GaN-based blue and green light-emitting diode epitaxial structure, its preparation method, and LED

Abstract

The present invention discloses a GaN-based blue / green light-emitting diode epitaxial structure, a preparation method thereof, and an LED, relating to the technical field of optoelectronic manufacturing. Among them, the preparation method of the blue / green light-emitting diode is as follows: a first AlGaN layer, a second AlGaN layer, an undoped GaN layer, a u-GaN layer, an n-GaN layer, a multi-quantum well layer, a low-temperature p-GaN layer, a p-AlGaN layer, a high-temperature p-GaN layer, and a p-GaN contact layer are sequentially grown on a substrate; finally, annealing treatment is carried out at 600-900 °C for 3-15 min to obtain the product. Among them, the growth temperature of the first AlGaN layer is 500-900 °C, the growth pressure is 100-600 Torr, and the V / III ratio is 50-1000; the growth temperature of the second AlGaN layer is 800-1000 °C, the growth pressure is 200-500 Torr, and the V / III ratio is 500-2500. Implementing the present invention can improve the antistatic strength and light-emitting intensity of the light-emitting diode.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic manufacturing technology, and particularly to a GaN-based blue / green light-emitting diode epitaxial structure, a preparation method thereof, and an LED. Background Art

[0002] In recent years, the research and application of GaN materials have developed rapidly, which is mainly related to the improvement of GaN growth process, P-type doping, and the successful realization of InGaN quantum wells.

[0003] Currently, the quality of grown GaN is poor and the dislocation density is high. The main reason is the lack of a suitable substrate with lattice matching. The fundamental solution to this problem depends on the successful preparation of large-area single crystals of group III nitrides. Currently, existing GaN single-crystal substrates are either too small in area and expensive, or have a relatively high dislocation density themselves. Therefore, currently, heteroepitaxial growth of GaN is only adopted. Some people have grown GaN on two different mismatch substrates, namely C-plane sapphire and R-plane sapphire, and the crystal quality has been significantly improved by improving the buffer layer. According to the successful experience of epitaxially growing GaAs on Si substrates, a suitable buffer layer is indeed extremely important in heteroepitaxial growth.

[0004] Traditional LED epitaxy uses low-temperature GaN or AlN as a buffer layer, and then raises the temperature to grow high-quality GaN. Using GaN or AlN as a buffer layer does play a good buffering role in the subsequent growth of GaN, effectively controlling the epitaxial dislocation density and effectively improving the crystal quality of GaN. However, it is very difficult to grasp the relationship between the high-temperature GaN layer and the buffer layer. When growing GaN at high temperature, the high temperature has an adverse effect on the GaN or AlN buffer layer. Especially when directly raising the temperature to grow GaN after growing the low-temperature GaN buffer layer on a PSS substrate, it is very difficult to obtain high-quality GaN and it is very difficult to control the surface morphology of GaN epitaxy. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method for a GaN-based blue / green light-emitting diode epitaxial structure, which can improve the anti-static performance and luminous intensity of the diode.

[0006] Another technical problem to be solved by the present invention is to provide a GaN-based blue / green light-emitting diode.

[0007] Another technical problem to be solved by the present invention is to provide a blue / green light-emitting LED.

[0008] To solve the above technical problems, the present invention provides a preparation method for a GaN-based blue / green light-emitting diode epitaxial structure, which includes:

[0009] (1) Providing a substrate;

[0010] (2) Grow a first AlGaN layer on the substrate; wherein, the growth temperature of the first AlGaN layer is 500 - 900 °C, the growth pressure is 100 - 600 Torr, the V / III ratio is 50 - 1000; its thickness is 10 - 300 nm;

[0011] (3) Grow a second AlGaN layer on the first AlGaN layer; wherein, the growth temperature of the second AlGaN layer is 800 - 1000 °C, the growth pressure is 200 - 500 Torr, the V / III ratio is 500 - 2500; its thickness is 10 - 300 nm;

