 5121, a first high barrier AlGaN-2 layer 5122 and a first high barrier GaN-3 layer 5123, which are stacked and grown sequentially from bottom to top.

[0056] Both the first high barrier GaN-1 layer 5121 and the first high barrier GaN-3 layer 5123 are doped with Si.

[0057] The third short-wavelength multi-quantum well high barrier layer 532 includes a third high barrier GaN-1 layer 5321, a third high barrier AlGaInN-2 layer 5322, a third high barrier AlGaN-3 layer 5323, and a third high barrier GaN-4 layer 5324, which are stacked from bottom to top.

[0058] Both the third high-barrier AlGaInN-2 layer 5322 and the third high-barrier GaN-4 layer 5324 are doped with Mg.

[0059] It is worth noting that the first short-wavelength multi-quantum well high barrier layer 512 of this technical solution is a multilayer structure composed of a first high barrier GaN-1 layer 5121, a first high barrier AlGaN-2 layer 5122, and a first high barrier GaN-3 layer 5123 grown sequentially from bottom to top. The first high barrier GaN-1 layer 5121 and the first high barrier GaN-3 layer 5123 are doped with Si elements, while the first high barrier AlGaN-2 layer 5122 is not intentionally doped. The second long-wavelength multi-quantum well low barrier layer 522 is a single-layer or multilayer GaN structure without intentional doping. The third short-wavelength multi-quantum-well high-barrier layer 532 is a multilayer structure composed of a third high-barrier GaN-1 layer 5321, a third high-barrier AlGaInN-2 layer 5322, a third high-barrier AlGaN-3 layer 5323, and a third high-barrier GaN-4 layer 5324, which are stacked sequentially from bottom to top. The third high-barrier GaN-1 layer 5321 and the third high-barrier AlGaN-3 layer 5323 are not intentionally doped, while the third high-barrier AlGaInN-2 layer 5322 and the third high-barrier GaN-4 layer 5324 are lightly doped or undoped with Mg atoms. Preferably, the third high-barrier AlGaInN-2 layer 5322 and the third high-barrier GaN-4 layer 5324 are low-doped with Mg; that is, the barrier layer design of the multi-quantum well light-emitting layer 500 is a multi-layer structure of high barrier layer + low barrier layer + high barrier layer. The barrier layer design of this structure and process can effectively confine the charge carrier electrons and holes in the region of the second long-wavelength multi-quantum well layer 520, thereby improving the matching degree of electron and hole concentration in the light-emitting quantum well region (i.e., the region of the second long-wavelength multi-quantum well layer 520) and improving the luminous efficiency of Micro-LED at low operating current density. Meanwhile, the high-barrier materials in the third short-wavelength multi-quantum well high-barrier layer 532, namely the third high-barrier AlGaInN-2 layer 5322 and the third high-barrier AlGaN-3 layer 5323, can bind electrons in front of the third short-wavelength multi-quantum well high-barrier layer 532, thereby blocking electrons and reducing their movement speed, preventing electrons from being injected into the P-type semiconductor layer 600 and causing electron leakage, thus improving the yield and other performance of Micro-LED.

[0060] In a preferred embodiment of this technical solution, both the first high-barrier GaN-1 layer 5121 and the first high-barrier GaN-3 layer 5123 are doped with Si, and both the third high-barrier AlGaInN-2 layer 5322 and the third high-barrier GaN-4 layer 5324 are doped with Mg. These dopants can provide some electrons and holes to the second long-wavelength multi-quantum-well layer 520 to participate in radiative recombination luminescence, thereby further improving the luminous efficacy of the Micro-LED at low operating current density.

[0061] To further explain, the proportion of In component in the first short-wavelength multi-quantum well InGaN layer 511 is 0.02 to 0.4, the thickness is 2.05 nm to 3.95 nm, the growth temperature is 716 °C to 920 °C, and the pressure is 50 torr to 360 torr.

[0062] Preferably, the first short-wavelength multi-quantum-well InGaN layer 511 is an InGaN single-layer or multi-layer structure without intentional doping.

