InGaN red LED device based on variable Al component electron blocking layer for enhancing polarization effect and preparation method thereof

Abstract

The application discloses an InGaN red light LED device based on a variable Al component electron blocking layer to enhance a polarization effect and a preparation method thereof. The InGaN red light LED device comprises, from bottom to top, a substrate, a low-temperature buffer layer, a high-temperature buffer layer, a non-doped GaN layer, an n-type doped GaN layer, a superlattice layer and / or a low-temperature GaN layer, a quantum well active region, a p-type AlGaN electron blocking layer and a p-type region; wherein the atomic percentage content of Al in the p-type AlGaN electron blocking layer is 22-30%, and the thickness of the p-type AlGaN electron blocking layer is 5-15 nm. By controlling the p-type AlGaN electron blocking layer, long-wavelength emission of a low-In component active region can be realized, and problems such as poor crystal quality of a high-In component active region of an existing long-wavelength InGaN red light LED and difficulty in obtaining the same are avoided.

Description

TECHNICAL FIELD

[0001] The application relates to an InGaN red light LED device based on a variable Al component electron blocking layer to enhance polarization effect and a preparation method thereof, and belongs to the technical field of light emitting diodes. BACKGROUND

[0002] In the field of light emitting diodes (LEDs), the development of new display technologies represented by AR / VR has put forward new requirements for display devices. One of the most notable features is that the resolution requirement has significantly improved. Currently, the blue light, green light InGaN, and red light AlGaInP technologies in Micro-LEDs are relatively mature. However, the carrier mobility of AlGaInP material is very high, which leads to more carriers participating in the non-radiative recombination of the sidewall when the chip size is reduced, resulting in a rapid decrease in light-emitting efficiency. At the same time, there are difficulties in monolithic integration of AlGaInP material and InGaN material, so the red light Micro-LED required for full-color Micro-LED die integration still needs to be improved.

[0003] Therefore, InGaN-based red LEDs have become the focus of industry and academia. Due to the low carrier mobility in GaN material, the size effect is relatively insignificant, and the performance is relatively better at high temperature. In addition, the use of InGaN material for full-color LEDs perfectly solves the difficulty of RGB single-chip integration. Zhuang et al. reported the growth of high-In-content InGaN by introducing AlN / AlGaN barriers to compensate for strain and mixed QWs, achieving a peak wavelength of 633 nm and an external quantum efficiency of 1.6% (Z. Zhuang, D. Iida, and K. Ohkawa, “InGaN-based red light-emitting diodes: from traditional to micro-LEDs,” Jpn. J. Appl. Phys. 61(SA) (2022).). Sang et al. reported a 40-μm chip size, 603-nm emission wavelength, and a peak electro-optical conversion efficiency of 4.3% for orange-red Micro-LEDs using an epitaxial tunnel junction contact (Y. M. Sang, Z. Zhuang, K. Xing, D. Q. Zhang, J. J. Yan, Z. Y. Jiang, C. X. Li, K. Chen, Y. Ding, T. Tao, D. Iida, K. Wang, C. Li, K. Huang, K. Ohkawa, R. Zhang, and B. Liu, “High-temperature performance of InGaN-based amber micro-light-emitting diodes using an epitaxial tunnel junction contact,” Appl. Phys. Lett. 124(14) (2024).).Chen et al. reported a composite buffer layer to increase the surface lattice constant of GaN, successfully improving the incorporation efficiency of In in the active region, achieving an InGaN red mini-LED chip with a peak wavelength of 629 nm and an external quantum efficiency of 7.4% (Z. Y. Chen, B. W. Sheng, F. Liu, S. F. Liu, D. Li, Z. X. Yuan, T. Wang, X. Rong, J. S. Huang, J. Y. Qiu, W. J. Liang, C. L. Zhao, L. Yan, J. S. Hu, S. P. Guo, W. K. Ge, B. Shen, and X. Q. Wang, “High-Efficiency InGaN Red Mini-LEDs on Sapphire Toward Full-Color Nitride Displays: Effect of Strain Modulation,” Adv. Funct. Mater. 33(26) (2023).

[0004] In the prior art, long-wavelength InGaN red active regions usually require 35% or even 40% In composition, which is a very great challenge to epitaxy. The lattice mismatch between GaN and InN reaches 11%, and such a high In composition inevitably leads to a decrease in the quality of the active region and generates a large number of defects and non-radiative recombination centers, affecting the light-emitting efficiency. In terms of growth temperature, the bond energy of In-N is smaller than that of Ga-N, and InN is more likely to decompose and desorb at high temperatures, so lower growth temperatures are required, but low-temperature epitaxy usually leads to insufficient atomic migration, further deteriorating the crystal quality. In summary, it is very difficult to achieve long-wavelength InGaN red LEDs, and the efficiency in existing reports does not exceed 10%, making it impossible to meet current demands. SUMMARY

[0005] To solve at least one of the above technical problems, the purpose of the present application is to provide an InGaN red LED device based on a variable Al composition electron blocking layer to enhance the polarization effect and a preparation method thereof. By controlling the p-type AlGaN electron blocking layer, the present application can achieve long-wavelength emission of a low-In composition active region.

