High light efficiency GaN-based mini LED epitaxial structure and preparation method thereof

Abstract

The application relates to the fields of semiconductor photoelectric devices and semiconductor display manufacturing, and particularly relates to a preparation method of a high-light-efficiency GaN-based Mini LED epitaxial structure. The preparation method comprises an ohmic contact layer, the ohmic contact layer comprises a P-type MgN / GaN superlattice structure and a P-type AlGaN structure which are sequentially grown, the P-type MgN / GaN superlattice structure is MgN Delta doped, and the Al doping concentration of the ohmic contact layer is 5x10 20 ~1x10 21 cm ‑3 -. The ohmic contact layer of the epitaxial structure grows the P-type MgN / GaN superlattice structure doped with MgN Delta, can grow thinner P-type GaN, reduces the injection of light-absorbing holes of the P-type GaN, and thus improves the light-emitting efficiency; then grows the P-type AlGaN structure with high Al content, and the structure can cooperate with the GTO technology of the chip to improve the brightness of the LED while keeping low voltage and high ESD.

Description

Technical Field

[0001] This invention relates to the fields of semiconductor optoelectronic devices and semiconductor display manufacturing, and particularly to high-efficiency GaN-based Mini LED epitaxial structures and their fabrication methods. Background Technology

[0002] Currently, III-V group semiconductor light-emitting materials are increasingly used in the display and lighting fields due to their physical and chemical properties such as large band gap, high breakdown electric field, and high electron saturation mobility. However, how to improve the luminous efficacy of these materials is an urgent problem to be solved.

[0003] Chinese invention patent application number 201910819227.1 discloses a light-emitting diode with a composite current-blocking layer and its fabrication method. The composite current-blocking layer specifically comprises metal particles and an insulating layer with a roughened structure. The metal particles can alter the path of incident light, improving light extraction efficiency. The metal particles can also give the interface between the insulating layer and the metal particle a wavy, roughened structure, thereby improving the robustness of the P-electrode and further enhancing light extraction efficiency. However, this method is not applicable to chip GTO (gate-controlled thyristor) technology, and its improvement in light extraction efficiency can be further optimized. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: a high-efficiency GaN-based Mini LED epitaxial structure and its preparation method. The epitaxial structure is suitable for the GTO technology of the chip and can simultaneously achieve low voltage and high light output efficiency.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a high-efficiency GaN-based Mini LED epitaxial structure, comprising an ohmic contact layer, wherein the ohmic contact layer comprises a P-type MgN / GaN superlattice structure and a P-type AlGaN structure grown sequentially, wherein the P-type MgN / GaN superlattice structure is MgN Delta doped, and the Al doping concentration of the ohmic contact layer is 5 × 10⁻⁶. 20 ~1×10 21 cm -3 .

[0006] Another technical solution adopted in this invention is: the above-mentioned method for preparing a high-efficiency GaN-based Mini LED epitaxial structure, wherein the ohmic contact layer is grown in a reaction chamber, the temperature of the reaction chamber is 900-1000℃, the pressure is 180-220 Torr, the rotation speed is 800-1200 rpm, and H2 carrier gas is used.

[0007] The beneficial effects of this invention are as follows: the ohmic contact layer of the epitaxial structure of this invention first grows a MgN Delta-doped P-type MgN / GaN superlattice structure, which can grow a thinner P-type GaN and reduce the injection of PGaN light-absorbing holes, thereby improving the light extraction efficiency; then, a high-Al-content P-type AlGaN structure is grown, which, in conjunction with the chip's GTO technology, can improve the brightness of the LED while maintaining low voltage and high ESD. Detailed Implementation

[0008] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments.

[0009] A high-efficiency GaN-based Mini LED epitaxial structure includes an ohmic contact layer. The ohmic contact layer comprises a P-type MgN / GaN superlattice structure and a P-type AlGaN structure grown sequentially. The P-type MgN / GaN superlattice structure is MgN Delta-doped, and the Al doping concentration of the ohmic contact layer is 5 × 10⁻⁶. 20 ~1×10 21 cm -3 .

