A deep ultraviolet LED with an injection efficiency-improving layer structure and a method for preparing the same

Abstract

The present invention discloses a deep ultraviolet LED with an injection efficiency improvement layer structure and a preparation method thereof. The deep ultraviolet LED comprises a sapphire substrate, an AlN intrinsic layer, an n-type AlGaN electron injection layer, a current expansion layer, a quantum well active layer, a first carrier injection efficiency improvement layer, a second carrier injection efficiency improvement layer, an electron blocking layer, a p-type AlGaN hole injection layer and a p-type GaN contact layer, which are sequentially stacked. The first carrier injection efficiency improvement layer is composed of several Al a Ga 1‑a N layer and Al b Ga 1‑b The present invention comprises an unintentionally doped superlattice structure composed of periodic alternating N layers. The second carrier injection improvement layer has a growth temperature lower than the minimum growth temperature of the quantum well active layer and is an AlGaN structure p-type doped with Mg. This invention solves the prior art technical problem of low luminous efficiency in deep ultraviolet LED devices due to the structural design of the electron blocking layer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronic technology, and in particular to a deep ultraviolet LED with an injection efficiency-improving layer structure and a preparation method thereof. Background Art

[0002] In typical AlGaN-based deep-UV LEDs, a high-composition electron blocking layer is placed between the p-type injection layer and the quantum well active region. This layer serves to prevent electrons from the n-type layer from diffusing into the p-type layer, but it also hinders the injection of holes from the p-type injection layer into the quantum well. In typical structural design, a compromise is made between these two factors: the electron blocking layer should be neither too high, which would affect the hole injection efficiency, nor too low, which would reduce the electron blocking effect and result in poor luminescence efficiency. Furthermore, the p-type material of deep-UV LEDs typically uses high-composition AlGaN material, which is typically grown at a high temperature. This results in a generally low Mg doping concentration, which also seriously affects the luminescence efficiency of deep-UV LED devices.

[0003] Therefore, a new UV LED solution is urgently needed to solve the problems existing in the existing technology. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies, provide a deep ultraviolet LED with an injection efficiency improvement layer structure and a preparation method thereof, and solve the technical problem in the prior art of low luminous efficiency of deep ultraviolet LED devices caused by the structural design of the electron blocking layer.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a deep ultraviolet LED with an injection efficiency improvement layer structure, comprising a sapphire substrate, an AlN intrinsic layer, an n-type AlGaN electron injection layer, a current spreading layer, a quantum well active layer, a first carrier injection efficiency improvement layer, a second carrier injection efficiency improvement layer, an electron blocking layer, a p-type AlGaN hole injection layer, and a p-type GaN contact layer, which are stacked in sequence;

[0007] The first carrier injection efficiency improvement layer is composed of a plurality of Al a Ga 1-a N layer and Al b Ga 1-b The superlattice structure is composed of an unintentionally doped N layer periodically alternating, and the first carrier injection efficiency improvement layer is formed by Al a Ga 1-a The N layer is in contact with the quantum well active layer barrier, and the first carrier injection efficiency improvement layer is connected to the quantum well active layer barrier through Al b Ga 1-bThe N layer contacts the potential well of the second carrier injection efficiency improvement layer. The growth temperature of the second carrier injection improvement layer is lower than the lowest growth temperature of the quantum well active layer, and the second carrier injection improvement layer is an AlGaN structure p-type doped with Mg.

[0008] In one embodiment, the Al a Ga 1-a The N layer and the Al b Ga 1-b The N layers satisfy 50%≤b≤a≤100%.

[0009] In one embodiment, the superlattice period of the first carrier injection efficiency improvement layer is 1 to 50, and the Al a Ga 1-a The thickness of the N layer is 0.1nm~20nm, and the Al b Ga 1-b The thickness of the N layer is 0.1 nm to 20 nm.

[0010] In one embodiment, the second carrier injection efficiency improving layer is an AlGaN single layer structure, and the Al composition is 40% to 100%.

[0011] In one embodiment, the thickness of the second carrier injection efficiency improvement layer is 1 nm to 50 nm, and the entire layer uses Mg as a p-type dopant with a doping concentration of 1×10 17 cm -3 ~1×10 22 cm -3 .

