A high-light-efficiency LED epitaxial structure and preparation method thereof

Abstract

The present invention discloses a high-light-efficiency LED epitaxial structure and a preparation method thereof, and relates to the technical field of semiconductor devices. In the high-light-efficiency LED epitaxial structure, a multi-quantum well light-emitting layer includes a high-resistance multi-quantum well layer, a medium-resistance multi-quantum well layer, and a low-resistance multi-quantum well layer stacked in sequence; wherein the high-resistance multi-quantum well layer includes a first multi-quantum well InGaN layer and a first variable resistance value regulating barrier layer that are periodically alternately stacked, the medium-resistance multi-quantum well layer includes a second multi-quantum well InGaN layer and a second variable resistance value regulating barrier layer that are periodically alternately stacked, and the low-resistance multi-quantum well layer includes a third multi-quantum well InGaN layer and a third variable resistance value regulating barrier layer that are periodically alternately stacked. The high-light-efficiency LED epitaxial structure of the present invention can improve the hole injection efficiency of P-type semiconductor materials, improve the matching degree of electrons and holes in the multi-quantum well light-emitting layer, so as to improve the radiation recombination efficiency in the multi-quantum well layer, thereby improving the brightness and light efficiency of the LED device.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a high-light-efficiency LED epitaxial structure and a preparation method thereof. Background Art

[0002] Light Emitting Diode (LED) is a new type of energy-saving and environmentally friendly light source, which is widely used in indication, display, backlight and projection. At present, the most studied LED is GaN-based LED, which is an LED device using gallium nitride (GaN) as the epitaxial structure. Compared with LED devices made of other material systems, GaN-based LED has obvious advantages in luminous efficiency and reliability.

[0003] Although GaN-based LEDs currently have high luminous efficiency and reliability, there are still some areas that need to be improved. For the GaN material system, since electrons have higher mobility and smaller effective mass than holes, and electrons are easier to activate and have higher concentrations, the concentration of electrons injected into the active area will not match the concentration of holes, making the quantum wells close to the N-type semiconductor layer almost non-luminescent, while electrons can be easily injected into the active area, and even enter the P-type semiconductor layer, causing electron leakage. In addition, the electron blocking layer, which is the main functional layer of the light-emitting diode, not only blocks the injection of electrons into the P-type semiconductor layer, but may also block the injection of holes into the active area, resulting in a low effective hole concentration injected into the active area by the P-type material, further reducing the hole concentration in the active area, resulting in a more serious problem of mismatch between the electron concentration and the hole concentration in the active area, which seriously affects the luminous efficiency of the LED. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a high-light-efficiency LED epitaxial structure and a preparation method thereof, which can improve the hole injection efficiency of P-type semiconductor materials, improve the phenomenon of insufficient hole concentration in the multi-quantum well light-emitting layer, and improve the matching degree of electron concentration and hole concentration in the multi-quantum well light-emitting layer, so as to improve the radiation recombination efficiency in the multi-quantum well layer, thereby improving the brightness and light efficiency of the LED device.

[0005] In order to solve the above technical problems, the present invention provides a high-light-efficiency LED epitaxial structure, comprising a substrate, and a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, an electron blocking layer and a P-type semiconductor layer sequentially stacked on the substrate;

[0006] The multi-quantum well light-emitting layer comprises a high-resistance multi-quantum well layer, a medium-resistance multi-quantum well layer and a low-resistance multi-quantum well layer stacked in sequence;

[0007] The high-resistance multi-quantum well layer comprises a first multi-quantum well InGaN layer and a first variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the first variable resistance value regulating barrier layer comprises a first Si-doped GaN layer, a first AlGaN layer, a second Si-doped GaN layer, a second AlGaN layer and a third Si-doped GaN layer which are stacked in sequence;

[0008] The medium-resistance multi-quantum well layer includes a second multi-quantum well InGaN layer and a second variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the second variable resistance value regulating barrier layer includes a fourth Si-doped GaN layer, a third AlGaN layer, an undoped GaN layer, a fourth AlGaN layer and a fifth Si-doped GaN layer which are stacked in sequence;

[0009] The low-resistance multi-quantum well layer includes a third multi-quantum well InGaN layer and a third variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the third variable resistance value regulating barrier layer includes a sixth Si-doped GaN layer, a fifth AlGaN layer, a seventh Si-doped GaN layer, a sixth AlGaN layer and an eighth Si-doped GaN layer which are stacked in sequence;

[0010] The proportion of Al component in the first AlGaN layer>the proportion of Al component in the second AlGaN layer≥the proportion of Al component in the third AlGaN layer>the proportion of Al component in the fourth AlGaN layer≥the proportion of Al component in the fifth AlGaN layer>the proportion of Al component in the sixth AlGaN layer.

[0011] As an improvement of the above technical solution, the thickness of the second AlGaN layer ≥ the thickness of the fourth AlGaN layer ≥ the thickness of the sixth AlGaN layer;

[0012] The Si doping concentration of the second Si-doped GaN layer is greater than or equal to the Si doping concentration of the seventh Si-doped GaN layer.

[0013] As an improvement of the above technical solution, the thickness of the second AlGaN layer is greater than the thickness of the first AlGaN layer;

[0014] The thickness of the fourth AlGaN layer is greater than the thickness of the third AlGaN layer;

[0015] The thickness of the sixth AlGaN layer is greater than the thickness of the fifth AlGaN layer.

[0016] As an improvement of the above technical solution, the proportion of Al component in the first AlGaN layer is 0.09-0.39, and the proportion of Al component in the second AlGaN layer is 0.07-0.25;

[0017] The proportion of Al component in the third AlGaN layer is 0.07-0.25, and the proportion of Al component in the fourth AlGaN layer is 0.05-0.17;

[0018] The proportion of Al component in the fifth AlGaN layer is 0.05-0.17, and the proportion of Al component in the sixth AlGaN layer is 0.01-0.10.

[0019] As an improvement of the above technical solution, the thickness of the second AlGaN layer is 1 nm to 2.5 nm, the thickness of the fourth AlGaN layer is 0.8 nm to 2.2 nm, and the thickness of the sixth AlGaN layer is 0.5 nm to 1.8 nm;

[0020] The thickness of the first AlGaN layer, the third AlGaN layer and the fifth AlGaN layer are all 0.3 nm to 1 nm.

[0021] As an improvement of the above technical solution, the Si doping concentration of the second Si-doped GaN layer is 2.35×10 17 atoms / cm³~7.36×10 18 atoms / cm³;

[0022] The Si doping concentration of the seventh Si-doped GaN layer is 1.15×10 17 atoms / cm³~5.26×10 18 atoms / cm³.

[0023] As an improvement of the above technical solution, the thickness of the first Si-doped GaN layer, the third Si-doped GaN layer, the fourth Si-doped GaN layer, the fifth Si-doped GaN layer, the sixth Si-doped GaN layer and the eighth Si-doped GaN layer are all 0.5nm~5nm, and the Si doping concentration is 1.15×10 17 atoms / cm³~7.36×10 18 atoms / cm³;

[0024] The thickness of the second Si-doped GaN layer, the undoped GaN layer and the seventh Si-doped GaN layer are all 1 nm to 8 nm.

[0025] As an improvement of the above technical solution, the proportion of In component in the first multi-quantum well InGaN layer is 0.06-0.39, and the thickness is 2.18nm-4.75nm;

[0026] The proportion of In component in the second multi-quantum well InGaN layer is 0.06-0.39, and the thickness is 2.18nm-4.75nm;

[0027] The proportion of In component in the third multi-quantum well InGaN layer is 0.06-0.39, and the thickness is 2.18nm-4.75nm.