[0006] In order to achieve the above object, the first aspect of the present application provides an InGaN red light LED device based on a variable Al component electron blocking layer to enhance polarization effect, which comprises, from bottom to top, a substrate, a low-temperature buffer layer grown on the substrate, a high-temperature buffer layer grown on the low-temperature buffer layer, a non-doped GaN layer grown on the high-temperature buffer layer, an n-type doped GaN layer grown on the non-doped GaN layer, a superlattice layer and / or a low-temperature GaN layer grown on the n-type doped GaN layer, a quantum well active region grown on the superlattice layer or the low-temperature GaN layer, a p-type AlGaN electron blocking layer grown on the quantum well active region, and a p-type region grown on the p-type AlGaN electron blocking layer; wherein the quantum well active region comprises a composite layer of a red light quantum well layer-red light barrier layer; the atomic percentage content of Al in the p-type AlGaN electron blocking layer is 22-30% based on the total atomic number of Al and Ga in AlGaN being 100%; and the thickness of the p-type AlGaN electron blocking layer is 5-15 nm.

[0007] The main function of the electron blocking layer in the prior art is to prevent electron overflow to improve the light-emitting efficiency. The present inventor has found that by controlling the Al component content in the p-type AlGaN electron blocking layer and the thickness of the p-type AlGaN electron blocking layer within the range of the present application, the polarization effect can be enhanced to increase the light-emitting wavelength while ensuring a relatively high light-emitting intensity. If the Al component content in the p-type AlGaN electron blocking layer is higher than the range of the present application, the light-emitting intensity of the InGaN red light LED will be reduced; if the Al component content in the p-type AlGaN electron blocking layer is lower than the range of the present application, it is difficult to achieve the effect of increasing the light-emitting wavelength. If the thickness of the p-type AlGaN electron blocking layer is higher than the range of the present application, it will be difficult for holes to be injected into the red light well, resulting in a decrease in the light-emitting intensity; if the thickness of the p-type AlGaN electron blocking layer is lower than the range of the present application, the electron blocking ability will be poor and the polarization effect will be weakened, thereby reducing the light-emitting intensity and the light-emitting wavelength.

[0008] It should be noted that in the present application, InGaN refers to indium gallium nitride, and does not specify the ratio of the elements In, Ga and N.

[0009] According to the specific embodiments of the present application, preferably, the substrate comprises a c-plane sapphire substrate or a c-plane GaN substrate to ensure that the GaN material and the InGaN material on the substrate are also polar surface materials.

[0010] According to the specific embodiments of the present application, preferably, the size of the substrate is 2-8 inches, for example, it can be 2 inches, 4 inches, 6 inches or 8 inches, etc.

[0011] According to the specific embodiment of the present application, preferably, the material of the low-temperature buffer layer comprises GaN material, and the growth temperature is 550-600℃; the material of the high-temperature buffer layer comprises GaN material, and the growth temperature is 1000-1050℃.

[0012] According to the specific embodiment of the present application, preferably, the thickness of the low-temperature buffer layer is 0.2-0.5μm; the thickness of the high-temperature buffer layer is 0.1-0.5μm.

[0013] According to the specific embodiment of the present application, preferably, the thickness of the non-doped GaN layer is 2-4μm.

[0014] According to the specific embodiment of the present application, preferably, the thickness of the n-type doped GaN layer is 1-3μm.

[0015] According to the specific embodiment of the present application, preferably, the doping element in the n-type doped GaN layer is silicon, and the doping concentration is 1E18-5E18 cm -3 .

[0016] According to the specific embodiment of the present application, preferably, the InGaN red LED device comprises a superlattice layer and a low-temperature GaN layer grown on the n-type doped GaN layer, and the low-temperature GaN layer is grown on the superlattice layer, and the quantum well active region is grown on the low-temperature GaN layer.

[0017] According to the specific embodiment of the present application, preferably, the superlattice layer comprises InGaN / GaN superlattice with 2-30 periods.

[0018] According to the specific embodiment of the present application, preferably, the InGaN / GaN superlattice comprises InGaN layer with thickness of 1-3nm and GaN layer with thickness of 2-15nm.

[0019] According to the specific embodiment of the present application, preferably, the content of In in the InGaN layer in the InGaN / GaN superlattice is 3-8% based on 100% of the total number of In and Ga atoms in the InGaN layer.

[0020] According to the specific embodiment of the present application, preferably, the superlattice layer is a silicon-doped superlattice layer or a non-doped superlattice layer. More preferably, the superlattice layer is a silicon-doped superlattice layer, and the doping concentration is 1E18-5E18 cm -3 .

[0021] According to the specific embodiment of the present application, preferably, the material of the low-temperature GaN layer comprises non-doped GaN material, and the growth temperature is 700-850℃, more preferably 820-840℃.

[0022] According to the embodiment of the present application, preferably, the thickness of the low-temperature GaN layer is 5-100 nm.

[0023] According to the embodiment of the present application, preferably, the quantum well active region comprises 1-5 periods of red quantum well layer-red barrier layer.

[0024] According to the embodiment of the present application, preferably, the material of the red quantum well layer comprises undoped InGaN material, wherein the atomic percentage of In is 25-35% based on 100% of the total atomic number of In and Ga in the undoped InGaN material. The red quantum well layer is the main light-emitting structure under electrical injection.

[0025] According to the embodiment of the present application, preferably, the thickness of the red quantum well layer is 2-4 nm.

[0026] According to the embodiment of the present application, preferably, the material of the red barrier layer comprises undoped GaN material or undoped InGaN material, wherein the atomic percentage of In in the red barrier layer is 0-10% based on 100% of the total atomic number of In (if any) and Ga in the undoped GaN material or undoped InGaN material.

[0027] According to the embodiment of the present application, preferably, the thickness of the red barrier layer is 3-20 nm.

[0028] According to the embodiment of the present application, preferably, the quantum well active region further comprises 1-5 periods of blue quantum well layer-blue barrier layer, and the red quantum well layer-red barrier layer is grown on the blue quantum well layer-blue barrier layer.

[0029] According to the embodiment of the present application, preferably, the material of the blue quantum well layer comprises undoped InGaN material, wherein the atomic percentage of In is 3-10% based on 100% of the total atomic number of In and Ga in the undoped InGaN material.