[0012] (4) Grow an undoped GaN layer on the second AlGaN layer; wherein, the growth temperature of the undoped GaN layer is 900 - 1100 °C, the growth pressure is 200 - 500 Torr, the V / III ratio is 500 - 2500; its thickness is 0.5 - 1.5 μm;

[0013] (5) Grow a u-GaN layer on the undoped GaN layer;

[0014] (6) Grow an n-GaN layer on the u-GaN layer;

[0015] (7) Grow a multi-quantum well layer on the n-GaN layer;

[0016] (8) Grow a low-temperature p-GaN layer on the multi-quantum well layer;

[0017] (9) Grow a p-AlGaN layer on the low-temperature p-GaN layer;

[0018] (10) Grow a high-temperature p-GaN layer on the p-AlGaN layer;

[0019] (11) Grow a p-GaN contact layer on the high-temperature p-GaN layer;

[0020] (12) Anneal the substrate obtained in step (11) at 600 - 900 °C for 3 - 15 min to obtain the finished product of the GaN-based blue-green light-emitting diode epitaxial structure.

[0021] As an improvement of the above technical solution, in step (3), the growth temperature of the second AlGaN layer is uniformly increased, and the growth pressure is uniformly decreased.

[0022] As an improvement of the above technical solution, in step (3), the thickness of the AlGaN layer is 10 - 300 nm, the Al component is 2% - 5%, the AlGaN is a 2 - 10 period AlGaN / GaN superlattice structure, the thickness of the AlGaN is 5 - 10 nm, and the thickness of the GaN is 10 - 20 nm.

[0023] In step (5), the growth temperature of the u-GaN layer is 1100 - 1150 °C, the growth pressure is 200 - 500 Torr, and the V / III ratio is 500 - 2500;

[0024] In step (6), the growth temperature of the n-GaN layer is 1100 - 1150 °C, the growth pressure is 200 - 500 Torr, and the V / III ratio is 500 - 2500;

[0025] The total thickness of the u-GaN layer and the n-GaN layer is 3 - 5 μm.

[0026] As an improvement to the above technical solution, in step (7), the multi-quantum well layer includes a shallow well layer and an active layer. The shallow well layer includes 3 - 10 stacked In x Ga 1-x N well layers and GaN barrier layers; the active layer includes 6 - 20 stacked In y Ga 1-y N well layers and n-type doped GaN barrier layers; where x is 0 - 0.1 and y is 0.2 - 0.5;

[0027] Among them, the thickness of the In x Ga 1-x N well layer is 1 - 5 nm, and the thickness of the GaN barrier layer is 10 - 30 nm; the thickness of the In y Ga 1-y N well layer is 2 - 5 nm, and the thickness of the n-type doped GaN barrier layer is 5 - 15 nm.

[0028] As an improvement to the above technical solution, the growth temperature of the In x Ga 1-x N well layer is 850 - 950 °C, the growth pressure is 100 - 500 Torr, and the V / III ratio is 500 - 10000;

[0029] The growth temperature of the GaN barrier layer is 850 - 950 °C, the growth pressure is 100 - 500 Torr, and the V / III ratio is 500 - 10000;

[0030] The growth temperature of the In y Ga 1-y N well layer is 750 - 850 °C, the growth pressure is 100 - 500 Torr, and the V / III ratio is 2000 - 20000;

[0031] The growth temperature of the n-type doped GaN barrier layer is 850 - 950 °C, the growth pressure is 100 - 500 Torr, and the V / III ratio is 2000 - 20000.

[0032] As an improvement of the above technical solution, in step (8), the growth temperature of the low-temperature p-GaN layer is 650-800 °C, the growth pressure is 100-500 Torr, and the V / III ratio is 500-3500; the thickness of the low-temperature p-GaN layer is 30-120 nm;

[0033] In step (9), the growth temperature of the p-AlGaN layer is 900-1000 °C, the growth pressure is 50-300 Torr, the V / III ratio is 500-10000, the molar content of Al in the p-AlGaN layer is 5%-30%, and its thickness is 30-130 nm;

[0034] In step (10), the growth temperature of the high-temperature p-GaN layer is 900-1000 °C, the growth pressure is 100-500 Torr, and the V / III ratio is 500-3500; the thickness of the high-temperature p-GaN layer is 50-300 nm;

[0035] In step (11), the growth temperature of the p-GaN contact layer is 650-850 °C, the growth pressure is 100-500 Torr, and the V / III ratio is 10000-20000; the thickness of the p-GaN contact layer is 2-10 nm.