[0028] Accordingly, the present invention also provides a method for preparing a high-light-efficiency LED epitaxial structure, which is used to prepare the above-mentioned high-light-efficiency LED epitaxial structure, comprising the following steps:

[0029] (1) Select substrate;

[0030] (2) growing a buffer layer on the substrate;

[0031] (3) growing an N-type semiconductor layer on the buffer layer;

[0032] (4) growing a low-temperature stress release layer on the N-type semiconductor layer;

[0033] (5) growing a multi-quantum well light-emitting layer on the low-temperature stress release layer;

[0034] (6) growing an electron blocking layer on the multi-quantum well light-emitting layer;

[0035] (7) growing a P-type semiconductor layer on the electron blocking layer;

[0036] The multi-quantum well light-emitting layer comprises a high-resistance multi-quantum well layer, a medium-resistance multi-quantum well layer and a low-resistance multi-quantum well layer stacked in sequence;

[0037] The high-resistance multi-quantum well layer comprises a first multi-quantum well InGaN layer and a first variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the first variable resistance value regulating barrier layer comprises a first Si-doped GaN layer, a first AlGaN layer, a second Si-doped GaN layer, a second AlGaN layer and a third Si-doped GaN layer which are stacked in sequence;

[0038] The medium-resistance multi-quantum well layer includes a second multi-quantum well InGaN layer and a second variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the second variable resistance value regulating barrier layer includes a fourth Si-doped GaN layer, a third AlGaN layer, an undoped GaN layer, a fourth AlGaN layer and a fifth Si-doped GaN layer which are stacked in sequence;

[0039] The low-resistance multi-quantum well layer includes a third multi-quantum well InGaN layer and a third variable resistance value regulation barrier layer which are periodically and alternately stacked in sequence; the third variable resistance value regulation barrier layer includes a sixth Si-doped GaN layer, a fifth AlGaN layer, a seventh Si-doped GaN layer, a sixth AlGaN layer and an eighth Si-doped GaN layer which are stacked in sequence.

[0040] As an improvement of the above technical solution, the growth temperature of the third Si-doped GaN layer>the growth temperature of the second Si-doped GaN layer>the growth temperature of the first Si-doped GaN layer;

[0041] The growth temperature of the fifth Si-doped GaN layer>the growth temperature of the undoped GaN layer>the growth temperature of the fourth Si-doped GaN layer;

[0042] The growth temperature of the eighth Si-doped GaN layer is greater than the growth temperature of the seventh Si-doped GaN layer and greater than the growth temperature of the sixth Si-doped GaN layer.

[0043] As an improvement of the above technical solution, the growth temperatures of the first Si-doped GaN layer, the fourth Si-doped GaN layer and the sixth Si-doped GaN layer are all 815° C. to 928° C., and the growth pressures are all 50 torr to 360 torr;

[0044] The growth temperatures of the second Si-doped GaN layer, the undoped GaN layer and the seventh Si-doped GaN layer are all 825° C. to 938° C., and the growth pressures are all 50 torr to 360 torr;

[0045] The growth temperatures of the third Si-doped GaN layer, the fifth Si-doped GaN layer and the eighth Si-doped GaN layer are all 835° C. to 950° C., and the growth pressures are all 50 torr to 360 torr;

[0046] The growth temperatures of the first AlGaN layer, the second AlGaN layer, the third AlGaN layer, the fourth AlGaN layer, the fifth AlGaN layer and the sixth AlGaN layer are all 825° C. to 938° C., and the growth pressures are all 50 torr to 360 torr;

[0047] The growth temperatures of the first multi-quantum well InGaN layer, the second multi-quantum well InGaN layer and the third multi-quantum well InGaN layer are all 672° C. to 918° C., and the growth pressures are all 50 torr to 360 torr.

[0048] The implementation of the present invention has the following beneficial effects: by optimizing and designing the structure of the multi-quantum well light-emitting layer, and by regulating the proportion of the Al component in the AlGaN material in the first variable resistance value regulating barrier layer, the second variable resistance value regulating barrier layer and the third variable resistance value regulating barrier layer in the multi-quantum well light-emitting layer, the resistance value of the barrier layer in the multi-quantum well light-emitting layer and the current expansion performance of the semiconductor material are regulated, thereby achieving the purpose of improving the hole injection efficiency of the P-type semiconductor material and regulating the concentration distribution of electrons and holes in the multi-quantum well light-emitting layer, so as to improve the light efficiency of the LED device. The LED chip prepared by the high light-efficiency LED epitaxial structure of this embodiment can effectively improve the hole injection efficiency of the P-type semiconductor material, thereby increasing the hole concentration injected into the multi-quantum well light-emitting layer, improving the phenomenon of insufficient hole concentration in the multi-quantum well light-emitting layer, and improving the matching degree of the electron concentration and the hole concentration in the multi-quantum well light-emitting layer, so as to improve the radiation recombination efficiency of the multi-quantum well light-emitting layer, thereby improving the brightness and light efficiency of the LED device. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a schematic structural diagram of a high-light-efficiency LED epitaxial structure in Embodiment 1 of the present invention;

[0050] Figure 2 yes Figure 1 The schematic diagram of the structure of the multi-quantum well light-emitting layer in the high-efficiency LED epitaxial structure shown;

[0051] Figure 3 yes Figure 2 The enlarged view of S1 in the middle;

[0052] Figure 4 yes Figure 2 The enlarged view of S2 in the middle;

[0053] Figure 5 yes Figure 2 A magnified view of S3 in the middle;

[0054] Wherein: substrate 1, buffer layer 2, N-type semiconductor layer 3, low-temperature stress release layer 4, multi-quantum well light-emitting layer 5, electron blocking layer 6, P-type semiconductor layer 7, high-resistance multi-quantum well layer 51, medium-resistance multi-quantum well layer 52, low-resistance multi-quantum well layer 53, first multi-quantum well InGaN layer 511, first variable resistance value control barrier layer 512, second multi-quantum well InGaN layer 521, second variable resistance value control barrier layer 522, third multi-quantum well InGaN layer 531, third variable resistance value control barrier layer 532, first Si-doped GaN layer 5121, first AlGaN layer 5122, second Si-doped GaN layer 5123, second AlGaN layer 5124, third Si-doped GaN layer 5125, fourth Si-doped GaN layer 5221, third AlGaN layer 5222, undoped GaN layer 5223, fourth AlGaN layer 5224, fifth Si-doped GaN layer 5225, sixth Si-doped GaN layer 5321, fifth AlGaN layer 5322, seventh Si-doped GaN layer 5323, sixth AlGaN layer 5324, and eighth Si-doped GaN layer 5325. DETAILED DESCRIPTION

[0055] To make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0056] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. Raw materials used without specifying the manufacturer are all conventional products that can be obtained through commercial purchase.

[0057] like Figure 1 and Figure 2 As shown, a high-light-efficiency LED epitaxial structure includes a substrate 1, and a buffer layer 2, an N-type semiconductor layer 3, a low-temperature stress release layer 4, a multi-quantum well light-emitting layer 5, an electron blocking layer 6 and a P-type semiconductor layer 7 stacked in sequence on the substrate 1; in this embodiment and the illustration, the stacking direction is from bottom to top, and the same applies below.

