High hole injection efficiency LED epitaxial structure and preparation method thereof

Abstract

The application relates to the technical field of semiconductors, in particular to a high-hole-injection-efficiency LED epitaxial structure, which comprises a substrate, wherein the substrate is provided with a buffer layer, an N-type semiconductor layer, a front-well electron blocking layer, a first multi-quantum-well light-emitting layer, a middle-well electron blocking layer, a second multi-quantum-well light-emitting layer, a rear-well electron blocking layer and a P-type semiconductor layer which are sequentially stacked along an epitaxial direction; the front-well electron blocking layer comprises a front-well AlGaN layer and a front-well InGaN layer which are periodically and alternately stacked along the epitaxial direction; the middle-well electron blocking layer comprises a middle-well AlGaN layer; and the rear-well electron blocking layer comprises a rear-well AlGaN layer and a rear-well InGaN layer which are periodically and alternately stacked along the epitaxial direction. The LED epitaxial structure prepared by the application has high hole injection efficiency and high active region carrier matching degree, thereby improving the light-emitting efficiency of the LED device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an LED epitaxial structure with high hole injection efficiency and its fabrication method. Background Technology

[0002] Light-emitting diodes (LEDs), as a new type of energy-saving and environmentally friendly light source, have received considerable attention in recent years, with many countries regarding LED-related semiconductor lighting as a strategic technology. Through extensive research and experimentation, semiconductor lighting technology has made rapid progress, truly realizing the commercialization of semiconductor lighting. Various types of LEDs are widely used in indication, display, backlighting, and projection fields. These achievements in semiconductor lighting are mainly attributed to advancements in GaN-based LED technology. Compared to other material systems, GaN-based LEDs have significant advantages in both efficiency and reliability.

[0003] For the AlGaInN material system, electrons have a higher mobility and lower effective mass compared to holes. Electrons are also easier to activate and have a higher concentration, leading to a severe mismatch between electron and hole concentrations injected into the active region. Quantum wells near the N-type semiconductor layer emit almost no light, while electrons can easily be injected into the active region and even into the P-type semiconductor layer, causing electron leakage. Furthermore, obtaining high-quality, high-hole-concentration P-type materials for LEDs is extremely difficult because the ionization rate of Mg in the AlGaInN system is low, resulting in generally low hole concentrations in P-type semiconductor materials. In addition, the electron blocking layer, as the main functional layer of the LED, not only blocks electron injection into the P-type layer for light emission but also blocks hole injection into the active region, further reducing the hole concentration and exacerbating the electron-hole concentration mismatch problem in the active region. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides an LED epitaxial structure with high hole injection efficiency and its preparation method. The prepared LED epitaxial structure has high hole injection efficiency and high active region carrier matching degree, thereby improving the luminous efficiency of LED devices.

[0005] To address the aforementioned issues, this invention proposes an LED epitaxial structure with high hole injection efficiency, comprising a substrate on which a buffer layer, an N-type semiconductor layer, a pre-well electron blocking layer, a first multiple quantum well light-emitting layer, a middle-well electron blocking layer, a second multiple quantum well light-emitting layer, a post-well electron blocking layer, and a P-type semiconductor layer are sequentially stacked along the epitaxial direction. The in-well electron blocking layer comprises an in-well AlGaN layer and an in-well InGaN layer that are periodically and alternately stacked along the epitaxial direction. The electron blocking layer in the well includes an AlGaN layer in the well; The back-well electron blocking layer comprises a back-well AlGaN layer and a back-well InGaN layer that are periodically and alternately stacked along the epitaxial direction.

[0006] As an improvement to the above technical solution, the in-well electron blocking layer includes an in-well AlGaN layer and an in-well InGaN layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6. The AlGaN layer in the well may be a single AlGaN layer or multiple AlGaN layers; The back-well electron blocking layer comprises back-well AlGaN layers and back-well InGaN layers that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6.

[0007] As an improvement to the above technical solution, the Si doping concentration of the AlGaN layer before the well is 2×10⁻⁶. 17 / cm 3 ~6×10 18 / cm 3 The Al component content is 0.2~0.8%, and the thickness is 0.2nm~3nm; The in-well InGaN layer is undoped, with an In content of 0.01~0.12 and a thickness of 0.2nm~3nm. The AlGaN layer in the well is undoped, with an Al content of 0.05~1 and a thickness of 0.5nm~6.8nm. The AlGaN layer behind the well is not doped, the Al content is 0.2~1, and the thickness is 0.2nm~3nm; The Mg doping concentration of the InGaN layer behind the well is 2 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 The In component content is 0.02~0.15, and the thickness is 0.2nm~3nm.

[0008] As an improvement to the above technical solution, the thickness ratio of the electron blocking layer before the well, the electron blocking layer in the well, and the electron blocking layer after the well is 1:(0.08~0.15):(0.8~1.2).

[0009] As an improvement to the above technical solution, the first multi-quantum-well light-emitting layer includes a first InGaN layer and a first GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8. The first InGaN layer is undoped, with an In content of 0.03~0.39 and a thickness of 2nm~5nm; The Si doping concentration of the first GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness is 6nm~16nm; The second quantum well light-emitting layer comprises a second InGaN layer and a second GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; The second InGaN layer is undoped, with an In content of 0.03~0.39 and a thickness of 1.8nm~4.8nm; The Si doping concentration of the second GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness is 5nm~15nm.

[0010] As an improvement to the above technical solution, the thickness of the first InGaN layer is greater than that of the second InGaN layer, and the thickness of the first GaN barrier layer is greater than that of the second GaN barrier layer.

[0011] As an improvement to the above technical solution, the ratio of the thickness of the first quantum well light-emitting layer to the thickness of the second quantum well light-emitting layer is 1:(0.4~0.7).