[0010] As can be seen from the above description, the beneficial effects of the present invention are as follows: The epitaxial structure of the present invention has a novel ohmic contact layer, which includes a P-type MgN / GaN superlattice structure and a high-Al-content P-type AlGaN structure. The P-type MgN / GaN superlattice structure employs MgN Delta doping, resulting in better current spread. This not only reduces voltage and improves ESD (electrostatic discharge), but also has higher Mg activation efficiency, providing holes and enabling the growth of thinner P-type GaN, reducing the injection of light-absorbing holes in PGaN, thereby reducing P-type GaN light absorption and improving light extraction efficiency. Growing a high-Al-content P-type AlGaN structure on the basis of the P-type MgN / GaN superlattice structure increases brightness but also leads to a voltage increase, which can compensate for the voltage congestion caused by the P-type MgN / GaN superlattice structure.

[0011] The P-type AlGaN structure can also be perfectly matched with the chip's GTO technology. The high Al content AlGaN structure can improve the brightness of the LED, but at the same time it will lead to increased voltage and worse ESD. The chip's GTO technology can reduce voltage and improve ESD. Combining the high Al content P-type AlGaN structure with the chip's GTO technology can improve the brightness of the LED while maintaining low voltage and high ESD.

[0012] Furthermore, the Mg doping concentration of the ohmic contact layer is 2 × 10⁻⁶. 19 ~1×10 20 cm -3 .

[0013] As described above, both excessively high and low Mg doping concentrations will affect brightness. Therefore, the Mg doping concentration of the ohmic contact layer should be controlled at 2 × 10⁻⁶. 19 ~1×10 20 cm -3 .

[0014] Another technical solution adopted in this invention is as follows: In the above-mentioned method for preparing the high-efficiency GaN-based Mini LED epitaxial structure, the ohmic contact layer is grown in a reaction chamber at a temperature of 900-1000℃, a pressure of 180-220 Torr, a rotation speed of 800-1200 rpm, and H2 carrier gas.

[0015] As can be seen from the above description, in order to ensure the lattice quality, a higher growth temperature is used in the preparation process of this ohmic contact layer, and a lower pressure and a faster growth rate are used in order to increase the growth rate.

[0016] Furthermore, during the growth of the P-type MgN / GaN superlattice structure, CP2Mg and NH3 are first introduced to grow P-type MgN, and then TMGa and NH3 are introduced to grow P-type GaN. P-type MgN and P-type GaN are grown alternately for 1 to 7 cycles.

[0017] As can be seen from the above description, too many periods in the P-type MgN / GaN superlattice structure will result in an overly thick structure, reducing light absorption brightness; if too few periods, the structure will be too thin, increasing voltage and worsening ESD (electrostatic discharge).

[0018] Furthermore, in the P-type MgN / GaN superlattice structure, the thickness of P-type MgN is 1–3 nm, and the thickness of P-type GaN is 3–9 nm.

[0019] As can be seen from the above description, if the thickness of P-type MgN is too thick, it will reduce the light absorption brightness, while if it is too thin, its surface growth will be uneven and produce V-shaped pits, thereby reducing ESD; if the thickness of P-type GaN is too thick, it will reduce the light absorption brightness, while if it is too thin, it will increase the voltage and affect the subsequent growth of P-type AlGaN.

[0020] Furthermore, the thickness of the ohmic contact layer is 1–10 nm.

[0021] Preferably, the thickness of the ohmic contact layer is 1–5 nm.

[0022] Furthermore, an AlGaN / GaN buffer layer, a high-temperature undoped UGaN layer, a high-temperature doped NGaN layer, an n-AlGaN layer, a multi-period Si-doped NGaN layer, a superlattice InGaN / GaN stress relief layer, a multi-quantum well active region layer, an AlGaN electron blocking layer, a first p-GaN layer, a p-AlGaN layer, a second p-GaN layer, and an ohmic contact layer are sequentially grown on the AlN substrate.

