Micro-LED epitaxial structure suitable for low working current density and preparation method thereof

Abstract

The invention discloses a Micro-LED epitaxial structure suitable for low working current density and a preparation method thereof, and relates to the technical field of semiconductor devices. The Micro-LED epitaxial structure comprises a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer and a P-type semiconductor layer. The multi-quantum well light-emitting layer comprises a first short-wave multi-quantum well layer, a second long-wave multi-quantum well layer and a third short-wave multi-quantum well layer which are sequentially arranged from bottom to top; the In component in the first short-wave multi-quantum well layer and the In component in the third short-wave multi-quantum well layer are both smaller than the In component in the second long-wave multi-quantum well layer. According to the Micro-LED epitaxial structure, the quality of a multi-quantum well light-emitting layer can be remarkably improved, the matching degree of electron hole concentration in a light-emitting quantum well area is improved, the radiation recombination efficiency of the light-emitting quantum well area is improved, and therefore the lighting effect of a Micro-LED chip under the low working current density is improved, and the service life of the Micro-LED chip is prolonged. The problem that an epitaxial structure of a traditional visible light LED is low in luminous efficiency under the low working current density is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a Micro-LED epitaxial structure suitable for low operating current density and a preparation method thereof. Background Art

[0002] With the booming development of emerging wearable and portable technologies, micron-sized LED chips (Micro LED) have received great attention and research from scientific research institutions and enterprises due to their application prospects in display, visible light communication and biomedicine. In addition, Micro LED display has nanosecond (ns) level high-speed response performance, stable characteristics of inorganic materials, high light efficiency, high reliability, high color purity, high contrast and transparency. The combination of these characteristics is difficult to achieve with liquid crystal display (LCD) and organic LED (OLED).

[0003] Although Micro LED has many excellent characteristics, it also faces challenges in manufacturing technology and material device physics. For example, the problem of the decrease in device peak EQE and the increase in corresponding current density as the chip size decreases has not been completely solved. The operating current density is between 0.01 and 0.5 A / cm 2 The efficiency of Micro LEDs in this range is still obviously insufficient. In fact, even conventional-sized chips for general lighting and backlight display applications have relatively low efficiency at this current density. The reason is that conventional-sized chips usually have an operating current density of 20A / cm2 in order to balance efficiency and cost factors. 2 Up to 40A / cm 2 The corresponding epitaxial structure design and material growth aim to improve the efficiency at high current density, with a peak EQE of 1 to 4 A / cm 2 The current density range is not concerned with the device efficiency at low current density. Under different current densities, the dominant reasons for the light-emitting mechanism of LED devices are different, and the corresponding epitaxial layer structure should also change. For example, in the Micro LED working range of 0.01~0.5A / cm 2 At low current density, the carrier concentration in the quantum well is relatively low, the proportion of Auger recombination is small, and the corresponding quantum well recombination volume can be reduced, which means that the number of quantum wells can be reduced, the number of defects can be reduced, and the EQE of the device at low current density can be improved; at the same time, electron leakage has not occurred or the proportion is very low at low current density, and the electron blocking layer structure not only has no effect of blocking electrons, but will block the injection of holes, reducing the quantum efficiency of the device. Therefore, in-depth mechanism research, design and growth of the epitaxial layer structure under the low current density working conditions of Micro LED is a necessary key technology for the development of high-efficiency Micro LED devices driven by low working current density.

[0004] The epitaxial structure design of traditional visible light LEDs is basically based on the traditional application scenarios of large chips, high currents, and high powers. However, the display applications of Micro LEDs require small size, low current, and low power. LEDs designed with traditional epitaxial structures are no longer able to meet the application requirements of Micro LEDs. Therefore, redesigning the epitaxial structure of Micro LEDs suitable for small size, low current, and low power, and improving their electro-optical conversion efficiency, is an important challenge currently faced by both academia and industry. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present 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, and improve the matching degree of the electron-hole concentration in the light-emitting quantum well region, thereby improving the radiation recombination efficiency of the light-emitting quantum well region, thereby improving the luminous efficiency of the Micro-LED chip at low operating current density, and solving the problem of low luminous efficiency of the epitaxial structure of traditional visible light LEDs at low operating current density.

[0006] Another object of the present invention is to provide a method for preparing a Micro-LED epitaxial structure suitable for low operating current density, which is used to prepare the above-mentioned Micro-LED epitaxial structure suitable for low operating current density.