[0012] Accordingly, the present invention also provides a method for fabricating an LED epitaxial structure with high hole injection efficiency, comprising the following steps: Provide substrate; A buffer layer is deposited on the substrate; An N-type semiconductor layer is deposited on the buffer layer; Deposit a front-well electron blocking layer on the N-type semiconductor layer; A first multi-quantum well light-emitting layer is deposited on the electron blocking layer in front of the well; An electron blocking layer is deposited in the trap on the first multi-quantum-well light-emitting layer; A second multiple quantum well light-emitting layer is deposited on the electron blocking layer in the well; An electron blocking layer is deposited behind the trap on the second quantum well light-emitting layer; A P-type semiconductor layer is deposited on the electron blocking layer behind the well; The in-well electron blocking layer comprises an in-well AlGaN layer and an in-well InGaN layer that are periodically and alternately stacked along the epitaxial direction. The electron blocking layer in the well includes an AlGaN layer in the well; The back-well electron blocking layer comprises a back-well AlGaN layer and a back-well InGaN layer that are periodically and alternately stacked along the epitaxial direction.

[0013] As an improvement to the above technical solution, the in-well electron blocking layer includes an in-well AlGaN layer and an in-well InGaN layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6. The Si doping concentration of the AlGaN layer before the well is 2 × 10⁻⁶. 17 / cm 3 ~6×10 18 / cm 3 The Al content is 0.2~0.8%, the thickness is 0.2nm~3nm, the growth temperature is 750℃~1050℃, and the growth pressure is 30torr~360torr; The in-well InGaN layer is undoped, with an In content of 0.01~0.12, a thickness of 0.2nm~3nm, a growth temperature of 750℃~1050℃, and a growth pressure of 30torr~360torr. The AlGaN layer in the well may be a single AlGaN layer or multiple AlGaN layers; The AlGaN layer in the well is undoped, with an Al content of 0.05~1, a thickness of 0.5nm~6.8nm, a growth temperature of 750℃~980℃, and a growth pressure of 30torr~360torr. The back-well electron blocking layer comprises back-well AlGaN layers and back-well InGaN layers that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6. The AlGaN layer behind the well is not doped, the Al content is 0.2~1, the thickness is 0.2nm~3nm, the growth temperature is 750℃~1050℃, and the growth pressure is 30torr~360torr. The Mg doping concentration of the InGaN layer behind the well is 2 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 The In content is 0.02~0.15, the thickness is 0.2nm~3nm, the growth temperature is 750℃~1050℃, and the growth pressure is 30torr~360torr.

[0014] As an improvement to the above technical solution, the first multi-quantum-well light-emitting layer includes a first InGaN layer and a first GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8. The first InGaN layer is undoped, with an In content of 0.03~0.39, a thickness of 2nm~5nm, a growth temperature of 650℃~900℃, and a growth pressure of 30torr~360torr; The Si doping concentration of the first GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness is 6nm~16nm, the growth temperature is 750℃~980℃, and the growth pressure is 30torr~360torr; The second quantum well light-emitting layer comprises a second InGaN layer and a second GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; The second InGaN layer is undoped, with an In content of 0.03~0.39, a thickness of 1.8nm~4.8nm, a growth temperature of 650℃~900℃, and a growth pressure of 30torr~360torr; The Si doping concentration of the second GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness is 5nm~15nm, the growth temperature is 750℃~980℃, and the growth pressure is 30torr~360torr.

[0015] The implementation of this invention has the following beneficial effects: The LED epitaxial structure of this invention has multiple electron blocking layer structures, including a pre-well electron blocking layer disposed between the N-type semiconductor layer and the first multi-quantum-well light-emitting layer, a mid-well electron blocking layer disposed between the first multi-quantum-well light-emitting layer and the second multi-quantum-well light-emitting layer, and a post-well electron blocking layer disposed between the second multi-quantum-well light-emitting layer and the P-type semiconductor layer. These electron blocking layer structures can effectively prevent electron overflow from the active region and simultaneously reduce the blocking effect of the electron blocking layer material on hole injection from the P-type semiconductor layer to the multi-quantum-well light-emitting layer, thereby improving the hole injection efficiency of the P-type semiconductor layer material. This results in better electron-hole matching in the active region, thereby improving the luminous efficiency of the LED device. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an LED epitaxial structure with high hole injection efficiency according to an embodiment of the present invention; Figure 2 This is a schematic diagram of an embodiment of the electron blocking layer in front of the well according to the present invention; Figure 3 This is a schematic diagram of the first multi-quantum-well light-emitting layer according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the second multi-quantum-well light-emitting layer according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the electron blocking layer behind the trap according to an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0018] See Figure 1 , Figure 2 and Figure 5 As shown, this embodiment of the invention provides an LED epitaxial structure with high hole injection efficiency, including a substrate 100. The substrate 100 is provided with a buffer layer 200, an N-type semiconductor layer 300, a front-well electron blocking layer 400, a first multi-quantum-well light-emitting layer 500, a well-in-well electron blocking layer 600, a second multi-quantum-well light-emitting layer 700, a back-well electron blocking layer 800, and a P-type semiconductor layer 900, which are stacked sequentially along the epitaxial direction. The in-well electron blocking layer 400 includes an in-well AlGaN layer 410 and an in-well InGaN layer 420 that are periodically and alternately stacked along the epitaxial direction. The electron blocking layer 600 in the well includes an AlGaN layer in the well; The back-well electron blocking layer 800 includes a back-well AlGaN layer 810 and a back-well InGaN layer 820 that are periodically and alternately stacked along the epitaxial direction.