[0063] The proportion of In component in the first short-wavelength multi-quantum well InGaN layer 511 of this technical solution is 0.02 to 0.4%, with exemplary values ​​of 0.02, 0.05, 0.08, 0.1, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.35, 0.38, and 0.4, but not limited to these. The thickness of the first short-wavelength multi-quantum well InGaN layer 511 is 2.05 nm to 3.95 nm, with exemplary values ​​of 2.05 nm, 2.50 nm, 2.80 nm, 3 nm, 3.2 nm, 3.5 nm, 3.8 nm, and 3.95 nm, but not limited to these. The growth temperature of the first short-wavelength multi-quantum well InGaN layer 511 is 716℃ to 920℃, with exemplary values ​​of 716℃, 750℃, 780℃, 788℃, 800℃, 850℃, 880℃, 900℃, and 920℃, but not limited thereto. The growth pressure of the first short-wavelength multi-quantum well InGaN layer 511 is 50 torr to 360 torr, with exemplary values ​​of 50 torr, 100 torr, 150 torr, 180 torr, 200 torr, 250 torr, 300 torr, 350 torr, and 360 torr, but not limited thereto.

[0064] Further explanation: the thickness of the first high-barrier GaN-1 layer 5121 is 2nm to 6nm, and the Si doping concentration is 1.2×10⁻⁶. 17 ~7.6×10 18 atoms / cm3, growth temperature 820℃~935℃, pressure 50torr~360torr;

[0065] The first high-barrier AlGaN-2 layer 5122 has an Al content of 0.02-0.3%, a thickness of 1.2 nm-5 nm, a growth temperature of 820℃-935℃, and a pressure of 50 torr-360 torr.

[0066] The thickness of the first high-barrier GaN-3 layer 5123 is 2nm to 6nm, and the Si doping concentration is 1.2×10⁻⁶. 17 ~7.6×10 18 atoms / cm 3The growth temperature is 820℃-935℃, and the pressure is 50 torr-360 torr.

[0067] Specifically, the first high-barrier GaN-1 layer 5121 is a lightly doped GaN material with a Si doping concentration of 1.2 × 10⁻⁶. 17 ~7.6×10 18 atoms / cm 3 An example is 1.2 × 10 17 3.6×10 17 4.0×10 17 4.8×10 17 5×10 17 7×10 17 8.8×10 17 9.5×10 17 1.2×10 18 5×10 18 7.6×10 18 However, this is not limited to the above. The thickness of the first high-barrier GaN-1 layer 5121 is 2nm to 6nm, with 2nm, 3nm, 4nm, 5nm, and 6nm being exemplary, but not limited to this. The growth temperature of the first high-barrier GaN-1 layer 5121 is 820℃ to 935℃, with 820℃, 850℃, 880℃, 900℃, and 935℃ being exemplary, but not limited to this. The growth pressure of the first high-barrier GaN-1 layer 5121 is 50 torr to 360 torr, with 50 torr, 80 torr, 100 torr, 120 torr, 150 torr, 175 torr, 200 torr, 220 torr, 250 torr, 280 torr, 300 torr, 350 torr, and 360 torr being exemplary, but not limited to this.

[0068] The first high-barrier AlGaN-2 layer 5122 in this technical solution is an undoped AlGaN material with an Al composition of 0.02 ≤ X ≤ 0.3. Exemplary Al compositions are 0.02, 0.05, 0.08, 0.1, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, and 0.3, but are not limited to these. The thickness of the first high-barrier AlGaN-2 layer 5122 is 1.2 nm to 5 nm, with exemplary thicknesses of 1.2 nm, 1.5 nm, 1.8 nm, 2 nm, 2.3 nm, 2.5 nm, 2.8 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, and 5 nm, but are not limited to these. The growth temperature of the first high-barrier AlGaN-2 layer 5122 is 820℃ to 935℃, with exemplary temperatures of 820℃, 850℃, 880℃, 900℃, and 935℃, but are not limited to these. The growth pressure of the first high barrier AlGaN-2 layer 5122 is 50 torr to 360 torr, with examples being 50 torr, 80 torr, 100 torr, 120 torr, 150 torr, 175 torr, 200 torr, 220 torr, 250 torr, 280 torr, 300 torr, 350 torr, and 360 torr, but not limited to these.

[0069] In this technical solution, the first high-barrier GaN-3 layer, 5123, is a lightly doped GaN material with Si doping concentration of 1.2 × 10⁻⁶. 17 ~7.6×10 18 atoms / cm 3 An example is 1.2 × 10 17 3.6×10 17 4.0×10 17 4.8×10 17 5×10 17 7×10 17 8.8×10 17 9.5×10 17 1.2×10 18 5×10 18 7.6×10 18However, this is not limited to the above. The thickness of the first high-barrier GaN-3 layer 5123 is 2nm to 6nm, with 2nm, 3nm, 4nm, 5nm, and 6nm being exemplary, but not limited to this. The growth temperature of the first high-barrier GaN-3 layer 5123 is 820℃ to 935℃, with 820℃, 850℃, 880℃, 900℃, and 935℃ being exemplary, but not limited to this. The growth pressure of the first high-barrier GaN-3 layer 5123 is 50 torr to 360 torr, with 50 torr, 80 torr, 100 torr, 120 torr, 150 torr, 175 torr, 200 torr, 220 torr, 250 torr, 280 torr, 300 torr, 350 torr, and 360 torr being exemplary, but not limited to this.

