AlGaN-based deep ultraviolet light emitting diode epitaxial structure and preparation method thereof

Abstract

The invention provides an AlGaN-based deep ultraviolet light emitting diode epitaxial structure and a preparation method thereof. By utilizing the energy band design of the quantum barrier in the active region, the lattice mismatch problem between the quantum well and the quantum barrier in the active region is effectively relieved, the polarization electric field in the active region is reduced, the quantum limited stark effect is weakened, and the space wave function overlapping rate of an electron hole is improved; meanwhile, positive polarization charges at an LQB / EBL interface can be converted into negative polarization charges, electron leakage is inhibited, hole injection is promoted, the carrier concentration in an active region is increased, electrons and holes are more concentrated in a middle quantum well due to improved energy band distribution, the utilization rate of carriers can be increased, and the efficiency of the device is improved. Therefore, the radiative recombination rate, the external quantum efficiency and the light output power of the device can be improved, and more possibilities are provided for commercial application of the AlGaN-based deep ultraviolet light emitting diode.

Description

Technical Field

[0001] The invention relates to an AlGaN-based deep ultraviolet light-emitting diode epitaxial structure and a preparation method thereof, belonging to the technical field of integrated circuits. Background Art

[0002] Compared with traditional mercury-based fluorescent lamps, AlGaN-based ultraviolet light-emitting diodes have the advantages of small size, low power consumption, environmental friendliness and adjustable ultraviolet band (365nm~200nm). They have broad application prospects in drug treatment, environmental purification and solid-state light sources, and have therefore attracted widespread research interest. However, after several years of development, the external quantum efficiency of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) is still generally lower than 10%, and is accompanied by a serious efficiency drop problem at high current density, which seriously limits the further development and popularization of AlGaN-based DUV LEDs. The main reasons are the quantum confinement Stark effect caused by the strong polarization electric field in the active region, the low hole injection efficiency and the serious electron leakage. First, due to the inherent spontaneous polarization of AlGaN materials and the piezoelectric polarization caused by lattice mismatch at the AlGaN / AlGaN heterojunction interface inside the active region, a large number of positive and negative polarization charges are generated at the heterojunction interface, and then a large polarization electric field is generated inside the active region, which separates the electron and hole wave functions and reduces the radiation recombination rate; secondly, the effective mass of electrons in AlGaN materials is much lower than the effective mass of holes, which also causes the mobility of electrons to be much higher than the mobility of holes, resulting in unbalanced carrier transport in the active region, and a large number of electrons leak into the p-type region and consume holes, thereby reducing device performance. Generally, a p-type electron blocking layer (EBL) with a high Al content is grown between the active region and the p-type hole injection layer to suppress electron leakage. However, the discontinuity of the Al content at the interface between the last quantum barrier (LQB) and the EBL causes a large amount of positive polarization charge to be generated at this interface, which attracts some electrons to gather near this interface and consume holes. At the same time, the EBL with a high Al content will also increase the effective barrier height of the valence band, hinder hole injection, reduce the hole concentration in the active region, and thus weaken the radiative recombination efficiency in the active region. All of the above factors will have a negative impact on the carrier injection efficiency of AlGaN-based DUV LEDs, limiting the improvement of the external quantum efficiency of AlGaN-based DUV LEDs.

[0003] Based on the above analysis, it is necessary to design a structure that can effectively improve the carrier distribution inside the active region and simultaneously improve the external quantum efficiency and light output power. This structure can effectively solve the problem of carrier concentration in the last quantum well in the active region and the decrease in efficiency, providing more possibilities for the commercial application of AlGaN-based DUV LEDs. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides an AlGaN-based deep ultraviolet light-emitting diode epitaxial structure and a preparation method thereof. The present invention utilizes the energy band design of the quantum barrier in the active region to effectively alleviate the lattice mismatch problem between the quantum well and the quantum barrier in the active region, reduce the polarization electric field in the active region, weaken the quantum confined Stark effect, and increase the spatial wave function overlap rate of electron holes; at the same time, the positive polarization charge at the LQB / EBL interface can be converted into negative polarization charge, inhibiting electron leakage and promoting hole injection, increasing the carrier concentration in the active region, and the improved energy band distribution makes electrons and holes more concentrated in the middle quantum well, which can improve the utilization rate of carriers, thereby helping to improve the radiation recombination rate, external quantum efficiency and light output power of the device, and providing more possibilities for the commercial application of AlGaN-based deep ultraviolet light-emitting diodes.