[0030] According to the embodiment of the present application, preferably, the thickness of the blue quantum well layer is 2-4 nm.

[0031] According to the embodiment of the present application, preferably, the material of the blue barrier layer comprises undoped GaN material or undoped InGaN material, wherein the atomic percentage of In in the blue barrier layer is 0-5% based on 100% of the total atomic number of In (if any) and Ga in the undoped GaN material or undoped InGaN material.

[0032] According to the embodiment of the present application, preferably, the thickness of the blue light barrier layer is 3-20 nm.

[0033] According to the embodiment of the present application, preferably, the atomic percentage of Al in the p-type AlGaN electron blocking layer is 25-29%, more preferably 26-28%, and further preferably 27%, based on 100% of the total atomic number of Al and Ga in AlGaN; and the thickness of the p-type AlGaN electron blocking layer is 8-12 nm, more preferably 9.5-10.5 nm, and further preferably 10 nm.

[0034] According to the embodiment of the present application, preferably, the p-type AlGaN electron blocking layer is doped with Mg element, and the doping concentration of Mg is 1E18-2E20 cm -3 .

[0035] According to the embodiment of the present application, preferably, the material of the p-type region comprises GaN material and is doped with Mg element, and the doping concentration of Mg is 1E18-2E20 cm -3 .

[0036] According to the embodiment of the present application, preferably, the thickness of the p-type region is 100-300 nm.

[0037] The second aspect of the present application provides a preparation method of the above-mentioned InGaN red light LED device based on variable Al component electron blocking layer to enhance polarization effect, which comprises the following steps:

[0038] (1) sequentially epitaxially growing a low-temperature buffer layer, a high-temperature buffer layer, an undoped GaN layer, an n-type doped GaN layer, a superlattice layer and / or a low-temperature GaN layer on a substrate;

[0039] (2) epitaxially growing a quantum well active region on the superlattice layer or the low-temperature GaN layer;

[0040] (3) sequentially epitaxially growing a p-type AlGaN electron blocking layer and a p-type region on the quantum well active region to obtain the InGaN red light LED device based on variable Al component electron blocking layer to enhance polarization effect.

[0041] According to the specific embodiment of the present application, preferably, step (1) comprises: sequentially epitaxially growing a low-temperature buffer layer, a high-temperature buffer layer, an undoped GaN layer, an n-type doped GaN layer, and a superlattice layer and / or a low-temperature GaN layer on the substrate by using an epitaxial growth method of MOCVD (metal organic chemical vapor deposition), and the growth conditions include: a growth pressure of 50-1000 mbar, a Ga source flow rate of 10-200 sccm, an In source flow rate of 20-300 sccm, an N source flow rate of 2-10 slm, a carrier gas of nitrogen or hydrogen, a growth temperature of the low-temperature buffer layer of 550-600 ℃, a growth temperature of the high-temperature buffer layer of 1000-1050 ℃, a growth temperature of the undoped GaN layer of 1000-1050 ℃, a growth temperature of the n-type doped GaN layer of 1000-1050 ℃, a growth temperature of the superlattice layer of 700-850 ℃, and a growth temperature of the low-temperature GaN layer of 700-850 ℃. More preferably, the doped element in the n-type doped GaN layer is silicon, the doping source includes silane, and the doping concentration is 1E18-5E18 cm -3 . More preferably, the superlattice layer is a silicon-doped superlattice layer, the doping source includes silane, and the doping concentration is 1E18-5E18 cm -3 . More preferably, the growth temperature of the low-temperature GaN layer is 820-840 ℃.

[0042] According to the specific embodiment of the present application, preferably, step (2) comprises: epitaxially growing a quantum well active region on the superlattice layer or the low-temperature GaN layer by using an epitaxial growth method of MOCVD, and the quantum well active region includes a composite layer of a red light quantum well layer-red light barrier layer, and the growth conditions include: a growth pressure of 50-1000 mbar, a Ga source flow rate of 10-200 sccm, an In source flow rate of 20-500 sccm, an N source flow rate of 2-10 slm, a carrier gas of nitrogen or hydrogen, a growth temperature of the red light quantum well layer of 650-730 ℃, and a growth temperature of the red light barrier layer of 750-900 ℃. More preferably, the quantum well active region further includes a composite layer of a blue light quantum well layer-blue light barrier layer with a period number of 1-5, and the composite layer of the red light quantum well layer-red light barrier layer is grown on the composite layer of the blue light quantum well layer-blue light barrier layer; the growth conditions of the composite layer of the blue light quantum well layer-blue light barrier layer include: a growth pressure of 50-1000 mbar, a Ga source flow rate of 10-200 sccm, an In source flow rate of 20-500 sccm, an N source flow rate of 2-10 slm, a carrier gas of nitrogen or hydrogen, a growth temperature of the blue light quantum well layer of 720-750 ℃, and a growth temperature of the blue light barrier layer of 750-900 ℃.

[0043] According to the specific embodiment of the present application, preferably, step (3) comprises: using the epitaxial growth mode of MOCVD to epitaxially grow a p-type AlGaN electron blocking layer and a p-type region on the quantum well active region in sequence, and the growth conditions comprise: the growth pressure is 50-1000 mbar, the Ga source flow is 10-200 sccm, the Al source flow is 10-400 sccm, the N source flow is 2-10 slm, the carrier gas is nitrogen or hydrogen, the growth temperature of the p-type AlGaN electron blocking layer is 900-1000 ℃, and the growth temperature of the p-type region is 900-1000 ℃. More preferably, the p-type AlGaN electron blocking layer is doped with Mg elements, the doping source comprises Cp2Mg (dimethyl magnesium), and the doping concentration of Mg is 1E18-2E20 cm -3 . More preferably, the p-type region is doped with Mg elements, the doping source comprises Cp2Mg (dimethyl magnesium), and the doping concentration of Mg is 1E18-2E20 cm -3 .