[0007] To achieve this object, the present invention adopts the following technical solutions:

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

[0009] The multi-quantum well light-emitting layer comprises a first short-wave multi-quantum well layer, a second long-wave multi-quantum well layer and a third short-wave multi-quantum well layer which are stacked and grown in sequence from bottom to top; the In component in the first short-wave multi-quantum well layer and the In component in the third short-wave multi-quantum well layer are both less than the In component in the second long-wave multi-quantum well layer;

[0010] The first short-wave multi-quantum well layer comprises a first short-wave multi-quantum well InGaN layer and a first short-wave multi-quantum well high-potential barrier layer which are periodically and alternately grown from bottom to top;

[0011] The second long-wavelength multi-quantum well layer comprises a second long-wavelength multi-quantum well InGaN layer and a second long-wavelength multi-quantum well low-potential barrier layer which are periodically and alternately grown from bottom to top;

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

[0013] Preferably, the first short-wavelength multi-quantum well high-potential barrier layer comprises a first high-potential barrier GaN-1 layer, a first high-potential barrier AlGaN-2 layer and a first high-potential barrier GaN-3 layer 3 which are sequentially stacked and grown from bottom to top;

[0014] The first high barrier GaN-1 layer and the first high barrier GaN-3 layer are both doped with Si element;

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

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

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

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

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

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

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

[0022] Preferably, the second long-wavelength multi-quantum well low-potential barrier layer is a GaN single layer or multilayer 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-wave multi-quantum well InGaN layer is 0.02-0.4, the thickness is 2.05 nm-3.95 nm, the growth temperature is 716° C.-920° C., and the pressure is 50 torr-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 component ratio of 0.02-0.3, an In component ratio of 0.01-0.08, a thickness of 0.8 nm-5 nm, and a Mg doping concentration of 3.6×10 18 ~7.8×10 19 atoms / cm 3 , the growth temperature is 820℃~935℃, and the pressure is 50torr~360torr;

[0026] The proportion of Al component in the third high barrier AlGaN-3 layer is 0.02-0.3, the thickness is 0.5nm-3nm, the growth temperature is 820℃-935℃, and the pressure is 50torr-360torr;

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

[0028] Preferably, the number of cycles of the alternating growth of the first short-wavelength multi-quantum well layer is 2 to 6;

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

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

[0031] A method for preparing a Micro-LED epitaxial structure suitable for low operating current density, for preparing the above-mentioned Micro-LED epitaxial structure suitable for low operating current density, comprises the following steps:

[0032] (1) Selecting a substrate;

[0033] (2) growing a buffer layer on the substrate;

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

[0035] (4) growing a low-temperature stress release layer on the N-type semiconductor layer;

[0036] (5) growing a multi-quantum well light-emitting layer on the low-temperature stress release layer;

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

[0038] The implementation of the present invention has the following beneficial effects: the present technical solution redesigns the epitaxial structure of Micro-LEDs suitable for small size, low current and low power. First, the structure of the multi-quantum well light-emitting layer is innovatively designed. The multi-quantum well light-emitting layer of the present technical solution includes three sub-layers stacked and grown from bottom to top, namely, the first short-wave multi-quantum well layer, the second long-wave multi-quantum well layer and the third short-wave multi-quantum well layer, wherein the In component in the second long-wave multi-quantum well layer is higher than the In component in the first short-wave multi-quantum well layer and the third short-wave multi-quantum well layer, and the light-emitting wavelength is longer, and the second long-wave multi-quantum well layer is the light-emitting unit of the Micro-LED of the present technical solution at low working current density. Compared with the structure and process design of the multi-quantum well light-emitting layer of the same light-emitting wavelength, the Micro-LED chip prepared by the epitaxial structure of the present technical solution can significantly improve the quality of the multi-quantum well light-emitting layer, improve the matching degree of the electron-hole concentration in the light-emitting quantum well region, and improve the radiation recombination efficiency in the light-emitting quantum well region, thereby improving the light efficiency of the Micro-LED chip at low working current density. In addition, the present technical solution does not set a conventional electron blocking layer on the multi-quantum well light-emitting layer. Since electron leakage has not occurred or the proportion is very low under the low operating current density of Micro-LED, the electron blocking layer structure not only does not block electrons, but will block the injection of holes, reducing the radiation recombination efficiency of the device. Therefore, the present technical solution does not set an electron blocking layer on the multi-quantum well light-emitting layer, 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, and further improve the matching degree of the electron-hole concentration in the multi-quantum well light-emitting layer region. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0042] Figure 4 yes Figure 2 A schematic structural diagram of a third short-wave multi-quantum well high potential barrier layer 532 in a multi-quantum well light-emitting layer;

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

[0044] To make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0045] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. Raw materials used without specifying the manufacturer are all conventional products that can be obtained through commercial purchase.