[0023] As described above, the AlGaN / GaN buffer layer can balance the lattice mismatch between the GaN lattice and the substrate; the high-temperature undoped UGaN layer serves to form a multi / single-crystal GaN buffer layer from the low-temperature long amorphous buffer layer through high temperature; the high-temperature doped NGaN layer can reduce voltage and improve ESD while reducing dislocations; the n-AlGaN layer acts to block the extension of defects in the underlying layer and improve crystal quality; the multi-period Si-doped NGaN layer is an electron-providing layer that affects voltage and ESD brightness; the superlattice InGaN / GaN stress relief layer is a transition layer between N-type GaN and multiple quantum wells, which can release stress, block defects and dislocations generated in N-GaN and previously generated ones, and open V-PITS, affecting brightness; the AlGaN electron blocking layer prevents electron overflow; the first p-GaN layer can improve brightness and perform interface treatment from quantum wells to p-AlGaN; the p-AlGaN layer is a high-energy-order electron blocking layer with normal structure, which can prevent electron overflow; the second p-GaN layer provides holes.

[0024] Furthermore, the number of periods in the multi-period Si-doped GaN layer is 50 to 100.

[0025] As can be seen from the above description, periodic growth can reduce stress.

[0026] Furthermore, the number of cycles for growing the superlattice InGaN / GaN stress-relieving layer is 5 to 10.

[0027] As can be seen from the above description, it can reduce the dislocations and stress generated by the growth of N layers.

[0028] Furthermore, the growth of the second p-GaN layer is carried out in a reaction chamber at a temperature of 900–1050 °C. The thickness of the second p-GaN layer is 10–50 nm, and the doping concentration is 1 × 10⁻⁶. 18 ~1×10 20 cm -3 .

[0029] Embodiment 1 of the present invention is: a method for fabricating a high-efficiency GaN-based Mini LED epitaxial structure, comprising the following steps:

[0030] S1: Place the AlN substrate in the reaction chamber.

[0031] S2: A high-temperature AlGaN / GaN buffer layer is grown on an AlN substrate. The reaction chamber temperature is 800℃, the pressure is 200 Torr, the rotation speed is 1000 rpm, H2 carrier gas is used, and the V / III molar ratio is 70.

[0032] S3: A high-temperature undoped UGaN layer is grown on an AlGaN / GaN buffer layer. The reaction chamber temperature is 1000℃, the pressure is 200 Torr, the rotation speed is 1000 rpm, H2 carrier gas is used, the V / III molar ratio is 200, and the thickness of the high-temperature undoped UGaN layer is 2μm.

[0033] S4: A high-temperature doped NGaN layer was grown on a high-temperature undoped UGaN layer. The reaction chamber temperature was 1000℃, the pressure was 200 Torr, the rotation speed was 1000 rpm, H2 was used as the carrier gas, the V / III molar ratio was 200, the thickness of the high-temperature doped NGaN layer was 1 μm, and the Si doping concentration was 7 × 10⁻⁶. 18 cm -3 .

[0034] S5: An n-AlGaN layer was grown on a high-temperature doped NGaN layer. The reaction chamber temperature was 1000℃, the pressure was 100 Torr, the rotation speed was 1000 rpm, H2 carrier gas was used, the V / III molar ratio was 100, and the Al doping concentration was 1E+17 atom / cm³. -3 .

[0035] S6: A multi-period Si-doped NGaN layer was grown on an n-AlGaN layer. The reaction chamber temperature was 1000℃, the pressure was 1800 Torr, the rotation speed was 1200 rpm, H2 carrier gas was used, the V / III molar ratio was 200, the thickness of the n-AlGaN layer was 1.8 μm, and the number of periods of the multi-period Si-doped GaN was 80. Periodic growth can reduce stress.

[0036] S7: A superlattice InGaN / GaN stress relief layer is grown on a multi-period Si-doped NGaN layer. The reaction chamber temperature is 900℃, the pressure is 170 Torr, the rotation speed is 600 rpm, H2 carrier gas is used, the V / III molar ratio is 3000, and the number of periods of the superlattice InGaN / GaN is 7, which can reduce the dislocations and stress generated by the growth of the N layer.

