Light emitting diode epitaxial wafer and preparation method thereof, and light emitting diode

Abstract

The application discloses an epitaxial wafer of a light emitting diode, a preparation method of the epitaxial wafer and the light emitting diode, and relates to the field of semiconductor photoelectric devices. The epitaxial wafer of the light emitting diode comprises a substrate, an AlN layer, a buffer layer, a U-GaN layer, an N-GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a P-GaN layer which are sequentially grown on the substrate; wherein the buffer layer is a periodic structure, each period comprises an AlGaN layer, a polycrystalline GaN layer, an HT-GaN layer and a low-doped GaN layer which are sequentially stacked, the number of periods of the buffer layer is greater than or equal to 2, and the doping concentration of the low-doped GaN layer is 1.5*10 17 cm ‑3 -8*10 18 cm ‑3 -8*10 ‑3 . By implementing the application, the light emitting efficiency of the light emitting diode can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor optoelectronic devices, in particular to a light emitting diode epitaxial wafer and a preparation method thereof, and a light emitting diode. BACKGROUND

[0002] GaN-based LED often uses sapphire, SiC and Si as a substrate to grow light emitting diode epitaxial layers. There is a significant lattice mismatch between GaN and the general substrate, which produces a large stress in the initial stage of epitaxial growth, thereby generating a large number of dislocations and defects, which affects the light emitting efficiency of the light emitting diode. In the prior art, AlN film is often introduced to reduce the lattice mismatch, but the AlN film and the U-GaN layer are still different materials, and there is still a lattice mismatch to produce stress, causing crystal defects of the barrier crystal, reducing the quality of the epitaxial barrier crystal, thereby reducing the light emitting efficiency of the light emitting diode and the anti-static ability. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a light emitting diode epitaxial wafer and a preparation method thereof, which can effectively improve the light emitting efficiency of the light emitting diode.

[0004] The technical problem to be solved by the present application is to provide a light emitting diode, which has high light emitting efficiency.

[0005] In order to solve the above problems, the present application discloses a light emitting diode epitaxial wafer, which comprises a substrate and an AlN layer, a buffer layer, a U-GaN layer, an N-GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a P-GaN layer successively grown on the substrate; wherein the buffer layer is a periodic structure, each period comprises an AlGaN layer, a polycrystalline GaN layer, an HT-GaN layer and a low-doped GaN layer successively stacked, the number of periods of the buffer layer is ≥2, and the doping concentration of the low-doped GaN layer is 1.5x10 17 cm -3 -8x10 18 cm -3 .

[0006] As an improvement of the above technical solution, the number of periods of the buffer layer is 2-100, and the thickness of the buffer layer is 500nm-5000nm.

[0007] As an improvement of the above technical solution, the thickness of a single AlGaN layer is 5nm-20nm, the thickness of a single polycrystalline GaN layer is 10nm-30nm, the thickness of a single HT-GaN layer is 0.1um-1um, and the thickness of a single low-doped GaN layer is 3nm-20nm.

[0008] As the improvement of the above technical scheme, the Al component content in the AlGaN layer gradually decreases with the increase of the period.

[0009] As the improvement of the above technical scheme, the Al component content in the AlGaN layer gradually decreases from 0.8 to 0.1 with the increase of the period number.

[0010] As the improvement of the above technical scheme, the doping concentration of the U-GaN layer is 5×10 18 cm -3 -5×10 19 cm -3 , and the doping concentration of the N-GaN layer is 2×10 19 cm -3 -9×10 22 cm -3 .

[0011] Correspondingly, the application also discloses a preparation method of the light emitting diode epitaxial wafer.

[0012] Providing an epitaxial wafer;

[0013] Growing an AlN layer, a buffer layer, a U-GaN layer, an N-GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a P-GaN layer on the epitaxial wafer in sequence; wherein the buffer layer is a periodic structure, each period includes an AlGaN layer, a polycrystalline GaN layer, an HT-GaN layer and a low-doped GaN layer which are stacked in sequence, the period number of the buffer layer is greater than or equal to 2, and the doping concentration of the low-doped GaN layer is 1.5×10 17 cm -3 -8×10 18 cm -3 .

[0014] As the improvement of the above technical scheme, the growth temperature of the AlGaN layer is 750-900℃, and the growth pressure is 100-200torr;

[0015] The growth temperature of the polycrystalline GaN layer is 1030-1100℃, and the growth pressure is 450-550torr;

[0016] The growth temperature of the HT-GaN layer is 1120-1150℃, and the growth pressure is 150-200torr;

[0017] The growth temperature of the low-doped GaN layer is 1120-1150℃, and the growth pressure is 150-200torr.

[0018] As the improvement of the above technical solution, the growth temperature of the AlGaN layer < the growth temperature of the polycrystalline GaN layer < the growth temperature of the HT-GaN layer < the growth temperature of the low-doped GaN layer.

[0019] Correspondingly, the application further discloses a light emitting diode comprising the light emitting diode epitaxial wafer.