[0036] As an improvement of the above technical solution, step (1) includes:

[0037] (1.1) Provide a sapphire substrate;

[0038] (1.2) Grow a 10-20 nm AlN layer on the sapphire substrate;

[0039] (1.3) Treat the sapphire substrate obtained in step (1.2) in a hydrogen atmosphere or a nitrogen atmosphere at 1000-1200 °C for 1-5 min.

[0040] Implementing the present invention has the following beneficial effects:

[0041] The preparation method of the GaN-based blue-green light-emitting diode epitaxial structure of the present invention grows a second AlGaN layer on the substrate under different conditions, which effectively reduces the lattice mismatch between the substrate and the GaN epitaxial layer, effectively reduces the GaN epitaxial dislocation density, improves the surface morphology of the GaN epitaxial layer, thereby effectively improving the crystal quality of GaN and increasing the antistatic strength and the light-emitting intensity of the light-emitting diode. Detailed implementation manners

[0042] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below.

[0043] The present invention discloses a preparation method of a GaN-based blue-green light-emitting diode epitaxial structure, which comprises the following steps:

[0044] S1: Provide a substrate;

[0045] Specifically, S1 includes:

[0046] S11: Provide a sapphire substrate;

[0047] S12: Form an AlN layer with a thickness of 10-20 nm on the sapphire substrate;

[0048] S13: Treat the sapphire substrate obtained in step S12 in a hydrogen atmosphere at 100-1200 °C for 1-5 min.

[0049] S2: Grow a first AlGaN layer on the substrate;

[0050] Specifically, an aluminum source gas (including but not limited to trimethylaluminum), a gallium source gas (including but not limited to trimethylgallium), and a nitrogen source gas (including but not limited to ammonia) are introduced into an MOCVD device, and the first AlGaN layer is grown under the conditions of a temperature of 500-900 °C, a pressure of 100-600 Torr, and a V / III ratio of 50-1000. After growth is completed, the thickness of the first AlGaN layer is 10-300 nm.

[0051] S3: Grow a second AlGaN layer on the first AlGaN layer;

[0052] Specifically, an aluminum source gas (including but not limited to trimethylaluminum), a gallium source gas (including but not limited to trimethylgallium), and a nitrogen source gas (including but not limited to ammonia) are introduced into an MOCVD device, and the second AlGaN layer is grown under the conditions of a temperature of 800-1000 °C, a pressure of 200-500 Torr, and a V / III ratio of 500-2500. After growth is completed, the thickness of the second AlGaN layer is 10-300 nm.

[0053] The growth temperature of the second AlGaN layer increases uniformly, the growth pressure decreases uniformly, or the second AlGaN layer uses an AlGaN / GaN superlattice structure, which can more effectively reduce the lattice mismatch between the substrate and the subsequently grown GaN epitaxial layer, more effectively relieve the compressive stress generated during the growth of GaN, improve the surface morphology of the GaN epitaxial layer, enhance the crystal quality of the GaN epitaxial layer, thereby reducing the epitaxial defects in the light-emitting region, improving the antistatic strength of the light-emitting diode and the light-emitting intensity of the light-emitting diode.

[0054] Further, in an embodiment of the present invention, during the growth of the second AlGaN layer, the growth temperature increases uniformly and the growth pressure decreases uniformly. Specifically, the uniform increase may be a linear uniform increase, a non-linear uniform increase, or a gradient uniform increase, but is not limited thereto; the uniform decrease may be a linear uniform decrease, a non-linear uniform decrease, or a gradient uniform decrease, but is not limited thereto. By the above method, the GaN epitaxial dislocation density can be further reduced and the surface morphology of the GaN epitaxial layer can be improved. Specifically, the growth time of the second AlGaN layer is 200 - 500 s.