[0019] In this invention, the electron blocking layer is distributed between the N-type semiconductor layer 300, the first multi-quantum-well light-emitting layer 500, the second multi-quantum-well light-emitting layer 700, and the P-type semiconductor layer 900. This dispersed structure serves to block electrons from entering the active region while simultaneously reducing the obstruction effect of the electron blocking layer material on hole injection from the P-type semiconductor layer 900 into the multi-quantum-well light-emitting layer, thereby improving the hole injection efficiency of the P-type semiconductor layer 900. This improved hole injection efficiency and enhanced electron-hole matching in the active region ultimately increases the luminous efficiency of the LED device.

[0020] In some embodiments, the pre-well electron blocking layer 400 includes pre-well AlGaN layers 410 and pre-well InGaN layers 420 that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6; the period number can be 2, 3, 4, 5, or 6. The AlGaN layer 600 in the well includes a single AlGaN layer or multiple AlGaN layers; The back-well electron blocking layer 800 includes a back-well AlGaN layer 810 and a back-well InGaN layer 820 that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6; the period number can be 2, 3, 4, 5, or 6.

[0021] Preferably, the Si doping concentration of the AlGaN layer 410 before the well is 2 × 10⁻⁶. 17 / cm 3 ~6×10 18 / cm 3 The Al content is 0.2~0.8%, and the thickness is 0.2nm~3nm; the Si doping concentration can be 2×10⁻⁶. 17 / cm 3 5×10 17 / cm 3 8×10 17 / cm 3 1.2×10 18 / cm 3 3×10 18 / cm 3 3.5×10 18 / cm 3 4×10 18 / cm 3 5×10 18 / cm 3 6×10 18 / cm 3 However, it is not limited to these; the Al component content can be 0.2, 0.25, 0.29, 0.31, 0.38, 0.56, 0.63, 0.75, 0.8, but is not limited to these; the thickness can be 0.2nm, 1.2nm, 1.5nm, 1.7nm, 1.9nm, 2.3nm, 2.5nm, 3nm, but is not limited to these.

[0022] The in-well InGaN layer 420 is undoped, with an In content of 0.01~0.12 and a thickness of 0.2nm~3nm; the In content can be 0.01, 0.05, 0.07, 0.09, 0.11, 0.12, but is not limited to these; the thickness can be 0.2nm, 1.2nm, 1.5nm, 1.7nm, 1.9nm, 2.3nm, 2.5nm, 3nm, but is not limited to these.

[0023] The AlGaN layer 600 in the well is undoped, with an Al content of 0.05~1 and a thickness of 0.5nm~6.8nm. The Al content can be 0.05, 0.25, 0.29, 0.31, 0.38, 0.56, 0.63, 0.75, 0.8, 0.9, or 1, but is not limited to these values. The thickness can be 0.5nm, 1.2nm, 1.5nm, 3.7nm, 5.9nm, 6.3nm, 6.5nm, or 6.8nm, but is not limited to these values.

[0024] The AlGaN layer 810 behind the well is undoped, with an Al content of 0.2 to 1 and a thickness of 0.2 nm to 3 nm. The Al content can be 0.2, 0.29, 0.31, 0.38, 0.56, 0.63, 0.75, 0.8, 0.9, or 1, but is not limited to these values. The thickness can be 0.2 nm, 0.5 nm, 0.7 nm, 0.8 nm, 0.9 nm, or 1 nm, but is not limited to these values.

[0025] The Mg doping concentration of the InGaN layer 820 behind the well is 2 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 The In content is 0.02~0.15%, and the thickness is 0.2nm~3nm; the Mg doping concentration can be 2×10⁻⁶. 18 / cm 3 5×10 18 / cm 3 8×10 18 / cm 3 1.2×10 19 / cm 3 3×10 19 / cm 3 3.5×10 19 / cm 3 4×10 19 / cm 3 5×10 19 / cm 3 However, it is not limited to these; the In component content can be 0.02, 0.08, 0.09, 0.11, 0.13, 0.14, 0.15, but is not limited to these; the thickness can be 0.2nm, 1.2nm, 1.5nm, 2.7nm, 2.9nm, 3nm, but is not limited to these.

[0026] The pre-well electron blocking layer 410 initially regulates and blocks electrons injected from the N-type semiconductor layer 300, preventing them from entering the active region prematurely or excessively, thus buffering strain and improving the quality of the subsequent quantum well crystal. The in-well electron blocking layer 600 forms a significant electron barrier between the first multi-quantum-well light-emitting layer 500 and the second multi-quantum-well light-emitting layer 700, preventing unrecombined electrons in the first multi-quantum-well light-emitting layer 500 from diffusing further to the second multi-quantum-well light-emitting layer 700 or the P-type semiconductor layer 900. It confines unrecombined electrons in the first multi-quantum-well light-emitting layer 500, promoting electron-hole recombination in this region. The post-well electron blocking layer prevents electrons from leaking from the active region to the P-type semiconductor layer 900, while simultaneously reducing the obstruction to holes injected from the P-type semiconductor layer 900.

[0027] More preferably, the thickness ratio of the pre-well electron blocking layer 400, the in-well electron blocking layer 600, and the post-well electron blocking layer 800 is 1:(0.08~0.15):(0.8~1.2). The thickness ratio can be 1:0.08:0.8, 1:0.1:1, 1:0.12, or 1.2, but is not limited to these.

[0028] Because the electron-in-the-well (I-I) barrier layer 600 uses a high Al composition, its conduction band barrier height is dominated by the Al composition rather than its thickness, thus achieving an effective electron barrier even with an ultra-thin design. Located between the first and second quantum well light-emitting layers 500 and 700, the ultra-thin design of the I-I 600 prevents electrons from penetrating the barrier through quantum tunneling, confining unrecombined electrons to the first quantum well light-emitting layer 500. Furthermore, the accumulation of polarization charge due to lattice mismatch in the thin I-I 600 layer prevents electron leakage caused by band bending.