[0005] The technical solution of the present invention is as follows:

[0006] An AlGaN-based deep ultraviolet light-emitting diode epitaxial structure comprises, from bottom to top, a substrate, a buffer layer, an n-type semiconductor electron injection layer, a multi-quantum well active layer, a p-type electron blocking layer, a p-type AlGaN hole injection layer, a p-type GaN hole injection layer, a p-type contact layer, and a p-type electrode, wherein an n-type electrode is arranged above one side of the n-type semiconductor electron injection layer; wherein the multi-quantum well active layer is composed of barrier layers and potential well layers arranged alternately; the Al component content in the barrier layers first decreases linearly from bottom to top, and then increases in a mirror-image linear manner; and the Al component content in each potential well layer is the same.

[0007] Preferably, according to the present invention, the multi-quantum well active layer is composed of 6 barrier layers and 5 potential well layers arranged alternately, and the barrier layer is arranged above one side of the n-type semiconductor electron injection layer.

[0008] Preferably according to the present invention, the thickness of each barrier layer is 8-12 nm, and the thickness of each well layer is 2-4 nm.

[0009] According to the preferred embodiment of the present invention, the barrier layer is Al m Ga 1-m N, where 0.5≤m≤1; the gradient of the Al component content m in a single barrier layer is 0.01, 0.02, 0.03, 0.04 or 0.05, and the gradient of the Al component content in each barrier layer is the same; while keeping the Al component content in the barrier layer at the interface between each potential well layer and the barrier layer the same. Preferably, the m value of the highest Al component content in the barrier layer is 0.64, and the gradient of the Al component content m in a single barrier layer is 0.04.

[0010] According to the preferred embodiment of the present invention, the potential well layer is Aln Ga 1-n N, where the range of n is 0 ≤ n < m, preferably 0.45.

[0011] Preferably according to the present invention, the highest Al component content in the barrier layer can be higher than, lower than, or equal to the Al component content in the n-type semiconductor electron injection layer; the lowest Al component content in the barrier layer is higher than the Al component content in the quantum well layer.

[0012] Preferably according to the present invention, the substrate is one of sapphire, silicon carbide, aluminum nitride, gallium nitride, or silicon, and the substrate is a polar plane substrate.

[0013] Preferably according to the present invention, the buffer layer is Al x0 Ga 1-x0 N, where 0 ≤ x0 ≤ 1; preferably, x0 is 1.

[0014] Preferably according to the present invention, the n-type semiconductor electron injection layer is n-type Al x1 Ga 1-x1 N, where 0 ≤ x1 ≤ 1, and the thickness is 3.5 - 4 μm. Preferably, x1 is 0.6, the thickness is 4 μm, where the doping concentration of Si is 8 × 10 18 atoms / cm 3 ³.

[0015] Preferably according to the present invention, the p-type electron blocking layer is p-type Al x2 Ga 1-x2 N, where 0.6 ≤ x2 ≤ 1, and the thickness is 5 - 10 nm. Preferably, x2 is 0.6, the thickness is 10 nm, where the doping concentration of Mg is 2 × 10 19 atoms / cm 3 ³.

[0016] Preferably according to the present invention, the p-type AlGaN hole injection layer is p-type Al x3 Ga 1-x3 N, where 0 < x3 < 1, and the thickness is 45 - 55 nm. Preferably, x3 is 0.4, the thickness is 50 nm, where the doping concentration of Mg is 4 × 10 19 atoms / cm 3 ³.

[0017] Preferably according to the present invention, the thickness of the p-type GaN hole injection layer is 50 nm, where the doping concentration of Mg is 4 × 10 19 atoms / cm 3 ³.

[0018] Preferably according to the present invention, the p-type contact layer is a heavily doped p-type GaN layer; preferably, the thickness is 20 nm, where the doping concentration of Mg is 1 × 1020 atoms / cm 3 .

[0019] Preferably according to the present invention, the p-type electrode is metal Ni / Au.