[0070] To further explain, the proportion of In component in the second long-wavelength multi-quantum-well InGaN layer 521 is 0.08 to 0.46, the thickness is 2.25 nm to 4.65 nm, the growth temperature is 680 °C to 920 °C, and the pressure is 50 torr to 360 torr.

[0071] Specifically, the second long-wavelength multi-quantum-well InGaN layer 521 in this technical solution is an undoped InGaN single-layer or multi-layer structure. The proportion of In component in the second long-wavelength multi-quantum-well InGaN layer 521 is 0.08 to 0.46, with exemplary values ​​of 0.08, 0.10, 0.15, 0.18, 0.2, 0.25, 0.28, 0.3, 0.32, 0.35, 0.37, 0.4, 0.43, and 0.46, but not limited to these. The thickness of the second long-wavelength multi-quantum-well InGaN layer 521 is 2.25 nm to 4.65 nm, with exemplary thicknesses of 2.25 nm, 2.5 nm, 2.88 nm, 3.0 nm, 3.30 nm, 3.55 nm, 3.8 nm, 4.0 nm, 4.3 nm, and 4.65 nm, but not limited to these; the growth temperature is 680 °C to 920 °C, with exemplary temperatures of 680 °C, 700 °C, 720 °C, 750 °C, 770 °C, and 800 °C. Temperatures range from 820℃, 850℃, 880℃, 900℃, to 920℃, but are not limited to these; pressures range from 50 torr to 360 torr, with examples including 50 torr, 80 torr, 100 torr, 120 torr, 150 torr, 175 torr, 200 torr, 220 torr, 250 torr, 280 torr, 300 torr, 350 torr, to 360 torr, but are not limited to these.

[0072] To further explain, the second long-wavelength multi-quantum well low barrier layer 522 is a GaN single-layer or multi-layer structure with a growth thickness of 7.5 nm to 16.5 nm, a growth temperature of 820 °C to 935 °C, and a pressure of 50 torr to 360 torr.

[0073] It should be noted that the second long-wavelength multi-quantum-well low-barrier layer 522 is an undoped GaN monolayer or multilayer structure. The growth thickness of the second long-wavelength multi-quantum-well low-barrier layer 522 is 7.5nm to 16.5nm, with exemplary thicknesses of 7.5nm, 8.0nm, 8.5nm, 9.0nm, 9.5nm, 10nm, 10.5nm, 11nm, 11.5nm, 12nm, 12.5nm, 13nm, 13.5nm, 14nm, 14.5nm, 15nm, 15.5nm, and 16nm. 0.5nm; growth temperature is 820℃~935℃, exemplary values ​​are 820℃, 850℃, 880℃, 900℃, 935℃, but not limited thereto; pressure is 50torr~360torr, exemplary values ​​are 50torr, 80torr, 100torr, 120torr, 150torr, 175torr, 200torr, 220torr, 250torr, 280torr, 300torr, 350torr, 360torr, but not limited thereto.

[0074] To further explain, the proportion of In component in the third short-wavelength multi-quantum well InGaN layer 531 is 0.02 to 0.4, the thickness is 2.05 nm to 3.95 nm, the growth temperature is 716 °C to 920 °C, and the pressure is 50 torr to 360 torr.

[0075] It is worth noting that the third short-wavelength multi-quantum-well InGaN layer 531 in this technical solution is an undoped InGaN single-layer or multi-layer structure. The proportion of In component in the third short-wavelength multi-quantum-well InGaN layer 531 is 0.02 to 0.4%, with exemplary values ​​of 0.02, 0.05, 0.08, 0.1, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.35, 0.38, and 0.4, but not limited to these. The growth temperature is 7. The temperature range is 16℃ to 920℃, with examples including 716℃, 750℃, 780℃, 788℃, 800℃, 830℃, 850℃, 880℃, 900℃, and 920℃, but not limited to these; the pressure range is 50 torr to 360 torr, with examples including 50 torr, 100 torr, 150 torr, 180 torr, 200 torr, 250 torr, 300 torr, 350 torr, and 360 torr, but not limited to these.