[0058] The multi-quantum well light-emitting layer 5 comprises a high-resistance multi-quantum well layer 51, a medium-resistance multi-quantum well layer 52 and a low-resistance multi-quantum well layer 53 stacked in sequence;

[0059] The high-resistance multi-quantum well layer 51 includes a first multi-quantum well InGaN layer 511 and a first variable resistance value regulating barrier layer 512 which are periodically and alternately stacked in sequence; the first variable resistance value regulating barrier layer 512 includes a first Si-doped GaN layer 5121, a first AlGaN layer 5122, a second Si-doped GaN layer 5123, a second AlGaN layer 5124 and a third Si-doped GaN layer 5125 which are stacked in sequence;

[0060] The medium-resistance multi-quantum well layer 52 includes a second multi-quantum well InGaN layer 521 and a second variable resistance value regulating barrier layer 522 which are periodically and alternately stacked in sequence; the second variable resistance value regulating barrier layer 522 includes a fourth Si-doped GaN layer 5221, a third AlGaN layer 5222, an undoped GaN layer 5223, a fourth AlGaN layer 5224 and a fifth Si-doped GaN layer 5225 which are stacked in sequence;

[0061] The low-resistance multi-quantum well layer 53 includes a third multi-quantum well InGaN layer 531 and a third variable resistance value regulating barrier layer 532 which are periodically and alternately stacked in sequence; the third variable resistance value regulating barrier layer 532 includes a sixth Si-doped GaN layer 5321, a fifth AlGaN layer 5322, a seventh Si-doped GaN layer 5323, a sixth AlGaN layer 5324 and an eighth Si-doped GaN layer 5325 which are stacked in sequence;

[0062] The proportion of Al component in the first AlGaN layer 5122 is greater than the proportion of Al component in the second AlGaN layer 5124 ≥ the proportion of Al component in the third AlGaN layer 5222 > the proportion of Al component in the fourth AlGaN layer 5224 ≥ the proportion of Al component in the fifth AlGaN layer 5322 > the proportion of Al component in the sixth AlGaN layer 5324 .

[0063] Based on the above, the structure of the multi-quantum well light-emitting layer 5 is optimized and designed, and by adjusting the proportion of the Al component in the AlGaN material in the first variable resistance value regulating barrier layer 512, the second variable resistance value regulating barrier layer 522 and the third variable resistance value regulating barrier layer 532 in the multi-quantum well light-emitting layer 5, the resistance value of the barrier layer in the multi-quantum well light-emitting layer 5 and the current expansion performance of the semiconductor material are adjusted, thereby achieving the purpose of improving the hole injection efficiency of the P-type semiconductor material and adjusting the concentration distribution of electrons and holes in the multi-quantum well light-emitting layer 5, so as to improve the light efficiency of the LED device. The LED chip prepared by the high light-efficiency LED epitaxial structure of this embodiment can effectively improve the hole injection efficiency of the P-type semiconductor material, significantly improve the phenomenon of insufficient hole concentration in the multi-quantum well light-emitting layer 5, and improve the matching degree of electron concentration and hole concentration in the multi-quantum well light-emitting layer 5, so as to improve the radiation recombination efficiency of the multi-quantum well light-emitting layer 5, thereby improving the brightness and light efficiency of the LED device.

[0064] To further explain, by structurally optimizing and designing the barrier layers of the multi-quantum well light-emitting layer 5 (i.e., the first variable resistance value regulating barrier layer 512, the second variable resistance value regulating barrier layer 522, and the third variable resistance value regulating barrier layer 532), the first variable resistance value regulating barrier layer 512, the second variable resistance value regulating barrier layer 522, and the third variable resistance value regulating barrier layer 532 are all designed to have a structure including five sub-layers stacked in sequence. Among them, the first Si-doped GaN layer 5121, the second Si-doped GaN layer 5123, the third Si-doped GaN layer 5125, the fourth Si-doped GaN layer 5221, the fifth Si-doped GaN layer 5225, the sixth Si-doped GaN layer 5321, the seventh Si-doped GaN layer 5323 and the eighth Si-doped GaN layer 5325 are all doped with Si element, the undoped GaN layer 5223 is not doped with Si element, and the first AlGaN layer 5122, the second AlGaN layer 5124, the third AlGaN layer 5222, the fourth AlGaN layer 5224, the fifth AlGaN layer 5322 and the sixth AlGaN layer 5324 are not intentionally doped. The above structural improvement makes the barrier layer material designed as a low barrier + high barrier + low barrier + high barrier + low barrier and a multilayer structure of doped + non-doped + doped + non-doped + doped. The barrier layer of this structural design can significantly improve the current expansion performance of the semiconductor material in the multi-quantum well light-emitting layer 5, and improve the product's light uniformity, reliability, and yield rate. At the same time, the proportion of Al components in the AlGaN material in the multi-quantum well light-emitting layer 5 is set to: the proportion of Al components in the first AlGaN layer 5122> the proportion of Al components in the second AlGaN layer 5124≥ the proportion of Al components in the third AlGaN layer 5222> the proportion of Al components in the fourth AlGaN layer 5224≥ the proportion of Al components in the fifth AlGaN layer 5322> the proportion of Al components in the sixth AlGaN layer 5324, which can make the barrier height of the barrier layer of the multi-quantum well light-emitting layer 5 designed to decrease from bottom to top. In the barrier layer design of this structure, the low barrier near the P-type semiconductor layer 7 is made The low-resistance multi-quantum well layer 53 can reduce the blocking effect on hole injection into the P-type semiconductor layer 7, increase the hole concentration injected from the P-type semiconductor layer 7 to the multi-quantum well light-emitting layer, and allow the quantum wells close to the N-type semiconductor layer 3 to participate in the light emission, effectively improving the matching degree between the electron concentration and the hole concentration in the multi-quantum well light-emitting layer 5, thereby improving the brightness and light efficiency of the LED device. At the same time, the high-resistance multi-quantum well layer 51 with a high potential barrier in the multi-quantum well light-emitting layer 5 can bind electrons in front of the high-resistance multi-quantum well layer 51, thereby blocking electrons and reducing the electron movement rate, and can effectively prevent electrons from being injected into the P-type semiconductor layer 7 to cause electron leakage, thereby improving the performance of the LED device such as the yield rate.

[0065] Preferably, the number of periods of the periodic alternating stacking of the high-resistance multi-quantum well layer 51 is 2 to 5, exemplarily 2, 3, 4, 5, but not limited thereto; the number of periods of the periodic alternating stacking of the medium-resistance multi-quantum well layer 52 is 2 to 8, exemplarily 2, 3, 4, 5, 6, 7, 8, but not limited thereto; the number of periods of the periodic alternating stacking of the low-resistance multi-quantum well layer 53 is 2 to 5, exemplarily 2, 3, 4, 5, but not limited thereto.

[0066] Specifically, the first AlGaN layer 5122 , the second AlGaN layer 5124 , the third AlGaN layer 5222 , the fourth AlGaN layer 5224 , the fifth AlGaN layer 5322 , and the sixth AlGaN layer 5324 are all AlGaN materials that are not intentionally doped.

[0067] Specifically, the substrate 1 can be a sapphire substrate, a silicon carbide substrate or a silicon substrate; the buffer layer 2, the N-type semiconductor layer 3, the low-temperature stress release layer 4, the electron blocking layer 6 and the P-type semiconductor layer 7 are all grown using existing processes and raw materials, and are not further elaborated in this embodiment.

[0068] In one embodiment, the thickness of the second AlGaN layer 5124 is greater than or equal to the thickness of the fourth AlGaN layer 5224 and greater than or equal to the thickness of the sixth AlGaN layer 5324;

[0069] The Si doping concentration of the second Si-doped GaN layer 5123 is greater than or equal to the Si doping concentration of the seventh Si-doped GaN layer 5323 .

[0070] By further controlling the thickness relationship among the second AlGaN layer 5124, the fourth AlGaN layer 5224 and the sixth AlGaN layer 5324, and controlling the Si doping concentration of the second Si-doped GaN layer 5123 and the seventh Si-doped GaN layer 5323, the current spreading performance of the semiconductor material in the multi-quantum well light-emitting layer 5 can be further improved, and the hole concentration injected from the P-type semiconductor layer 7 into the multi-quantum well light-emitting layer can be further increased, so that the matching degree between electrons and holes in the multi-quantum well light-emitting layer 5 is higher, and the brightness and light efficiency of the LED device can be further improved.

[0071] In one embodiment, the thickness of the second AlGaN layer 5124 is greater than the thickness of the first AlGaN layer 5122;

[0072] The thickness of the fourth AlGaN layer 5224 is greater than the thickness of the third AlGaN layer 5222;

[0073] The thickness of the sixth AlGaN layer 5324 is greater than the thickness of the fifth AlGaN layer 5322 .