[0020] Preferably according to the present invention, the n-type electrode is metal Ti / Al / Ti / Au.

[0021] The method for preparing the AlGaN-based deep ultraviolet light-emitting diode epitaxial structure comprises the following steps:

[0022] (1) In the MOCVD reaction chamber, a buffer layer is grown on the substrate surface;

[0023] (2) In a MOCVD reaction chamber, an n-type semiconductor electron injection layer is subsequently grown on the buffer layer in (1);

[0024] (3) In a MOCVD reaction chamber, barrier layers and potential well layers are alternately grown on the n-type semiconductor electron injection layer in (2), so as to obtain a multi-quantum well active layer;

[0025] (4) In a MOCVD reaction chamber, a p-type electron blocking layer is subsequently grown on the multi-quantum well active layer in (3);

[0026] (5) In a MOCVD reaction chamber, growing a p-type AlGaN hole injection layer on the surface of the p-type electron blocking layer in (4);

[0027] (6) In a MOCVD reaction chamber, a p-type GaN hole injection layer is subsequently grown on the surface of the p-type AlGaN hole injection layer obtained in (5);

[0028] (7) In a MOCVD reaction chamber, a p-type contact layer is subsequently grown on the surface of the p-type GaN hole injection layer obtained in (6);

[0029] (8) A mesa is etched on the surface of the n-type semiconductor electron injection layer to expose a portion of the n-type semiconductor electron injection layer, and then a p-type electrode and an n-type electrode are formed by electron beam evaporation.

[0030] Preferably according to the present invention, trimethylgallium or triethylgallium is used as the gallium source, trimethylaluminum is used as the aluminum source, ammonia is used as the nitrogen source, silane is used as the Si doping source, and bismuth magnesium is used as the Mg doping source.

[0031] The technical features and beneficial effects of the present invention are as follows:

[0032] 1. The present invention provides a DUV LEDs structure in which the Al component content of the quantum barrier changes in a V-shape: the structure compared with the present invention is a standard DUV LEDs containing quantum barriers with a fixed Al component content. The active region of the present invention is composed of quantum wells and quantum barriers alternately, and the Al component content in the quantum barriers first decreases linearly from bottom to top, and then increases linearly in a mirror image; the Al component content in the quantum wells is the same. By optimizing the Al component of the V-shaped quantum barrier, the present invention can effectively alleviate the lattice mismatch problem between the quantum wells and quantum barriers in the active region, reduce the polarization electric field in the active region, weaken the quantum confined Stark effect, and increase the spatial wave function overlap rate of electrons and holes, thereby improving the radiation recombination rate and external quantum efficiency of AlGaN-based DUV LEDs.

[0033] 2. The V-shaped quantum barrier of the present invention can convert the positive polarization charge at the LQB / EBL interface into negative polarization charge by redesigning the quantum barrier energy band of the active region, thereby inhibiting electron leakage and promoting hole injection, increasing the carrier concentration in the active region, and at the same time, the improved energy band distribution makes electrons and holes more concentrated in the middle quantum well, thereby improving the utilization rate of carriers and helping to improve the radiation recombination rate and external quantum efficiency of DU V LEDs.

[0034] 3. The device of the present invention has a high radiation recombination rate, external quantum efficiency and light output power, providing more possibilities for the commercial application of AlGaN-based deep ultraviolet light-emitting diodes. The AlGaN-based deep ultraviolet light-emitting diode of the present invention does not significantly change the forward characteristics of the device, and the manufacturing process is simple and easy with strong repeatability. In the present invention, TCAD simulation is used to assist in analyzing the impact of the V-shaped quantum barrier on the performance of DUV LEDs, which can save a lot of time and cost and better guide the subsequent preparation process of DUV LEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention provides a schematic structural diagram of an AlGaN-based deep ultraviolet light-emitting diode epitaxial structure, wherein 101 is a substrate, 102 is a buffer layer, 103 is an n-type semiconductor electron injection layer, 104 is a multi-quantum well active layer, 104a to 104f are quantum barriers in which the Al component content varies in a V-shape, 105 is a p-type electron blocking layer, 106 is a p-type AlGaN hole injection layer, 107 is a p-type GaN hole injection layer, 108 is a p-type contact layer, 109 is a p-type electrode, and 110 is an n-type electrode.