[0044] According to the specific embodiment of the present application, preferably, the Ga source in steps (1)-(3) can comprise TMGa (trimethyl gallium) or the like, the N source can comprise ammonia or the like, the In source can comprise TMIn (trimethyl indium) or the like, and the Al source can comprise TMAl (trimethyl aluminum) or the like.

[0045] The present application has at least the following beneficial effects:

[0046] The present application provides an InGaN red light LED device based on a variable Al component electron blocking layer to enhance the polarization effect and a preparation method thereof. Due to the energy level structure and the blocking effect of the p-type AlGaN electron blocking layer (EBL) of the present application on the carriers, in addition to improving the wave function overlap of the electron-hole pairs in the active region and improving the light intensity of the LED, the polarization electric field of the active region is also intensified, thereby increasing the band tilting degree of the active region, reducing the equivalent band gap width of the InGaN material, and thus increasing the light wavelength of the InGaN red light LED, so that a long-wavelength InGaN red light LED with a low-In component active region is obtained. By controlling the Al component content and thickness of the p-type AlGaN electron blocking layer within the range of the present application, the light wavelength of the LED is red-shifted, long-wavelength emission of the low-In component active region can be realized, and the problems such as poor crystal quality of the high-In component active region of the existing long-wavelength InGaN red light LED and difficulty in obtaining the long-wavelength InGaN red light LED are avoided. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 FIG. 1 is a structure schematic diagram of an InGaN red light LED device based on a variable Al component electron blocking layer to enhance the polarization effect according to an embodiment of the present application.

[0048] Figure 2 Process flow chart for preparing the Micro-LED chip of the embodiment of the present application.

[0049] Figure 3 Photograph of light emission for the point indium ball test of Example 1 and the integrating sphere light collection spectrum of Example 1 and Comparative Examples 1-3.

[0050] Figure 4 Performance test results of the Micro-LED chip made of the InGaN red light LED device of Example 1 under different electrical injection.

[0051] Figure 5 Peak wavelength curve of the Micro-LED chip made of the InGaN red light LED device of Example 1 and Comparative Example 1 under different electrical injection.

[0052] Figure 6 Peak wavelength curve of the LED with different Al component contents in Test Example 3.

[0053] BRIEF DESCRIPTION OF DRAWINGS

[0054] 1-substrate; 2-low temperature buffer layer; 3-high temperature buffer layer; 4-undoped GaN layer; 5-n-type doped GaN layer; 6-superlattice layer; 7-low temperature GaN layer; 8-quantum well active region; 9-p-type AlGaN electron blocking layer; 10-p-type region;

[0055] 801-composite layer of blue light quantum well layer-blue light barrier layer; 802-composite layer of red light quantum well layer-red light barrier layer. DETAILED DESCRIPTION

[0056] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the present application will be described in detail below, but it cannot be understood as limiting the implementable scope of the present application.

[0057] Example 1

[0058] The present embodiment provides an InGaN red light LED device based on a variable Al component electron blocking layer to enhance the polarization effect, as shown in FIG. 1, which includes, from bottom to top, a substrate 1, a low temperature buffer layer 2 grown on the substrate 1, a high temperature buffer layer 3 grown on the low temperature buffer layer 2, an undoped GaN layer 4 grown on the high temperature buffer layer 3, an n-type doped GaN layer 5 grown on the undoped GaN layer 4, a superlattice layer 6 grown on the n-type doped GaN layer 5, a low temperature GaN layer 7 grown on the superlattice layer 6, a quantum well active region 8 grown on the low temperature GaN layer 7, a p-type AlGaN electron blocking layer 9 grown on the quantum well active region 8, and a p-type region 10 grown on the p-type AlGaN electron blocking layer 9. Figure 1 The present embodiment provides an InGaN red light LED device based on a variable Al component electron blocking layer to enhance the polarization effect, as shown in FIG. 1, which includes, from bottom to top, a substrate 1, a low temperature buffer layer 2 grown on the substrate 1, a high temperature buffer layer 3 grown on the low temperature buffer layer 2, an undoped GaN layer 4 grown on the high temperature buffer layer 3, an n-type doped GaN layer 5 grown on the undoped GaN layer 4, a superlattice layer 6 grown on the n-type doped GaN layer 5, a low temperature GaN layer 7 grown on the superlattice layer 6, a quantum well active region 8 grown on the low temperature GaN layer 7, a p-type AlGaN electron blocking layer 9 grown on the quantum well active region 8, and a p-type region 10 grown on the p-type AlGaN electron blocking layer 9.

[0059] In this embodiment, the substrate 1 is a c-plane sapphire substrate with a size of 4 inches. The material of the low-temperature buffer layer 2 includes GaN material, and the growth temperature is 575°C. The thickness of the low-temperature buffer layer 2 is 0.4 μm. The material of the high-temperature buffer layer 3 includes GaN material, and the growth temperature is 1020°C. The thickness of the high-temperature buffer layer 3 is 0.2 μm. The thickness of the undoped GaN layer 4 is 3 μm. The thickness of the n-type doped GaN layer 5 is 2 μm. The doping element in the n-type doped GaN layer 5 is silicon, and the doping concentration is 1E18 cm -3 .