[0029] In some embodiments, see Figure 3 and Figure 4 As shown, the first multi-quantum well light-emitting layer 500 includes a first InGaN layer 510 and a first GaN barrier layer 520 that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; the period number can be 2, 3, 4, 5, 6, 7, or 8. The first InGaN layer 510 is undoped, with an In content of 0.03~0.39 and a thickness of 2nm~5nm; the In content can be 0.03, 0.08, 0.11, 0.17, 0.19, 0.23, 0.25, 0.29, 0.33, 0.37, 0.39, but is not limited to these; the thickness can be 2nm, 2.7nm, 3.6nm, 4.8nm, 5nm, but is not limited to these. The Si doping concentration of the first GaN barrier layer 520 is 1.5 × 10⁻⁶. 17 / cm 3~8.6×10 17 / cm 3 The thickness ranges from 6 nm to 16 nm; the Si doping concentration can be 1.5 × 10⁻⁶. 17 / cm 3 2.5×10 17 / cm 3 3.3×10 17 / cm 3 4.6×10 17 / cm 3 4.9×10 17 / cm 3 5.1×10 17 / cm 3 5.7×10 17 / cm 3 6.8×10 17 / cm 3 7.3×10 17 / cm 3 7.9×10 17 / cm 3 8.6×10 17 / cm 3 However, it is not limited to these; the thickness can be 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 13nm, 15nm, 16nm, but is not limited to these. The second multi-quantum-well light-emitting layer 700 includes a second InGaN layer 710 and a second GaN barrier layer 720 that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; the period number can be 2, 3, 4, 5, 6, 7, 8, or 9. The second InGaN layer 710 is undoped, with an In content of 0.03~0.39 and a thickness of 1.8nm~4.8nm; the In content can be 0.03, 0.08, 0.11, 0.17, 0.19, 0.23, 0.25, 0.29, 0.33, 0.37, 0.39, but is not limited to these; the thickness can be 1.8nm, 2.7nm, 3.6nm, 4.8nm, but is not limited to these. The Si doping concentration of the second GaN barrier layer 720 is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness ranges from 5 nm to 15 nm. The Si doping concentration can be 1.5 × 10⁻⁶. 17 / cm 3 2.5×10 17 / cm 3 3.3×10 17 / cm 3 4.6×10 17 / cm 3 4.9×10 17 / cm 3 5.1×10 17 / cm 3 5.7×10 17 / cm 3 6.8×10 17 / cm 3 7.3×10 17 / cm 3 7.9×10 17 / cm 3 8.6×10 17 / cm 3 However, it is not limited to these; the thickness can be 5nm, 7nm, 8nm, 9nm, 10nm, 11nm, 13nm, 15nm, but is not limited to these.

[0030] Preferably, the thickness of the first InGaN layer 510 is greater than that of the second InGaN layer 710, and the thickness of the first GaN barrier layer 520 is greater than that of the second GaN barrier layer 720.

[0031] The thickness of the first multi-quantum well light-emitting layer 500 is greater than that of the second multi-quantum well light-emitting layer 700. The asymmetric well thickness design structure can effectively increase the depth of hole injection from the P-type semiconductor layer 900 into the multi-quantum well light-emitting layer, allowing the quantum wells near the N-type semiconductor layer 300 to also participate in light emission, thereby improving the matching degree of electrons and holes in the active region and improving the luminous efficiency of the LED device.

[0032] Specifically, thickening the first InGaN layer 510 increases the carrier holding capacity of the first multi-quantum well light-emitting layer 500 near the N-type semiconductor layer 300, allowing more electrons to remain in the first multi-quantum well light-emitting layer 500 and reducing leakage to the P-region. Thinning the second InGaN layer 710 lowers the hole injection barrier near the P-type semiconductor layer 900, making it easier for holes to penetrate into the deep well layer. Thickening the first GaN barrier layer 520 forms a high barrier to prevent electron backflow, confining electrons to the first multi-quantum well light-emitting layer 500. Thinning the second GaN barrier layer 720 reduces hole transport resistance, promoting hole migration to the first multi-quantum well light-emitting layer 500.

[0033] Optimal, the thickness ratio of the first multi-quantum-well emitting layer 500 to the thickness of the second multi-quantum-well emitting layer 700 is 1:(0.4~0.7). The thickness ratio can be 1:0.4, 1:0.5, 1:0.6, or 1:0.7, but is not limited to these. When the thickness ratio is less than 0.4, carrier localization fails, electron leakage rate increases, crystal quality degrades, and non-radiative recombination centers increase. When the thickness ratio is greater than 0.7, the second multi-quantum-well emitting layer 700 is too thick, hole injection is blocked, the thick barrier layer increases the hole transport barrier height, hole migration paths are obstructed, the hole concentration in the first multi-quantum-well emitting layer 500 is insufficient, and the luminescence intensity decreases.

[0034] Accordingly, the present invention also provides a method for fabricating an LED epitaxial structure with high hole injection efficiency, comprising the following steps: Provide substrate; Preferably, the substrate can be a sapphire substrate, a SiO2 sapphire composite substrate, a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, or a zinc oxide substrate, but is not limited thereto; more preferably, it is a sapphire substrate, as sapphire is currently the most commonly used GaN-based LED substrate material. Sapphire substrates have mature manufacturing processes, low prices, are easy to clean and process, and have good stability at high temperatures.

[0035] A buffer layer is deposited on the substrate; Preferably, the buffer layer is an AlN buffer layer. The AlN buffer layer provides nucleation centers with the same orientation as the substrate, releasing the stress caused by the lattice mismatch between GaN and the substrate, as well as the thermal stress caused by the mismatch of thermal expansion coefficients. This provides a flat nucleation surface for further growth, reduces the contact angle of nucleation growth, and enables the island-grown GaN grains to connect into a surface within a smaller thickness, transforming into two-dimensional epitaxial growth.