[0046] like Figures 1 to 4As shown, the present technical solution is a Micro-LED epitaxial structure suitable for low working current density, including a substrate 100, and also including a buffer layer 200, an N-type semiconductor layer 300, a low-temperature stress release 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-wave multi-quantum well layer 510, a second long-wave multi-quantum well layer 520 and a third short-wave multi-quantum well layer 530 that are stacked and grown in sequence from bottom to top; the In component in the first short-wave multi-quantum well layer 510 and the In component in the third short-wave multi-quantum well layer 530 are both less than the In component in the second long-wave multi-quantum well layer 520;

[0048] The first short-wave multi-quantum well layer 510 includes a first short-wave multi-quantum well InGaN layer 511 and a first short-wave multi-quantum well high-potential barrier layer 512 which 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-potential barrier layer 522 which are periodically and alternately grown from bottom to top;

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

[0051] It is worth noting that the present technical solution redesigns the epitaxial structure of Micro-LEDs suitable for small size, low current and low power. First, the structure of the multi-quantum well light-emitting layer 500 is innovatively designed. The multi-quantum well light-emitting layer 500 of the present technical solution includes three sub-layers stacked and grown from bottom to top, namely, a first short-wave multi-quantum well layer 510, a second long-wave multi-quantum well layer 520 and a third short-wave multi-quantum well layer 530. The In component in the second long-wave multi-quantum well layer 520 is higher than that in the first short-wave multi-quantum well layer 510 and the third short-wave multi-quantum well layer 530, and the emission wavelength is longer. The second long-wave multi-quantum well layer 520 is the light-emitting unit of the Micro-LED of the present technical solution at a low operating current density. Compared with the structure and process design of the multi-quantum well light-emitting layer of the same light-emitting wavelength, the Micro-LED chip prepared by the epitaxial structure of the present technical solution can significantly improve the quality of the multi-quantum well light-emitting layer 500, improve the matching degree of the electron-hole concentration in the light-emitting quantum well region, and improve the radiation recombination efficiency of the light-emitting quantum well region, thereby improving the light efficiency of the Micro-LED chip at low operating current density. In addition, the present technical solution does not set a conventional electron blocking layer on the multi-quantum well light-emitting layer 500. Since electron leakage has not yet occurred or the proportion is very low under the low operating current density of the Micro-LED, the electron blocking layer structure not only has no effect of blocking electrons, but will block the injection of holes, reducing the radiation recombination efficiency of the device. Therefore, the present technical solution does not set an electron blocking layer on the multi-quantum well light-emitting layer 500, which can eliminate the blocking effect of the electron blocking layer structure on hole injection, and can significantly improve the hole injection efficiency of the P-type semiconductor layer 600 and further improve the matching degree of the electron-hole concentration in the multi-quantum well light-emitting layer region.

[0052] Further explanation, based on the above-mentioned epitaxial structure and process design for low operating current density Micro-LED, on the one hand, the In component in the first short-wave multi-quantum well layer 510 and the In component in the third short-wave multi-quantum well layer 530 of the present technical solution are both smaller than the In component in the second long-wave multi-quantum well layer 520, so that the InGaN material of the multi-quantum well light-emitting layer 500 forms an InGaN / barrier layer superlattice structure in which the In component first increases and then decreases. This structure and process design can effectively reduce the lattice mismatch stress between the second long-wave multi-quantum well InGaN layer 521 and the first short-wave multi-quantum well high-potential barrier layer 512, and improve the quality of the light-emitting quantum well region (i.e., the second long-wave multi-quantum well layer 520) under low operating current density, thereby improving the radiation recombination efficiency of the active region. Secondly, the In component in the second long-wave multi-quantum well layer 520 of the technical solution is higher than the In component in the first short-wave multi-quantum well layer 510 and the In component in the third short-wave multi-quantum well layer 530, and the luminescent wavelength is longer, that is, in terms of the growth temperature of the InGaN material, the growth temperature of the first short-wave multi-quantum well layer 510 and the growth temperature of the third short-wave multi-quantum well layer 530 are both higher than the growth temperature of the second long-wave multi-quantum well layer 520. The InGaN material adopts high-temperature growth with high atomic mobility and is more inclined to two-dimensional material growth. The defects in the InGaN material will be significantly reduced, and it is easier to obtain high-quality InGaN material. At the same time, the InGaN material in the first short-wave multi-quantum well InGaN layer 511 and the third short-wave multi-quantum well InGaN layer 531 has a lower In component than the InGaN material in the second long-wave multi-quantum well InGaN layer 521, and 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, which 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 radiation recombination efficiency of the active region, thereby improving the luminous efficiency and yield of the Micro-LED at low operating current density. Third, the barrier layer design of the multi-quantum well light-emitting layer 500 of the present technical solution is a multi-layer structure of high-potential barrier layer + low-potential barrier layer + high-potential barrier layer. The barrier layer design of this structure and process can effectively confine the carrier electron holes in the second long-wave multi-quantum well layer 520 region, thereby improving the matching degree of the electron-hole concentration in the light-emitting quantum well region (i.e., the second long-wave multi-quantum well layer 520 region), and further improving the luminous efficiency of Micro-LED at low operating current density.

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

[0054] Preferably, the first short-wave multi-quantum well high-potential barrier layer 512 is preferably grown with a total thickness of 7.8 nm to 17 nm.