[0060] The superlattice layer 6 includes InGaN / GaN superlattices with a period number of 24. The InGaN / GaN superlattices include InGaN layers with a thickness of 1.3 nm and GaN layers with a thickness of 2.5 nm, and the material of the InGaN layers includes In 0.05 Ga 0.95 N (i.e. the content of In in the InGaN layer is 5% based on the total number of In and Ga atoms in the InGaN layer in the InGaN / GaN superlattice being 100%). The superlattice layer 6 is a silicon-doped superlattice layer 6, and the doping concentration is 1E18 cm -3 .

[0061] The low-temperature GaN layer 7 includes undoped GaN material, and the growth temperature is 830°C. The thickness of the low-temperature GaN layer 7 is 7 nm.

[0062] The quantum well active region 8 includes a blue light quantum well layer-blue light barrier layer composite layer 801 with a period number of 2, and a red light quantum well layer-red light barrier layer composite layer 802 grown on the blue light quantum well layer-blue light barrier layer composite layer 801 with a period number of 1.

[0063] The material of the blue light quantum well layer includes undoped In 0.05 Ga 0.95 N (i.e. the atomic percentage content of In in the undoped InGaN material is 5% based on the total number of In and Ga atoms being 100%). The thickness of the blue light quantum well layer is 3 nm.

[0064] The material of the blue light barrier layer includes undoped GaN material. The thickness of the blue light barrier layer is 12 nm.

[0065] The material of the red light quantum well layer includes undoped In 0.30 Ga 0.70 N (i.e. the atomic percentage content of In in the undoped InGaN material is 30% based on the total number of In and Ga atoms being 100%). The thickness of the red light quantum well layer is 3 nm.

[0066] The material of the red light barrier layer includes undoped GaN material. The thickness of the red light barrier layer is 3 nm.

[0067] The atomic percentage of Al in the p-type AlGaN electron blocking layer 9 is 27% based on the total atomic number of Al and Ga in the AlGaN being 100%, i.e. the material of the p-type AlGaN electron blocking layer 9 includes p-Al 0.27 Ga 0.73 N. The thickness of the p-type AlGaN electron blocking layer is 10 nm. The p-type AlGaN electron blocking layer 9 is doped with Mg element, and the doping concentration of Mg is 1E20 cm -3 .

[0068] The material of the p-type region 10 includes GaN material, and is doped with Mg element, and the doping concentration of Mg is 1E20 cm -3 . The thickness of the p-type region 10 is 160 nm.

[0069] The embodiment also provides a preparation method of the InGaN red light LED device based on the variable Al component electron blocking layer to enhance the polarization effect as described above, which includes the following steps:

[0070] (1) The low temperature buffer layer 2, the high temperature buffer layer 3, the undoped GaN layer 4, the n-type doped GaN layer 5, the superlattice layer 6 and the low temperature GaN layer 7 are sequentially epitaxially grown on the substrate 1 by using the epitaxial growth mode of MOCVD, and the growth conditions include: the growth pressure is 200 mbar, the Ga source flow is 67 sccm; the In source flow is 60 sccm; the N source flow is 5 slm; the carrier gas is hydrogen; the growth temperature of the low temperature buffer layer 2 is 575°C; the growth temperature of the high temperature buffer layer 3 is 1020°C; the growth temperature of the undoped GaN layer 4 is 1040°C; the growth temperature of the n-type doped GaN layer 5 is 1040°C, the doped element in the n-type doped GaN layer 5 is silicon, the doping source is silane, and the doping concentration is 1E18 cm -3 ; the growth temperature of the superlattice layer 6 is 830°C, the superlattice layer 6 is a silicon-doped superlattice layer 6, the doping source is silane, and the doping concentration is 1E18 cm -3 ; the growth temperature of the low temperature GaN layer 7 is 830°C;

[0071] (2) The quantum well active region 8 is epitaxially grown on the low-temperature GaN layer 7 by MOCVD, and the growth conditions of the composite layer 801 of the blue quantum well layer and the blue barrier layer include: a growth pressure of 200 mbar, a Ga source flow of 67 sccm, an In source flow of 60 sccm, an N source flow of 5 slm, a carrier gas of nitrogen, a growth temperature of the blue quantum well layer of 730 DEG C, and a growth temperature of the blue barrier layer of 850 DEG C; the growth conditions of the composite layer 802 of the red quantum well layer and the red barrier layer include: a growth pressure of 200 mbar, a Ga source flow of 25 sccm, an In source flow of 340 sccm, an N source flow of 5 slm, a carrier gas of nitrogen, a growth temperature of the red quantum well layer of 690 DEG C, and a growth temperature of the red barrier layer of 870 DEG C;

[0072] (3) The p-type AlGaN electron blocking layer 9 and the p-type region 10 are epitaxially grown on the quantum well active region 8 by MOCVD, and the growth conditions include: a growth pressure of 200 mbar, a Ga source flow of 67 sccm, an Al source flow of 50 sccm, an N source flow of 5 slm, a carrier gas of hydrogen, a growth temperature of the p-type AlGaN electron blocking layer 9 of 945 DEG C, the p-type AlGaN electron blocking layer 9 doped with Mg, a doping source of Cp2Mg, and a doping concentration of Mg of 1E20 cm -3 -3; a growth temperature of the p-type region 10 of 945 DEG C, the p-type region 10 doped with Mg, a doping source of Cp2Mg, and a doping concentration of Mg of 1E20 cm -3 -3, to obtain the InGaN red LED device based on the Al component variable electron blocking layer to enhance the polarization effect.

[0073] In the steps (1)-(3), the Ga source is TMGa, the N source is ammonia, the In source is TMIn, and the Al source is TMAl.