[0012] In one embodiment, the second carrier injection efficiency improvement layer is composed of a plurality of Al x Ga 1-x N layer and Al y Ga 1- y The superlattice structure composed of N layers is alternately periodic, and the Al x Ga 1-x The N layer and the Al b Ga 1-b N layer potential well contact, the Al y Ga 1-y The N layer is in contact with the electron blocking layer.

[0013] In one embodiment, the Al x Ga 1-x The N layer and the Al y Ga 1-y The N layers satisfy 50%≤y≤x≤100%.

[0014] In one embodiment, the superlattice period of the second carrier injection efficiency improvement layer is 1 to 50, and the entire layer uses Mg as a p-type dopant with a doping concentration of 1×10 17 cm -3 ~1×10 22 cm -3 , the Al x Ga 1-x The thickness of the N layer is 0.1nm~20nm, and the Al y Ga 1-y The thickness of the N layer is 0.1 nm to 20 nm.

[0015] In one embodiment, the growth temperature of the second carrier injection improvement layer is 20° C. to 300° C. lower than the lowest growth temperature of the quantum well active layer.

[0016] In a second aspect, the present invention further provides a method for preparing the deep ultraviolet LED having the above-mentioned injection efficiency improved layer structure, comprising the following steps:

[0017] (1) Growing an AlN intrinsic layer: growing a buffer layer in the AlN intrinsic layer on a sapphire substrate at 400-800°C, with a thickness of 10-50 nm, then raising the temperature to 1200-1400°C, and growing an AlN intrinsic layer on the buffer layer in the AlN intrinsic layer, with a total thickness of 500-4000 nm;

[0018] (2) growing an n-type AlGaN electron injection layer: cooling the temperature to 800-1200° C., and growing an n-type AlGaN electron injection layer on the AlN intrinsic layer, wherein the Al component percentage is 20-90% and the thickness is 500-4000 nm;

[0019] (3) growing a current spreading layer: cooling the temperature to 700-1100° C. and growing a current spreading layer on one side of the n-type AlGaN electron injection layer;

[0020] (4) Growing a quantum well active layer: maintaining a temperature of 700-1100° C., and growing a quantum well active layer on one side of the current spreading layer;

[0021] (5) Growing a first carrier injection efficiency improvement layer: maintaining a temperature of 700-1100° C., growing a first carrier injection efficiency improvement layer on the quantum well active layer, with a thickness of 1-50 nm;

[0022] (6) growing a second carrier injection efficiency improvement layer: cooling the temperature to 500° C. to 1050° C., and growing a second carrier injection efficiency improvement layer on the first carrier injection efficiency improvement layer;

[0023] (7) growing an electron blocking layer: heating the temperature to 700° C. to 1100° C., and growing an electron blocking layer on the second carrier injection efficiency improvement layer, wherein the electron blocking layer is a single-layer AlGaN structure or an AlGaN / AlGaN superlattice structure, wherein the average Al composition is 50% to 100% and the thickness is 0.1 nm to 200 nm;

[0024] (8) Growing a p-type AlGaN hole injection layer: Growing a p-type AlGaN hole injection layer on the electron blocking layer at 700-1100° C., wherein the Al component percentage is 10%-100%, the thickness is 1-50 nm, and Mg is used as a p-type dopant;

[0025] (9) Growth of a p-type GaN contact layer: Growing a p-type GaN contact layer on the p-type AlGaN hole injection layer at 400-900° C. with a thickness of 1-20 nm, and using Mg as a p-type dopant.