[0020] The application has the following beneficial effects:

[0021] The light emitting diode epitaxial wafer of the application adds the multi-period AlGaN layer / polycrystalline GaN layer / HT-GaN layer / low-doped GaN layer between the AlN layer and the U-GaN layer, which provides a transition period from the AlN layer to the U-GaN layer, slowly transitions between the layers, reduces the compressive stress caused by different materials, effectively reduces the bottom layer barrier defect density, improves the crystal quality of the GaN-based light emitting diode, increases the multi-quantum well compound light emitting efficiency, improves the anti-static ability of the light emitting diode based on the epitaxial wafer, and improves the reverse voltage. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 1 is a structure schematic diagram of a light emitting diode epitaxial wafer in an embodiment of the application;

[0023] Figure 2 Fig. 2 is a structure schematic diagram of a buffer layer in an embodiment of the application;

[0024] Figure 3 Fig. 3 is a flow chart of a preparation method of a light emitting diode epitaxial wafer in an embodiment of the application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the application more clear, the application is further described in detail below.

[0026] Reference Figure 1 and Figure 2The application discloses a light emitting diode epitaxial wafer, which comprises a substrate 1 and an AlN layer 2, a buffer layer 3, a U-GaN layer 4, an N-GaN layer 5, a stress release layer 6, a multi-quantum well layer 7, an electron blocking layer 8 and a P-GaN layer 9 which are sequentially grown on the substrate 1. The buffer layer 3 is a periodic structure, the number of periods of which is greater than or equal to 2, and each period comprises an AlGaN layer 31, a polycrystalline GaN layer 32, an HT-GaN layer 33 and a low-doped GaN layer 34 which are sequentially stacked. The buffer layer 3 provides a transition period from the AlN layer 2 to the U-GaN layer 4, slowly transitions between the layers, reduces the compressive stress caused by different materials, effectively reduces the bottom barrier crystal defect density, improves the crystal quality of the GaN-based light emitting diode, increases the multi-quantum well compound light emitting efficiency, improves the anti-static ability of the light emitting diode based on the epitaxial wafer and improves the reverse voltage of the light emitting diode.

[0027] The AlGaN layer 31 contains Al components, and the lattice constant of the AlGaN layer 31 is similar to that of the AlN layer 2, so that the buffer stress mismatch is facilitated. The proportion of the Al components in the AlGaN layer 31 is 0.05-0.9 (mole fraction), and the proportion is exemplarily 0.08, 0.12, 0.25, 0.32, 0.45, 0.58, 0.66 or 0.82, but is not limited thereto. Specifically, in one embodiment of the application, the proportion of the Al components in each AlGaN layer 31 in the periodic structure of the buffer layer 3 is the same. In another embodiment of the application, the content of the Al components in the plurality of AlGaN layers 31 gradually decreases with the increase of the period in the periodic structure of the buffer layer 3, but is not limited thereto. Preferably, the content of the Al components in the plurality of AlGaN layers 31 gradually decreases with the increase of the period, and the gradual and gentle transition is formed by the structure, so that the stress of the AlN layer 2 is reduced. More preferably, the content of the Al components in the plurality of AlGaN layers 31 gradually decreases from 0.8 to 0.1, and the proportion of the Al components in each AlGaN layer 31 is constant.

[0028] The thickness of each AlGaN layer 31 in the periodic structure of the buffer layer 3 is 5nm-20nm, and the thickness is exemplarily 6nm, 8nm, 10nm, 12nm, 14nm, 16nm or 18nm, but is not limited thereto.

[0029] The polycrystalline GaN layer 32 is a loose polycrystalline structure, which can release the compressive stress generated by the AlN layer 2 and the AlGaN layer 31, and effectively block the upward extension of the AlGaN layer crystal defects, so as to lay a good foundation for the growth of the subsequent HT-GaN layer 33. Specifically, the thickness of each polycrystalline GaN layer 32 in the periodic structure of the buffer layer 3 is 10nm-30nm, and the thickness is exemplarily 13nm, 16nm, 19nm, 22nm, 25nm or 29nm, but is not limited thereto.

[0030] The HT-GaN layer 33 is a GaN layer with a good crystal structure grown at high temperature. It is made of the same material as the polycrystalline GaN layer 32, and therefore will not experience stress due to differences in lattice constants, thus preventing a decrease in the stacking quality. Furthermore, because the polycrystalline GaN layer 32 provides a sufficient site for stress release and to block defect propagation, the HT-GaN layer 33 exhibits an extremely low defect density, resulting in a significant improvement in stacking quality. Specifically, in the periodic structure of the buffer layer 3, the thickness of a single HT-GaN layer 33 is 0.1 μm-1 μm, exemplarily 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.4 μm, 0.6 μm, or 0.9 μm, but is not limited to these values.