[0076] Further explanation: the thickness of the third high-barrier GaN-1 layer 5321 is 0.5nm to 3nm, the growth temperature is 820℃ to 935℃, and the pressure is 50 torr to 360 torr;

[0077] The third high-barrier AlGaInN-2 layer 5322 has an Al content of 0.02–0.3%, an In content of 0.01–0.08%, a thickness of 0.8 nm–5 nm, and a Mg doping concentration of 3.6 × 10⁻⁶. 18 ~7.8×10 19 atoms / cm 3 The growth temperature is 820℃~935℃, and the pressure is 50 torr~360 torr;

[0078] The third high-barrier AlGaN-3 layer 5323 has an Al content of 0.02-0.3%, a thickness of 0.5nm-3nm, a growth temperature of 820℃-935℃, and a pressure of 50torr-360torr.

[0079] The thickness of the third high-barrier GaN-4 layer 5324 is 0.8 nm to 5 nm, and the Mg doping concentration is 3.6 × 10⁻⁶. 18 ~7.8×10 19 atoms / cm 3 The growth temperature is 820℃~935℃, and the pressure is 50 torr~360 torr.

[0080] It is worth noting that the third high-barrier GaN-1 layer 5321 is GaN material without intentional doping. The third high-barrier AlGaInN-2 layer 5322 in this technical solution is AlGaInN material with low or no Mg doping. Preferably, the third high-barrier AlGaInN-2 layer 5322 is doped with Mg, and the Mg doping concentration is 3.6 × 10⁻⁶. 18 ~7.8×10 19 atoms / cm 3 An example is 3.6 × 10 18 5.6×10 18 7.2×10 18 8.5×10 18 2.5×10 19 5.8×10 19 7.8×10 19 atoms / cm 3However, it is not limited to this. In the third high barrier AlGaInN-2 layer 5322, the proportion of Al component is 0.02 to 0.3, and the proportion of In component is 0.01 to 0.08. Exemplary Al components are 0.02, 0.08, 0.1, 0.15, 0.2, 0.25, and 0.3, and exemplary In components are 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, and 0.08, but it is not limited to this.

[0081] The third high barrier AlGaN-3 layer 5323 in this technical solution is an AlGaN material that is not intentionally doped, and the proportion of Al component is 0.02 to 0.3, with examples being 0.02, 0.08, 0.1, 0.15, 0.2, 0.25, and 0.3, but not limited to these.

[0082] In this technical solution, the third high-barrier GaN-4 layer 5324 is a GaN material with low or no Mg doping. Preferably, the third high-barrier GaN-4 layer 5324 is doped with Mg, and the Mg doping concentration is 3.6 × 10⁻⁶. 18 ~7.8×10 19 atoms / cm 3 An example is 3.6 × 10 18 5.6×10 18 7.2×10 18 8.5×10 18 2.5×10 19 5.8×10 19 7.8×10 19 atoms / cm 3 However, it is not limited to this.

[0083] The thickness of the third high-barrier GaN-1 layer 5321 and the third high-barrier AlGaN-3 layer 5323 in this technical solution is 0.5nm to 3nm, with exemplary thicknesses of 0.5nm, 0.8nm, 1nm, 1.2nm, 1.5nm, 2nm, 2.5nm, 2.8nm, and 3nm, but not limited to these. The thickness of the third high-barrier AlGaInN-2 layer 5322 and the third high-barrier GaN-4 layer 5324 is 0.8nm to 5nm, with exemplary thicknesses of 0.8nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, and 5nm, but not limited to these.

[0084] The growth temperatures of the third high-barrier GaN-1 layer 5321, the third high-barrier AlGaInN-2 layer 5322, the third high-barrier AlGaN-3 layer 5323, and the third high-barrier GaN-4 layer 5324 in this technical solution are all between 820℃ and 935℃, with examples of 820℃, 850℃, 880℃, 900℃, and 935℃, but not limited to these. The growth temperatures of the four layers can be the same or different. The growth pressures are all between 50 torr and 360 torr, with examples of 50 torr, 100 torr, 150 torr, 180 torr, 200 torr, 250 torr, 300 torr, 350 torr, and 360 torr, but not limited to these. The growth pressures of the four layers can be the same or different from each other.

[0085] Preferably, the total thickness of the third short-wavelength multi-quantum-well high barrier layer 532 is 7.2 nm to 16 nm.