[0036] Figure 2 Schematic diagram of the energy band structure of the active layer, electron blocking layer and part of the hole injection layer of the AlGaN-based deep ultraviolet light-emitting diode in Example 1.

[0037] Figure 3The electric field distribution of the standard deep ultraviolet light-emitting diode and the deep ultraviolet light-emitting diode of Example 1 in the active region and the EBL (a), and the hole concentration distribution in the LQB and the EBL (b).

[0038] Figure 4 The graphs (a) and (b) are the distribution diagrams of the integral of the electron concentration in each quantum well of the standard deep ultraviolet light-emitting diode and the deep ultraviolet light-emitting diode of Example 1 in the active layer and the integral of the hole concentration in each quantum well in the active layer.

[0039] Figure 5 Graph (a) showing the relationship between external quantum efficiency and current density of a standard deep ultraviolet light emitting diode and the deep ultraviolet light emitting diode of Example 1, and graph (b) showing the relationship between light output power and current density.

[0040] Figure 6 Graph showing the relationship between current density and voltage of a standard deep ultraviolet light emitting diode and the deep ultraviolet light emitting diode of Example 1.

[0041] Figure 7 (a) is a graph showing the relationship between the external quantum efficiency and current density of a standard deep ultraviolet light-emitting diode and the deep ultraviolet light-emitting diode of Examples 1-4, and (b) is a graph showing the relationship between the light output power and current density.

[0042] Specific embodiment

[0043] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings, but is not limited thereto.

[0044] Meanwhile, the methods used in the examples are all existing methods unless otherwise specified; the materials and equipment used are all commercially available unless otherwise specified.

[0045] Example 1

[0046] An AlGaN-based deep ultraviolet light-emitting diode epitaxial structure, such as Figure 1 As shown, along the epitaxial growth direction, it includes a sapphire substrate (polar surface substrate) 101, a buffer layer AlN 102 with a thickness of 100nm, an n-type semiconductor electron injection layer 103 with a thickness of 4μm (n-Al 0.6 Ga 0.4 N, where the doping concentration of Si is 8×10 18 atoms / cm 3 ), a multi-quantum well active layer 104, a p-type electron blocking layer 105 (p-Al 0.6 Ga 0.4 N, where the Mg doping concentration is 2×10 19 atoms / cm 3), a p-type AlGaN hole injection layer 106 (p-Al 0.4 Ga 0.6 N, where the Mg doping concentration is 4×10 19 atoms / cm 3 ), a p-type GaN hole injection layer 107 with a thickness of 50 nm (Mg doping concentration is 4×10 19 atoms / cm 3 ), a p-type contact layer 108 with a thickness of 20 nm (p-type heavily doped GaN, Mg doping concentration of 1×10 20 atoms / cm 3 ), the material of the p-type electrode 109 is Ni / Au (5 / 5nm), and an n-type electrode 110 is provided above one side of the n-type semiconductor electron injection layer 103, and the material of the n-type electrode 110 is Ti / Al / Ti / Au (30 / 120 / 30 / 200nm).

[0047] The multi-quantum well active layer 104 is composed of 6 barrier layers ( 104 a - f ) and 5 potential well layers arranged alternately, and the barrier layer 104 a is disposed above one side of the n-type semiconductor electron injection layer 103 .

[0048] The barrier layer is Al m Ga 1-m N; the Al component content in the barrier layer first decreases linearly from m value 0.64 to 0.52 from bottom to top, and then increases linearly to 0.64 in a mirror-like manner. The change gradient of the Al component content m in a single barrier layer is 0.04, that is, the m value in the 104a barrier layer decreases linearly from 0.64 to 0.6 from bottom to top, the m value in the 104b barrier layer decreases linearly from 0.6 to 0.56 from bottom to top, the m value in the 104c barrier layer decreases linearly from 0.56 to 0.52 from bottom to top, the m value in the 104d barrier layer increases linearly from 0.52 to 0.56 from bottom to top, the m value in the 104e barrier layer increases linearly from 0.56 to 0.6 from bottom to top, and the m value in the 104f barrier layer increases linearly from 0.6 to 0.64 from bottom to top. The thickness of each barrier layer is 10 nm, and the Al component content in the barrier layer at the interface between each potential well layer and the barrier layer on both sides is the same.