[0037] S8: A multi-quantum-well active region layer was grown on a superlattice InGaN / GaN stress-relief layer. The reaction chamber temperature was 900℃, the well-barrier temperature difference was 120℃, and a long-well GaN / Inx1GaN layer was grown under a pressure of 200 Torr and a rotation speed of 500 rpm using H2 carrier gas. 1－x1 N / Inx2 Ga 1－x2 N / GaN and long-barrier GaN / Al y1 Ga 1－y1 N; The active region of the multi-quantum well uses GaN / Inx1Ga 1－x1 N / Inx2 Ga 1－x2 N / GaN, GaN / Aly1 Ga 1－y1 The N-type In composition structure, the x1 and x2 contents are adjusted by temperature to reduce well-barrier mismatch and thus alleviate the Stark effect. The quantum barrier is made of Si-doped GaN, which can reduce dislocations.

[0038] S9: An AlGaN electron blocking layer is grown on the active region of a multi-quantum well. The reaction chamber temperature is 900℃, the pressure is 200 Torr, the rotation speed is 500 rpm, H2 carrier gas is used, the V / III molar ratio is 200, and the thickness of the electron blocking layer is 8 nm.

[0039] S10: The first p-GaN layer is grown on the AlGaN electron-blocking layer. The reaction chamber temperature is 780℃, the pressure is 200 Torr, the rotation speed is 600 rpm, and H2 carrier gas is used. The Mg doping concentration of the first p-GaN layer is 1×10⁻⁶. 20 cm -3 .

[0040] S11: A p-AlGaN layer is grown on the first p-GaN layer. The reaction chamber temperature is 980℃, the pressure is 130 Torr, the rotation speed is 1000 rpm, H2 carrier gas is used, the thickness of the p-AlGaN layer is 50 nm, and the Mg doping concentration is 1×10⁻⁶. 20 cm -3 The Al doping concentration is 1×10 20 cm -3 .

[0041] S12: A second p-GaN layer is grown on top of the p-AlGaN layer. The reaction chamber temperature is 1000℃, the pressure is 200 Torr, and the rotation speed is 1000 rpm. 30 sccm of TMGa and 2500 sccm of Cp₂Mg are introduced. The thickness of the second p-GaN layer is 30 nm, and the Mg doping concentration is 1×10⁻⁶. 19 cm -3 .

[0042] S13: An ohmic contact layer is grown on the second p-GaN layer. The reaction chamber temperature is 900–1000℃, the pressure is 200 Torr, the rotation speed is 1000 rpm, and H2 carrier gas is used. The Al doping concentration of the ohmic contact layer is 7 × 10⁻⁶. 20 cm -3 The Mg doping concentration is 5 × 10⁻⁶. 19 cm -3The thickness is 5 nm; the ohmic contact layer is composed of sequentially grown P-type MgN / GaN superlattice structure and P-type AlGaN structure. The P-type MgN / GaN superlattice structure is MgN Delta doped. During the growth of the P-type MgN / GaN superlattice structure, CP2Mg and NH3 are first introduced to grow P-type MgN, and then TMGa and NH3 are introduced to grow P-type GaN. P-type MgN and P-type GaN are grown alternately for one cycle. The thickness of P-type MgN in the P-type MgN / GaN superlattice structure is 1 nm, and the thickness of P-type GaN is 3 nm.

[0043] Comparative Example 1 of the present invention is:

[0044] The only difference between Comparative Example 1 and Example 1 is that there is no ohmic contact layer on the epitaxial structure.

[0045] LED chips were fabricated using the epitaxial structures of Example 1 and Comparative Example 1, respectively (the specific steps were: epitaxial wafer cleaning -> MESA -> CBL -> ITO -> MET -> PV -> electro-alloying -> COW testing -> grinding and thinning -> scratching -> sorting and full testing). The LED chips were made into 10*28mil LED chips. Then, the two types of LED chips were combined with GTO technology (i.e., adding a metal layer between ITO and MET), and their performance was tested. The test results are shown in Table 1.

[0046] Table 1

[0047]

[0048] As shown in Table 1, the epitaxial structure prepared by the method of the present invention has a 4% higher luminous efficacy than that of Comparative Example 1 with GTO technology, which is a significant improvement in luminous efficacy.