[0086] To further explain, the number of alternating growth cycles of the first short-wavelength multi-quantum well layer 510 is 2 to 6;

[0087] The number of alternating growth cycles of the second long-wavelength multi-quantum well layer 520 is 2 to 9;

[0088] The number of alternating growth cycles of the third short-wavelength multi-quantum well layer 530 is 1 to 5.

[0089] The first short-wavelength multiple quantum well layer 510 is a superlattice structure composed of a first short-wavelength multiple quantum well InGaN layer 511 and a first short-wavelength multiple quantum well high barrier layer 512 that are periodically alternating from bottom to top. The number of alternating growth periods is 2 to 6, with 2, 3, 4, 5, and 6 being exemplary.

[0090] The second long-wavelength multi-quantum well layer 520 is a superlattice structure composed of a second long-wavelength multi-quantum well InGaN layer 521 and a second long-wavelength multi-quantum well low barrier layer 522, which are periodically alternatingly grown from bottom to top. The period range of the alternating growth of the second long-wavelength multi-quantum well layer 520 is 2 to 9; an exemplary period is 2, 3, 4, 5, 6, 7, 8, 9.

[0091] The third short-wavelength multi-quantum well layer 530 described in this technical solution is a superlattice structure composed of a third short-wavelength multi-quantum well InGaN layer 531 and a third short-wavelength multi-quantum well high barrier layer 532 that are periodically and alternately grown from bottom to top. The number of alternating growth periods is 1 to 5, with 1, 2, 3, 4, and 5 being exemplary.

[0092] A method for fabricating a Micro-LED epitaxial structure suitable for low operating current density, comprising the following steps:

[0093] (1) Select substrate 100;

[0094] (2) A buffer layer 200 is grown on the substrate 100;

[0095] (3) Introduce a Si doping source and grow an N-type semiconductor layer 300 on the buffer layer 200;

[0096] (4) A low-temperature stress relief layer 400 is grown on the N-type semiconductor layer 300;

[0097] (5) A multi-quantum-well light-emitting layer 500 is grown on the low-temperature stress-relieving layer 400;

[0098] (6) A P-type semiconductor layer 600 is placed on the multi-quantum well light-emitting layer 500.

[0099] The technical solution of the present invention will be further described below through embodiments and comparative examples.

[0100] Example 1

[0101] The Micro-LED epitaxial structure applicable to low operating current density in this embodiment includes, from bottom to top, a substrate 100, and a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress relief layer 400, a multi-quantum well light-emitting layer 500 and a P-type semiconductor layer 600 sequentially stacked on the substrate 100.

[0102] The multi-quantum well light-emitting layer 500 includes a first short-wavelength multi-quantum well layer 510, a second long-wavelength multi-quantum well layer 520 and a third short-wavelength multi-quantum well layer 530, which are stacked sequentially from bottom to top; the In content in the first short-wavelength multi-quantum well layer 510 and the In content in the third short-wavelength multi-quantum well layer 530 are both smaller than the In content in the second long-wavelength multi-quantum well layer 520.

[0103] The first short-wavelength multi-quantum well layer 510 includes a first short-wavelength multi-quantum well InGaN layer 511 and a first short-wavelength multi-quantum well high barrier layer 512 that are periodically alternating from bottom to top, with a period number of 4. The first short-wavelength multi-quantum well high barrier layer 512 includes a first high barrier GaN-1 layer 5121, a first high barrier AlGaN-2 layer 5122 and a first high barrier GaN-3 layer 5123 that are stacked from bottom to top.

[0104] The second long-wavelength multi-quantum well layer 520 includes a second long-wavelength multi-quantum well InGaN layer 521 and a second long-wavelength multi-quantum well low barrier layer 522 that are periodically alternating from bottom to top, with a number of alternating growth periods of 6.

[0105] The third short-wavelength multi-quantum well layer 530 includes a third short-wavelength multi-quantum well InGaN layer 531 and a third short-wavelength multi-quantum well high barrier layer 532 that are periodically alternating from bottom to top, with a period of 3 alternating growths; wherein, the third short-wavelength multi-quantum well high barrier layer 532 includes a third high barrier GaN-1 layer 5321, a third high barrier AlGaInN-2 layer 5322, a third high barrier AlGaN-3 layer 5323 and a third high barrier GaN-4 layer 5324 that are stacked from bottom to top.