[0036] Furthermore, the buffer layer is grown using PVD, and the thickness of the buffer layer is 10nm~50nm. Specifically, it can be deposited using an AMEC A7 MOCVD (Metal Organic Chemical Vapor Deposition) system.

[0037] An N-type semiconductor layer is deposited on the buffer layer; The device was placed in an environment of 1050℃~1200℃, and the growth pressure was controlled at 100 torr~600 torr. NH3, TMGa and SiH4 were introduced to generate an N-type GaN layer with a thickness of 2μm~3μm and a Si doping concentration of 1×10⁻⁶. 19 atoms / cm 3 ~5×10 19 atoms / cm 3.

[0038] Deposit a front-well electron blocking layer on the N-type semiconductor layer; A first multi-quantum well light-emitting layer is deposited on the electron blocking layer in front of the well; An electron blocking layer is deposited in the trap on the first multi-quantum-well light-emitting layer; A second multiple quantum well light-emitting layer is deposited on the electron blocking layer in the well; An electron blocking layer is deposited behind the trap on the second quantum well light-emitting layer; A P-type semiconductor layer is deposited on the electron blocking layer behind the well; The in-well electron blocking layer comprises an in-well AlGaN layer and an in-well InGaN layer that are periodically and alternately stacked along the epitaxial direction. The electron blocking layer in the well includes an AlGaN layer in the well; The back-well electron blocking layer comprises a back-well AlGaN layer and a back-well InGaN layer that are periodically and alternately stacked along the epitaxial direction.

[0039] Preferably, the electron blocking layer in front of the well comprises a pre-well AlGaN layer and a pre-well InGaN layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6. The Si doping concentration of the AlGaN layer before the well is 2 × 10⁻⁶. 17 / cm 3 ~6×10 18 / cm 3 The Al content is 0.2~0.8%, the thickness is 0.2nm~3nm, the growth temperature is 750℃~1050℃, and the growth pressure is 30torr~360torr. The growth temperature can be 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, but is not limited to these. The growth pressure can be 30torr, 70torr, 100torr, 220torr, 250torr, 300torr, 330torr, 360torr, but is not limited to these. The in-well InGaN layer is undoped, with an In content of 0.01~0.12, a thickness of 0.2nm~3nm, a growth temperature of 750℃~1050℃, and a growth pressure of 30 torr~360 torr. The growth temperature can be 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, or 1050℃, but is not limited to these. The growth pressure can be 30 torr, 70 torr, 100 torr, 220 torr, 250 torr, 300 torr, 330 torr, or 360 torr, but is not limited to these. The AlGaN layer in the well may be a single AlGaN layer or multiple AlGaN layers; The AlGaN layer in the well is undoped, with an Al content of 0.05-1, a thickness of 0.5 nm-6.8 nm, a growth temperature of 750℃-980℃, and a growth pressure of 30 torr-360 torr. The growth temperature can be 750℃, 800℃, 850℃, 900℃, 950℃, or 980℃, but is not limited to these values. The growth pressure can be 30 torr, 70 torr, 100 torr, 220 torr, 250 torr, 300 torr, 330 torr, or 360 torr, but is not limited to these values. The back-well electron blocking layer comprises back-well AlGaN layers and back-well InGaN layers that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6. The AlGaN layer after the well is undoped, with an Al content of 0.2-1, a thickness of 0.2 nm-3 nm, a growth temperature of 750℃-1050℃, and a growth pressure of 30 torr-360 torr. The growth temperature can be 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, or 1050℃, but is not limited to these. The growth pressure can be 30 torr, 70 torr, 100 torr, 220 torr, 250 torr, 300 torr, 330 torr, or 360 torr, but is not limited to these. The Mg doping concentration of the InGaN layer behind the well is 2 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 The In content is 0.02~0.15, the thickness is 0.2nm~3nm, the growth temperature is 750℃~1050℃, and the growth pressure is 30torr~360torr. The growth temperature can be 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, but is not limited to these. The growth pressure can be 30torr, 70torr, 100torr, 220torr, 250torr, 300torr, 330torr, 360torr, but is not limited to these.

[0040] Preferably, the first multi-quantum-well light-emitting layer comprises a first InGaN layer and a first GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; The first InGaN layer is undoped, with an In content of 0.03~0.39, a thickness of 2nm~5nm, a growth temperature of 650℃~900℃, and a growth pressure of 30 torr~360 torr. The growth temperature can be 650℃, 700℃, 750℃, 800℃, 850℃, or 900℃, but is not limited to these. The growth pressure can be 30 torr, 70 torr, 100 torr, 220 torr, 250 torr, 300 torr, 330 torr, or 360 torr, but is not limited to these. The Si doping concentration of the first GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness is 6nm~16nm, the growth temperature is 750℃~980℃, and the growth pressure is 30torr~360torr; the growth temperature can be 750℃, 800℃, 850℃, 900℃, 950℃, 980℃, but is not limited to these; the growth pressure can be 30torr, 70torr, 100torr, 220torr, 250torr, 300torr, 330torr, 360torr, but is not limited to these. The second quantum well light-emitting layer comprises a second InGaN layer and a second GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; The second InGaN layer is undoped, with an In content of 0.03~0.39, a thickness of 1.8nm~4.8nm, a growth temperature of 650℃~900℃, and a growth pressure of 30torr~360torr. The growth temperature can be 650℃, 700℃, 750℃, 800℃, or 900℃, but is not limited to these. The growth pressure can be 30torr, 70torr, 100torr, 220torr, 250torr, 300torr, 330torr, or 360torr, but is not limited to these. The Si doping concentration of the second GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3The thickness is 5nm~15nm, the growth temperature is 750℃~980℃, and the growth pressure is 30torr~360torr; the growth temperature can be 750℃, 800℃, 850℃, 900℃, 950℃, 980℃, but is not limited to these; the growth pressure can be 30torr, 70torr, 100torr, 220torr, 250torr, 300torr, 330torr, 360torr, but is not limited to these.