[0031] In this design, the low-doped GaN layer 34 is an N-type doped GaN layer, and its doping element is Si or Ge, but not limited to these. Si is preferred. The doping concentration of the low-doped GaN layer 34 is less than the doping concentration of the U-GaN layer 4, which is less than the doping concentration of the N-GaN layer 5. This arrangement allows the lattice constants of the subsequently grown layers to change gradually and slowly, improving the crystal quality of the GaN-based light-emitting diode. Specifically, in one embodiment of the present invention, the doping concentration of the low-doped GaN layer 34 is 1.5 × 10⁻⁶. 17 cm -3 -8×10 18 cm -3 The doping concentration of U-GaN layer 4 is 5 × 10⁴. 18 cm -3 -5×10 19 cm -3 The doping concentration of N-GaN layer 5 is 2×10⁵. 19 cm -3 -9×10 22 cm -3 .

[0032] Specifically, in the periodic structure of the buffer layer 3, the thickness of a single HT-GaN layer 33 is 0.1μm-1μm, exemplarily 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.4μm, 0.6μm or 0.9μm, but not limited thereto.

[0033] Specifically, the number of periods of the buffer layer 3 is 2-100, preferably 2-20, and exemplarily 4, 8, 12, 14 or 18, but not limited thereto. By the multi-period buffer layer 3 structure, the gradual and slow change of the lattice constant of each layer is controlled, further improving the crystal quality of the GaN-based light-emitting diode and improving the light-emitting efficiency. In addition, the total thickness of the buffer layer 3 is controlled to be 500 nm-5000 nm. Exemplarily, it is 550 nm, 600 nm, 1200 nm, 1800 nm, 2400 nm, 2600 nm, 3200 nm, 3800 nm, 4400 nm or 4800 nm.

[0034] The substrate 1 can be a sapphire substrate, a silicon substrate, a silicon carbide substrate, but not limited thereto.

[0035] The thickness of the AlN layer 2 is 10 nm-80 nm, and exemplarily 14 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm or 75 nm, but not limited thereto.

[0036] The thickness of the U-GaN layer 4 is 1 μm-5 μm, and exemplarily 1.4 μm, 1.8 μm, 2.2 μm, 2.6 μm, 3 μm, 3.4 μm, 3.8 μm, 4.2 μm or 4.6 μm, but not limited thereto. In addition, after the growth of the U-GaN layer 4 is completed, the N-type dopant (such as SiH4, etc.) will inevitably be doped into the U-GaN layer 4 to some extent during the growth of the N-GaN layer 5, so that the U-GaN layer 4 has N-type doping. Specifically, the doping concentration is 5×10 18 cm -3 -5×10 19 cm -3 .

[0037] The doping element of the N-GaN layer 5 is Si, but not limited thereto. The doping concentration of the N-GaN layer 5 is 2×10 19 cm -3 -9×10 22 cm -3 The thickness of the N-GaN layer 5 is 2 μm-6 μm, and exemplarily 2.3 μm, 2.6 μm, 2.9 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4.1 μm, 4.4 μm, 4.7 μm, 5.3 μm, 5.5 μm or 5.8 μm, but not limited thereto.

[0038] The stress release layer 6 is an InGaN layer, the In component ratio of which is 0.1-0.2, and the thickness thereof is 100 nm-800 nm, and exemplarily 150 nm, 200 nm, 250 nm, 300 nm, 400 nm, 500 nm or 700 nm, but not limited thereto.

[0039] The multi-quantum well layer 7 is a periodic structure formed by a plurality of InGaN well layers and a plurality of GaN barrier layers, and the number of periods is 3-15. Specifically, the thickness of a single InGaN well layer is 2-5 nm, and the In content is 0.2-0.3, and the thickness of a single GaN barrier layer is 5-15 nm.

[0040] The electron blocking layer 8 is an AlxGayN layer, where x is 0.05-0.2, and y is 0.1-0.5. The thickness of the electron blocking layer 8 is 20-150 nm, and examples are 45 nm, 70 nm, 95 nm, 110 nm, 125 nm or 140 nm, but the application is not limited thereto. x In y Ga 1-x-y N layer, where x is 0.05-0.2, and y is 0.1-0.5. The thickness of the electron blocking layer 8 is 20-150 nm, and examples are 45 nm, 70 nm, 95 nm, 110 nm, 125 nm or 140 nm, but the application is not limited thereto.

[0041] The doping element in the P-GaN layer 9 is Mg, but the application is not limited thereto. The doping concentration of Mg in the P-GaN layer 9 is 2×1019 cm-2-2×1021 cm-2. 19 cm -3 -2×1019 cm-2-2×1021 cm-2. 20 cm -3 The thickness of the P-GaN layer 9 is 200-300 nm. Examples are 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm or 290 nm, but the application is not limited thereto.

[0042] Correspondingly, with reference to Figure 3 The application also discloses a preparation method of a light-emitting diode epitaxial wafer, which is used for preparing the light-emitting diode epitaxial wafer and comprises the following steps.

[0043] S100: providing a substrate;

[0044] Specifically, the substrate is a sapphire substrate, a silicon substrate or a silicon carbide substrate, but the application is not limited thereto. Preferably, the substrate is a patterned sapphire substrate.