[0049] Embodiment 2 of the present invention is a high-efficiency GaN-based MiniLED epitaxial structure prepared by the preparation method of Embodiment 1.

[0050] Embodiment 3 of the present invention is: a method for fabricating a high-efficiency GaN-based Mini LED epitaxial structure, the steps of which are as follows:

[0051] S1: Place the AlN substrate in the reaction chamber.

[0052] S2: A high-temperature AlGaN / GaN buffer layer is grown on an AlN substrate. The reaction chamber temperature is 700℃, the pressure is 100 Torr, the rotation speed is 800 rpm, H2 carrier gas is used, and the V / III molar ratio is 60.

[0053] S3: A high-temperature undoped UGaN layer is grown on an AlGaN / GaN buffer layer. The reaction chamber temperature is 1050℃, the pressure is 150 Torr, the rotation speed is 800 rpm, H2 carrier gas is used, the V / III molar ratio is 100, and the thickness of the high-temperature undoped UGaN layer is 1 μm.

[0054] S4: A high-temperature doped NGaN layer was grown on a high-temperature undoped UGaN layer. The reaction chamber temperature was 1050℃, the pressure was 150 Torr, the rotation speed was 800 rpm, H2 carrier gas was used, the V / III molar ratio was 100–300, the thickness of the high-temperature doped NGaN layer was 0.5 μm, and the Si doping concentration was 5 × 10⁻⁶. 18 cm -3 .

[0055] S5: An n-AlGaN layer was grown on a high-temperature doped NGaN layer. The reaction chamber temperature was 1000℃, the pressure was 100 Torr, the rotation speed was 1000 rpm, H2 carrier gas was used, the V / III molar ratio was 100, and the Al doping concentration was 1.3E+17 atom / cm³. -3 The thickness of the n-AlGaN layer is 10 nm.

[0056] S6: A multi-period Si-doped NGaN layer was grown on an n-AlGaN layer. The reaction chamber temperature was 950℃, the pressure was 150 Torr, the rotation speed was 1200 rpm, H2 carrier gas was used, the V / III molar ratio was 100, the thickness of the n-AlGaN layer was 1.5 μm, and the number of periods of the multi-period Si-doped GaN was 50. Periodic growth can reduce stress.

[0057] S7: A superlattice InGaN / GaN stress relief layer is grown on a multi-period Si-doped NGaN layer. The reaction chamber temperature is 850℃, the pressure is 150 Torr, the rotation speed is 600 rpm, H2 carrier gas is used, the V / III molar ratio is 1000, and the number of periods of the superlattice InGaN / GaN is 5, which can reduce the dislocations and stress generated by the growth of the N layer.

[0058] S8: A multi-quantum-well active region layer was grown on a superlattice InGaN / GaN stress-relief layer. The reaction chamber temperature was 850℃, the well-barrier temperature difference was 100℃, and a long-well GaN / Inx1GaN layer was grown under a pressure of 200 Torr and a rotation speed of 500 rpm using H2 carrier gas. 1－x1 N / Inx2 Ga 1－x2 N / GaN and long-barrier GaN / Al y1 Ga 1－y1 N; The active region of the multi-quantum well uses GaN / Inx1Ga 1－x1 N / Inx2 Ga 1－x2N / GaN, GaN / Al y1 Ga 1－y1 The N-type In composition structure, the x1 and x2 contents are adjusted by temperature to reduce well-barrier mismatch and thus alleviate the Stark effect. The quantum barrier is made of Si-doped GaN, which can reduce dislocations.

[0059] S9: An AlGaN electron blocking layer was grown on the active region of a multi-quantum well. The reaction chamber temperature was 850℃, the pressure was 200 Torr, the rotation speed was 500 rpm, H2 carrier gas was used, the V / III molar ratio was 100, and the thickness of the electron blocking layer was 5 nm.

[0060] S10: The first p-GaN layer is grown on the AlGaN electron-blocking layer. The reaction chamber temperature is 750℃, the pressure is 200 Torr, the rotation speed is 600 rpm, and H2 carrier gas is used. The Mg doping concentration of the first p-GaN layer is 5 × 10⁻⁶. 190 cm -3 .