[0041] The present invention will be further described below with reference to specific embodiments: Example 1 (I) This embodiment provides an LED epitaxial structure with high hole injection efficiency, including a substrate, on which a buffer layer, an N-type semiconductor layer, a front-well electron blocking layer, a first multiple quantum well light-emitting layer, a middle-well electron blocking layer, a second multiple quantum well light-emitting layer, a back-well electron blocking layer and a P-type semiconductor layer are stacked sequentially along the epitaxial direction. The electron blocking layer in front of the well includes a pre-well AlGaN layer and a pre-well InGaN layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 4. The Si doping concentration of the AlGaN layer before the well is 3 × 10⁻⁶. 18 / cm 3 The Al content was 0.5%, the thickness was 1.6 nm, the growth temperature was 900℃, and the growth pressure was 150 torr. The in-well InGaN layer is undoped, has an In content of 0.06, a thickness of 1.5 nm, a growth temperature of 865 °C, and a growth pressure of 150 torr. The first multi-quantum-well light-emitting layer comprises a first InGaN layer and a first GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 6; The first InGaN layer is undoped, has an In content of 0.21, a thickness of 3.5 nm, a growth temperature of 775 °C, and a growth pressure of 150 torr; The Si doping concentration of the first GaN barrier layer is 3.6 × 10⁻⁶. 17 / cm 3 The thickness is 11 nm, the growth temperature is 865℃, and the growth pressure is 150 torr; The AlGaN layer in the well may be a single AlGaN layer or multiple AlGaN layers; The AlGaN layer in the well is undoped, with an Al content of 0.5%, a thickness of 3.7 nm, a growth temperature of 865 °C, and a growth pressure of 150 torr. The second quantum well light-emitting layer comprises a second InGaN layer and a second GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 6; The second InGaN layer is undoped, has an In content of 0.21, a thickness of 3.3 nm, a growth temperature of 650℃~900℃, and a growth pressure of 30 torr~360 torr; The Si doping concentration of the second GaN barrier layer is 3.6 × 10⁻⁶. 17 / cm 3 The thickness is 10 nm, the growth temperature is 865℃, and the growth pressure is 150 torr; The back-well electron blocking layer comprises back-well AlGaN layers and back-well InGaN layers that are periodically and alternately stacked along the epitaxial direction, with a period number of 4. The AlGaN layer behind the well is undoped, has an Al content of 0.6%, a thickness of 1.5 nm, a growth temperature of 900 °C, and a growth pressure of 150 torr. The Mg doping concentration of the InGaN layer behind the well is 2.6 × 10⁻⁶. 19 / cm 3 The In content was 0.09%, the thickness was 1.5 nm, the growth temperature was 900℃, and the growth pressure was 150 torr.

[0042] The thickness of the first quantum well light-emitting layer is 87 nm, the thickness of the second quantum well light-emitting layer is 79.8 nm, and the ratio of the thickness of the first quantum well light-emitting layer to the thickness of the second quantum well light-emitting layer is 1:0.9. The thickness of the electron blocking layer in front of the well is 12.4 nm, the thickness of the electron blocking layer in the well is 3.7 nm, and the thickness of the electron blocking layer behind the well is 12 nm, with a thickness ratio of 1:0.3:1.

[0043] (II) This embodiment also provides a method for fabricating an LED epitaxial structure with high hole injection efficiency, including the following steps: Provide substrate; A buffer layer is deposited on the substrate; An N-type semiconductor layer is deposited on the buffer layer; Deposit a front-well electron blocking layer on the N-type semiconductor layer; A first multi-quantum well light-emitting layer is deposited on the electron blocking layer in front of the well; An electron blocking layer is deposited in the trap on the first multi-quantum-well light-emitting layer; A second multiple quantum well light-emitting layer is deposited on the electron blocking layer in the well; An electron blocking layer is deposited behind the trap on the second quantum well light-emitting layer; A P-type semiconductor layer is deposited on the electron blocking layer behind the well; The in-well electron blocking layer comprises an in-well AlGaN layer and an in-well InGaN layer that are periodically and alternately stacked along the epitaxial direction. The electron blocking layer in the well includes an AlGaN layer in the well; The back-well electron blocking layer comprises a back-well AlGaN layer and a back-well InGaN layer that are periodically and alternately stacked along the epitaxial direction.

[0044] Example 2 The difference between this embodiment and Embodiment 1 is that: The AlGaN layer in the well may be a single AlGaN layer or multiple AlGaN layers; The AlGaN layer in the well is undoped, with an Al content of 0.5%, a thickness of 1.5 nm, a growth temperature of 865 °C, and a growth pressure of 150 torr. The thickness of the first quantum well light-emitting layer is 87 nm, the thickness of the second quantum well light-emitting layer is 79.8 nm, and the ratio of the thickness of the first quantum well light-emitting layer to the thickness of the second quantum well light-emitting layer is 1:0.9. The thickness of the electron blocking layer in front of the well is 12.4 nm, the thickness of the electron blocking layer in the well is 1.5 nm, and the thickness of the electron blocking layer behind the well is 12 nm, with a thickness ratio of 1:0.12:1.