[0045] S200: sequentially growing an AlN layer, a buffer layer, a U-GaN layer, an N-GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a P-GaN layer on the substrate;

[0046] Specifically, S200 comprises:

[0047] S201: growing an AlN layer on the substrate;

[0048] Specifically, the AlN layer can be grown by PVD, but the application is not limited thereto.

[0049] S202: growing an AlGaN layer on the substrate obtained in step S201;

[0050] In one embodiment of the present application, the AlGaN layer is grown in MOCVD. The growth temperature is 400-500°C, and the growth pressure is 100-200 torr.

[0051] S203: growing a polycrystalline GaN layer on the AlGaN layer;

[0052] In one embodiment of the present application, the polycrystalline GaN layer is grown in MOCVD. The growth temperature is 1030-1100°C, and the growth pressure is 450-550 torr.

[0053] S204: growing an HT-GaN layer on the polycrystalline GaN layer;

[0054] In one embodiment of the present application, the HT-GaN layer is grown in MOCVD. The growth temperature is 1120-1150°C, and the growth pressure is 150-200 torr.

[0055] S205: growing a low-doped GaN layer on the HT-GaN layer;

[0056] In one embodiment of the present application, the HT-GaN layer is grown in MOCVD. The growth temperature is 1120-1150°C, and the growth pressure is 150-200 torr. SiH4 is introduced as the N-type dopant during growth.

[0057] Preferably, in one embodiment of the present application, the growth temperature of the AlGaN layer < the growth temperature of the polycrystalline GaN layer < the growth temperature of the HT-GaN layer < the growth temperature of the low-doped GaN layer, which helps to form a structure with slow transition.

[0058] S206: periodically repeating steps S203-S205 to obtain a buffer layer;

[0059] S207: growing a U-GaN layer on the buffer layer;

[0060] In one embodiment of the present application, the U-GaN layer is grown in MOCVD. The growth temperature is 1120-1150°C, and the growth pressure is 150-200 torr. No N-type dopant is introduced during growth.

[0061] S208: growing an N-GaN layer on the U-GaN layer;

[0062] Specifically, in one embodiment of the present application, the N-GaN layer is grown in MOCVD, the growth temperature is 1120-1150℃, and the growth pressure is 150-200 torr. During the growth, SiH4 is introduced as the N-type dopant.

[0063] S209: growing a stress release layer on the N-GaN layer;

[0064] Specifically, in one embodiment of the present application, the stress release layer is grown in MOCVD, the growth temperature is 750-950℃, and the growth pressure is 150-300 torr.

[0065] S210: growing a multi-quantum well layer on the stress release layer;

[0066] In one embodiment of the present application, the multi-quantum well layer is grown in MOCVD. Specifically, InGaN well layers and GaN barrier layers are alternately grown on the stress release layer, and the process is repeated for 3-15 cycles, thereby obtaining the multi-quantum well layer. The growth temperature of the InGaN well layer is 700-800℃, the growth temperature of the GaN barrier layer is 800-900℃, and the growth pressure of both is 150-250 torr.

[0067] S211: growing an electron blocking layer on the multi-quantum well layer;

[0068] In one embodiment of the present application, the electron blocking layer is grown in MOCVD. The growth temperature is 900-1000℃, and the growth pressure is 300-500 torr.

[0069] S212: growing a P-GaN layer on the electron blocking layer;

[0070] In one embodiment of the present application, the P-GaN layer is grown in MOCVD. The growth temperature is 800-1000℃, and the growth pressure is 300-500 torr.

[0071] The present application is further described below with reference to specific embodiments:

[0072] Embodiment 1

[0073] This embodiment provides a light emitting diode epitaxial wafer, which is grown by MOCVD. Figure 1 and Figure 2, which comprises a substrate 1 and an AlN layer 2, a buffer layer 3, a U-GaN layer 4, an N-GaN layer 5, a stress release layer 6, a quantum well layer 7, an electron blocking layer 8 and a P-GaN layer 9 grown on the substrate 1 in sequence. The buffer layer 3 is a periodic structure, and the number of periods is 3. Each period comprises an AlGaN layer 31, a polycrystalline GaN layer 32, an HT-GaN layer 33 and a low-doped GaN layer 34 stacked in sequence.

[0074] In each period, the thickness of the AlGaN layer 31 is 10 nm, and the Al component accounts for 0.35. The thickness of the polycrystalline GaN layer 32 is 20 nm, and the thickness of the HT-GaN layer 33 is 0.1 μm. The thickness of the low-doped GaN layer 34 is 10 nm, the doping element is Si, and the doping concentration is 5×10 17 cm -3 In the plurality of periodic structures, the Al component of the AlGaN layer 31 is constant.