[0106] The first short-wavelength multi-quantum-well InGaN layer 511 has an In content of 0.15, a thickness of 2.8 nm, a growth temperature of 850 °C, and a pressure of 150 torr; the first high-barrier GaN-1 layer 5121 has a thickness of 4 nm and a Si doping concentration of 1.2 × 10⁻⁶. 17 atoms / cm 3 The growth temperature was 880℃ and the pressure was 120 torr; the Al composition in the first high-barrier AlGaN-2 layer 5122 was 0.18%, the thickness was 2.5 nm, and the growth temperature was 880℃ and the pressure was 120 torr; the thickness of the first high-barrier GaN-3 layer 5123 was 4 nm, and the Si doping concentration was 9.5 × 10⁻⁶. 17 atoms / cm 3 The growth temperature was 880℃ and the pressure was 120 torr;

[0107] The second long-wavelength multi-quantum well InGaN layer 521 has an In content of 0.37, a thickness of 3.8 nm, a growth temperature of 750 °C, and a pressure of 120 torr; the second long-wavelength multi-quantum well low barrier layer 522 is a GaN monolayer structure with a growth thickness of 10 nm, a growth temperature of 880 °C, and a pressure of 150 torr.

[0108] The third short-wavelength multi-quantum-well InGaN layer 531 has an In content of 0.2%, a thickness of 2.8 nm, a growth temperature of 830 °C, and a pressure of 120 torr; the third high-barrier GaN-1 layer 5321 has a thickness of 2.5 nm, a growth temperature of 880 °C, and a pressure of 150 torr; the third high-barrier AlGaInN-2 layer 5322 has an Al content of 0.15%, an In content of 0.05%, a thickness of 3.5 nm, and a Mg doping concentration of 8.5 × 10⁻⁶. 18 atoms / cm 3The growth temperature was 880℃ and the pressure was 150 torr; the third high-barrier AlGaN-3 layer 5323 had an Al content of 0.1%, a thickness of 2.5 nm, and was grown at 880℃ under 150 torr; the third high-barrier GaN-4 layer 5324 had a thickness of 3.5 nm and a Mg doping concentration of 5.6 × 10⁻⁶. 18 atoms / cm 3 The growth temperature is 880℃ and the pressure is 150 torr.

[0109] This embodiment applies to the fabrication method of Micro-LED epitaxial structures with low operating current density, and includes the following steps:

[0110] (1) Select substrate 100;

[0111] (2) A buffer layer 200 is grown on the substrate 100;

[0112] (3) Introduce a Si doping source and grow an N-type semiconductor layer 300 on the buffer layer 200;

[0113] (4) A low-temperature stress relief layer 400 is grown on the N-type semiconductor layer 300;

[0114] (5) A multi-quantum-well light-emitting layer 500 is grown on the low-temperature stress-relieving layer 400;

[0115] (6) A P-type semiconductor layer 600 is placed on the multi-quantum well light-emitting layer 500.

[0116] Example 2

[0117] This embodiment provides a Micro-LED epitaxial structure suitable for low operating current density, which is basically the same as that in Embodiment 1, except that:

[0118] In this embodiment, the proportion of In component in the first short-wavelength multi-quantum well InGaN layer 511 is 0.08, the thickness is 2.05 nm, the growth temperature is 880 °C, and the pressure is 150 orr.

[0119] The second long-wavelength multi-quantum-well InGaN layer 521 has an In content of 0.37, a thickness of 3.0 nm, a growth temperature of 720 °C, and a pressure of 100 torr.

[0120] The third short-wavelength multi-quantum well InGaN layer 531 has an In content of 0.15, a thickness of 0.35, a growth temperature of 850℃, and a pressure of 180 torr.

[0121] Example 3

[0122] This embodiment provides a Micro-LED epitaxial structure suitable for low operating current density, which is basically the same as that in Embodiment 1, except that:

[0123] In this embodiment, the Si doping concentration in the first high-barrier GaN-1 layer 5121 is 7 × 10⁻⁶. 17 atoms / cm3;

[0124] The Si doping concentration in the first high-barrier GaN-3 layer (5123) is 1.2 × 10⁻⁶. 18 atoms / cm 3 ;

[0125] The Mg doping concentration in the third high-barrier AlGaInN-2 layer 5322 is 2.5 × 10⁻⁶. 19 atoms / cm 3 ;

[0126] The Mg doping concentration in the third high-barrier GaN-4 layer 5324 is 8.5 × 10⁻⁶. 18 atoms / cm 3 .