[0061] S11: A p-AlGaN layer is grown on the first p-GaN layer. The reaction chamber temperature is 950℃, the pressure is 100 Torr, the rotation speed is 1000 rpm, H2 carrier gas is used, the thickness of the p-AlGaN layer is 10 nm, and the Mg doping concentration is 1×10⁻⁶. 18 cm -3 The Al doping concentration is 1×10 19 cm -3 .

[0062] S12: A second p-GaN layer is grown on top of the p-AlGaN layer. The reaction chamber temperature is 700℃, the reaction chamber temperature is 900℃, the pressure is 200 Torr, the rotation speed is 1000 rpm, and 25 sccm of TMGa and 2000 sccm of Cp2Mg are introduced. The thickness of the second p-GaN layer is 100 nm, and the Mg doping concentration is 1×10⁻⁶. 18 cm -3 .

[0063] S13: An ohmic contact layer is grown on the second p-GaN layer. The reaction chamber temperature is 900–1000℃, the pressure is 180 Torr, the rotation speed is 800 rpm, and H2 carrier gas is used. The Al doping concentration of the ohmic contact layer is 5 × 10⁻⁶. 20 cm -3 The Mg doping concentration is 2×10 19 cm -3The thickness is 7 nm; the ohmic contact layer consists of a P-type MgN / GaN superlattice structure and a P-type AlGaN structure grown sequentially. The P-type MgN / GaN superlattice structure is MgN Delta doped. During the growth of the P-type MgN / GaN superlattice structure, CP2Mg and NH3 are first introduced to grow P-type MgN, and then TMGa and NH3 are introduced to grow P-type GaN. P-type MgN and P-type GaN are grown alternately for 2 cycles. The thickness of P-type MgN in the P-type MgN / GaN superlattice structure is 2 nm, and the thickness of P-type GaN is 4 nm.

[0064] Embodiment four of the present invention is: a method for fabricating a high-efficiency GaN-based Mini LED epitaxial structure, the steps of which are as follows:

[0065] S1: Place the AlN substrate in the reaction chamber.

[0066] S2: A high-temperature AlGaN / GaN buffer layer is grown on an AlN substrate. The reaction chamber temperature is 900℃, the pressure is 300 Torr, the rotation speed is 1200 rpm, H2 carrier gas is used, and the V / III molar ratio is 100.

[0067] S3: A high-temperature undoped UGaN layer is grown on an AlGaN / GaN buffer layer. The reaction chamber temperature is 1100℃, the pressure is 300 Torr, the rotation speed is 1200 rpm, H2 carrier gas is used, the V / III molar ratio is 1300, and the thickness of the high-temperature undoped UGaN layer is 3μm.

[0068] S4: A high-temperature doped NGaN layer was grown on a high-temperature undoped UGaN layer. The reaction chamber temperature was 1100℃, the pressure was 300 Torr, the rotation speed was 1200 rpm, H2 was used as the carrier gas, the V / III molar ratio was 300, the thickness of the high-temperature doped NGaN layer was 2 μm, and the Si doping concentration was 10 × 10⁻⁶. 18 cm -3 .

[0069] S5: An n-AlGaN layer was grown on a high-temperature doped NGaN layer. The reaction chamber temperature was 1000℃, the pressure was 100 Torr, the rotation speed was 1000 rpm, H2 carrier gas was used, the V / III molar ratio was 100, and the Al doping concentration was 1.5E+17 atom / cm³. -3 The thickness of the n-AlGaN layer is 100 nm.

[0070] S6: A multi-period Si-doped NGaN layer is grown on an n-AlGaN layer. The reaction chamber temperature is 1050℃, the pressure is 200 Torr, the rotation speed is 1200 rpm, H2 carrier gas is used, the V / III molar ratio is 300, the thickness of the n-AlGaN layer is 2μm, and the number of periods of the multi-period Si-doped GaN is 100. Periodic growth can reduce stress.

[0071] S7: A superlattice InGaN / GaN stress relief layer is grown on a multi-period Si-doped NGaN layer. The reaction chamber temperature is 950℃, the pressure is 200 Torr, the rotation speed is 600 rpm, H2 carrier gas is used, the V / III molar ratio is 5000, and the number of periods of the superlattice InGaN / GaN is 10, which can reduce the dislocations and stress generated by the growth of the N layer.