[0075] The substrate 1 is a sapphire substrate, the thickness of the AlN layer 2 is 30 nm, the thickness of the U-GaN layer 4 is 2.2 μm, the doping element is Si, and the doping concentration is 6.2×10 18 cm -3 The doping concentration of Si in the N-GaN layer 5 is 9.8×10 19 cm -3 , and the thickness is 4 μm. The stress release layer 6 is an InGaN layer, the In component accounts for 0.14, and the thickness is 320 nm.

[0076] The multi-quantum well layer 7 is a periodic structure with a period number of 10 formed by a plurality of InGaN well layers and a plurality of GaN barrier layers. The thickness of a single InGaN well layer (In component accounts for 0.25) is 3 nm, and the thickness of a single AlGaN barrier layer is 10.5 nm.

[0077] The electron blocking layer 8 is an Al x In y Ga 1-x-y N layer, wherein x is 0.1 and y is 0.4, and the thickness is 80 nm. The doping concentration of Mg in the P-GaN layer 9 is 9.5×10 19 cm -3 , and the thickness is 280 nm.

[0078] The preparation method of the light emitting diode epitaxial wafer in the embodiment comprises the following steps:

[0079] (1) providing a substrate;

[0080] (2) growing an AlN layer on the substrate;

[0081] Specifically, the AlN layer is deposited by PVD.

[0082] (3) growing an AlGaN layer on the substrate obtained in step (2);

[0083] Specifically, the AlGaN layer is grown in MOCVD at a growth temperature of 420°C and a growth pressure of 160 torr.

[0084] (4) growing a polycrystalline GaN layer on the AlGaN layer;

[0085] Specifically, the polycrystalline GaN layer is grown in MOCVD at a growth temperature of 1050°C and a growth pressure of 520 torr.

[0086] (5) growing an HT-GaN layer on the polycrystalline GaN layer;

[0087] Specifically, the HT-GaN layer is grown in MOCVD at a growth temperature of 1140°C and a growth pressure of 160 torr.

[0088] (6) growing a low-doped GaN layer on the HT-GaN layer;

[0089] Specifically, the low-doped GaN layer is grown in MOCVD at a growth temperature of 1140°C and a growth pressure of 160 torr, and SiH4 is introduced as an N-type dopant during the growth.

[0090] (7) periodically repeating steps (3) - (5) until a buffer layer is obtained;

[0091] (8) growing a U-GaN layer on the buffer layer;

[0092] Specifically, the U-GaN layer is grown in MOCVD at a growth temperature of 1140°C and a growth pressure of 160 torr. No N-type dopant is introduced during the growth.

[0093] (9) growing an N-GaN layer on the U-GaN layer;

[0094] Specifically, the U-GaN layer is grown in MOCVD at a growth temperature of 1140°C and a growth pressure of 160 torr. SiH4 is introduced as an N-type dopant during the growth.

[0095] (10) growing a stress release layer on the N-GaN layer;

[0096] Specifically, the InGaN layer is grown in MOCVD as a stress release layer at a growth temperature of 850°C and a growth pressure of 180 torr.

[0097] (11) growing a multiple quantum well layer on the stress release layer;

[0098] Specifically, InGaN well layers and GaN barrier layers are periodically grown in MOCVD to form a multi-quantum well layer. The growth temperature of the InGaN well layer is 780℃, the growth temperature of the GaN barrier layer is 860℃, and the growth pressure of both is 200 torr.

[0099] (12) Grow an electron blocking layer on a multi-quantum-well layer;

[0100] Specifically, growing Al in MOCVD x In y Ga 1-x-y The N-layer serves as an electron blocking layer. The growth temperature is 940℃, and the growth pressure is 450 torr.

[0101] (13) A P-GaN layer is grown on the electron blocking layer;

[0102] Specifically, P-GaN layers were grown in MOCVD at a temperature of 920℃ and a pressure of 340 torr.

[0103] Example 2

[0104] This embodiment provides a light-emitting diode epitaxial wafer, referenced... Figure 1 and Figure 2 It includes a substrate 1 and an AlN layer 2, a buffer layer 3, a U-GaN layer 4, an N-GaN layer 5, a stress relief layer 6, a quantum well layer 7, an electron blocking layer 8, and a P-GaN layer 9 sequentially grown on the substrate 1. Among them, the buffer layer 3 has a periodic structure with 3 periods, and each period includes an AlGaN layer 31, a polycrystalline GaN layer 32, an HT-GaN layer 33, and a low-doped GaN layer 34 sequentially stacked.

[0105] In each periodic structure, the AlGaN layer 31 has a thickness of 10 nm, the polycrystalline GaN layer 32 has a thickness of 20 nm, and the HT-GaN layer 33 has a thickness of 0.1 μm. The low-doped GaN layer 34 has a thickness of 10 nm, and the doping element is Si with a doping concentration of 5 × 10⁻⁶. 17 cm -3 In multiple periodic structures, the Al content of the AlGaN layer 31 gradually decreases from 0.8 to 0.1. That is, in the first period, the Al content in the AlGaN layer is 0.8, in the second period, the Al content in the AlGaN layer is 0.45, and in the third period, the Al content in the AlGaN layer is 0.1.