[0026] Compared to the prior art, the deep ultraviolet LED with an injection efficiency-improving layer structure provided by the present invention and its preparation method incorporates two epitaxial layers between the quantum well active layer and the electron blocking layer to improve carrier injection efficiency. The first carrier injection efficiency-improving layer is an unintentionally doped superlattice. While assisting the electron blocking layer in blocking electrons, it also prevents the high concentration of Mg in the low-temperature-grown second carrier injection efficiency-improving layer from diffusing into the quantum well active layer during epitaxial growth, thereby affecting luminous efficiency. The second carrier injection efficiency-improving layer is a low-temperature-grown AlGaN material that provides a high concentration of holes to the quantum well active layer, ultimately improving the device's luminous efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of a deep ultraviolet LED with an injection efficiency improvement layer structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] See also Figure 1The deep ultraviolet LED with an injection efficiency improvement layer structure provided by the embodiment of the present invention comprises a sapphire substrate 1, an AlN intrinsic layer 2, an n-type AlGaN electron injection layer 3, a current spreading layer 4, a quantum well active layer 5, a first carrier injection efficiency improvement layer 6, a second carrier injection efficiency improvement layer 7, an electron blocking layer 8, a p-type AlGaN hole injection layer 9 and a p-type GaN contact layer 10, which are stacked in sequence. The first carrier injection efficiency improvement layer 6 is composed of several Al a Ga 1- a N layer and Al b Ga 1-b The superlattice structure is composed of an unintentionally doped N layer periodically alternating, and the first carrier injection efficiency improvement layer 6 is formed by Al a Ga 1-a The N layer is in barrier contact with the quantum well active layer 5, and the first carrier injection efficiency improvement layer 6 is formed by Al b Ga 1-b The N layer is in contact with the potential well of the second carrier injection efficiency improvement layer 7. The growth temperature of the second carrier injection efficiency improvement layer 7 is lower than the minimum growth temperature of the quantum well active layer 5, and it is an AlGaN structure p-type doped with Mg. The present invention adds two layers of epitaxial structure between the quantum well active layer and the electron blocking layer to improve the carrier injection efficiency, wherein the first carrier injection efficiency improvement layer 6 is an unintentionally doped superlattice. While assisting the electron blocking layer 8 in blocking electrons, it can prevent the high concentration of Mg in the low-temperature grown second carrier injection efficiency improvement layer 7 from diffusing into the quantum well active layer 5 during the epitaxial growth process, thereby affecting the luminescence efficiency. The second carrier injection efficiency improvement layer 7 is a low-temperature grown AlGaN material used to provide a high concentration of holes to the quantum well active layer 5, ultimately improving the luminescence efficiency of the device.

[0030] Preferably, the Al a Ga 1-a The N layer and the Al b Ga 1-b The N layer satisfies 50%≤b≤a≤100%, the superlattice period of the first carrier injection efficiency improvement layer 6 is 1 to 50, and the Al a Ga 1-a The thickness of the N layer is 0.1nm~20nm, and the Al b Ga 1-b The thickness of the N layer is 0.1 nm to 20 nm.

[0031] Preferably, the second carrier injection efficiency improving layer 7 has two structural modes, specifically as follows:

[0032] First, the second carrier injection efficiency improvement layer 7 is an AlGaN single layer structure, and the Al component is 40% to 100%; wherein, the thickness of the second carrier injection efficiency improvement layer is 1nm to 50nm, and the entire layer uses Mg as a p-type dopant with a doping concentration of 1×10 17 cm -3 ~1×10 22 cm -3 .

[0033] Secondly, the second carrier injection efficiency improvement layer 7 is composed of a plurality of Al x Ga 1-x N layer and Al y Ga 1-y The superlattice structure composed of N layers is alternately periodic, and the Al x Ga 1-x The N layer and the Al b Ga 1-b N layer potential well contact, the Al y Ga 1-y The N layer is in contact with the electron blocking layer. x Ga 1-x The N layer and the Al y Ga 1-y The N layer satisfies 50%≤y≤x≤100%. The superlattice period of the second carrier injection efficiency improvement layer is 1 to 50, and the entire layer uses Mg as a p-type dopant with a doping concentration of 1×10 17 cm -3 ~1×10 22 cm -3 , the Al x Ga 1-x The thickness of the N layer is 0.1nm~20nm, and the Al y Ga 1-y The thickness of the N layer is 0.1 nm to 20 nm.

[0034] In one embodiment, the growth temperature of the second carrier injection improving layer 7 is 20° C. to 300° C. lower than the lowest growth temperature of the quantum well active layer 5 .

[0035] In this embodiment, the deep ultraviolet LED with a modulated doped electron blocking layer structure is fabricated using the MOCVD method. Si is used as the n-type dopant in the n-type AlGaN electron injection layer 3, and Mg is used as the p-type dopant in the p-type AlGaN hole injection layer 9 and the p-type GaN contact layer 10. Furthermore, an n-electrode 11 is provided on the n-type AlGaN electron injection layer 3, and a p-electrode 12 is provided on the p-type GaN contact layer 10 using conventional methods, which will not be described in detail here.