[0072] S8: A multi-quantum-well active region layer was grown on a superlattice InGaN / GaN stress-relief layer. The reaction chamber temperature was 950℃, the well-barrier temperature difference was 150℃, and a long-well GaN / Inx1GaN layer was grown under a pressure of 200 Torr and a rotation speed of 500 rpm using H2 carrier gas. 1－x1 N / Inx2 Ga 1－x2 N / GaN and long-barrier GaN / Al y1 Ga 1－y1 N; The active region of the multi-quantum well uses GaN / Inx1Ga 1－x1 N / Inx2 Ga 1－x2 N / GaN, GaN / Al y1 Ga 1－y1 The N-type In composition structure, the x1 and x2 contents are adjusted by temperature to reduce well-barrier mismatch and thus alleviate the Stark effect. The quantum barrier is made of Si-doped GaN, which can reduce dislocations.

[0073] S9: An AlGaN electron blocking layer was grown on the active region of a multi-quantum well. The reaction chamber temperature was 950℃, the pressure was 200 Torr, the rotation speed was 500 rpm, H2 carrier gas was used, the V / III molar ratio was 300, and the thickness of the electron blocking layer was 10 nm.

[0074] S10: The first p-GaN layer is grown on the AlGaN electron-blocking layer. The reaction chamber temperature is 800℃, the pressure is 200 Torr, the rotation speed is 600 rpm, and H2 carrier gas is used. The Mg doping concentration of the first p-GaN layer is 1.5 × 10⁻⁶. 20 cm -3 .

[0075] S11: A p-AlGaN layer is grown on the first p-GaN layer. The reaction chamber temperature is 1000℃, the pressure is 150 Torr, the rotation speed is 1000 rpm, H2 carrier gas is used, the thickness of the p-AlGaN layer is 100 nm, and the Mg doping concentration is 2 × 10⁻⁶. 20 cm -3 The Al doping concentration is 1×10 21 cm -3 .

[0076] S12: A second p-GaN layer is grown on top of the p-AlGaN layer. The reaction chamber temperature is 1050℃, the pressure is 200 Torr, the rotation speed is 1000 rpm, and 50 sccm of TMGa and 3000 sccm of Cp2Mg are introduced. The thickness of the second p-GaN layer is 50 nm, and the Mg doping concentration is 1×10⁻⁶. 20 cm -3 .

[0077] S13: An ohmic contact layer is grown on the second p-GaN layer. The reaction chamber temperature is 1000℃, the pressure is 220 Torr, the rotation speed is 1200 rpm, and H2 carrier gas is used. The Al doping concentration of the ohmic contact layer is 1×10⁻⁶. 21 cm -3 The Mg doping concentration is 1×10 20 cm -3 The thickness is 10 nm; the ohmic contact layer consists of a P-type MgN / GaN superlattice structure and a P-type AlGaN structure grown sequentially. The P-type MgN / GaN superlattice structure is MgN Delta doped. During the growth of the P-type MgN / GaN superlattice structure, CP2Mg and NH3 are first introduced to grow P-type MgN, and then TMGa and NH3 are introduced to grow P-type GaN. P-type MgN and P-type GaN are grown alternately for 7 cycles. The thickness of P-type MgN in the P-type MgN / GaN superlattice structure is 3 nm, and the thickness of P-type GaN is 5 nm.

[0078] In summary, the method for fabricating a high-efficiency GaN-based Mini LED epitaxial structure provided by this invention yields a novel ohmic contact layer. This ohmic contact layer comprises a sequentially grown P-type MgN / GaN superlattice structure and a high-Al-content P-type AlGaN structure, and has the following advantages:

[0079] 1. The P-type MgN / GaN superlattice structure has good current expansion, which can reduce voltage and improve ESD, but it will bring some voltage congestion. Growing a P-type AlGaN structure with high Al content on the basis of the P-type MgN / GaN superlattice structure can increase the brightness but also lead to an increase in voltage, which can compensate for the voltage congestion caused by the P-type MgN / GaN superlattice structure.