[0106] In this design, substrate 1 is a sapphire substrate, AlN layer 2 has a thickness of 30 nm, U-GaN layer 4 has a thickness of 2.2 μm, and the doping element is Si with a doping concentration of 6.2 × 10⁻⁶. 18 cm -3The doping concentration of Si in the N-GaN layer 5 is 9.8x10 19 cm -3 The stress release layer 6 is an InGaN layer with an In composition ratio of 0.14 and a thickness of 320 nm.

[0107] The multi-quantum well layer 7 is a periodic structure formed by a plurality of InGaN well layers and a plurality of GaN barrier layers, and the period number is 10. The thickness of a single InGaN well layer (In composition ratio of 0.25) is 3 nm, and the thickness of a single AlGaN barrier layer is 10.5 nm.

[0108] The electron blocking layer 8 is an Al x In y Ga 1-x-y N layer, where x is 0.1 and y is 0.4, and the thickness is 80 nm. The doping concentration of Mg in the P-GaN layer 9 is 9.5x10 19 cm -3 , and the thickness is 280 nm.

[0109] The preparation method of the light emitting diode epitaxial wafer in the embodiment includes the following steps:

[0110] (1) providing a substrate;

[0111] (2) growing an AlN layer on the substrate;

[0112] Specifically, the AlN layer is deposited by PVD.

[0113] (3) growing an AlGaN layer on the substrate obtained in step (2);

[0114] Specifically, the AlGaN layer is grown in MOCVD, and the growth temperature is 420℃ and the growth pressure is 160 torr.

[0115] (4) growing a polycrystalline GaN layer on the AlGaN layer;

[0116] Specifically, the polycrystalline GaN layer is grown in MOCVD, and the growth temperature is 1050℃ and the growth pressure is 520 torr.

[0117] (5) growing an HT-GaN layer on the polycrystalline GaN layer;

[0118] Specifically, the HT-GaN layer is grown in MOCVD. The growth temperature is 1140℃ and the growth pressure is 160 torr.

[0119] (6) growing a low-doped GaN layer on the HT-GaN layer;

[0120] Specifically, the low-doped GaN layer is grown in MOCVD, the growth temperature is 1140°C, the growth pressure is 160 torr, and SiH4 is introduced as N-type dopant during the growth.

[0121] (7) repeating steps (3) - (5) periodically until the buffer layer is obtained;

[0122] (8) growing a U-GaN layer on the buffer layer;

[0123] Specifically, the U-GaN layer is grown in MOCVD, the growth temperature is 1140°C, the growth pressure is 160 torr, and no N-type dopant is introduced during the growth.

[0124] (9) growing a N-GaN layer on the U-GaN layer;

[0125] Specifically, the U-GaN layer is grown in MOCVD, the growth temperature is 1140°C, the growth pressure is 160 torr, and SiH4 is introduced as N-type dopant during the growth.

[0126] (10) growing a stress release layer on the N-GaN layer;

[0127] Specifically, the InGaN layer is grown in MOCVD as the stress release layer, the growth temperature is 850°C, and the growth pressure is 180 torr.

[0128] (11) growing a multiple quantum well layer on the stress release layer;

[0129] Specifically, the InGaN well layer and GaN barrier layer are periodically grown in MOCVD as the multiple quantum well layer. The growth temperature of the InGaN well layer is 780°C, the growth temperature of the GaN barrier layer is 860°C, and the growth pressure of both is 200 torr.

[0130] (12) growing an electron blocking layer on the multiple quantum well layer;

[0131] Specifically, the Al x In y Ga 1-x-y N layer is grown in MOCVD as the electron blocking layer. The growth temperature is 940°C, and the growth pressure is 450 torr.

[0132] (13) growing a P-GaN layer on the electron blocking layer;

[0133] Specifically, the P-GaN layer is grown in MOCVD, the growth temperature is 920°C, and the growth pressure is 340 torr.

[0134] Example 3

[0135] The embodiment provides a light emitting diode epitaxial wafer, which refers to Figure 1 and Figure 2 comprises a substrate 1 and an AlN layer 2, a buffer layer 3, a U-GaN layer 4, an N-GaN layer 5, a stress release layer 6, a quantum well layer 7, an electron blocking layer 8 and a P-GaN layer 9 sequentially grown on the substrate 1. The buffer layer 3 is a periodic structure, and the number of periods is 3. Each period comprises an AlGaN layer 31, a polycrystalline GaN layer 32, an HT-GaN layer 33 and a low-doped GaN layer 34 sequentially stacked.

[0136] In each periodic structure, the thickness of the AlGaN layer 31 is 10 nm, the thickness of the polycrystalline GaN layer 32 is 20 nm, and the thickness of the HT-GaN layer 33 is 0.1 μm. The thickness of the low-doped GaN layer 34 is 10 nm, the doping element is Si, and the doping concentration is 5×10 17 cm -3 In the multiple periodic structures, the Al component of the AlGaN layer 31 gradually decreases from 0.8 to 0.1, that is, the Al component of the AlGaN layer is 0.8 in the first period, the Al component of the AlGaN layer is 0.45 in the second period, and the Al component of the AlGaN layer is 0.1 in the third period.