[0074] The InGaN red LED device prepared by the above method is an epitaxial wafer, and the epitaxial wafer is subjected to substrate thinning and plating of a distributed Bragg reflector (DBR) by a conventional method in the art, and then is cut, wired, and TO packaged (the packaging material includes resin) to obtain a Micro-LED chip. Figure 2

[0075] Embodiment 2

[0076] This embodiment is basically the same as Embodiment 1, except that the atomic percentage of Al in the p-type AlGaN electron blocking layer 9 is 25% based on the total atomic number of Al and Ga in the AlGaN, that is, the material of the p-type AlGaN electron blocking layer 9 includes p-Al 0.25 Ga​0.75 N. The p-type AlGaN electron-blocking layer 9 was doped with Mg, and the Mg doping concentration was the same as in Example 1. The thickness of the p-type AlGaN electron-blocking layer 9 was 12 nm. The rest was the same as in Example 1.

[0077] Example 3

[0078] This example was basically the same as Example 1, except that the atomic percentage of Al in the p-type AlGaN electron-blocking layer 9 was 29% based on the total atomic number of Al and Ga in AlGaN, i.e., the material of the p-type AlGaN electron-blocking layer 9 included p-Al 0.29 Ga 0.71 N. The p-type AlGaN electron-blocking layer 9 was doped with Mg, and the Mg doping concentration was the same as in Example 1. The thickness of the p-type AlGaN electron-blocking layer 9 was 8 nm. The rest was the same as in Example 1.

[0079] Comparative Example 1

[0080] This comparative example was basically the same as Example 1, except that the atomic percentage of Al in the p-type AlGaN electron-blocking layer 9 was 20% based on the total atomic number of Al and Ga in AlGaN, i.e., the material of the p-type AlGaN electron-blocking layer 9 included p-Al 0.2 Ga 0.8 N. The p-type AlGaN electron-blocking layer 9 was doped with Mg, and the Mg doping concentration was the same as in Example 1. The thickness of the p-type AlGaN electron-blocking layer 9 was still 10 nm. The rest was the same as in Example 1.

[0081] Comparative Example 2

[0082] This comparative example was basically the same as Example 1, except that the atomic percentage of Al in the p-type AlGaN electron-blocking layer 9 was 35% based on the total atomic number of Al and Ga in AlGaN, i.e., the material of the p-type AlGaN electron-blocking layer 9 included p-Al 0.35 Ga 0.65 N. The p-type AlGaN electron-blocking layer 9 was doped with Mg, and the Mg doping concentration was the same as in Example 1. The thickness of the p-type AlGaN electron-blocking layer 9 was still 10 nm. The rest was the same as in Example 1.

[0083] Comparative Example 3

[0084] This comparative example was basically the same as Example 1, except that the thickness of the p-type AlGaN electron-blocking layer 9 was 20 nm. The material of the p-type AlGaN electron-blocking layer 9 included p-Al 0.27 Ga 0.73N, same as example 1. The p-type AlGaN electron blocking layer 9 is doped with Mg element, and the doping concentration of Mg is same as example 1. The rest is same as example 1.

[0085] Test Example 1

[0086] The LED devices (i.e. LED epitaxial wafers) of examples 1-3 and comparative examples 1-3 were tested under the same electrical injection conditions (10 mA) for surface point indium ball testing. The test system used in this test mainly includes: a manual probe station and an integrating sphere. The specific functions and parameters of each module of the test system are as follows: manual probe station: model FormFactor EPS150TRIAX, which realizes the electrical connection between the epitaxial wafer sample and the digital source table by adjusting the three-dimensional probe seat, and provides support for the integrating sphere; integrating sphere: model Instrument Systems ISP 75, which receives the light emitted by the epitaxial wafer sample.

[0087] The method of surface point indium ball testing is to pierce the indium ball with a metal probe and apply an external current (10 mA) for lighting test.

[0088] Figure 3 The left graph in the point measurement luminescence photo of example 1 Figure 3 and the right graph in the integrating sphere light receiving spectrum of examples 1 and comparative examples 1-3 Figure 3 . It can be seen from Figure 3 that the emission wavelength of comparative examples 1 and 3 is shorter than that of example 1, and the point measurement intensity is lower; although the emission wavelength of comparative example 2 is similar to that of example 1, the Al content of the EBL is too high, which makes the point measurement intensity significantly lower than that of example 1; the point measurement intensity reflects the emission intensity, so the emission intensity of example 1 is higher than that of comparative examples 1-3. In addition, the peak wavelength of example 2 is 622.2 nm, and the peak wavelength of example 3 is 622.7 nm; and the point measurement intensity of examples 2 and 3 is close to that of example 1.

[0089] Test Example 2

[0090] The test system used in this test mainly includes: a high-precision fast spectral radiometer, an integrating sphere and a digital source table. The specific functions and parameters of each module of the test system are as follows:

[0091] (1) High-precision fast spectral radiometer: model YUANFANG HAAS-2000, which is connected with the integrating sphere to measure the optical properties of the Micro-LED chip sample. The main technical indicators are: spectral range 380-780 nm; wavelength accuracy ±0.3 nm, optical bandwidth 2.5 nm; luminous flux measurement range 0.01-2000 lm.

[0092] (2) Integrating sphere: Model: 50cm diameter integrating sphere for far field LED, the sample is put into the sphere to receive the light from the sample at 360°. The sphere has a PTFE R98 coating that reaches 97% reflectance in the visible range with high long-term stability, suitable for the spectral range of 380-1500nm.

[0093] (3) Digital source meter: Model: Keithley 2430, used to apply electrical signal to the Micro-LED chip sample and conduct electrical test.