[0055] Further explanation, the first short-wave 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] The first high barrier GaN-1 layer 5121 and the first high barrier GaN-3 layer 5123 are both doped with Si element;

[0057] The third short-wave 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 and grown sequentially from bottom to top;

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

[0059] It is worth noting that the first short-wave multi-quantum well high barrier layer 512 of the present 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 which are stacked in sequence from bottom to top, and the first high barrier GaN-1 layer 5121 and the first high barrier GaN-3 layer 5123 are doped with Si elements, and the first high barrier AlGaN-2 layer 5122 is not intentionally doped; the second long-wave multi-quantum well low barrier layer 522 is a GaN single-layer or multilayer structure that is not intentionally doped. The third short-wave 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 sequentially stacked from bottom to top, wherein the third high barrier GaN-1 layer 5321 and the third high barrier AlGaN-3 layer 5323 are not intentionally doped, and the third high barrier AlGaInN-2 layer 5322 and the third high barrier GaN-4 layer 5324 are low-doped or not doped with Mg element. Element, preferably, the third high barrier AlGaInN-2 layer 5322 and the third high barrier GaN-4 layer 5324 are low-doped with Mg element; 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 carrier electron holes in the second long-wave multi-quantum well layer 520 region, thereby improving the matching degree of the electron hole concentration in the light-emitting quantum well region (that is, the second long-wave multi-quantum well layer 520 region) and improving the light efficiency of Micro-LED at low operating current density. At the same time, the high barrier materials in the third short-wave multi-quantum well high-potential barrier layer 532, 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-wave multi-quantum well high-potential barrier layer 532, thereby blocking electrons and reducing the electron mobility, preventing electrons from being injected into the P-type semiconductor layer 600 to cause electron leakage, and improving the yield and other performance of Micro-LED.

[0060] In a preferred embodiment of the present technical solution, the first high-barrier GaN-1 layer 5121 and the first high-barrier GaN-3 layer 5123 are both doped with Si elements, and the third high-barrier AlGaInN-2 layer 5322 and the third high-barrier GaN-4 layer 5324 are both doped with Mg elements, which can respectively provide part of the electrons and holes to the second long-wave multi-quantum well layer 520 to participate in radiative recombination luminescence, so as to further improve the luminous efficiency of the Micro-LED at low operating current density.

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

[0062] Preferably, the first short-wavelength multi-quantum well InGaN layer 511 is an InGaN single layer or multilayer structure that is not intentionally doped.

[0063] In the present technical solution, the proportion of In component in the first short-wave multi-quantum well InGaN layer 511 is 0.02-0.4, and exemplary ones are 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, 0.4, but not limited thereto. The thickness of the first short-wave multi-quantum well InGaN layer 511 is 2.05nm-3.95nm, and exemplary ones are 2.05nm, 2.50nm, 2.80nm, 3nm, 3.2nm, 3.5nm, 3.8nm, 3.95nm, but not limited thereto. The growth temperature of the first short-wave multi-quantum well InGaN layer 511 is 716° C. to 920° C., and examples thereof are 716° C., 750° C., 780° C., 788° C., 800° C., 850° C., 880° C., 900° C., and 920° C., but not limited thereto. The growth pressure of the first short-wave multi-quantum well InGaN layer 511 is 50 torr to 360 torr, and examples thereof are 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 doping concentration of Si element is 1.2×10 17 ~7.6×10 18 atoms / cm3, growth temperature is 820℃~935℃, pressure is 50torr~360torr;

[0065] The first high barrier AlGaN-2 layer 5122 has an Al component ratio of 0.02 to 0.3, a thickness of 1.2 nm to 5 nm, a growth temperature of 820° C. to 935° C., and a pressure of 50 torr to 360 torr;

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

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

[0068] The first high barrier AlGaN-2 layer 5122 of the present technical solution is an AlGaN material that is not intentionally doped, with an Al component of 0.02≤X≤0.3, and exemplary Al components are 0.02, 0.05, 0.08, 0.1, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, but not limited thereto. The thickness of the first high barrier AlGaN-2 layer 5122 is 1.2nm to 5nm, and exemplary ones are 1.2nm, 1.5nm, 1.8nm, 2nm, 2.3nm, 2.5nm, 2.8nm, 3nm, 3.5nm, 4nm, 4.5nm, 5nm, but not limited thereto. The growth temperature of the first high barrier AlGaN-2 layer 5122 is 820℃ to 935℃, and exemplary ones are 820℃, 850℃, 880℃, 900℃, 935℃, but not limited thereto. The growth pressure of the first high barrier AlGaN-2 layer 5122 is 50 torr to 360 torr, and examples include 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 is not limited thereto.