[0055] Further, in an embodiment of the present invention, the second AlGaN layer is a 2 - 10 period AlGaN / GaN superlattice structure, the Al component is 2% - 5%, the thickness of a single period of AlGaN is 5 - 10 nm, and the thickness of GaN is 10 - 20 nm. The structure of the low-temperature and high-pressure AlGaN / GaN superlattice can more effectively relieve the stress caused by the lattice mismatch between the substrate and GaN, effectively reduce the GaN dislocation density, and improve the GaN growth quality.

[0056] S4: Grow an undoped GaN layer on the second AlGaN layer;

[0057] Specifically, a nitrogen source gas (including but not limited to ammonia gas) is introduced into the MOCVD equipment, and the undoped GaN layer is grown under the conditions of a temperature of 900 - 1100 °C, a growth pressure of 200 - 500 Torr, and a V / III ratio of 500 - 2500. After growth, the thickness of the undoped GaN layer is 0.5 - 1.5 μm.

[0058] S5: Grow a u-GaN layer on the undoped GaN layer;

[0059] Specifically, a gallium source gas (including but not limited to trimethylgallium), a nitrogen source gas (including but not limited to ammonia gas), and a silicon source gas (including but not limited to silane) are introduced into the MOCVD equipment, and the u-GaN layer is grown under the conditions of a temperature of 1100 - 1150 °C, a growth pressure of 200 - 500 Torr, and a V / III ratio of 500 - 2500. After growth, the thickness of the u-GaN layer is 1 - 2 μm.

[0060] S6: Grow an n-GaN layer on the u-GaN layer;

[0061] Specifically, in an MOCVD device, a gallium source gas (including but not limited to trimethylgallium), a nitrogen source gas (including but not limited to ammonia), and a silicon source gas (including but not limited to silane) are introduced. The n-GaN layer is grown under the conditions of a temperature of 1100 - 1150 °C, a growth pressure of 200 - 500 Torr, and a V / III ratio of 500 - 2500. After growth is completed, the thickness of the n-GaN layer is 2 - 4 μm, and the total thickness of the u-GaN layer and the n-GaN layer is 3 - 5 μm.

[0062] S7: Grow a multi-quantum well layer on the n-GaN layer;

[0063] Among them, the multi-quantum well layer includes a shallow well layer and an active layer. The shallow well layer includes 3 - 10 sequentially stacked In x Ga 1-x N potential well layers and GaN barrier layers; the active layer includes 6 - 20 sequentially stacked InyGa1-yN potential well layers and n-type doped GaN barrier layers; where x is 0 - 0.1 and y is 0.2 - 0.5.

[0064] In x Ga 1-x The thickness of the N potential well layer is 1 - 5 nm, and the thickness of the GaN barrier layer is 10 - 30 nm; the thickness of the In y Ga 1-y N potential well layer is 2 - 5 nm, and the thickness of the n-type doped GaN barrier layer is 5 - 15 nm.

[0065] Specifically, S7 includes:

[0066] S71: Grow a shallow well layer on the n-GaN layer;

[0067] Specifically, in an MOCVD device, an indium source gas (including but not limited to trimethylindium), a gallium source gas (including but not limited to trimethylgallium), and a nitrogen source gas (including but not limited to ammonia) are introduced. The In x Ga 1-x N potential well layer is grown under the conditions of a temperature of 850 - 950 °C, a growth pressure of 100 - 500 Torr, and a V / III ratio of 500 - 10000. Then, only the gallium source gas and the nitrogen source gas are introduced, and the GaN barrier layer is grown under the conditions of a temperature of 850 - 950 °C, a growth pressure of 100 - 500 Torr, and a V / III ratio of 500 - 10000. The above steps are repeated sequentially until 3 - 10 stacked In x Ga 1-x N potential well layers and GaN barrier layers are formed, that is, the shallow well layer is obtained.