[0036] Another embodiment of the present invention provides a method for preparing a deep ultraviolet LED having an injection efficiency improvement layer structure as described in the above embodiment, comprising the following steps:

[0037] (1) Growth of an AlN intrinsic layer. In this step, a buffer layer in the AlN intrinsic layer is grown on a sapphire substrate at 400-800°C to a thickness of 10-50 nm. The temperature is then raised to 1200-1400°C to grow an AlN intrinsic layer on the buffer layer in the AlN intrinsic layer. The total thickness of the AlN intrinsic layer is 500-4000 nm.

[0038] (2) Growth of n-type AlGaN electron injection layer: In this step, the temperature is lowered to 800-1200° C., and an n-type AlGaN electron injection layer is grown on the AlN intrinsic layer, wherein the Al component percentage is 20-90% and the thickness is 500-4000 nm.

[0039] (3) Growing a current spreading layer: In this step, the temperature is lowered to 700-1100° C., and a current spreading layer is grown on one side of the n-type AlGaN layer.

[0040] (4) Growing a quantum well active layer: In this step, the temperature is maintained at 700-1100° C., and a quantum well active layer is grown on one side of the current spreading layer.

[0041] (5) Growth of the first carrier injection efficiency improvement layer. In this step, the temperature is maintained at 700-1100°C, and the first carrier injection efficiency improvement layer is grown on the quantum well active layer with a thickness of 1-50nm. The first carrier injection efficiency improvement layer is composed of several Al a Ga 1-a N layer and Al b Ga 1-b The non-intentionally doped superlattice structure is composed of N layers alternating periods, with a period of 1 to 50. a Ga 1-a The N layer and the Al b Ga 1-b The N layer satisfies 50%≤b≤a≤100%, and the Al a Ga 1-a The thickness of the N layer is 0.1nm~20nm, and the Al b Ga 1-b The thickness of the N layer is 0.1 nm to 20 nm.

[0042] (6) Growth of a second carrier injection efficiency improvement layer. In this step, the temperature is lowered to 500°C to 1050°C, and a second carrier injection efficiency improvement layer is grown on the first carrier injection efficiency improvement layer. The second carrier injection efficiency improvement layer is an AlGaN single layer structure or a layer composed of several AlGaN layers.x Ga 1-x N layer and Al y Ga 1-y The superlattice structure is composed of alternating N layers. When the second carrier injection improvement layer is an AlGaN single layer structure, the Al component is 40% to 100%, the thickness of the second carrier injection efficiency improvement layer is 1nm to 50nm, and the entire layer uses Mg as a p-type dopant with a doping concentration of 1×10 17 cm -3 ~1×10 22 cm -3 , when the second carrier injection efficiency improvement layer is composed of a plurality of Al x Ga 1-x N layer and Al y Ga 1-y When the superlattice structure is composed of N layers with alternating periods, the period is 1 to 50, and the entire layer uses Mg as a p-type dopant with a doping concentration of 1×10 17 cm -3 ~1×10 22 cm -3 , the Al x Ga 1-x The N layer and the Al y Ga 1-y The N layer satisfies 50%≤y≤x≤100%, and the Al x Ga 1-x The thickness of the N layer is 0.1nm~20nm, and the Al y Ga 1-y The thickness of the N layer is 0.1 nm to 20 nm.

[0043] (7) Growing an electron blocking layer. In this step, the temperature is raised to 700°C to 1100°C, and an electron blocking layer is grown on the second carrier injection efficiency improvement layer. The electron blocking layer is a single-layer AlGaN structure or an AlGaN / AlGaN superlattice structure, with an average Al composition of 50% to 100% and a thickness of 0.1 nm to 200 nm.

[0044] (8) Growth of p-type AlGaN hole injection layer: In this step, a p-type AlGaN injection layer is grown on the electron blocking layer at 700-1100°C, with an Al content of 10%-100% and a thickness of 1-50 nm. Mg is used as a p-type dopant.

[0045] (9) Growth of p-type GaN contact layer: In this step, a p-type GaN contact layer is grown on the p-type AlGaN hole injection layer at 400-900° C. with a thickness of 1-20 nm, and Mg is used as the p-type dopant.

[0046] The performance of the deep ultraviolet LED with the injection efficiency improvement layer structure is characterized by specific examples below.