[0049] The potential well layer is Al n Ga 1-n N, n is 0.45, the Al component content in each potential well layer is the same, and the thickness of each potential well layer is 3 nm.

[0050] The method for preparing the AlGaN-based deep ultraviolet light-emitting diode epitaxial structure comprises the following steps:

[0051] (1) In the MOCVD reaction chamber, a buffer layer is grown on the substrate surface.

[0052] (2) In a MOCVD reaction chamber, an n-type semiconductor electron injection layer is subsequently grown on the buffer layer in (1);

[0053] (3) In a MOCVD reaction chamber, barrier layers and well layers are alternately grown on the n-type semiconductor electron injection layer in (2), so as to form a multi-quantum well active layer; the Al component content of the graded barrier layer is controlled by controlling the flow rate of the Al source;

[0054] (4) In a MOCVD reaction chamber, a p-type electron blocking layer is subsequently grown on the multi-quantum well active layer in (3);

[0055] (5) In a MOCVD reaction chamber, growing a p-type AlGaN hole injection layer on the surface of the p-type electron blocking layer in (4);

[0056] (6) In a MOCVD reaction chamber, a p-type GaN hole injection layer is subsequently grown on the surface of the p-type AlGaN hole injection layer obtained in (5);

[0057] (7) In a MOCVD reaction chamber, a p-type contact layer is subsequently grown on the surface of the p-type GaN hole injection layer obtained in (6);

[0058] (8) A mesa is etched on the surface of the n-type semiconductor electron injection layer to expose a portion of the n-type semiconductor electron injection layer, and then a p-type electrode and an n-type electrode are formed by electron beam evaporation.

[0059] Among them, trimethylgallium or triethylgallium is used as a gallium source, trimethylaluminum is used as an aluminum source, ammonia is used as a nitrogen source, silane is used as a Si doping source, and bismuthocene magnesium is used as a Mg doping source.

[0060] Figure 2 Schematic diagram of the energy band structure of the active layer, electron blocking layer and part of the hole injection layer of the AlGaN-based deep ultraviolet light-emitting diode. The negative polarization charge at the interface between LQB and EBL is marked with "-". The effective electron barrier height ΔΦ e1 ~ΔΦ e5 , effective hole barrier height ΔΦ h1 ~ΔΦ h5 , and E c represents the conduction band, E fn represents the electron Fermi level, E fp represents the hole Fermi level, E v Represents the valence band. ΔΦ e1 ~ΔΦ e4 The minimum value in is ΔΦ e2 (83.8meV), ΔΦ h1 ~ΔΦ h4The minimum value in is ΔΦ h3 (116.6meV), the effective electron barrier height of the electron blocking layer (ΔΦ e5 ) and the effective hole barrier height (ΔΦ h5 ), respectively, from 333.5meV of standard DUV LEDs to 390.3meV and from 465.5meV to 261.1meV, which effectively suppresses electron leakage and promotes hole injection into the active region, and at the same time helps electrons and holes to gather in the middle quantum well.

[0061] Figure 3 (a) is the distribution diagram of the electric field distribution in the active region and EBL of the standard deep ultraviolet light-emitting diode and the deep ultraviolet light-emitting diode of this embodiment. It can be seen that the V-shaped quantum barrier can improve the lattice mismatch problem at the interface between the well and barrier in the active region, reduce the polarization electric field, and alleviate the quantum confinement Stark effect.

[0062] Figure 3 (b) is a distribution diagram of the hole concentration distribution in the LQB and QBL of the standard deep ultraviolet light-emitting diode and the deep ultraviolet light-emitting diode of this embodiment. It can be seen that the V-shaped quantum barrier proposed by the present invention greatly improves the hole concentration.

[0063] Figure 4 (a) is a distribution diagram of the integral of the electron concentration in each quantum well of the standard deep ultraviolet light-emitting diode and the deep ultraviolet light-emitting diode of this embodiment in the active layer. It can be seen that the electron concentration of the deep ultraviolet light-emitting diode proposed by the present invention is effectively improved and concentrated in the middle quantum well.