[0127] Comparative Example 1 – (with an electron blocking layer and a conventional structure for the multi-quantum well light-emitting layer)

[0128] This comparative example provides a Micro-LED epitaxial structure, comprising, from bottom to top: a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum-well light-emitting layer, an electron blocking layer, and a P-type semiconductor layer. The multi-quantum-well light-emitting layer of this comparative example includes InGaN quantum well layers and GaN quantum barrier layers that are periodically and alternately grown from bottom to top, with a period number of 5. The InGaN quantum well layer has an In content of 0.37%, a thickness of 3.8 nm, a growth temperature of 750 °C, and a pressure of 120 torr. The GaN quantum barrier layer is made of GaN material, has a growth thickness of 10 nm, a growth temperature of 880 °C, and a pressure of 150 torr.

[0129] Comparative Example 2

[0130] This comparative example provides a Micro-LED epitaxial structure suitable for low operating current density, which is basically the same as that in Example 1, except that:

[0131] In this comparative example, an electron blocking layer is provided between the multi-quantum well light-emitting layer 500 and the P-type semiconductor layer 600.

[0132] Comparative Example 3

[0133] This comparative example provides a Micro-LED epitaxial structure suitable for low operating current density, which is basically the same as that in Example 1, except that:

[0134] In this comparative example, the In component in the first short-wavelength multi-quantum well InGaN layer 511 is equal to the In component in the second long-wavelength multi-quantum well InGaN layer 521 and the In component in the third short-wavelength multi-quantum well InGaN layer 531, all of which are 0.12.

[0135] Performance testing:

[0136] The Micro-LED epitaxial structures obtained in Examples 1-3 and Comparative Examples 1-3 were fabricated into 20μm×20μm Micro-LED chips using the same chip fabrication conditions. Their luminous efficiency was tested at an operating current of 0.5μA. Based on Comparative Example 1, the luminous efficiency improvement rate in each example and comparative example was calculated.

[0137] Light efficiency improvement rate = (improved light efficiency - original light efficiency) / original light efficiency × 100%;

[0138] In the above calculation formula: the original light effect is the same as the light effect of Comparative Example 1.

[0139] Specifically, the test results are shown in Table 1 below:

[0140] Table 1 Performance Test Results

[0141] Luminous efficacy improvement rate (%) Example 1 3.69 Example 2 3.21 Example 3 3.08 Comparative Example 1 —— Comparative Example 2 2.13 Comparative Example 3 1.95

[0142] The experimental data above show that the Micro-LED chip fabricated using the epitaxial structure of this technical solution can significantly improve the quality of the multi-quantum-well emitting layer and the matching degree of electron-hole concentration in the emitting quantum well region, thereby increasing the radiative recombination efficiency of the emitting quantum well region and improving the luminous efficacy of the Micro-LED chip at low operating current densities. Furthermore, this technical solution does not use a conventional electron blocking layer above the multi-quantum-well emitting layer. Since electron leakage has not yet occurred or is very low at the low operating current density of Micro-LEDs, the electron blocking layer structure not only fails to block electrons but also blocks hole injection, reducing the radiative recombination efficiency of the device. Therefore, this technical solution eliminates the electron blocking layer above the multi-quantum-well emitting layer, thus eliminating the blocking effect of the electron blocking layer structure on hole injection, significantly improving the hole injection efficiency of the P-type semiconductor layer, and further improving the matching degree of electron-hole concentration in the multi-quantum-well emitting layer region.