[0047] Example 1

[0048] In this embodiment, the steps for preparing a deep ultraviolet LED having an injection efficiency improvement layer structure are as follows:

[0049] (1) A buffer layer in an AlN intrinsic layer is grown on a sapphire substrate at 700° C. with a thickness of 20 nm. The temperature is then raised to 1200° C. to grow an AlN intrinsic layer on the buffer layer in the AlN intrinsic layer. The total thickness of the AlN intrinsic layer is 800 nm.

[0050] (2) Cooling the temperature to 1000° C., growing an n-type AlGaN electron injection layer on the AlN intrinsic layer, wherein the Al component percentage is 40% and the thickness is 1000 nm.

[0051] (3) Cooling to 850° C. and growing a current spreading layer on one side of the n-type AlGaN electron injection layer.

[0052] (4) Maintaining the temperature at 850° C., a quantum well active layer is grown on one side of the current spreading layer.

[0053] (5) Maintaining the temperature at 850°C, a first carrier injection efficiency improvement layer with a thickness of 35 nm is grown on the quantum well active layer, wherein the first carrier injection efficiency improvement layer is composed of several Al 0.7 Ga 0.3 N layer and Al 0.5 Ga 0.5 The unintentionally doped superlattice structure composed of alternating N layers has a period of 10. 0.7 Ga 0.3 N layer and Al 0.5 Ga 0.5 The thickness of the N layer is 2nm and 1.5nm respectively.

[0054] (6) Cooling to 800° C., growing a second carrier injection efficiency improvement layer on the first carrier injection efficiency improvement layer, wherein the second carrier injection efficiency improvement layer is an AlGaN single layer structure with a thickness of 20 nm and an Al component of 50%. The entire layer uses Mg as a p-type dopant with a doping concentration of 1×10 21 cm -3 .

[0055] (7) Growth of electron blocking layer: The temperature is raised to 850° C., and an electron blocking layer is grown on the second carrier injection efficiency improvement layer, with an average Al composition of 40% and a thickness of 30 nm.

[0056] (8) Growth of p-type AlGaN hole injection layer: A p-type AlGaN hole injection layer is grown on the electron blocking layer at 800° C., with an Al component percentage of 20% and a thickness of 20 nm, and Mg is used as a p-type dopant.

[0057] (9) Growth of p-type GaN contact layer: a p-type GaN contact layer with a thickness of 10 nm is grown on the p-type AlGaN hole injection layer at 800° C., and Mg is used as a p-type dopant.

[0058] Example 2

[0059] In this embodiment, based on the preparation steps of Example 1, only step (6) in Example 1 was adjusted, and the other steps remained consistent with Example 1. The adjusted step (6) is as follows:

[0060] The temperature is lowered to 800° C., and a second carrier injection efficiency improvement layer is grown on the first carrier injection efficiency improvement layer, wherein the second carrier injection efficiency improvement layer is composed of a plurality of Al 0.55 Ga 0.45 N layer and Al 0.45 Ga 0.55 The superlattice structure consists of N layers alternating periodically, with a total thickness of 20 nm and a period of 10. The entire layer uses Mg as a p-type dopant with a doping concentration of 1×10 21 cm -3 , Al 0.55 Ga 0.45 N layer and Al 0.45 Ga 0.55 The thicknesses of the N layers are 1 nm and 1 nm respectively.

[0061] Comparative Example

[0062] In this embodiment, based on the preparation steps of Example 1, only steps (5) and (6) in Example 1 are removed, that is, the prepared deep ultraviolet LED with an injection efficiency improvement layer structure does not contain the first carrier injection efficiency improvement layer and the second carrier injection efficiency improvement layer compared with Example 1, and the remaining components are the same.

[0063] Examples 1 and 2 were compared with the sample of Reference Document 1, and the optical output power was tested. The results are shown in the following table:

[0064] sample Optical power Example 1 10.2 Example 2 11.4 Comparative Example 9.5