[0064] Figure 4 (b) is a distribution diagram of the integral of the hole concentration in each quantum well of the standard deep ultraviolet light-emitting diode and the deep ultraviolet light-emitting diode of this embodiment in the active layer. It can be seen that the hole concentration of the deep ultraviolet light-emitting diode proposed by the present invention is effectively improved, and the middle quantum well concentration is the highest.

[0065] Figure 5 (a) is a graph showing the relationship between the external quantum efficiency and current density of a standard deep ultraviolet light-emitting diode and the deep ultraviolet light-emitting diode of this embodiment. It can be seen that the external quantum efficiency of the deep ultraviolet light-emitting diode proposed by the present invention is higher than that of the standard deep ultraviolet light-emitting diode and the efficiency drop problem at high current density is alleviated to a certain extent.

[0066] Figure 5 (b) is a graph showing the relationship between the light output power and the current density of a standard deep ultraviolet light emitting diode and the deep ultraviolet light emitting diode of this embodiment. It can be seen that the light output efficiency of the deep ultraviolet light emitting diode proposed by the present invention is higher than the external quantum efficiency of the standard deep ultraviolet light emitting diode.

[0067] Figure 6 : is a graph showing the relationship between the current density and the voltage of a standard deep ultraviolet light emitting diode and the deep ultraviolet light emitting diode of this embodiment. It can be seen that the deep ultraviolet light emitting diode proposed by the present invention will not significantly improve the forward voltage of the device.

[0068] Example 2

[0069] An AlGaN-based deep ultraviolet light-emitting diode epitaxial structure, as described in Example 1, except that: the barrier layer Al m Ga 1-m The Al component content in N remains unchanged, and m is 0.58; other structures and parameters are the same as in Example 1.

[0070] from Figure 7 It can be seen that although the average Al composition of the quantum barriers of Example 1 and Example 2 is the same, Example 1 having a V-shaped quantum barrier exhibits a more superior performance.

[0071] Example 3

[0072] An AlGaN-based deep ultraviolet light-emitting diode epitaxial structure, as described in Example 1, except that: in this embodiment, the barrier layer Al m Ga 1-m The Al component content in N decreases linearly from m value 0.59 to 0.47 from bottom to top, and then increases linearly to 0.59 in a mirror image. The change gradient of the Al component content m in a single barrier layer is 0.04. Other structures and parameters are the same as in Example 1.

[0073] Depend on Figure 7 It can be seen that Example 1 exhibits higher external quantum efficiency and light output power.

[0074] Example 4

[0075] An AlGaN-based deep ultraviolet light-emitting diode epitaxial structure, as described in Example 1, except that: in this embodiment, the barrier layer Al m Ga 1-m The Al component content in N decreases linearly from m value 0.80 to 0.68 from bottom to top, and then increases linearly to 0.80 in a mirror image. The change gradient of the Al component content m in a single barrier layer is 0.04. Other structures and parameters are the same as in Example 1.

[0076] Depend on Figure 7 It can be seen that Example 1 exhibits higher photoelectric performance.

Claims

1. An AlGaN-based deep ultraviolet light-emitting diode epitaxial structure, characterized in that: From bottom to top, it includes a substrate, a buffer layer, an n-type semiconductor electron injection layer, a multi-quantum well active layer, a p-type electron blocking layer, a p-type AlGaN hole injection layer, a p-type GaN hole injection layer, a p-type contact layer, and a p-type electrode. An n-type electrode is arranged above one side of the n-type semiconductor electron injection layer. Among them, the multi-quantum well active layer is composed of barrier layers and potential well layers arranged alternately. The Al component content in the barrier layer first decreases linearly from bottom to top, and then increases in a mirror-linear manner. The Al component content in each potential well layer is the same.

2. The AlGaN-based deep ultraviolet light-emitting diode epitaxial structure according to claim 1, characterized in that: The multi-quantum well active layer is composed of 6 potential barrier layers and 5 potential well layers arranged alternately, and the potential barrier layer is arranged above one side of the n-type semiconductor electron injection layer.