[0045] Example 3 The difference between this embodiment and Embodiment 2 is as follows: The AlGaN layer in the well may be a single AlGaN layer or multiple AlGaN layers; The AlGaN layer in the well is undoped, with an Al content of 0.5%, a thickness of 1.5 nm, a growth temperature of 865 °C, and a growth pressure of 150 torr. The second quantum well light-emitting layer comprises a second InGaN layer and a second GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 6; The second InGaN layer is undoped, has an In content of 0.21, a thickness of 3 nm, a growth temperature of 650℃~900℃, and a growth pressure of 30 torr~360 torr; The Si doping concentration of the second GaN barrier layer is 3.6 × 10⁻⁶. 17 / cm 3 The thickness is 5nm, the growth temperature is 865℃, and the growth pressure is 150 torr; The thickness of the first quantum well light-emitting layer is 87 nm, the thickness of the second quantum well light-emitting layer is 48 nm, and the ratio of the thickness of the first quantum well light-emitting layer to the thickness of the second quantum well light-emitting layer is 1:0.6. The thickness of the electron blocking layer in front of the well is 12.4 nm, the thickness of the electron blocking layer in the well is 1.5 nm, and the thickness of the electron blocking layer behind the well is 12 nm, with a thickness ratio of 1:0.12:1.

[0046] Example 4 The difference between this embodiment and Embodiment 1 is that: The second quantum well light-emitting layer comprises a second InGaN layer and a second GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 6; The second InGaN layer is undoped, has an In content of 0.21, a thickness of 3.5 nm, a growth temperature of 650℃~900℃, and a growth pressure of 30 torr~360 torr; The Si doping concentration of the second GaN barrier layer is 3.6 × 10⁻⁶. 17 / cm 3 The thickness is 11 nm, the growth temperature is 865℃, and the growth pressure is 150 torr; Wherein, the thickness of the first quantum well light-emitting layer is 87 nm, the thickness of the second quantum well light-emitting layer is 87 nm, and the ratio of the thickness of the first quantum well light-emitting layer to the thickness of the second quantum well light-emitting layer is 1:1; The thickness of the electron blocking layer in front of the well is 12.4 nm, the thickness of the electron blocking layer in the well is 3.7 nm, and the thickness of the electron blocking layer behind the well is 12 nm, with a thickness ratio of 1:0.3:1.

[0047] Example 5 The difference between this embodiment and embodiment 4 is that: The AlGaN layer in the well may be a single AlGaN layer or multiple AlGaN layers; The AlGaN layer in the well is undoped, with an Al content of 0.5%, a thickness of 1.5 nm, a growth temperature of 865 °C, and a growth pressure of 150 torr. Wherein, the thickness of the first quantum well light-emitting layer is 87 nm, the thickness of the second quantum well light-emitting layer is 87 nm, and the ratio of the thickness of the first quantum well light-emitting layer to the thickness of the second quantum well light-emitting layer is 1:1; The thickness of the electron blocking layer in front of the well is 12.4 nm, the thickness of the electron blocking layer in the well is 1.5 nm, and the thickness of the electron blocking layer behind the well is 12 nm, with a thickness ratio of 1:0.12:1.

[0048] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: No electron blocking layer, electron blocking layer in the well, or electron blocking layer after the well are provided; an electron blocking layer is only provided between the second quantum well light-emitting layer and the P-type semiconductor layer. The electron blocking layer is made of AlGaInN with an Al content of 0.05% and an In content of 0.1%, and has a growth thickness of 25 nm.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: An electron blocking layer is disposed between the N-type semiconductor layer and the first quantum well light-emitting layer, and an electron blocking layer is disposed between the second quantum well light-emitting layer and the P-type semiconductor layer.

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: An in-well electron blocking layer is placed only between the first and second multiple quantum well light-emitting layers.

[0051] Performance testing: The epitaxial structures obtained from the examples and comparative examples were made into 10mil×24mil chips. 300 LED chips were selected and tested at 120mA / 60mA currents. The luminous efficacy of the chips was tested, and the improvement in luminous efficacy was calculated based on Comparative Example 1.

[0052] The test results are shown in the table below:

[0053] Referring to Examples 1-5 and Comparative Examples 1-3, the pre-well electron blocking layer, in-well electron blocking layer, and post-well electron blocking layer of the present invention can effectively prevent electron overflow from the active region. Simultaneously, they can weaken the blocking effect of the electron blocking layer structure material on hole injection from the P-type semiconductor layer to the multi-quantum-well light-emitting layer, improving the hole injection efficiency of the P-type semiconductor layer material. This results in better electron-hole matching in the active region, thereby improving the luminous efficiency of the LED device. Furthermore, the thickness of the first multi-quantum-well light-emitting layer is greater than the thickness of the second multi-quantum-well light-emitting layer. This asymmetric well thickness design effectively increases the depth of hole injection from the P-type semiconductor layer to the multi-quantum-well light-emitting layer, allowing quantum wells near the N-type semiconductor layer to also participate in light emission. This further improves electron-hole matching in the active region, thereby enhancing the luminous efficiency of the LED device.

[0054] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A high hole injection efficiency LED epitaxial structure, characterized in that, Includes a substrate, on which are disposed a buffer layer, an N-type semiconductor layer, a front-well electron blocking layer, a first multiple quantum well light-emitting layer, a middle-well electron blocking layer, a second multiple quantum well light-emitting layer, a back-well electron blocking layer and a P-type semiconductor layer stacked sequentially along the epitaxial direction; The in-well electron blocking layer comprises an in-well AlGaN layer and an in-well InGaN layer that are periodically and alternately stacked along the epitaxial direction. The electron blocking layer in the well includes an AlGaN layer in the well; The back-well electron blocking layer comprises a back-well AlGaN layer and a back-well InGaN layer that are periodically and alternately stacked along the epitaxial direction.

2. The LED epitaxial structure with high hole injection efficiency as described in claim 1, characterized in that, The electron blocking layer in front of the well includes AlGaN and InGaN layers stacked alternately in front of the well along the epitaxial direction, with a period number of 2 to 6. The AlGaN layer in the well may be a single AlGaN layer or multiple AlGaN layers; The back-well electron blocking layer comprises back-well AlGaN layers and back-well InGaN layers that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6.