[0137] The substrate 1 is a sapphire substrate, the thickness of the AlN layer 2 is 30 nm, the thickness of the U-GaN layer 4 is 2.2 μm, the doping element is Si, and the doping concentration is 6.2×10 18 cm -3 ; the doping concentration of Si in the N-GaN layer 5 is 9.8×10 19 cm -3 , and the thickness is 4 μm. The stress release layer 6 is an InGaN layer, the In component accounts for 0.14, and the thickness is 320 nm.

[0138] The multiple quantum well layer 7 is a periodic structure with a period number of 10 formed by multiple InGaN well layers and multiple GaN barrier layers. The thickness of a single InGaN well layer (the In component accounts for 0.25) is 3 nm, and the thickness of a single AlGaN barrier layer is 10.5 nm.

[0139] The electron blocking layer 8 is an Al x In y Ga 1-x-y N layer, wherein x is 0.1 and y is 0.4, and the thickness is 80 nm. The doping concentration of Mg in the P-GaN layer 9 is 9.5×10 19 cm -3 , and the thickness is 280 nm.

[0140] The preparation method of the light emitting diode epitaxial wafer in the embodiment comprises the following steps:

[0141] (1) providing a substrate;

[0142] (2) growing an AlN layer on the substrate;

[0143] Specifically, the AlN layer is deposited by PVD.

[0144] (3) growing an AlGaN layer on the substrate obtained in step (2);

[0145] Specifically, the AlGaN layer is grown in MOCVD at a growth temperature of 420°C and a growth pressure of 160 torr.

[0146] (4) growing a polycrystalline GaN layer on the AlGaN layer;

[0147] Specifically, the polycrystalline GaN layer is grown in MOCVD at a growth temperature of 1050°C and a growth pressure of 520 torr.

[0148] (5) growing an HT-GaN layer on the polycrystalline GaN layer;

[0149] Specifically, the HT-GaN layer is grown in MOCVD at a growth temperature of 1140°C and a growth pressure of 160 torr.

[0150] (6) growing a low-doped GaN layer on the HT-GaN layer;

[0151] Specifically, the low-doped GaN layer is grown in MOCVD at a growth temperature of 1150°C and a growth pressure of 160 torr, and SiH4 is introduced as an N-type dopant during growth.

[0152] (7) periodically repeating steps (3)-(5) until a buffer layer is obtained;

[0153] (8) growing a U-GaN layer on the buffer layer;

[0154] Specifically, the U-GaN layer is grown in MOCVD at a growth temperature of 1140°C and a growth pressure of 160 torr. No N-type dopant is introduced during growth.

[0155] (9) growing an N-GaN layer on the U-GaN layer;

[0156] Specifically, the U-GaN layer is grown in MOCVD at a growth temperature of 1140°C and a growth pressure of 160 torr. SiH4 is introduced as an N-type dopant during growth.

[0157] (10) growing a stress release layer on the N-GaN layer;

[0158] Specifically, the InGaN layer is grown in MOCVD as a stress release layer, the growth temperature is 850℃, and the growth pressure is 180 torr.

[0159] (11) growing a multi-quantum well layer on the stress release layer;

[0160] Specifically, the InGaN well layer and the GaN barrier layer are periodically grown in MOCVD as a multi-quantum well layer. The growth temperature of the InGaN well layer is 780℃, the growth temperature of the GaN barrier layer is 860℃, and the growth pressure of both is 200 torr.

[0161] (12) growing an electron blocking layer on the multi-quantum well layer;

[0162] Specifically, the Al x In y Ga 1-x-y N layer is grown in MOCVD as an electron blocking layer. The growth temperature is 940℃, and the growth pressure is 450 torr.

[0163] (13) growing a P-GaN layer on the electron blocking layer;

[0164] Specifically, the P-GaN layer is grown in MOCVD, the growth temperature is 920℃, and the growth pressure is 340 torr.

[0165] Comparative Example 1

[0166] The difference between this comparative example and Example 1 is that the buffer layer 3 is not provided, and correspondingly, the step of preparing the buffer layer 3 (i.e., step 3-7) is also not provided, and the rest is the same as Example 1.

[0167] Comparative Example 2

[0168] The difference between this comparative example and Example 1 is that the low-doped GaN layer 34 is not provided, and correspondingly, the preparation step of preparing the low-doped GaN layer 34 (i.e., step 6) is also not provided, and the rest is the same as Example 1.

[0169] Comparative Example 3

[0170] The difference between this comparative example and Example 1 is that the HT-GaN layer 33 is not provided, and correspondingly, the preparation step of preparing the HT-GaN layer (i.e., step 5) is also not provided, and the rest is the same as Example 1.