[0069] The first high barrier GaN-3 layer 5123 of the technical solution is a GaN material with low doping of Si element, and the doping concentration of Si element is 1.2×10 17 ~7.6×10 18 atoms / cm 3 , an exemplary value 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, but not limited to this. The thickness of the first high barrier GaN-3 layer 5123 is 2nm to 6nm, and exemplarily is 2nm, 3nm, 4nm, 5nm, and 6nm, but not limited to this. The growth temperature of the first high barrier GaN-3 layer 5123 is 820℃ to 935℃, and exemplarily is 820℃, 850℃, 880℃, 900℃, and 935℃, but not limited to this. The growth pressure of the first high barrier GaN-3 layer 5123 is 50torr to 360torr, and exemplarily is 50torr, 80torr, 100torr, 120torr, 150torr, 175torr, 200torr, 220torr, 250torr, 280torr, 300torr, 350torr, and 360torr, but not limited to this.

[0070] Further explanation: the ratio of In component in the second long-wave multi-quantum well InGaN layer 521 is 0.08-0.46, the thickness is 2.25nm-4.65nm, the growth temperature is 680°C-920°C, and the pressure is 50torr-360torr.

[0071] Specifically, the second long-wavelength multi-quantum well InGaN layer 521 of the technical solution is an InGaN single layer or multilayer structure that is not intentionally doped. The proportion of In component in the second long-wavelength multi-quantum well InGaN layer 521 is 0.08-0.46, and exemplary ones are 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, 0.46, but not limited thereto. The thickness of the second long-wavelength multi-quantum well InGaN layer 521 is 2.25 nm to 4.65 nm, and is exemplarily 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 is not limited thereto; the growth temperature is 680° C. to 920° C., and is exemplarily 680° C., 700° C., 720° C., 750° C., 770° C., 800° C., 820℃, 850℃, 880℃, 900℃, 920℃, but not limited to these; the pressure is 50torr~360torr, exemplified by 50torr, 80torr, 100torr, 120torr, 150torr, 175torr, 200torr, 220torr, 250torr, 280torr, 300torr, 350torr, 360torr, but not limited to these.

[0072] To further illustrate, the second long-wavelength multi-quantum well low barrier layer 522 is a GaN single layer or multilayer 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-wave multi-quantum well low-potential barrier layer 522 is a GaN single-layer or multi-layer structure that is not intentionally doped, and the second long-wave multi-quantum well low-potential barrier layer 522 has a growth thickness of 7.5nm to 16.5nm, and exemplary thicknesses are 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, 16nm, 17nm, 18nm, 19nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, 40nm, 41nm, 42nm, 43nm, 44nm, 45nm, 46nm, 47nm, 48nm, 49nm, 50nm, 51nm, 52 .5nm; the growth temperature is 820℃~935℃, exemplified by 820℃, 850℃, 880℃, 900℃, 935℃, but not limited to these; the pressure is 50torr~360torr, exemplified by 50torr, 80torr, 100torr, 120torr, 150torr, 175torr, 200torr, 220torr, 250torr, 280torr, 300torr, 350torr, 360torr, but not limited to these.

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

[0075] It is worth noting that the third short-wave multi-quantum well InGaN layer 531 of the technical solution is an InGaN single layer or multilayer structure that is not intentionally doped, and the proportion of In component in the third short-wave multi-quantum well InGaN layer 531 is 0.02-0.4, and exemplary ones are 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, 0.4, but not limited thereto; the growth temperature is 7 The temperature is 16°C to 920°C, exemplified by 716°C, 750°C, 780°C, 788°C, 800°C, 830°C, 850°C, 880°C, 900°C, and 920°C, but not limited thereto; the pressure is 50 torr to 360 torr, exemplified by 50 torr, 100 torr, 150 torr, 180 torr, 200 torr, 250 torr, 300 torr, 350 torr, and 360 torr, but not limited thereto.

[0076] Further explanation, the thickness of the third high barrier GaN-1 layer 5321 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;

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

[0078] The proportion of Al component in the third high barrier AlGaN-3 layer 5323 is 0.02-0.3, the thickness is 0.5nm-3nm, the growth temperature is 820°C-935°C, and the pressure is 50torr-360torr;

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

[0080] It is worth noting that the third high barrier GaN-1 layer 5321 is a GaN material that is not intentionally doped. The third high barrier AlGaInN-2 layer 5322 of the present technical solution is an AlGaInN material that is low-doped or not doped with Mg. Preferably, the third high barrier AlGaInN-2 layer 5322 is doped with Mg, and the doping concentration of Mg is 3.6×10 18 ~7.8×10 19 atoms / cm 3 , an exemplary value 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 3The proportion of Al component in the third high barrier AlGaInN-2 layer 5322 is 0.02-0.3, the proportion of In component is 0.01-0.08, exemplary Al components are 0.02, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, and exemplary In components are 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, but not limited thereto.