[0094] Figure 4 The Micro-LED chip made for the InGaN red LED device of Example 1 is tested by using the above test system to obtain the performance test results under different electrical injection (as indicated in the table below). Figure 4 Figure 4 The test results of LED chips with different diameters (5pm, 10pm, 15pm, 20pm) are shown in the table below. Figure 4 It can be seen that the Micro-LED chip of Example 1 has both a higher peak wavelength and a higher WPE. Figure 5 The peak wavelength curves of the Micro-LED chip (diameter 15pm) made for the InGaN red LED device of Example 1 and Comparative Example 1 under different electrical injection are shown in the table below. Figure 5 It can be seen that, compared with Comparative Example 1, by controlling the Al component content and thickness of the p-type AlGaN electron blocking layer, the InGaN red LED of Example 1 increases the light emission wavelength, and realizes long-wavelength emission of the low-In component active region.

[0095] Test Example 3

[0096] The atomic percentage content of Al in the p-type AlGaN electron blocking layer 9 is adjusted to 0% (i.e. forming a GaN layer), 5%, 10%, 15%, 20% (i.e. Comparative Example 1), 23%, 25% and 30% respectively, the atomic percentage content of Al is calculated based on the total atomic number of Al and Ga in AlGaN as 100%, the thickness of the p-type AlGaN electron blocking layer 9 is 10nm, and the rest are the same as Example 1, thereby obtaining different Micro-LED chips. The SiLENSe software is used to simulate these Micro-LED chips, and the peak wavelength curves of different Al component contents are obtained, as shown in the table below. Figure 6 Figure 6 In combination with Figure 3 It can be seen that by controlling the Al component content in the p-type AlGaN electron blocking layer 9 and the thickness of the p-type AlGaN electron blocking layer within the scope of the present application, the polarization effect can be enhanced, thereby increasing the light emission wavelength, while also taking into account a higher light emission intensity.​​Figure 6 The comparative examples in which the atomic percentage of Al is not within the range of the present application do not have the effect of increasing the emission wavelength and the higher emission intensity at the same time.

Claims

1. An InGaN red LED device based on a variable Al composition electron blocking layer to enhance polarization effect, comprising, from bottom to top: The system comprises: a substrate; a low-temperature buffer layer grown on the substrate; a high-temperature buffer layer grown on the low-temperature buffer layer; an undoped GaN layer grown on the high-temperature buffer layer; an n-type doped GaN layer grown on the undoped GaN layer; a superlattice layer and / or a low-temperature GaN layer grown on the n-type doped GaN layer; a quantum well active region grown on the superlattice layer or the low-temperature GaN layer; a p-type AlGaN electron blocking layer grown on the quantum well active region; and a p-type region grown on the p-type AlGaN electron blocking layer. The quantum well active region includes a composite layer of a red quantum well layer and a red barrier layer. With the total number of Al and Ga atoms in AlGaN being 100%, the atomic percentage of Al in the p-type AlGaN electron blocking layer is 22-30%. The thickness of the p-type AlGaN electron blocking layer is 5-15 nm.

2. The InGaN red LED device according to claim 1, wherein, The low-temperature buffer layer is made of GaN material and grown at a temperature of 550-600℃; the high-temperature buffer layer is made of GaN material and grown at a temperature of 1000-1050℃.

3. The InGaN red LED device according to claim 1, wherein, The thickness of the low-temperature buffer layer is 0.2-0.5 μm; the thickness of the high-temperature buffer layer is 0.1-0.5 μm.

4. The InGaN red LED device according to claim 1, wherein, The thickness of the undoped GaN layer is 2-4 μm.

5. The InGaN red LED device according to claim 1, wherein, The thickness of the n-type doped GaN layer is 1-3 μm.

6. The InGaN red LED device according to claim 1, wherein, The doping element in the n-type doped GaN layer is silicon, with a doping concentration of 1E18-5E18 cm⁻¹. -3 .

7. The InGaN red LED device according to claim 1, wherein, The superlattice layer comprises an InGaN / GaN superlattice with 2-30 periods.

8. The InGaN red LED device according to claim 7, wherein, The InGaN / GaN superlattice comprises an InGaN layer with a thickness of 1-3 nm and a GaN layer with a thickness of 2-15 nm.

9. The InGaN red LED device according to claim 8, wherein, Assuming the total number of In and Ga atoms in the InGaN layer of the InGaN / GaN superlattice is 100%, the In content in the InGaN layer is 3-8%.

10. The InGaN red LED device according to claim 7, wherein, The superlattice layer is a silicon-doped superlattice layer or an undoped superlattice layer.

11. The InGaN red LED device according to claim 10, wherein, The superlattice layer is a silicon-doped superlattice layer with a doping concentration of 1E18-5E18 cm⁻¹. -3 .

12. The InGaN red LED device according to claim 1, wherein, The material of the low-temperature GaN layer includes undoped GaN material, and the growth temperature is 700-850℃.

13. The InGaN red LED device according to claim 1, wherein, The thickness of the low-temperature GaN layer is 5-100 nm.

14. The InGaN red LED device according to claim 1, wherein, The active region of the quantum well includes a composite layer of a red light quantum well layer and a red light barrier layer with a period of 1-5 periods.

15. The InGaN red LED device according to claim 1, wherein, The material of the red quantum well layer includes undoped InGaN material, with the total number of In and Ga atoms in the undoped InGaN material being 100%, and the atomic percentage of In being 25-35%.

16. The InGaN red LED device according to claim 1, wherein, The thickness of the red quantum well layer is 2-4 nm.

17. The InGaN red LED device according to claim 1, wherein, The material of the red light barrier layer includes undoped GaN material or undoped InGaN material. With the total number of In and Ga atoms in the undoped GaN material or undoped InGaN material being 100%, the atomic percentage of In in the red light barrier layer is 0-10%.