[0068] S72: Grow an active layer on the shallow well layer;

[0069] Specifically, indium source gas (including but not limited to trimethylindium), gallium source gas (including but not limited to trimethylgallium), and nitrogen source gas (including but not limited to ammonia) are introduced into the MOCVD equipment. Under the conditions of a temperature of 750 - 850 °C, a growth pressure of 100 - 500 Torr, and a V / III ratio of 2000 - 20000, In y Ga 1-y N potential well layer is grown. Then, silicon source gas (including but not limited to silane), gallium source gas, and nitrogen source gas are introduced. Under the conditions of a temperature of 850 - 950 °C, a growth pressure of 100 - 500 Torr, and a V / III ratio of 2000 - 20000, an n-type doped GaN barrier layer is grown. The above steps are repeated successively until 6 - 20 stacked In y Ga 1-y N potential well layers and n-type doped GaN barrier layers are formed, namely, the active layer is obtained.

[0070] S8: Grow a low-temperature p-GaN layer on the multi-quantum well layer;

[0071] Specifically, magnesium source gas (including but not limited to bis(cyclopentadienyl)magnesium), gallium source gas (including but not limited to trimethylgallium), and nitrogen source gas (including but not limited to ammonia) are introduced into the MOCVD equipment. Under the conditions of a temperature of 650 - 800 °C, a growth pressure of 100 - 500 Torr, and a V / III ratio of 500 - 3500, a low-temperature p-GaN layer is grown. After growth, the thickness of the low-temperature p-GaN layer is 30 - 120 nm.

[0072] S9: Grow a p-AlGaN layer on the low-temperature p-GaN layer;

[0073] Specifically, aluminum source gas (including but not limited to trimethylaluminum), magnesium source gas (including but not limited to bis(cyclopentadienyl)magnesium), gallium source gas (including but not limited to trimethylgallium), and nitrogen source gas (including but not limited to ammonia) are introduced into the MOCVD equipment. Under the conditions of a temperature of 900 - 1000 °C, a growth pressure of 50 - 300 Torr, and a V / III ratio of 500 - 10000, a p-AlGaN layer is grown. After growth, the thickness of the p-AlGaN layer is 30 - 120 nm. Further, control the molar content of Al in the p-AlGaN layer to be 5% - 30%.

[0074] S10: Grow a high-temperature p-GaN layer on the p-AlGaN layer;

[0075] Specifically, in an MOCVD device, a magnesium source gas (including but not limited to bis(cyclopentadienyl)magnesium), a gallium source gas (including but not limited to trimethylgallium), and a nitrogen source gas (including but not limited to ammonia) are introduced. A high-temperature p-GaN layer is grown under the conditions of a temperature of 900 - 1000 °C, a growth pressure of 100 - 500 Torr, and a V / III ratio of 500 - 3500. After growth, the thickness of the high-temperature p-GaN layer is 50 - 300 nm.

[0076] S11: Grow a p-GaN contact layer on the high-temperature p-GaN layer;

[0077] Specifically, in an MOCVD device, a magnesium source gas (including but not limited to bis(cyclopentadienyl)magnesium), a gallium source gas (including but not limited to trimethylgallium), and a nitrogen source gas (including but not limited to ammonia) are introduced. A p-GaN contact layer is grown under the conditions of a temperature of 650 - 850 °C, a growth pressure of 100 - 500 Torr, and a V / III ratio of 10000 - 20000. After growth, the thickness of the p-GaN contact layer is 2 - 10 nm.

[0078] S12: Anneal the substrate obtained in step S11 at 600 - 900 °C for 3 - 15 min to obtain a finished GaN-based blue / green light-emitting diode epitaxial structure.