[0074] Based on the above-mentioned design of the thickness of the second AlGaN layer 5124, the first AlGaN layer 5122, the fourth AlGaN layer 5224, the third AlGaN layer 5222, the sixth AlGaN layer 5324 and the fifth AlGaN layer 5322, the hole concentration in the multi-quantum well light-emitting layer 5 can be further increased, and the matching degree of electrons and holes in the multi-quantum well light-emitting layer 5 can be further improved, thereby further improving the brightness and light efficiency of the LED device.

[0075] More preferably, the thickness of the first AlGaN layer 5122 = the thickness of the third AlGaN layer 5222 = the thickness of the fifth AlGaN layer 5322 .

[0076] In one embodiment, the proportion of Al component in the first AlGaN layer 5122 is 0.09-0.39, exemplarily 0.09, 0.10, 0.15, 0.18, 0.2, 0.23, 0.25, 0.29, 0.3, 0.35, 0.39, but not limited thereto; the proportion of Al component in the second AlGaN layer 5124 is 0.07-0.25, exemplarily 0.07, 0.08, 0.10, 0.12, 0.15, 0.18, 0.20, 0.22, 0.25, but not limited thereto;

[0077] The proportion of Al component in the third AlGaN layer 5222 is 0.07-0.25, exemplarily 0.07, 0.08, 0.10, 0.13, 0.15, 0.18, 0.20, 0.22, 0.25, but not limited thereto; the proportion of Al component in the fourth AlGaN layer 5224 is 0.05-0.17, exemplarily 0.05, 0.08, 0.10, 0.13, 0.15, 0.17, but not limited thereto;

[0078] The proportion of Al component in the fifth AlGaN layer 5322 is 0.05~0.17, and exemplarily is 0.05, 0.08, 0.10, 0.12, 0.15, and 0.17, but not limited to this; the proportion of Al component in the sixth AlGaN layer 5324 is 0.01~0.10, and exemplarily is 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.10, but not limited to this.

[0079] By further limiting the proportion of the Al component in the first AlGaN layer 5122, the second AlGaN layer 5124, the third AlGaN layer 5222, the fourth AlGaN layer 5224, the fifth AlGaN layer 5322 and the sixth AlGaN layer 5324 within the above range, and setting the proportion of the Al component of the AlGaN material in the multi-quantum well light-emitting layer 5 to: the first AlGaN layer 5122>the second AlGaN layer 5124≥the third AlGaN layer 5222>the fourth AlGaN layer 5224≥the fifth AlGaN layer 5322>the sixth AlGaN layer 5324, the matching degree of the electron concentration and the hole concentration in the multi-quantum well light-emitting layer 5 can be further improved, and the brightness and light efficiency of the LED device can be further improved.

[0080] In one embodiment, the thickness of the second AlGaN layer 5124 is 1 nm to 2.5 nm, exemplarily 1 nm, 1.3 nm, 1.5 nm, 1.8 nm, 2 nm, 2.3 nm, and 2.5 nm, but not limited thereto; the thickness of the fourth AlGaN layer 5224 is 0.8 nm to 2.2 nm, exemplarily 0.8 nm, 1.0 nm, 1.2 nm, 1.5 nm, 1.7 nm, 2.0 nm, and 2.2 nm, but not limited thereto; the thickness of the sixth AlGaN layer 5324 is 0.5 nm to 1.8 nm, exemplarily 0.5 nm, 0.7 nm, 1.0 nm, 1.2 nm, 1.5 nm, and 1.8 nm, but not limited thereto;

[0081] The thickness of the first AlGaN layer 5122 , the third AlGaN layer 5222 , and the fifth AlGaN layer 5322 are all 0.3 nm to 1 nm, exemplarily 0.3 nm, 0.5 nm, 0.8 nm, and 1 nm, but not limited thereto.

[0082] In one embodiment, the Si doping concentration of the second Si-doped GaN layer 5123 is 2.35×10 17 atoms / cm³~7.36×10 18 atoms / cm³, exemplarily 2.35×10 17 atoms / cm³、5.5×10 17 atoms / cm³、7.55×10 17 atoms / cm³、9.0×10 17 atoms / cm³、1.65×10 18 atoms / cm³、2.35×10 18 atoms / cm³、5.0×10 18 atoms / cm³、6.5×1018 atoms / cm³、7.36×10 18 atoms / cm³, but not limited to this;

[0083] The Si doping concentration of the seventh Si-doped GaN layer 5323 is 1.15×10 17 atoms / cm³~5.26×10 18 atoms / cm³, exemplarily 1.15×10 17 atoms / cm³、3.5×10 17 atoms / cm³、5.0×10 17 atoms / cm³、6.83×10 17 atoms / cm³、8.25×10 17 atoms / cm³、1.05×10 18 atoms / cm³、3.5×10 18 atoms / cm³、5.26×10 18 atoms / cm³, but not limited to this.

[0084] In one embodiment, the thickness of the first Si-doped GaN layer 5121, the fourth Si-doped GaN layer 5221, and the sixth Si-doped GaN layer 5321 are all 0.5 nm to 5 nm, and the Si doping concentration is 1.15×10 17 atoms / cm³~7.36×10 18 atoms / cm³; the thicknesses of the three are exemplarily 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, and 5nm, but are not limited thereto; the Si doping concentrations of the three are exemplarily 1.15×10 17 atoms / cm³、3.5×10 17 atoms / cm³、5.0×10 17 atoms / cm³、6.83×10 17 atoms / cm³、8.25×10 17 atoms / cm³、1.05×10 18 atoms / cm³、3.5×10 18 atoms / cm³、5.26×10 18 atoms / cm³、7.36×10 18 atoms / cm³, but not limited to this.

[0085] The thickness of the second Si-doped GaN layer 5123, the undoped GaN layer 5223 and the seventh Si-doped GaN layer 5323 are all 1 nm to 8 nm, exemplarily 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, and 8 nm, but not limited thereto;

[0086] The thickness of the third Si-doped GaN layer 5125, the fifth Si-doped GaN layer 5225 and the eighth Si-doped GaN layer 5325 are all 0.5 nm to 5 nm, and the Si doping concentration is 1.15×10 17 atoms / cm³~7.36×10 18 atoms / cm³. The thicknesses of the three are exemplarily 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, and 5nm, but are not limited thereto; the Si doping concentrations of the three are exemplarily 1.15×10 17 atoms / cm³、3.5×10 17 atoms / cm³、5.0×10 17 atoms / cm³、6.83×10 17 atoms / cm³、8.25×10 17 atoms / cm³、1.05×10 18 atoms / cm³、3.5×10 18 atoms / cm³、5.26×10 18 atoms / cm³、7.36×10 18 atoms / cm³, but not limited to this.

[0087] More preferably, the Si doping concentration of the first Si-doped GaN layer 5121 = the Si doping concentration of the fourth Si-doped GaN layer 5221 = the Si doping concentration of the sixth Si-doped GaN layer 5321; the Si doping concentration of the third Si-doped GaN layer 5125 = the Si doping concentration of the fifth Si-doped GaN layer 5225 = the Si doping concentration of the eighth Si-doped GaN layer 5325.