[0081] The third high barrier AlGaN-3 layer 5323 of the present technical solution is an AlGaN material that is not intentionally doped, and the proportion of the Al component is 0.02-0.3, and exemplary ones are 0.02, 0.08, 0.1, 0.15, 0.2, 0.25, and 0.3, but not limited thereto.

[0082] The third high barrier GaN-4 layer 5324 of the present technical solution is a GaN material with low doping or no doping with Mg element. Preferably, the third high barrier GaN-4 layer 5324 is doped with Mg element, and the doping concentration of Mg element is 3.6×10 18 ~7.8×10 19 atoms / cm 3 , an exemplary value 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 , but 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 of the present technical solution are both 0.5nm to 3nm, and are exemplarily 0.5nm, 0.8nm, 1nm, 1.2nm, 1.5nm, 2nm, 2.5nm, 2.8nm, and 3nm, but are not limited thereto. The thickness of the third high barrier AlGaInN-2 layer 5322 and the third high barrier GaN-4 layer 5324 are both 0.8nm to 5nm, and are exemplarily 0.8nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, and 5nm, but are not limited thereto.

[0084] In the present technical scheme, 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 are all 820℃~935℃, exemplarily 820℃, 850℃, 880℃, 900℃, 935℃, but not limited to this, and the growth temperatures of the four can be the same or different; the growth pressures are all 50torr~360torr, exemplarily 50torr, 100torr, 150torr, 180torr, 200torr, 250torr, 300torr, 350torr, 360torr, but not limited to this, and the growth pressures of the four can be the same or different.

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

[0086] Further explanation, the number of cycles of the alternating growth of the first short-wave multi-quantum well layer 510 is 2 to 6;

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

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

[0089] The first short-wave multi-quantum well layer 510 is a superlattice structure composed of a first short-wave multi-quantum well InGaN layer 511 and a first short-wave multi-quantum well high-potential barrier layer 512 that are periodically and alternately grown from bottom to top, and the number of alternating growth periods is 2 to 6, exemplarily 2, 3, 4, 5, and 6.

[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 that are periodically and alternately 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; exemplary ones are 2, 3, 4, 5, 6, 7, 8, 9.

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

[0092] A method for preparing a Micro-LED epitaxial structure suitable for low operating current density, for preparing the above-mentioned Micro-LED epitaxial structure suitable for low operating current density, comprises the following steps:

[0093] (1) Selecting a substrate 100;

[0094] (2) growing a buffer layer 200 on the substrate 100;

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

[0096] (4) growing a low-temperature stress release layer 400 on the N-type semiconductor layer 300;

[0097] (5) growing a multi-quantum well light-emitting layer 500 on the low-temperature stress release layer 400;

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

[0099] The technical scheme of the present invention is further described below through examples and comparative examples.

[0100] Example 1

[0101] The micro-LED epitaxial structure suitable for low working current density of 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 release layer 400, a multi-quantum well light-emitting layer 500 and a P-type semiconductor layer 600 stacked on the substrate 100 in sequence;

[0102] The multi-quantum well light-emitting layer 500 includes a first short-wave multi-quantum well layer 510, a second long-wave multi-quantum well layer 520, and a third short-wave multi-quantum well layer 530 that are sequentially stacked and grown from bottom to top; the In component in the first short-wave multi-quantum well layer 510 and the In component in the third short-wave multi-quantum well layer 530 are both less than the In component in the second long-wave multi-quantum well layer 520;

[0103] The first short-wave multi-quantum well layer 510 includes a first short-wave multi-quantum well InGaN layer 511 and a first short-wave multi-quantum well high-potential barrier layer 512 that are periodically and alternately grown from bottom to top, and the number of cycles of the alternating growth is 4; wherein the first short-wave multi-quantum well high-potential barrier layer 512 includes a first high-potential barrier GaN-1 layer 5121, a first high-potential barrier AlGaN-2 layer 5122 and a first high-potential barrier GaN-3 layer 5123 that are sequentially stacked and grown 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 which are periodically and alternately grown from bottom to top, and the number of cycles of the alternating growth is 6;

[0105] The third short-wave multi-quantum well layer 530 includes a third short-wave multi-quantum well InGaN layer 531 and a third short-wave multi-quantum well high-potential barrier layer 532 that are periodically and alternately grown from bottom to top, and the number of cycles of alternating growth is 3; wherein, the third short-wave multi-quantum well high-potential barrier layer 532 includes a third high-potential GaN-1 layer 5321, a third high-potential AlGaInN-2 layer 5322, a third high-potential AlGaN-3 layer 5323 and a third high-potential GaN-4 layer 5324 that are stacked and grown in sequence from bottom to top.