[0079] The following further illustrates the present invention with specific examples:

[0080] Example 1

[0081] This example provides a method for preparing a GaN-based blue / green light-emitting diode epitaxial structure, which includes:

[0082] (1) Grow an AlN layer with a thickness of 17 nm on a sapphire substrate, then place it in an MOCVD machine and treat it at 1150 °C for 2 min;

[0083] (2) Grow a first AlGaN layer with a thickness of 25 nm under the conditions of 750 °C, 400 torr, and a V / III ratio of 250;

[0084] (3) Grow a second AlGaN layer with a thickness of 200 nm under the conditions of 950 °C, 500 torr, and a V / III ratio of 800;

[0085] (4) Grow an undoped GaN layer with a thickness of 1.5 μm under the conditions of 980 °C, 500 torr, and a V / III ratio of 800;

[0086] (5) Grow a u-GaN layer with a thickness of 1.5 μm under the conditions of 1150 °C, 300 torr, and a V / III ratio of 1000;

[0087] (6) Grow a 2.5-μm-thick n-GaN layer at 1150 °C, 300 torr, and a V / III ratio of 1000;

[0088] (7) Grow a 3.5-nm-thick In 0.05 Ga 0.95 N quantum well layer at 850 °C, 200 torr, and a V / III ratio of 2000, and then grow a 12-nm-thick GaN barrier layer at 850 °C, 200 torr, and a V / III ratio of 1000; Grow 15 cycles.

[0089] Then grow a 4-nm-thick In 0.2 Ga 0.8 N quantum well layer at 800 °C, 300 torr, and a V / III ratio of 10000, and then grow a 13-nm-thick n-type doped GaN barrier layer at 900 °C, 300 torr, and a V / III ratio of 10000; Grow 12 cycles.

[0090] (8) Grow a 50-nm-thick low-temperature p-GaN layer at 700 °C, 200 torr, and a V / III ratio of 800;

[0091] (9) Grow a 40-nm-thick p-AlGaN layer at 900 °C, 200 torr, and a V / III ratio of 800;

[0092] (10) Grow a 120-nm-thick high-temperature p-GaN layer at 950 °C, 300 torr, and a V / III ratio of 1200;

[0093] (11) Grow an 8-nm-thick p-GaN contact layer at 780 °C, 300 torr, and a V / III ratio of 15000;

[0094] (12) Anneal at 800 °C for 10 min to obtain.

[0095] Example 2

[0096] This example provides a method for preparing a GaN-based blue-green light-emitting diode epitaxial structure, which is different from Example 1 in that in step (3), when growing the second AlGaN layer, the temperature is uniformly increased from 900 °C to 950 °C, and the pressure is uniformly reduced from 500 torr to 300 torr; the rest are the same as in Example 1.

[0097] Example 3

[0098] This embodiment provides a method for preparing a GaN-based blue / green light-emitting diode epitaxial structure, which is different from that of Embodiment 2 in that in step (3), the second AlGaN layer is a 10-period AlGaN / GaN superlattice structure with an Al component of 5%, the thickness of a single-period AlGaN is 10 nm, and the thickness of GaN is 10 nm; the rest are the same as those in Embodiment 2.

[0099] Comparative Example 1

[0100] This comparative example provides a method for preparing a GaN-based blue / green light-emitting diode epitaxial structure, which is different from that of Embodiment 1 in that the second AlGaN layer is not grown, and the rest are the same as those in Embodiment 1.

[0101] Comparative Example 2

[0102] This comparative example provides a method for preparing a GaN-based blue / green light-emitting diode epitaxial structure, which is different from that of Embodiment 1 in that the first AlGaN layer and the second AlGaN layer are not grown, and a GaN buffer layer is grown. The specific growth conditions are as follows: 550 °C, 500 torr, V / III ratio of 300, and growth thickness of 35 nm; the rest are the same as those in Embodiment 1.

[0103] The blue / green light-emitting diode epitaxial structures obtained in Embodiments 1 to 3 and Comparative Examples 1 to 2 were tested. The specific method is as follows:

[0104] (1) The crystal quality of the epitaxial wafer is usually characterized by high-resolution X-ray diffraction analysis. The density of edge dislocations and mixed dislocations is represented by the full width at half maximum (FWHM) of the rocking curve of the (102) plane of the epitaxial wafer. The smaller the FWHM, the higher the crystal quality of the epitaxial wafer. We used XRD to test the samples and compared the sizes of the FWHMs.