[0088] The first multi-quantum well InGaN layer 511 , the second multi-quantum well InGaN layer 521 , and the third multi-quantum well InGaN layer 531 are all InGaN single-layer or multi-layer structures that are not intentionally doped, and are made of InGaN materials. In one embodiment, the proportion of In component in the first multi-quantum well InGaN layer 511 is 0.06-0.39, and the thickness is 2.18nm-4.75nm; the proportion of In component in the first multi-quantum well InGaN layer 511 is exemplarily 0.06, 0.09, 0.1, 0.13, 0.15, 0.19, 0.2, 0.23, 0.05, 0.28, 0.3, 0.33, 0.36, 0.39, but not limited thereto; the thickness of the first multi-quantum well InGaN layer 511 is exemplarily 2.18nm, 2.5nm, 2.75nm, 3nm, 3.18nm, 3.5nm, 3.75nm, 4nm, 4.5nm, 4.75nm, but not limited thereto;

[0089] The proportion of In component in the second multi-quantum well InGaN layer 521 is 0.06-0.39, and the thickness is 2.18nm-4.75nm; the proportion of In component in the second multi-quantum well InGaN layer 521 is exemplarily 0.06, 0.09, 0.1, 0.13, 0.15, 0.19, 0.2, 0.23, 0.05, 0.28, 0.3, 0.33, 0.36, 0.39, but not limited thereto; the thickness of the second multi-quantum well InGaN layer 521 is exemplarily 2.18nm, 2.5nm, 2.75nm, 3nm, 3.18nm, 3.5nm, 3.75nm, 4nm, 4.5nm, 4.75nm, but not limited thereto;

[0090] The proportion of In component in the third multi-quantum well InGaN layer 531 is 0.06~0.39, and the thickness is 2.18nm~4.75nm. The proportion of In component in the third multi-quantum well InGaN layer 531 is exemplarily 0.06, 0.09, 0.1, 0.13, 0.15, 0.19, 0.2, 0.23, 0.05, 0.28, 0.3, 0.33, 0.36, and 0.39, but is not limited to this; the thickness of the third multi-quantum well InGaN layer 531 is exemplarily 2.18nm, 2.5nm, 2.75nm, 3nm, 3.18nm, 3.5nm, 3.75nm, 4nm, 4.5nm, and 4.75nm, but is not limited to this.

[0091] The present invention also discloses a method for preparing a high-light-efficiency LED epitaxial structure, which is used to prepare the above-mentioned high-light-efficiency LED epitaxial structure, comprising the following steps:

[0092] (1) Select substrate 1;

[0093] (2) growing a buffer layer 2 on the substrate 1;

[0094] (3) introducing a Si doping source to grow an N-type semiconductor layer 3 on the buffer layer 2;

[0095] (4) growing a low-temperature stress release layer 4 on the N-type semiconductor layer 3;

[0096] (5) growing a multi-quantum well light-emitting layer 5 on the low-temperature stress release layer 4;

[0097] (6) growing an electron blocking layer 6 on the multi-quantum well light-emitting layer 5;

[0098] (7) growing a P-type semiconductor layer 7 on the electron blocking layer 6;

[0099] The multi-quantum well light-emitting layer 5 comprises a high-resistance multi-quantum well layer 51, a medium-resistance multi-quantum well layer 52 and a low-resistance multi-quantum well layer 53 stacked in sequence;

[0100] The high-resistance multi-quantum well layer 51 includes a first multi-quantum well InGaN layer 511 and a first variable resistance value regulating barrier layer 512 which are periodically and alternately stacked in sequence; the first variable resistance value regulating barrier layer 512 includes a first Si-doped GaN layer 5121, a first AlGaN layer 5122, a second Si-doped GaN layer 5123, a second AlGaN layer 5124 and a third Si-doped GaN layer 5125 which are stacked in sequence;

[0101] The medium-resistance multi-quantum well layer 52 includes a second multi-quantum well InGaN layer 521 and a second variable resistance value regulating barrier layer 522 which are periodically and alternately stacked in sequence; the second variable resistance value regulating barrier layer 522 includes a fourth Si-doped GaN layer 5221, a third AlGaN layer 5222, an undoped GaN layer 5223, a fourth AlGaN layer 5224 and a fifth Si-doped GaN layer 5225 which are stacked in sequence;

[0102] The low-resistance multi-quantum well layer 53 includes a third multi-quantum well InGaN layer 531 and a third variable resistance value regulating barrier layer 532 which are periodically and alternately stacked in sequence; the third variable resistance value regulating barrier layer 532 includes a sixth Si-doped GaN layer 5321, a fifth AlGaN layer 5322, a seventh Si-doped GaN layer 5323, a sixth AlGaN layer 5324 and an eighth Si-doped GaN layer 5325 which are stacked in sequence.

[0103] In one embodiment, the growth temperature of the third Si-doped GaN layer 5125 is greater than the growth temperature of the second Si-doped GaN layer 5123 and greater than the growth temperature of the first Si-doped GaN layer 5121 ;

[0104] The growth temperature of the fifth Si-doped GaN layer 5225 is greater than the growth temperature of the undoped GaN layer 5223 and greater than the growth temperature of the fourth Si-doped GaN layer 5221;

[0105] The growth temperature of the eighth Si-doped GaN layer 5325 is greater than the growth temperature of the seventh Si-doped GaN layer 5323 and greater than the growth temperature of the sixth Si-doped GaN layer 5321 .

[0106] Based on the above improvement on the growth process, the growth temperature of the GaN material in the first variable resistance value regulating barrier layer 512, the second variable resistance value regulating barrier layer 522 and the third variable resistance value regulating barrier layer 532 is increased from bottom to top, so that the growth temperature of the first Si-doped GaN layer 5121, the fourth Si-doped GaN layer 5221 and the sixth Si-doped GaN layer 5321 close to the first multi-quantum well InGaN layer 511, the second multi-quantum well InGaN layer 521 and the third multi-quantum well InGaN layer 531 is lower, which can prevent the high temperature growth from damaging the multi-quantum well InGa N material quality; and the third Si-doped GaN layer 5125, the fifth Si-doped GaN layer 5225 and the eighth Si-doped GaN layer 5325 which are far away from the first multi-quantum well InGaN layer 511, the second multi-quantum well InGaN layer 521 and the third multi-quantum well InGaN layer 531 have a higher growth temperature, and adopt a high-temperature growth mode. Due to the higher mobility of atoms during high-temperature growth, it is more inclined to the growth of two-dimensional materials, which is beneficial to the merging of defects in semiconductor materials and the acquisition of high-quality epitaxial layer materials, which can further improve the brightness and yield rate of LED devices and other performance.

[0107] In one embodiment, the growth temperatures of the first Si-doped GaN layer 5121, the fourth Si-doped GaN layer 5221, and the sixth Si-doped GaN layer 5321 are all 815°C to 928°C, and the growth pressures are all 50 torr to 360 torr; the growth temperatures of the three are exemplarily 815°C, 835°C, 850°C, 865°C, 880°C, 900°C, 915°C, and 928°C, but are not limited thereto, and the growth temperatures of the first Si-doped GaN layer 5121, the fourth Si-doped GaN layer 5221, and the sixth Si-doped GaN layer 5321 may be the same or different; the first The growth pressure of the Si-doped GaN layer 5121, the fourth Si-doped GaN layer 5221 and the sixth Si-doped GaN layer 5321 is exemplarily 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 250 torr, 280 torr, 300 torr, 330 torr, and 360 torr, but is not limited thereto, and the growth pressure of the first Si-doped GaN layer 5121, the fourth Si-doped GaN layer 5221 and the sixth Si-doped GaN layer 5321 may be the same or different.