[0106] The first short-wave multi-quantum well InGaN layer 511 has an In component ratio 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 17 atoms / cm 3 , the growth temperature is 880℃, the pressure is 120torr; the Al component in the first high barrier AlGaN-2 layer 5122 accounts for 0.18, the thickness is 2.5nm, the growth temperature is 880℃, the pressure is 120torr; the thickness of the first high barrier GaN-3 layer 5123 is 4nm, and the doping concentration of Si element is 9.5×10 17 atoms / cm 3 , the growth temperature is 880℃ and the pressure is 120torr;

[0107] The second long-wavelength multi-quantum well InGaN layer 521 has an In component ratio 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 single-layer structure, with a growth thickness of 10 nm, a growth temperature of 880° C., and a pressure of 150 torr;

[0108] The third short-wave multi-quantum well InGaN layer 531 has an In component ratio 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 component ratio of 0.15, an In component ratio of 0.05, a thickness of 3.5 nm, and a Mg doping concentration of 8.5×10 18 atoms / cm 3, the growth temperature is 880℃, the pressure is 150torr; the third high barrier AlGaN-3 layer 5323 has an Al component ratio of 0.1, a thickness of 2.5nm, a growth temperature of 880℃, and a pressure of 150torr; the third high barrier GaN-4 layer 5324 has a thickness of 3.5nm, and a Mg doping concentration of 5.6×10 18 atoms / cm 3 , the growth temperature is 880℃ and the pressure is 150torr.

[0109] This embodiment is applicable to a method for preparing a Micro-LED epitaxial structure with a low operating current density, and includes the following steps:

[0110] (1) Selecting a substrate 100;

[0111] (2) growing a buffer layer 200 on the substrate 100;

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

[0113] (4) growing a low-temperature stress release layer 400 on the N-type semiconductor layer 300;

[0114] (5) growing a multi-quantum well light-emitting layer 500 on the low-temperature stress release layer 400;

[0115] (6) A P-type semiconductor layer 600 is formed 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 Embodiment 1, except that:

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

[0119] The second long-wavelength multi-quantum well InGaN layer 521 has an In component ratio 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-wave multi-quantum well InGaN layer 531 has an In component ratio of 0.15, a thickness of 0.35, a growth temperature of 850° C., 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 Embodiment 1, except that:

[0123] The doping concentration of Si element in the first high barrier GaN-1 layer 5121 of this embodiment is 7×10 17 atoms / cm3;

[0124] The doping concentration of Si element in the first high barrier GaN-3 layer 5123 is 1.2×10 18 atoms / cm 3 ;

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

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

[0127] Comparative Example 1 - (An electron blocking layer is provided, and the multi-quantum well light-emitting layer is a traditional structure)

[0128] The present comparative example provides a Micro-LED epitaxial structure, which includes, from bottom to top: a substrate, a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, an electron blocking layer and a P-type semiconductor layer, wherein the multi-quantum well light-emitting layer of the present comparative example includes an InGaN quantum well layer and a GaN quantum barrier layer that are periodically and alternately grown from bottom to top, with a period number of 5; wherein the proportion of In component in the InGaN material of the InGaN quantum well layer is 0.37, the thickness is 3.8nm, the growth temperature is 750°C, and the pressure is 120torr; the GaN quantum barrier layer is a GaN material, with a growth thickness of 10nm, a growth temperature of 880°C, and a pressure of 150torr.

[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 Example 1, except that:

[0131] In this comparative example, an electron blocking layer is disposed 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 Example 1, except that:

[0134] In this comparative example, the In component in the first short-wave multi-quantum well InGaN layer 511 = the In component in the second long-wave multi-quantum well InGaN layer 521 = the In component in the third short-wave multi-quantum well InGaN layer 531, both of which are 0.12;

[0135] Performance Test:

[0136] The Micro-LED epitaxial structures obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were prepared into 20 μm×20 μm Micro-LED chips using the same chip process conditions, and their luminous efficiency was tested at a working current of 0.5 μA. 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 light effect of comparative example 1.

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

[0140] Table 1 Performance test results

[0141] Light efficiency 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] It can be seen from the above experimental data that the Micro-LED chip prepared by the epitaxial structure of the present technical solution can significantly improve the quality of the multi-quantum well light-emitting layer, improve the matching degree of the electron-hole concentration in the light-emitting quantum well region, and improve the radiation recombination efficiency of the light-emitting quantum well region, thereby improving the light efficiency of the Micro-LED chip at low operating current density. In addition, the present technical solution does not set a conventional electron blocking layer on the multi-quantum well light-emitting layer. Since electron leakage has not yet occurred or the proportion is very low under the low operating current density of Micro-LED, the electron blocking layer structure not only has no effect of blocking electrons, but will block the injection of holes, reducing the radiation recombination efficiency of the device. Therefore, the present technical solution does not set an electron blocking layer on the multi-quantum well light-emitting layer, 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, and further improve the matching degree of the electron-hole concentration in the multi-quantum well light-emitting layer region.