[0143] 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 Micro-LED epitaxial structure suitable for low operating current density, comprising a substrate, characterized in that, It also includes a buffer layer, an N-type semiconductor layer, a low-temperature stress relief layer, a multi-quantum well light-emitting layer and a P-type semiconductor layer stacked sequentially on the substrate, and no electron blocking layer is provided above the multi-quantum well light-emitting layer; The multi-quantum-well light-emitting layer comprises a first short-wavelength multi-quantum-well layer, a second long-wavelength multi-quantum-well layer, and a third short-wavelength multi-quantum-well layer, which are stacked sequentially from bottom to top; the In composition in the first short-wavelength multi-quantum-well layer and the In composition in the third short-wavelength multi-quantum-well layer are both smaller than the In composition in the second long-wavelength multi-quantum-well layer. The first short-wavelength multi-quantum well layer includes a first short-wavelength multi-quantum well InGaN layer and a first short-wavelength multi-quantum well high barrier layer that are periodically and alternately grown from bottom to top. The second long-wavelength multi-quantum-well layer includes a second long-wavelength multi-quantum-well InGaN layer and a second long-wavelength multi-quantum-well low-barrier layer that are periodically alternating from bottom to top. The third short-wavelength multi-quantum well layer comprises a third short-wavelength multi-quantum well InGaN layer and a third short-wavelength multi-quantum well high barrier layer that are periodically and alternately grown from bottom to top. The first short-wavelength multi-quantum-well high barrier layer includes a first high barrier GaN-1 layer, a first high barrier AlGaN-2 layer and a first high barrier GaN-3 layer, which are stacked and grown sequentially from bottom to top. Both the first high-barrier GaN-1 layer and the first high-barrier GaN-3 layer are doped with Si. The third short-wavelength multi-quantum-well high barrier layer includes a third high barrier GaN-1 layer, a third high barrier AlGaInN-2 layer, a third high barrier AlGaN-3 layer and a third high barrier GaN-4 layer, which are stacked sequentially from bottom to top. Both the third high-barrier AlGaInN-2 layer and the third high-barrier GaN-4 layer are doped with Mg. The thickness of the first high-barrier GaN-1 layer is 2nm~6nm, and the Si doping concentration is 1.2×10⁻⁶. 17 ~7.6×10 18 atoms / cm 3 The growth temperature is 820℃~935℃, and the pressure is 50 torr~360 torr; The first high-barrier AlGaN-2 layer has an Al content of 0.02~0.3%, a thickness of 1.2nm~5nm, a growth temperature of 820℃~935℃, and a pressure of 50torr~360torr. The thickness of the first high-barrier GaN-3 layer is 2nm~6nm, and the Si doping concentration is 1.2×10⁻⁶. 17 ~7.6×10 18 atoms / cm 3 The growth temperature is 820℃~935℃, and the pressure is 50 torr~360 torr; The thickness of the third high-barrier GaN-1 layer is 0.5nm~3nm, the growth temperature is 820℃~935℃, and the pressure is 50torr~360torr; The third high-barrier AlGaInN-2 layer has an Al content of 0.02–0.3%, an In content of 0.01–0.08%, a thickness of 0.8 nm–5 nm, and a Mg doping concentration of 3.6 × 10⁻⁶. 18 ~7.8×10 19 atoms / cm 3 The growth temperature is 820℃~935℃, and the pressure is 50 torr~360 torr; The third high-barrier AlGaN-3 layer has an Al content of 0.02~0.3%, a thickness of 0.5nm~3nm, a growth temperature of 820℃~935℃, and a pressure of 50torr~360torr. The thickness of the third high-barrier GaN-4 layer is 0.8 nm to 5 nm, and the Mg doping concentration is 3.6 × 10⁻⁶. 18 ~7.8×10 19 atoms / cm 3 The growth temperature is 820℃~935℃, and the pressure is 50 torr~360 torr.

2. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that, The first short-wavelength multi-quantum-well InGaN layer has an In content of 0.02~0.4%, a thickness of 2.05nm~3.95nm, a growth temperature of 716℃~920℃, and a pressure of 50torr~360torr.

3. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that, The second long-wavelength multi-quantum-well InGaN layer has an In content of 0.08~0.46, a thickness of 2.25nm~4.65nm, a growth temperature of 680℃~920℃, and a pressure of 50torr~360torr.

4. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that, The second long-wavelength multi-quantum-well low barrier layer is a GaN single-layer or multi-layer structure with a growth thickness of 7.5nm~16.5nm, a growth temperature of 820℃~935℃, and a pressure of 50torr~360torr.

5. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that, The third short-wavelength multi-quantum-well InGaN layer has an In content of 0.02~0.4%, a thickness of 2.05nm~3.95nm, a growth temperature of 716℃~920℃, and a pressure of 50torr~360torr.

6. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that, The number of alternating growth cycles of the first short-wavelength multi-quantum well layer is 2 to 6; The number of alternating growth cycles of the second long-wavelength multi-quantum-well layer is 2 to 9; The number of cycles for the alternating growth of the third short-wavelength multi-quantum well layer is 1 to 5.

7. A method for fabricating Micro-LED epitaxial structures suitable for low operating current densities, characterized in that, The method for preparing the Micro-LED epitaxial structure suitable for low operating current density as described in any one of claims 1-6 comprises the following steps: (1) Selecting a substrate; (2) A buffer layer is grown on the substrate; (3) Introduce a Si doping source to grow an N-type semiconductor layer on the buffer layer; (4) A low-temperature stress relief layer is grown on the N-type semiconductor layer; (5) A multi-quantum well light-emitting layer is grown on the low-temperature stress relief layer; (6) A P-type semiconductor layer on a multi-quantum-well light-emitting layer.

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