[0105] (2) The epitaxial structures prepared in each embodiment and comparative example were fabricated into flip-chip LED chips according to the traditional method (refer to Document 201810417428.4), and then measured using existing equipment (CN202010143107.7). Specifically, the test temperature was 85 °C and the humidity was 90% RH; samples were taken out every 5 h and observed under a high-power microscope. If there was corrosion, the time of the previous measurement was taken as the maximum anti-hydrolysis duration; if there was no corrosion, the samples were put back into the equipment for continuous testing. The longer the anti-hydrolysis duration, the higher the crystal quality of the epitaxial layer.

[0106] The specific results are shown in the following table:

[0107] Test conditions Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 XRD FWHM 140 125 115 150 170 Maximum hydrolysis resistance duration (h) 310 335 350 290 270

[0108] As can be seen from the table, for the blue-green light-emitting diodes prepared by the preparation method of the present invention, their FWHM is significantly reduced, especially in Examples 2 and 3. At the same time, for the blue-green light-emitting diodes prepared by the preparation method of the present invention, their hydrolysis resistance is also significantly enhanced, indicating that the crystal quality of the experimental samples has been significantly improved. In Example 2, the growth temperature of the second AlGaN layer increased uniformly and the growth pressure decreased uniformly. In Example 3, the AlGaN / GaN superlattice structure was used for the second AlGaN layer, which effectively reduced the lattice mismatch between the substrate and the subsequently grown GaN epitaxial layer, more effectively relieved the compressive stress generated during the growth of GaN, improved the crystal quality of the GaN epitaxial layer, thereby reducing the epitaxial defects in the light-emitting region, and improving the electrostatic resistance and light-emitting intensity of the light-emitting diode.

[0109] The above is the preferred embodiment of the invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A method for preparing a GaN-based blue and green light-emitting diode epitaxial structure, characterized in that, Including: (1) Providing a substrate, which is a sapphire substrate; (2) Growing a first AlGaN layer on the substrate; wherein, the growth temperature of the first AlGaN layer is 500 - 900 °C, the growth pressure is 100 - 600 Torr, and the V / Ⅲ ratio is 50 - 1000; its thickness is 10 - 300 nm; (3) Growing a second AlGaN layer on the first AlGaN layer; wherein, the growth temperature of the second AlGaN layer is 800 - 1000 °C, the growth pressure is 200 - 500 Torr, and the V / Ⅲ ratio is 500 - 2500; its thickness is 10 - 300 nm; the second AlGaN layer is a 2 - 10 - period AlGaN / GaN superlattice structure, the thickness of AlGaN is 5 - 10 nm, the Al component is 2% - 5%, and the thickness of GaN is 10 - 20 nm; (4) Growing an undoped GaN layer on the second AlGaN layer; wherein, the growth temperature of the undoped GaN layer is 900 - 1100 °C, the growth pressure is 200 - 500 Torr, and the V / Ⅲ ratio is 500 - 2500; its thickness is 0.5 - 1.5 μm; (5) Growing a u - GaN layer on the undoped GaN layer; (6) Growing an n - GaN layer on the u - GaN layer; (7) Growing a multi - quantum well layer on the n - GaN layer; (8) Growing a low - temperature p - GaN layer on the multi - quantum well layer; (9) Growing a p - AlGaN layer on the low - temperature p - GaN layer; (10) Growing a high - temperature p - GaN layer on the p - AlGaN layer; (11) Growing a p - GaN contact layer on the high - temperature p - GaN layer; (12) Annealing the substrate obtained in step (11) at 600 - 900 °C for 3 - 15 min to obtain the finished GaN - based blue - green light - emitting diode epitaxial structure.