[0108] The growth temperatures of the second Si-doped GaN layer 5123, the undoped GaN layer 5223 and the seventh Si-doped GaN layer 5323 are all 825° C. to 938° C., and the growth pressures are all 50 torr to 360 torr; the growth temperatures of the three are exemplarily 825° C., 850° C., 865° C., 880° C., 895° C., 900° C., 928° C., and 938° C., but are not limited thereto, and the growth temperatures of the three may be the same or different; the growth pressures of the three are exemplarily 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 250 torr, 280 torr, 300 torr, 330 torr, and 360 torr, but are not limited thereto, and the growth pressures of the three may be the same or different;

[0109] The growth temperatures of the third Si-doped GaN layer 5125, the fifth Si-doped GaN layer 5225 and the eighth Si-doped GaN layer 5325 are all 835° C. to 950° C., and the growth pressures are all 50 torr to 360 torr; the growth temperatures of the three are exemplarily 835° C., 850° C., 865° C., 880° C., 900° C., 915° C., 935° C. and 950° C., but are not limited thereto, and the growth temperatures of the three may be the same or different; the growth pressures of the three are exemplarily 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 250 torr, 280 torr, 300 torr, 330 torr and 360 torr, but are not limited thereto, and the growth pressures of the three may be the same or different;

[0110] The growth temperatures of the first AlGaN layer 5122, the third AlGaN layer 5222, and the fifth AlGaN layer 5322 are all 825°C to 938°C, and the growth pressures are all 50 torr to 360 torr; the growth temperatures of the first AlGaN layer 5122, the third AlGaN layer 5222, and the fifth AlGaN layer 5322 are exemplarily 825°C, 850°C, 880°C, 895°C, 900°C, 928°C, and 938°C, but are not limited thereto, and the growth temperatures of the three are The growth pressures of the first AlGaN layer 5122, the third AlGaN layer 5222 and the fifth AlGaN layer 5322 are exemplarily 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 250 torr, 280 torr, 300 torr, 330 torr and 360 torr, but are not limited thereto, and the growth pressures of the three can be the same or different;

[0111] The growth temperatures of the second AlGaN layer 5124, the fourth AlGaN layer 5224 and the sixth AlGaN layer 5324 are all 825° C. to 938° C., and the growth pressures are all 50 torr to 360 torr. The growth temperatures of the second AlGaN layer 5124, the fourth AlGaN layer 5224 and the sixth AlGaN layer 5324 are exemplarily 825° C., 850° C., 880° C., 895° C., 900° C., 928° C., 938° C., but not limited thereto; the growth pressures of the second AlGaN layer 5124, the fourth AlGaN layer 5224, and the sixth AlGaN layer 5324 are exemplarily 50 torr, 100 torr, 120 torr, 150 torr, 180 torr, 200 torr, 220 torr, 250 torr, 280 torr, 300 torr, 330 torr, and 360 torr, but not limited thereto;

[0112] The growth temperatures of the first multi-quantum well InGaN layer 511 , the second multi-quantum well InGaN layer 521 , and the third multi-quantum well InGaN layer 531 are all 672° C. to 918° C., and the growth pressures are all 50 torr to 360 torr. The growth temperatures of the first multi-quantum well InGaN layer 511, the second multi-quantum well InGaN layer 521 and the third multi-quantum well InGaN layer 531 are exemplarily 672°C, 700°C, 730°C, 738°C, 750°C, 780°C, 800°C, 825°C, 850°C, 872°C, 900°C, and 918°C, but are not limited thereto; the growth pressures of the first multi-quantum well InGaN layer 511, the second multi-quantum well InGaN layer 521 and the third multi-quantum well InGaN layer 531 are exemplarily 50torr, 100torr, 120torr, 150torr, 180torr, 200torr, 220torr, 250torr, 280torr, 300torr, 330torr, and 360torr, but are not limited thereto.

[0113] The technical scheme of the present invention is further described below through examples and comparative examples.

[0114] Example 1

[0115] The high-light-efficiency LED epitaxial structure of this embodiment includes a substrate 1, and a buffer layer 2, an N-type semiconductor layer 3, a low-temperature stress release layer 4, a multi-quantum well light-emitting layer 5, an electron blocking layer 6 and a P-type semiconductor layer 7 stacked in sequence on the substrate 1;

[0116] The multi-quantum well light-emitting layer 5 comprises a high-resistance multi-quantum well layer 51, a medium-resistance multi-quantum well layer 52 and a low-resistance multi-quantum well layer 53 stacked in sequence;

[0117] The high resistance multi-quantum well layer 51 includes a first multi-quantum well InGaN layer 511 and a first variable resistance value regulating barrier layer 512 which are periodically and alternately stacked in sequence, and the number of periods is 4; the first variable resistance value regulating barrier layer 512 includes a first Si-doped GaN layer 5121, a first AlGaN layer 5122, a second Si-doped GaN layer 5123, a second AlGaN layer 5124 and a third Si-doped GaN layer 5125 which are stacked in sequence;

[0118] The medium resistance multi-quantum well layer 52 includes a second multi-quantum well InGaN layer 521 and a second variable resistance value regulating barrier layer 522 which are periodically and alternately stacked in sequence, and the number of periods is 6; the second variable resistance value regulating barrier layer 522 includes a fourth Si-doped GaN layer 5221, a third AlGaN layer 5222, an undoped GaN layer 5223, a fourth AlGaN layer 5224 and a fifth Si-doped GaN layer 5225 which are stacked in sequence;

[0119] The low-resistance multi-quantum well layer 53 includes a third multi-quantum well InGaN layer 531 and a third variable resistance value control barrier layer 532 which are periodically and alternately stacked in sequence, with a period number of 4; the third variable resistance value control barrier layer 532 includes a sixth Si-doped GaN layer 5321, a fifth AlGaN layer 5322, a seventh Si-doped GaN layer 5323, a sixth AlGaN layer 5324 and an eighth Si-doped GaN layer 5325 which are stacked in sequence.

[0120] The thickness of the first AlGaN layer 5122 is 0.3 nm, the Al component accounts for 0.15, the growth temperature is 825° C., and the growth pressure is 100 torr;

[0121] The thickness of the second AlGaN layer 5124 is 1 nm, the Al component ratio is 0.07, the growth temperature is 825° C., and the growth pressure is 100 torr;

[0122] The thickness of the third AlGaN layer 5222 is 0.3 nm, the Al component ratio is 0.07, the growth temperature is 825° C., and the growth pressure is 100 torr;

[0123] The thickness of the fourth AlGaN layer 5224 is 0.8 nm, the Al component ratio is 0.05, the growth temperature is 825° C., and the growth pressure is 100 torr;

[0124] The thickness of the fifth AlGaN layer 5322 is 0.3 nm, the Al component ratio is 0.05, the growth temperature is 825° C., and the growth pressure is 100 torr;

[0125] The thickness of the sixth AlGaN layer 5324 is 0.5 nm, the Al component ratio is 0.01, the growth temperature is 825° C., and the growth pressure is 100 torr;

[0126] The thickness of the first Si-doped GaN layer 5121, the fourth Si-doped GaN layer 5221, and the sixth Si-doped GaN layer 5321 are all 2 nm, and the Si doping concentration is 1.15×10 17 atoms / cm³, the growth temperature is 815℃, and the growth pressure is 150torr;

[0127] The thickness of the second Si-doped GaN layer 5123 is 3 nm, and the Si doping concentration is 2.35×10 17 atoms / cm³, growth temperature is 825℃, growth pressure is 150torr;

[0128] The thickness of the undoped GaN layer 5223 is 3 nm, the growth temperature is 825° C., and the growth pressure is 150 torr;

[0129] The thickness of the seventh Si-doped GaN layer 5323 is 3 nm, and the Si doping concentration is 1.15×10 17 atoms / cm³, growth temperature is 825℃, growth pressure is 150torr;

[0130] The thickness of the third Si-doped GaN layer 5125, the fifth Si-doped GaN layer 5225, and the eighth Si-doped GaN layer 5325 are all 2 nm, and the Si doping concentration is 1.15×10 17 atoms / cm³, the growth temperature is 835℃, and the growth pressure is 150torr;

[0131] The thickness of the first multi-quantum well InGaN layer 511 , the second multi-quantum well InGaN layer 521 , and the third multi-quantum well InGaN layer 531 are all 3 nm, the proportion of In component is all 0.19, the growth temperature is all 750° C., and the growth pressure is all 120 torr.

[0132] The method for preparing a high-light-efficiency LED epitaxial structure in this embodiment includes the following steps:

[0133] (1) Select substrate 1;

[0134] (2) growing a buffer layer 2 on the substrate 1;

[0135] (3) introducing a Si doping source to grow an N-type semiconductor layer 3 on the buffer layer 2;

[0136] (4) growing a low-temperature stress release layer 4 on the N-type semiconductor layer 3;

[0137] (5) growing a multi-quantum well light-emitting layer 5 on the low-temperature stress release layer 4;

[0138] (6) growing an electron blocking layer 6 on the multi-quantum well light-emitting layer 5;

[0139] (7) A P-type semiconductor layer 7 is grown on the electron blocking layer 6.