3. The AlGaN-based deep ultraviolet light-emitting diode epitaxial structure according to claim 1, characterized in that: The thickness of each barrier layer is 8-12 nm, and the thickness of each well layer is 2-4 nm.

4. The AlGaN-based deep ultraviolet light-emitting diode epitaxial structure according to claim 1, characterized in that: The barrier layer is Al m Ga 1-m N, wherein 0.5≤m≤1; the variation gradient of the Al component content m in a single barrier layer is 0.01, 0.02, 0.03, 0.04 or 0.05, and the variation gradient of the Al component content in each barrier layer is the same; and at the same time, the Al component content in the barrier layer at the interface between each potential well layer and the barrier layer on both sides is kept the same.

5. The AlGaN-based deep ultraviolet light-emitting diode epitaxial structure according to claim 4, characterized in that: The m value of the highest Al component content in the barrier layer is 0.64, and the variation gradient of the Al component content m in a single barrier layer is 0.

04.

6. The AlGaN-based deep ultraviolet light-emitting diode epitaxial structure according to claim 1, characterized in that: The potential well layer is Al n Ga 1-n N, wherein n is in the range of 0≤n<m, and is preferably 0.

45.

7. The AlGaN-based deep ultraviolet light-emitting diode epitaxial structure according to claim 1, characterized in that: The highest Al component content in the barrier layer can be higher than, lower than or equal to the Al component content in the n-type semiconductor electron injection layer; the lowest Al component content in the barrier layer is higher than the Al component content in the potential well layer.

8. The AlGaN-based deep ultraviolet light-emitting diode epitaxial structure according to claim 1, characterized in that: Includes one or more of the following conditions: i. The substrate is one of sapphire, silicon carbide, aluminum nitride, gallium nitride or silicon, and the substrate is a polar surface substrate; ii. Buffer layer is Al x0 Ga 1-x0 N, where 0≤x0≤1; iii. The n-type semiconductor electron injection layer is n-type Al x1 Ga 1-x1 N, where 0≤x1≤1, thickness is 3.5-4 μm; iv. The p-type electron blocking layer is p-type Al x2 Ga 1-x2 N, where 0.6≤x2≤1, thickness is 5 to 10 nm; v. The p-type AlGaN hole injection layer is p-type Al x3 Ga 1-x3 N, where 0 < x3 < 1 and the thickness is 45 to 55 nm; vi. The p-type contact layer is a heavily doped p-type GaN layer; vii. The p-type electrode is metal Ni / Au; viii. The n-type electrode is metal Ti / Al / Ti / Au.

9. The method for preparing an AlGaN-based deep ultraviolet light-emitting diode epitaxial structure according to any one of claims 1 to 8, comprising the steps of: (1) In the MOCVD reaction chamber, a buffer layer is grown on the substrate surface; (2) In a MOCVD reaction chamber, an n-type semiconductor electron injection layer is subsequently grown on the buffer layer in (1); (3) In a MOCVD reaction chamber, barrier layers and potential well layers are alternately grown on the n-type semiconductor electron injection layer in (2), so as to obtain a multi-quantum well active layer; (4) In a MOCVD reaction chamber, a p-type electron blocking layer is subsequently grown on the multi-quantum well active layer in (3); (5) In a MOCVD reaction chamber, growing a p-type AlGaN hole injection layer on the surface of the p-type electron blocking layer in (4); (6) In a MOCVD reaction chamber, a p-type GaN hole injection layer is subsequently grown on the surface of the p-type AlGaN hole injection layer obtained in (5); (7) In a MOCVD reaction chamber, a p-type contact layer is subsequently grown on the surface of the p-type GaN hole injection layer obtained in (6); (8) A mesa is etched on the surface of the n-type semiconductor electron injection layer to expose a portion of the n-type semiconductor electron injection layer, and then a p-type electrode and an n-type electrode are formed by electron beam evaporation.

10. The method for preparing an AlGaN-based deep ultraviolet light-emitting diode epitaxial structure according to claim 9, characterized in that: Trimethylgallium or triethylgallium is used as a gallium source, trimethylaluminum is used as an aluminum source, ammonia is used as a nitrogen source, silane is used as a Si doping source, and bis(cyclopentadienyl)magnesium is used as a Mg doping source.

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