2. The method for preparing the GaN-based blue and green light emitting diode epitaxial structure according to claim 1, characterized in that, In step (5), the growth temperature of the u - GaN layer is 1100 - 1150 °C, the growth pressure is 200 - 500 Torr, and the Ⅴ / Ⅲ ratio is 500 - 2500; In step (6), the growth temperature of the n - GaN layer is 1100 - 1150 °C, the growth pressure is 200 - 500 Torr, and the Ⅴ / Ⅲ ratio is 500 - 2500; The total thickness of the u - GaN layer and the n - GaN layer is 3 - 5 μm.

3. The manufacturing method of the GaN-based blue / green light-emitting diode epitaxial structure according to claim 1, characterized in that, In step (7), the multiple quantum well layer includes a shallow well layer and an active layer. The shallow well layer includes 3 to 10 sequentially stacked In x Ga 1-x N well layers and GaN barrier layers; the active layer includes 6 to 20 sequentially stacked In y Ga 1-y N well layers and n-type doped GaN barrier layers; where x is 0 to 0.1 and y is 0.2 to 0.5; Among them, In x Ga 1-x The thickness of the In y Ga 1-y N well layer is 1 - 5 nm, and the thickness of the GaN barrier layer is 10 - 30 nm; the thickness of the In y Ga 1-y N well layer is 2 - 5 nm, and the thickness of the n-type doped GaN barrier layer is 5 - 15 nm.

4. The method for preparing the GaN-based blue / green light-emitting diode epitaxial structure according to claim 3, wherein, The In x Ga 1-x growth temperature of the N potential well layer is 850 - 950 °C, the growth pressure is 100 - 500 Torr, and the V / III ratio is 500 - 10,000; The growth temperature of the GaN barrier layer is 850 - 950 °C, the growth pressure is 100 - 500 Torr, and the Ⅴ / Ⅲ ratio is 500 - 10000; The described In y Ga 1-y The growth temperature of the N potential well layer is 750 - 850 °C, the growth pressure is 100 - 500 Torr, and the V / III ratio is 2000 - 20000; The growth temperature of the n - type doped GaN barrier layer is 850 - 950 °C, the growth pressure is 100 - 500 Torr, and the Ⅴ / Ⅲ ratio is 2000 - 20000.

5. The preparation method of the GaN-based blue and green light emitting diode epitaxial structure according to claim 1, characterized in that, In step (8), the growth temperature of the low - temperature p - GaN layer is 650 - 800 °C, the growth pressure is 100 - 500 Torr, and the Ⅴ / Ⅲ ratio is 500 - 3500; the thickness of the low - temperature p - GaN layer is 20 - 120 nm; In step (9), the growth temperature of the p-AlGaN layer is 900 - 1000 °C, the growth pressure is 50 - 300 Torr, the V / III ratio is 500 - 10000, the molar content of Al in the p-AlGaN layer is 5% - 30%, and its thickness is 20 - 130 nm; In step (10), the growth temperature of the high-temperature p-GaN layer is 900 - 1000 °C, the growth pressure is 100 - 500 Torr, and the V / III ratio is 500 - 3500; the thickness of the high-temperature p-GaN layer is 30 - 300 nm; In step (11), the growth temperature of the p-GaN contact layer is 650 - 850 °C, the growth pressure is 100 - 500 Torr, and the V / III ratio is 10000 - 20000; the thickness of the p-GaN contact layer is 2 - 10 nm.

6. The preparation method of the GaN-based blue / green light-emitting diode epitaxial structure according to claim 1, characterized in that Step (1) includes: (1.1) Providing a sapphire substrate; (1.2) Growing a 10 - 20 nm AlN layer on the sapphire substrate; (1.3) Treating the sapphire substrate obtained in step (1.2) in a hydrogen atmosphere or a nitrogen atmosphere at 1000 - 1200 °C for 1 - 5 min.

7. A GaN-based blue / green light-emitting diode, characterized in that, It is prepared by the method for preparing a GaN-based blue-green light-emitting diode epitaxial structure according to any one of claims 1 - 6.

8. A blue-green LED chip, characterized in that, It includes a GaN-based blue-green light-emitting diode according to claim 7.