[0140] Example 2

[0141] The structural composition and preparation method of the high-light-efficiency LED epitaxial structure of this embodiment are basically the same as those of Embodiment 1, except that:

[0142] In this embodiment, the thickness of the first AlGaN layer 5122 is 0.5 nm, and the proportion of Al component is 0.3;

[0143] The thickness of the second AlGaN layer 5124 is 2 nm, and the proportion of Al component is 0.2;

[0144] The thickness of the third AlGaN layer 5222 is 0.5 nm, and the proportion of Al component is 0.2;

[0145] The thickness of the fourth AlGaN layer 5224 is 1.2 nm, and the proportion of Al component is 0.13;

[0146] The thickness of the fifth AlGaN layer 5322 is 0.5 nm, and the proportion of Al component is 0.12;

[0147] The thickness of the sixth AlGaN layer 5324 is 0.7 nm, and the proportion of Al component is 0.03.

[0148] Example 3

[0149] The structural composition and preparation method of the high-light-efficiency LED epitaxial structure of this embodiment are basically the same as those of Embodiment 1, except that:

[0150] In this embodiment, the growth temperature of the third Si-doped GaN layer 5125 is 880° C., the growth temperature of the second Si-doped GaN layer 5123 is 850° C., and the growth temperature of the first Si-doped GaN layer 5121 is 815° C.;

[0151] The growth temperature of the fifth Si-doped GaN layer 5225 is 880° C., the growth temperature of the undoped GaN layer 5223 is 850° C., and the growth temperature of the fourth Si-doped GaN layer 5221 is 835° C.;

[0152] The growth temperature of the eighth Si-doped GaN layer 5325 is 900°C, the growth temperature of the seventh Si-doped GaN layer 5323 is 865°C, and the growth temperature of the sixth Si-doped GaN layer 5321 is 835°C.

[0153] Example 4

[0154] The structural composition and preparation method of the high-light-efficiency LED epitaxial structure of this embodiment are basically the same as those of Embodiment 2, except that:

[0155] In this embodiment, the growth temperature of the third Si-doped GaN layer 5125 is 880° C., the growth temperature of the second Si-doped GaN layer 5123 is 850° C., and the growth temperature of the first Si-doped GaN layer 5121 is 815° C.;

[0156] The growth temperature of the fifth Si-doped GaN layer 5225 is 880° C., the growth temperature of the undoped GaN layer 5223 is 850° C., and the growth temperature of the fourth Si-doped GaN layer 5221 is 835° C.;

[0157] The growth temperature of the eighth Si-doped GaN layer 5325 is 900°C, the growth temperature of the seventh Si-doped GaN layer 5323 is 865°C, and the growth temperature of the sixth Si-doped GaN layer 5321 is 835°C.

[0158] Example 5

[0159] The structural composition and preparation method of the high-efficiency LED epitaxial structure of this embodiment are basically the same as those of Embodiment 4, except that: the Si doping concentration of the second Si-doped GaN layer 5123 of this embodiment is 9.0×10 17 atoms / cm³, and the Si doping concentration of the seventh Si-doped GaN layer 5323 is 5.0×10 17 atoms / cm³.

[0160] Comparative Example 1

[0161] The difference between the LED epitaxial structure of this comparative example and that of Example 1 is that the multi-quantum well light-emitting layer in the LED epitaxial structure of this comparative example is a traditional multi-quantum well light-emitting layer. Specifically, the multi-quantum well light-emitting layer of Comparative Example 1 includes periodically alternately stacked InGaN quantum well layers and GaN quantum barrier layers, with a period number of 9; wherein the thickness of the InGaN quantum well layer is 3nm, the proportion of In component is 0.19, the growth temperature is 750℃, and the growth pressure is 120torr; the thickness of the GaN quantum barrier layer is 9.6nm, and the Si doping concentration is 2.35×10 17 atoms / cm³, the growth temperature is 825℃, and the growth pressure is 150torr.

[0162] Comparative Example 2

[0163] The LED epitaxial structure of this comparative example is different from that of Example 1 in that: in Comparative Example 2, the thickness of the first AlGaN layer is 0.3 nm, and the proportion of the Al component is 0.07;

[0164] The thickness of the second AlGaN layer is 0.3nm, and the proportion of Al component is 0.07;

[0165] The thickness of the third AlGaN layer is 0.3nm, and the proportion of Al component is 0.07;

[0166] The thickness of the fourth AlGaN layer is 0.3 nm, and the proportion of Al component is 0.07;

[0167] The thickness of the fifth AlGaN layer is 0.3 nm, and the proportion of Al component is 0.07;

[0168] The thickness of the sixth AlGaN layer is 0.5 nm, and the proportion of Al component is 0.07.

[0169] Comparative Example 3

[0170] The LED epitaxial structure of this comparative example is different from that of Example 1 in that the second variable resistance value regulating barrier layer in Comparative Example 3 includes a fourth Si-doped GaN layer, a third AlGaN layer, a ninth Si-doped GaN layer, a fourth AlGaN layer and a fifth Si-doped GaN layer stacked in sequence; wherein the parameters of the fourth Si-doped GaN layer, the third AlGaN layer, the fourth AlGaN layer and the fifth Si-doped GaN layer are the same as those of Example 1, the thickness of the ninth Si-doped GaN layer is 3 nm, and the Si doping concentration is 1.15×10 17 atoms / cm³, the growth temperature is 825℃, and the growth pressure is 150torr; and the Si doping concentration of the second Si-doped GaN layer and the seventh Si-doped GaN layer in this comparative example is the same, both of which are 1.15×10 17 atoms / cm³.

[0171] Comparative Example 4

[0172] The LED epitaxial structure of this comparative example is different from that of Example 1 in that: the growth temperatures of the third Si-doped GaN layer, the second Si-doped GaN layer and the first Si-doped GaN layer in Comparative Example 4 are the same, all being 825°C;

[0173] The growth temperatures of the fifth Si-doped GaN layer, the undoped GaN layer and the fourth Si-doped GaN layer are the same, which is 825° C.;

[0174] The growth temperatures of the eighth Si-doped GaN layer, the seventh Si-doped GaN layer and the sixth Si-doped GaN layer are also the same, which is 825°C.

[0175] Performance Test:

[0176] The LED epitaxial structures obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were prepared into 20 mil×24 mil chips using the same chip process conditions, 300 LED chips were respectively extracted, the luminous efficiency was tested at an operating current of 120 mA, and the luminous efficiency improvement rate of Examples 1 to 5 and Comparative Examples 2 to 4 compared with Comparative Example 1 was calculated.

[0177] Specifically, the performance test results are shown in Table 1 below.

[0178] Table 1 Performance test results

[0179]

[0180] It can be seen from the above experimental data that the LED chip prepared by using the high-light-efficiency LED epitaxial structure of Examples 1 to 5 can effectively improve the hole injection efficiency of the P-type semiconductor material, significantly improve the phenomenon of insufficient hole concentration in the multi-quantum well light-emitting layer, and can improve the matching degree between the electron concentration and the hole concentration in the multi-quantum well light-emitting layer, so as to improve the radiation recombination efficiency of the multi-quantum well light-emitting layer, thereby improving the light efficiency of the LED device.