18. The InGaN red LED device according to claim 1, wherein, The thickness of the red light barrier layer is 3-20 nm.

19. The InGaN red LED device according to claim 1, wherein, The active region of the quantum well further includes a composite layer of blue quantum well layer and blue barrier layer with a period of 1-5 periods, and the composite layer of red quantum well layer and red barrier layer is grown on the composite layer of blue quantum well layer and blue barrier layer.

20. The InGaN red LED device according to claim 19, wherein, The material of the blue quantum well layer includes undoped InGaN material, with the total number of In and Ga atoms in the undoped InGaN material being 100%, and the atomic percentage of In being 3-10%.

21. The InGaN red LED device according to claim 19, wherein, The thickness of the blue quantum well layer is 2-4 nm.

22. The InGaN red LED device according to claim 19, wherein, The material of the blue light barrier layer includes undoped GaN material or undoped InGaN material. With the total number of In and Ga atoms in the undoped GaN material or undoped InGaN material being 100%, the atomic percentage of In in the blue light barrier layer is 0-5%.

23. The InGaN red LED device according to claim 19, wherein, The thickness of the blue light barrier layer is 3-20 nm.

24. The InGaN red LED device according to claim 1, wherein, With the total number of Al and Ga atoms in AlGaN being 100%, the atomic percentage of Al in the p-type AlGaN electron blocking layer is 25-29%; the thickness of the p-type AlGaN electron blocking layer is 8-12 nm.

25. The InGaN red LED device according to claim 1, wherein, With the total number of Al and Ga atoms in AlGaN being 100%, the atomic percentage of Al in the p-type AlGaN electron blocking layer is 27%; the thickness of the p-type AlGaN electron blocking layer is 10 nm.

26. The InGaN red LED device according to claim 1, wherein, The p-type AlGaN electron blocking layer is doped with Mg, and the Mg doping concentration is 1E18-2E20 cm⁻¹. -3 .

27. The InGaN red LED device according to claim 1, wherein, The p-type region is made of GaN material and is doped with Mg, with a Mg doping concentration of 1E18-2E20 cm⁻¹. -3 .

28. The InGaN red LED device according to claim 1, wherein, The thickness of the p-type region is 100-300 nm.

29. A method for fabricating an InGaN red LED device based on a variable Al composition electron blocking layer to enhance polarization effect, as described in any one of claims 1-28, comprising the following steps: (1) A low-temperature buffer layer, a high-temperature buffer layer, an undoped GaN layer, an n-type doped GaN layer, a superlattice layer, and / or a low-temperature GaN layer are epitaxially grown sequentially on the substrate. (2) Epitaxially growing a quantum well active region on the superlattice layer or the low-temperature GaN layer; (3) A p-type AlGaN electron blocking layer and a p-type region are epitaxially grown sequentially on the active region of the quantum well to obtain the InGaN red LED device based on the variable Al composition electron blocking layer to enhance the polarization effect.

30. The preparation method according to claim 29, wherein, Step (1) includes: using MOCVD epitaxial growth, sequentially growing a low-temperature buffer layer, a high-temperature buffer layer, an undoped GaN layer, an n-type doped GaN layer, and a superlattice layer and / or a low-temperature GaN layer on the substrate. The growth conditions include: a growth pressure of 50-1000 mbar, a Ga source flow rate of 10-200 sccm, an In source flow rate of 20-300 sccm, an N source flow rate of 2-10 slm, and a carrier gas of nitrogen or hydrogen. The growth temperature of the low-temperature buffer layer is 550-600℃; the growth temperature of the high-temperature buffer layer is 1000-1050℃; the growth temperature of the undoped GaN layer is 1000-1050℃; the growth temperature of the n-type doped GaN layer is 1000-1050℃; the growth temperature of the superlattice layer is 700-850℃; and the growth temperature of the low-temperature GaN layer is 700-850℃.

31. The preparation method according to claim 29, wherein, Step (2) includes: using MOCVD epitaxial growth, epitaxially growing a quantum well active region on the superlattice layer or the low-temperature GaN layer, which includes a composite layer of red quantum well layer and red barrier layer. The growth conditions include: growth pressure of 50-1000 mbar, Ga source flow rate of 10-200 sccm, In source flow rate of 20-500 sccm, N source flow rate of 2-10 slm, carrier gas of nitrogen or hydrogen, growth temperature of red quantum well layer of 650-730℃, and growth temperature of red barrier layer of 750-900℃.

32. The preparation method according to claim 31, wherein, In step (2), the active region of the quantum well further includes a composite layer of blue quantum well layer and blue barrier layer with a period of 1-5 periods, and the composite layer of red quantum well layer and red barrier layer is grown on the composite layer of blue quantum well layer and blue barrier layer; the growth conditions of the composite layer of blue quantum well layer and blue barrier layer include: growth pressure of 50-1000 mbar, Ga source flow rate of 10-200 sccm; In source flow rate of 20-500 sccm; N source flow rate of 2-10 slm; carrier gas of nitrogen or hydrogen; growth temperature of blue quantum well layer of 720-750℃; growth temperature of blue barrier layer of 750-900℃.

33. The preparation method according to claim 29, wherein, Step (3) includes: using MOCVD epitaxial growth, a p-type AlGaN electron blocking layer and a p-type region are epitaxially grown sequentially on the active region of the quantum well. The growth conditions include: growth pressure of 50-1000 mbar, Ga source flow rate of 10-200 sccm, Al source flow rate of 10-400 sccm, N source flow rate of 2-10 slm, carrier gas of nitrogen or hydrogen, growth temperature of p-type AlGaN electron blocking layer of 900-1000℃, and growth temperature of p-type region of 900-1000℃.

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