[0080] 2. The P-type MgN / GaN superlattice structure adopts MgN Delta doping, which has higher Mg activation efficiency, can provide holes, grow thinner P-type GaN, reduce the injection of light-absorbing holes in PGaN, thereby improving light extraction efficiency.

[0081] 3. High-Al content AlGaN structures can improve LED brightness, but at the same time, they will lead to increased voltage and worse ESD. Chip GTO technology can reduce voltage and improve ESD. By combining high-Al content P-type AlGaN structures with chip GTO technology, low voltage and high ESD can be maintained while improving LED brightness.

[0082] 4. Control the Mg doping concentration of the ohmic contact layer to 2×10⁻⁶. 19 ~1×10 20 cm -3 This is to prevent the brightness from being affected by Mg doping concentration that is too high or too low.

[0083] 5. Lower pressure and faster growth rate are used in the preparation of the ohmic contact layer to increase the growth rate, and higher growth temperature is used to ensure lattice quality.

[0084] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A high light efficiency GaN-based Mini LED epitaxial structure, characterized in that, The ohmic contact layer includes a P-type MgN / GaN superlattice structure grown sequentially and a P-type AlGaN structure, the P-type MgN / GaN superlattice structure is doped with MgN Delta, and the Al doping concentration of the ohmic contact layer is 5x10 20 ~1x10 21 cm -3 .

2. The high light efficiency GaN-based Mini LED epitaxial structure of claim 1, wherein, The Mg doping concentration of the ohmic contact layer is 2 x 10 19 ~ 1 x 10 20 cm -3 .

3. The preparation method of the high light efficiency GaN-based Mini LED epitaxial structure of claim 1 or 2, characterized in that, The ohmic contact layer is grown in a reaction chamber with a temperature of 900-1000 DEG C, a pressure of 180-220 Torr and a rotation speed of 800-1200 rpm, using H2 as carrier gas.

4. The preparation method of the high light efficiency GaN-based Mini LED epitaxial structure according to claim 3, characterized in that, The P-type MgN / GaN superlattice structure is grown by first introducing CP2Mg and NH3 to grow P-type MgN, and then introducing TMGa and NH3 to grow P-type GaN, and the P-type MgN and P-type GaN are alternately grown for 1-7 cycles.

5. The preparation method of the high light efficiency GaN-based Mini LED epitaxial structure according to claim 4, characterized in that, The thickness of the P-type MgN in the P-type MgN / GaN superlattice structure is 1-3 nm, and the thickness of the P-type GaN is 3-9 nm.

6. The preparation method of the high light efficiency GaN-based Mini LED epitaxial structure according to claim 3, characterized in that, The thickness of the ohmic contact layer is 1-10 nm.

7. The preparation method of the high light efficiency GaN-based Mini LED epitaxial structure according to claim 3, characterized in that, An AlGaN / GaN buffer layer, a high-temperature non-doped UGaN layer, a high-temperature doped NGaN layer, an n-AlGaN layer, a multi-cycle Si-doped NGaN layer, a superlattice InGaN / GaN stress release layer, a multi-quantum well active region layer, an AlGaN electron barrier layer, a first p-GaN layer, a p-AlGaN layer, a second p-GaN layer and an ohmic contact layer are sequentially grown on an AlN substrate.

8. The preparation method of the high light efficiency GaN-based Mini LED epitaxial structure according to claim 7, characterized in that, The number of cycles of the multi-cycle Si-doped GaN layer is 50-100.

9. The preparation method of the high light efficiency GaN-based Mini LED epitaxial structure according to claim 7, characterized in that, The number of cycles for growing the superlattice InGaN / GaN stress release layer is 5-10.

10. The preparation method of the high light efficiency GaN-based Mini LED epitaxial structure according to claim 7, characterized in that, The growth of the second p-GaN layer is performed in a reaction chamber having a temperature of 900 to 1050 °C, and the second p-GaN layer has a thickness of 10 to 50 nm and a doping concentration of 1 x 1018 to 1 x 1020 cm-3. 18 20 cm -3 .​

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