[0181] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A high-light-efficiency LED epitaxial structure, characterized in that: It comprises a substrate, and a buffer layer, an N-type semiconductor layer, a low-temperature stress release layer, a multi-quantum well light-emitting layer, an electron blocking layer and a P-type semiconductor layer stacked in sequence on the substrate; The multi-quantum well light-emitting layer comprises a high-resistance multi-quantum well layer, a medium-resistance multi-quantum well layer and a low-resistance multi-quantum well layer stacked in sequence; The high-resistance multi-quantum well layer comprises a first multi-quantum well InGaN layer and a first variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the first variable resistance value regulating barrier layer comprises a first Si-doped GaN layer, a first AlGaN layer, a second Si-doped GaN layer, a second AlGaN layer and a third Si-doped GaN layer which are stacked in sequence; The medium-resistance multi-quantum well layer includes a second multi-quantum well InGaN layer and a second variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the second variable resistance value regulating barrier layer includes a fourth Si-doped GaN layer, a third AlGaN layer, an undoped GaN layer, a fourth AlGaN layer and a fifth Si-doped GaN layer which are stacked in sequence; The low-resistance multi-quantum well layer includes a third multi-quantum well InGaN layer and a third variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the third variable resistance value regulating barrier layer includes a sixth Si-doped GaN layer, a fifth AlGaN layer, a seventh Si-doped GaN layer, a sixth AlGaN layer and an eighth Si-doped GaN layer which are stacked in sequence; The proportion of Al component in the first AlGaN layer>the proportion of Al component in the second AlGaN layer≥the proportion of Al component in the third AlGaN layer>the proportion of Al component in the fourth AlGaN layer≥the proportion of Al component in the fifth AlGaN layer>the proportion of Al component in the sixth AlGaN layer; The proportion of Al component in the first AlGaN layer is 0.09-0.39, and the proportion of Al component in the second AlGaN layer is 0.07-0.25; The proportion of Al component in the third AlGaN layer is 0.07-0.25, and the proportion of Al component in the fourth AlGaN layer is 0.05-0.17; The proportion of Al component in the fifth AlGaN layer is 0.05-0.17, and the proportion of Al component in the sixth AlGaN layer is 0.01-0.

10.

2. The high light efficiency LED epitaxial structure according to claim 1, characterized in that: The thickness of the second AlGaN layer is greater than or equal to the thickness of the fourth AlGaN layer and greater than or equal to the thickness of the sixth AlGaN layer; The Si doping concentration of the second Si-doped GaN layer is greater than or equal to the Si doping concentration of the seventh Si-doped GaN layer.

3. The high light efficiency LED epitaxial structure according to claim 2, characterized in that: The thickness of the second AlGaN layer is greater than the thickness of the first AlGaN layer; The thickness of the fourth AlGaN layer is greater than the thickness of the third AlGaN layer; The thickness of the sixth AlGaN layer is greater than the thickness of the fifth AlGaN layer.

4. The high light efficiency LED epitaxial structure according to claim 3, characterized in that: The thickness of the second AlGaN layer is 1 nm to 2.5 nm, the thickness of the fourth AlGaN layer is 0.8 nm to 2.2 nm, and the thickness of the sixth AlGaN layer is 0.5 nm to 1.8 nm; The thickness of the first AlGaN layer, the third AlGaN layer and the fifth AlGaN layer are all 0.3 nm to 1 nm.

5. The high light efficiency LED epitaxial structure according to claim 2, characterized in that: The Si doping concentration of the second Si-doped GaN layer is 2.35×10 17 atoms / cm³~7.36×10 18 atoms / cm³; The Si doping concentration of the seventh Si-doped GaN layer is 1.15×10 17 atoms / cm³~5.26×10 18 atoms / cm³.

6. The high light-efficiency LED epitaxial structure according to claim 1, characterized in that: The thickness of the first Si-doped GaN layer, the third Si-doped GaN layer, the fourth Si-doped GaN layer, the fifth Si-doped GaN layer, the sixth Si-doped GaN layer and the eighth Si-doped GaN layer are all 0.5 nm to 5 nm, and the Si doping concentration is 1.15×10 17 atoms / cm³~7.36×10 18 atoms / cm³; The thickness of the second Si-doped GaN layer, the undoped GaN layer and the seventh Si-doped GaN layer are all 1 nm to 8 nm.

7. The high light efficiency LED epitaxial structure according to claim 1, characterized in that: The first multi-quantum well InGaN layer has an In component ratio of 0.06-0.39 and a thickness of 2.18 nm-4.75 nm; The second multi-quantum well InGaN layer has an In component ratio of 0.06-0.39 and a thickness of 2.18 nm-4.75 nm; The proportion of In component in the third multi-quantum well InGaN layer is 0.06-0.39, and the thickness is 2.18nm-4.75nm.

8. A method for preparing a high-light-efficiency LED epitaxial structure, characterized in that: The method for preparing the high-light-efficiency LED epitaxial structure according to any one of claims 1 to 7 comprises the following steps: (1) Select substrate; (2) growing a buffer layer on the substrate; (3) growing an N-type semiconductor layer on the buffer layer; (4) growing a low-temperature stress release layer on the N-type semiconductor layer; (5) growing a multi-quantum well light-emitting layer on the low-temperature stress release layer; (6) growing an electron blocking layer on the multi-quantum well light-emitting layer; (7) growing a P-type semiconductor layer on the electron blocking layer; The multi-quantum well light-emitting layer comprises a high-resistance multi-quantum well layer, a medium-resistance multi-quantum well layer and a low-resistance multi-quantum well layer stacked in sequence; The high-resistance multi-quantum well layer comprises a first multi-quantum well InGaN layer and a first variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the first variable resistance value regulating barrier layer comprises a first Si-doped GaN layer, a first AlGaN layer, a second Si-doped GaN layer, a second AlGaN layer and a third Si-doped GaN layer which are stacked in sequence; The medium-resistance multi-quantum well layer includes a second multi-quantum well InGaN layer and a second variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the second variable resistance value regulating barrier layer includes a fourth Si-doped GaN layer, a third AlGaN layer, an undoped GaN layer, a fourth AlGaN layer and a fifth Si-doped GaN layer which are stacked in sequence; The low-resistance multi-quantum well layer includes a third multi-quantum well InGaN layer and a third variable resistance value regulating barrier layer which are periodically and alternately stacked in sequence; the third variable resistance value regulating barrier layer includes a sixth Si-doped GaN layer, a fifth AlGaN layer, a seventh Si-doped GaN layer, a sixth AlGaN layer and an eighth Si-doped GaN layer which are stacked in sequence; The growth temperature of the third Si-doped GaN layer>the growth temperature of the second Si-doped GaN layer>the growth temperature of the first Si-doped GaN layer; The growth temperature of the fifth Si-doped GaN layer>the growth temperature of the undoped GaN layer>the growth temperature of the fourth Si-doped GaN layer; The growth temperature of the eighth Si-doped GaN layer is greater than the growth temperature of the seventh Si-doped GaN layer and greater than the growth temperature of the sixth Si-doped GaN layer.

9. The method for preparing a high-light-efficiency LED epitaxial structure according to claim 8, characterized in that: The growth temperatures of the first Si-doped GaN layer, the fourth Si-doped GaN layer and the sixth Si-doped GaN layer are all 815° C. to 928° C., and the growth pressures are all 50 torr to 360 torr; The growth temperatures of the second Si-doped GaN layer, the undoped GaN layer and the seventh Si-doped GaN layer are all 825° C. to 938° C., and the growth pressures are all 50 torr to 360 torr; The growth temperatures of the third Si-doped GaN layer, the fifth Si-doped GaN layer and the eighth Si-doped GaN layer are all 835° C. to 950° C., and the growth pressures are all 50 torr to 360 torr; The growth temperatures of the first AlGaN layer, the second AlGaN layer, the third AlGaN layer, the fourth AlGaN layer, the fifth AlGaN layer and the sixth AlGaN layer are all 825° C. to 938° C., and the growth pressures are all 50 torr to 360 torr; The growth temperatures of the first multi-quantum well InGaN layer, the second multi-quantum well InGaN layer and the third multi-quantum well InGaN layer are all 672° C. to 918° C., and the growth pressures are all 50 torr to 360 torr.

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