[0143] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to 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 release layer, a multi-quantum well light-emitting layer and a P-type semiconductor layer stacked in sequence on the substrate; The multi-quantum well light-emitting layer comprises a first short-wave multi-quantum well layer, a second long-wave multi-quantum well layer and a third short-wave multi-quantum well layer which are stacked and grown in sequence from bottom to top; the In component in the first short-wave multi-quantum well layer and the In component in the third short-wave multi-quantum well layer are both less than the In component in the second long-wave multi-quantum well layer; The first short-wave multi-quantum well layer comprises a first short-wave multi-quantum well InGaN layer and a first short-wave multi-quantum well high-potential barrier layer which are periodically and alternately grown from bottom to top; The second long-wavelength multi-quantum well layer comprises a second long-wavelength multi-quantum well InGaN layer and a second long-wavelength multi-quantum well low-potential barrier layer which are periodically and alternately grown from bottom to top; The third short-wave multi-quantum well layer comprises a third short-wave multi-quantum well InGaN layer and a third short-wave multi-quantum well high potential barrier layer which are periodically and alternately grown from bottom to top.

2. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that: The first short-wave multi-quantum well high barrier layer comprises a first high barrier GaN-1 layer, a first high barrier AlGaN-2 layer and a first high barrier GaN-3 layer 3 which are sequentially stacked and grown from bottom to top; The first high barrier GaN-1 layer and the first high barrier GaN-3 layer are both doped with Si element; The third short-wave multi-quantum well high-potential barrier layer includes a third high-potential barrier GaN-1 layer, a third high-potential barrier AlGaInN-2 layer, a third high-potential barrier AlGaN-3 layer and a third high-potential barrier GaN-4 layer which are sequentially stacked and grown from bottom to top; The third high-barrier AlGaInN-2 layer and the third high-barrier GaN-4 layer are both doped with Mg element.

3. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that: The proportion of In component in the first short-wave multi-quantum well InGaN layer is 0.02-0.4, the thickness is 2.05nm-3.95nm, the growth temperature is 716°C-920°C, and the pressure is 50torr-360torr.

4. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that: The thickness of the first high barrier GaN-1 layer is 2nm to 6nm, and the doping concentration of Si element is 1.2×10 17 ~7.6×10 18 atoms / cm 3 , the growth temperature is 820℃~935℃, and the pressure is 50torr~360torr; The first high barrier AlGaN-2 layer has an Al component ratio of 0.02 to 0.3, a thickness of 1.2 nm to 5 nm, a growth temperature of 820° C. to 935° C., and a pressure of 50 torr to 360 torr; The thickness of the first high barrier GaN-3 layer is 2nm to 6nm, and the doping concentration of Si element is 1.2×10 17 ~7.6×10 18 atoms / cm 3 , the growth temperature is 820℃-935℃, and the pressure is 50torr-360torr.

5. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that: The proportion of In component in the second long-wave multi-quantum well InGaN layer is 0.08-0.46, the thickness is 2.25nm-4.65nm, the growth temperature is 680°C-920°C, and the pressure is 50torr-360torr.

6. 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 multilayer structure, with a growth thickness of 7.5nm to 16.5nm, a growth temperature of 820°C to 935°C, and a pressure of 50torr to 360torr.

7. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that: The proportion of In component in the third short-wave multi-quantum well InGaN layer is 0.02-0.4, the thickness is 2.05nm-3.95nm, the growth temperature is 716°C-920°C, and the pressure is 50torr-360torr.

8. The Micro-LED epitaxial structure suitable for low operating current density according to claim 1, characterized in that: 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; The third high barrier AlGaInN-2 layer has an Al component ratio of 0.02-0.3, an In component ratio of 0.01-0.08, a thickness of 0.8 nm-5 nm, and a Mg doping concentration of 3.6×10 18 ~7.8×10 19 atoms / cm 3 , the growth temperature is 820℃~935℃, and the pressure is 50torr~360torr; The proportion of Al component in the third high barrier AlGaN-3 layer is 0.02-0.3, the thickness is 0.5nm-3nm, the growth temperature is 820℃-935℃, and the pressure is 50torr-360torr; The thickness of the third high barrier GaN-4 layer is 0.8 nm to 5 nm, and the doping concentration of the Mg element is 3.6×10 18 ~7.8×10 19 atoms / cm3, the growth temperature is 820℃~935℃, and the pressure is 50torr~360torr.

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

10. A method for preparing a Micro-LED epitaxial structure suitable for low operating current density, characterized in that: The method for preparing the Micro-LED epitaxial structure suitable for low operating current density according to any one of claims 1 to 9 comprises the following steps: (1) Selecting a substrate; (2) growing a buffer layer on the substrate; (3) introducing a Si doping source to grow an N-type semiconductor layer on the buffer layer; (4) growing a low-temperature stress release layer on the N-type semiconductor layer; (5) growing a multi-quantum well light-emitting layer on the low-temperature stress release layer; (6) A P-type semiconductor layer on the multi-quantum well light-emitting layer.

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