3. The LED epitaxial structure with high hole injection efficiency as described in claim 1 or 2, characterized in that, The Si doping concentration of the AlGaN layer before the well is 2 × 10⁻⁶. 17 / cm 3 ~6×10 18 / cm 3 The Al component content is 0.2~0.8%, and the thickness is 0.2nm~3nm; The in-well InGaN layer is undoped, with an In content of 0.01~0.12 and a thickness of 0.2nm~3nm. The AlGaN layer in the well is undoped, with an Al content of 0.05~1 and a thickness of 0.5nm~6.8nm. The AlGaN layer behind the well is not doped, the Al content is 0.2~1, and the thickness is 0.2nm~3nm; The Mg doping concentration of the InGaN layer behind the well is 2 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 The In component content is 0.02~0.15, and the thickness is 0.2nm~3nm.

4. The LED epitaxial structure with high hole injection efficiency as described in claim 3, characterized in that, The thickness ratio of the electron blocking layer before the well, the electron blocking layer in the well, and the electron blocking layer after the well is 1:(0.08~0.15):(0.8~1.2).

5. The LED epitaxial structure with high hole injection efficiency as described in claim 1, characterized in that, The first multi-quantum-well light-emitting layer includes a first InGaN layer and a first GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; The first InGaN layer is undoped, with an In content of 0.03~0.39 and a thickness of 2nm~5nm; The Si doping concentration of the first GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness is 6nm~16nm; The second quantum well light-emitting layer comprises a second InGaN layer and a second GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; The second InGaN layer is undoped, with an In content of 0.03~0.39 and a thickness of 1.8nm~4.8nm; The Si doping concentration of the second GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness is 5nm~15nm.

6. The LED epitaxial structure with high hole injection efficiency as described in claim 5, characterized in that, The thickness of the first InGaN layer is greater than that of the second InGaN layer, and the thickness of the first GaN barrier layer is greater than that of the second GaN barrier layer.

7. The LED epitaxial structure with high hole injection efficiency as described in claim 6, characterized in that, The ratio of the thickness of the first quantum well light-emitting layer to the thickness of the second quantum well light-emitting layer is 1:(0.4~0.7).

8. A method for fabricating an LED epitaxial structure with high hole injection efficiency as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Provide substrate; A buffer layer is deposited on the substrate; An N-type semiconductor layer is deposited on the buffer layer; Deposit a front-well electron blocking layer on the N-type semiconductor layer; A first multi-quantum well light-emitting layer is deposited on the electron blocking layer in front of the well; An electron blocking layer is deposited in the trap on the first multi-quantum-well light-emitting layer; A second multiple quantum well light-emitting layer is deposited on the electron blocking layer in the well; An electron blocking layer is deposited behind the trap on the second quantum well light-emitting layer; A P-type semiconductor layer is deposited on the electron blocking layer behind the well; The in-well electron blocking layer comprises an in-well AlGaN layer and an in-well InGaN layer that are periodically and alternately stacked along the epitaxial direction. The electron blocking layer in the well includes an AlGaN layer in the well; The back-well electron blocking layer comprises a back-well AlGaN layer and a back-well InGaN layer that are periodically and alternately stacked along the epitaxial direction.

9. The method for fabricating the LED epitaxial structure with high hole injection efficiency as described in claim 8, characterized in that, The electron blocking layer in front of the well includes AlGaN and InGaN layers stacked alternately in front of the well along the epitaxial direction, with a period number of 2 to 6. The Si doping concentration of the AlGaN layer before the well is 2 × 10⁻⁶. 17 / cm 3 ~6×10 18 / cm 3 The Al content is 0.2~0.8%, the thickness is 0.2nm~3nm, the growth temperature is 750℃~1050℃, and the growth pressure is 30torr~360torr; The in-well InGaN layer is undoped, with an In content of 0.01~0.12, a thickness of 0.2nm~3nm, a growth temperature of 750℃~1050℃, and a growth pressure of 30torr~360torr. The AlGaN layer in the well may be a single AlGaN layer or multiple AlGaN layers; The AlGaN layer in the well is undoped, with an Al content of 0.05~1, a thickness of 0.5nm~6.8nm, a growth temperature of 750℃~980℃, and a growth pressure of 30torr~360torr. The back-well electron blocking layer comprises back-well AlGaN layers and back-well InGaN layers that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 6. The AlGaN layer behind the well is not doped, the Al content is 0.2~1, the thickness is 0.2nm~3nm, the growth temperature is 750℃~1050℃, and the growth pressure is 30torr~360torr. The Mg doping concentration of the InGaN layer behind the well is 2 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 The In content is 0.02~0.15, the thickness is 0.2nm~3nm, the growth temperature is 750℃~1050℃, and the growth pressure is 30torr~360torr.

10. The method for fabricating the LED epitaxial structure with high hole injection efficiency as described in claim 8, characterized in that, The first multi-quantum-well light-emitting layer includes a first InGaN layer and a first GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; The first InGaN layer is undoped, with an In content of 0.03~0.39, a thickness of 2nm~5nm, a growth temperature of 650℃~900℃, and a growth pressure of 30torr~360torr; The Si doping concentration of the first GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness is 6nm~16nm, the growth temperature is 750℃~980℃, and the growth pressure is 30torr~360torr; The second quantum well light-emitting layer comprises a second InGaN layer and a second GaN barrier layer that are periodically and alternately stacked along the epitaxial direction, with a period number of 2 to 8; The second InGaN layer is undoped, with an In content of 0.03~0.39, a thickness of 1.8nm~4.8nm, a growth temperature of 650℃~900℃, and a growth pressure of 30torr~360torr; The Si doping concentration of the second GaN barrier layer is 1.5 × 10⁻⁶. 17 / cm 3 ~8.6×10 17 / cm 3 The thickness is 5nm~15nm, the growth temperature is 750℃~980℃, and the growth pressure is 30torr~360torr.

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