[0171] Comparative Example 4

[0172] The difference between this comparative example and Example 1 is that the AlN layer 2 is not provided, and correspondingly, the preparation step of preparing the AlN layer 2 (i.e., step 2) is also not provided, and the rest is the same as Example 1.

[0173] The epitaxial wafer obtained from Example 1-3 and Comparative Example 1-4 is processed into 10x24mil LED chips with vertical structure, and the antistatic ability, luminous brightness and reverse voltage of the chips are tested;

[0174] The specific testing method of the chip is as follows:

[0175] (1) Antistatic performance test: the static instrument is used to test the antistatic performance of the base chip under the HBM (human body discharge model) model, and the passing rate of the chip under the reverse 6000V static is tested;

[0176] (2) Brightness: the luminous intensity of the obtained chip is tested when the current is 120mA;

[0177] (3) Reverse voltage: a multimeter is used for testing.

[0178] The specific test results are shown in the following table:

[0179] Brightness (mW) Antistatic properties (6000 V) Reverse voltage (V) Example 1 203.5 96.5％ 39.5 Example 2 208.5 98.4％ 40.8 Example 3 209.3 98.5％ 41.5 Comparative Example 1 194.4 92.1％ 34.5 Comparative Example 2 196.2 92.3％ 34.8 Comparative Example 3 195.5 93.6％ 35.1 Comparative Example 4 185.4 88.4％ 32.5

[0180] As can be seen from the table, after the buffer layer is introduced into the epitaxial structure, the luminous efficiency, antistatic performance and reverse voltage of the epitaxial wafer are all obviously improved.

[0181] The above is the preferred embodiment of the application. It should be pointed out that for those skilled in the art, some improvements and refinements can be made without departing from the principles of the application, and these improvements and refinements are also considered within the protection scope of the application.

Claims

1. A light emitting diode epitaxial wafer, characterized by, The application relates to a substrate and an AlN layer, a buffer layer, a U-GaN layer, an N-GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a P-GaN layer successively grown on the substrate; wherein the buffer layer is a periodic structure, each period comprising an AlGaN layer, a polycrystal GaN layer, an HT-GaN layer and a low-doped GaN layer successively stacked, the number of periods of the buffer layer is greater than or equal to 2, the doping concentration of the low-doped GaN layer is 1.5*10 17 cm -3 -8*10 18 cm -3 -5*10 18 cm -3 -5*10 19 cm -3 -9*10 19 cm -3 -9*10 22 cm -3 .

2. The light emitting diode epitaxial wafer of claim 1, wherein, The number of periods of the buffer layer is 2-100, and the thickness of the buffer layer is 500 nm-5000 nm.

3. The light emitting diode epitaxial wafer of claim 1, wherein, The thickness of the single AlGaN layer is 5 nm-20 nm, the thickness of the single polycrystalline GaN layer is 10 nm-30 nm, the thickness of the single HT-GaN layer is 0.1 μm-1 μm, and the thickness of the single low-doped GaN layer is 3 nm-20 nm.

4. The light emitting diode epitaxial wafer of claim 1, wherein, The Al component content in the AlGaN layer gradually decreases with the increase of the period.

5. The light emitting diode epitaxial wafer of claim 1, wherein, The Al component content in the AlGaN layer gradually decreases from 0.8 to 0.1 with the increase of the number of periods.

6. A method for producing a light emitting diode epitaxial wafer for producing a light emitting diode epitaxial wafer according to any one of claims 1 to 5, characterized in that It comprises: An epitaxial wafer is provided; An AlN layer, a buffer layer, a U-GaN layer, an N-GaN layer, a stress release layer, a multi-quantum well layer, an electron blocking layer and a P-GaN layer are sequentially grown on the epitaxial wafer; wherein the buffer layer is a periodic structure, each period includes an AlGaN layer, a polycrystalline GaN layer, an HT-GaN layer and a low-doped GaN layer which are sequentially stacked, the number of periods of the buffer layer is greater than or equal to 2, and the doping concentration of the low-doped GaN layer is 1.5*10 17 cm -3 -8*10 18 cm -3 .

7. The method of claim 6, wherein the epitaxial wafer is a light emitting diode epitaxial wafer. The growth temperature of the AlGaN layer is 750-900 ℃, and the growth pressure is 100-200 torr; The growth temperature of the polycrystalline GaN layer is 1030-1100 ℃, and the growth pressure is 450-550 torr; The growth temperature of the HT-GaN layer is 1120-1150 ℃, and the growth pressure is 150-200 torr; The growth temperature of the low-doped GaN layer is 1120-1150 ℃, and the growth pressure is 150-200 torr.

8. The method of claim 6, wherein the epitaxial wafer is a light emitting diode epitaxial wafer. The growth temperature of the AlGaN layer < the growth temperature of the polycrystalline GaN layer < the growth temperature of the HT-GaN layer < the growth temperature of the low-doped GaN layer.

9. A light emitting diode, comprising: It comprises the light-emitting diode epitaxial wafer according to any one of claims 1-4.

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