[0065] As can be seen from the table above, in Example 1, there are a first carrier injection efficiency improvement layer and a second carrier injection efficiency improvement layer that are not intentionally doped, wherein the second carrier injection efficiency improvement layer is an AlGaN single layer structure, and in Example 2, there are a first carrier injection efficiency improvement layer and a second carrier injection efficiency improvement layer that are not intentionally doped, wherein the second carrier injection efficiency improvement layer is composed of several Al 0.55 Ga 0.45 N layer and Al 0.45 Ga 0.55 The superlattice structure is composed of N layers of alternating periods, and the comparative example does not have the first carrier injection efficiency improvement layer and the second carrier injection efficiency improvement layer. It can be seen from the table that due to the addition of the first carrier injection efficiency improvement layer and the second carrier injection efficiency improvement layer, the light output power of the sample in Example 1 is increased by 7.3% compared with the conventional structure of the comparative example, and the light output power of the sample in Example 2 is increased by 20% compared with the conventional structure of the comparative example, thereby proving that adding two layers of epitaxial structure between the quantum well active layer and the electron blocking layer can significantly improve the carrier injection efficiency, thereby significantly improving the luminous efficiency of the deep ultraviolet LED device. In addition, the luminous efficiency of Example 2 is higher than that of Example 1, and its light output effect is the best.

[0066] In summary, the deep ultraviolet LED with an injection efficiency improvement layer structure provided by the present invention and its preparation method add two epitaxial structures between the quantum well active layer and the electron blocking layer to improve carrier injection efficiency. The first carrier injection efficiency improvement layer is an unintentionally doped superlattice. While assisting the electron blocking layer in blocking electrons, it can also prevent the high concentration of Mg in the low-temperature-grown second carrier injection efficiency improvement layer from diffusing into the quantum well active layer during epitaxial growth, thereby affecting the luminous efficiency. The second carrier injection efficiency improvement layer is a low-temperature-grown AlGaN material used to provide a high concentration of holes to the quantum well active layer, ultimately improving the luminous efficiency of the device.

[0067] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A deep ultraviolet LED having an injection efficiency improvement layer structure, characterized in that: The device comprises a sapphire substrate, an AlN intrinsic layer, an n-type AlGaN electron injection layer, a current spreading layer, a quantum well active layer, a first carrier injection efficiency improvement layer, a second carrier injection efficiency improvement layer, an electron blocking layer, a p-type AlGaN hole injection layer and a p-type GaN contact layer, which are stacked in sequence; The first carrier injection efficiency improvement layer is composed of a plurality of Al a Ga 1-a N layer and Al b Ga 1-b The superlattice structure is composed of an unintentionally doped N layer periodically alternating, and the first carrier injection efficiency improvement layer is formed by Al a Ga 1-a The N layer is in contact with the quantum well active layer barrier, and the first carrier injection efficiency improvement layer is connected to the quantum well active layer barrier through Al b Ga 1-b The N layer is in contact with the potential well of the second carrier injection efficiency improvement layer, the growth temperature of the second carrier injection improvement layer is lower than the lowest growth temperature of the quantum well active layer, and the second carrier injection improvement layer is an AlGaN structure p-type doped with Mg; The second carrier injection efficiency improvement layer is composed of a plurality of Al x Ga 1-x N layer and Al y Ga 1-y The superlattice structure composed of N layers is alternately periodic, and the Al x Ga 1-x The N layer and the Al b Ga 1-b N layer potential well contact, the Al y Ga 1-y The N layer is in contact with the electron blocking layer; The Al x Ga 1-x The N layer and the Al y Ga 1-y The N layers satisfy 50%≤y≤x≤100%.

2. The deep ultraviolet LED with an injection efficiency improvement layer structure according to claim 1, characterized in that: The Al a Ga 1-a The N layer and the Al b Ga 1-b The N layer satisfies 50%≤b≤a≤100%.

3. The deep ultraviolet LED with an injection efficiency improvement layer structure according to claim 2, characterized in that: The superlattice period of the first carrier injection efficiency improvement layer is 1 to 50, and the Al a Ga 1-a The thickness of the N layer is 0.1 nm~20 nm, and the Al b Ga 1-b The thickness of the N layer is 0.1 nm~20 nm.

4. The deep ultraviolet LED with an injection efficiency improvement layer structure according to claim 1, characterized in that: The superlattice period of the second carrier injection efficiency improvement layer is 1 to 50, and the entire layer uses Mg as a p-type dopant with a doping concentration of 1×10 17 cm -3 ~1×10 22 cm -3 , the Al x Ga 1-x The thickness of the N layer is 0.1 nm~20 nm, and the Al y Ga 1-y The thickness of the N layer is 0.1 nm~20 nm.

5. The deep ultraviolet LED with an injection efficiency improvement layer structure according to any one of claims 1 to 4, characterized in that: The growth temperature of the second carrier injection improvement layer is 20° C. to 300° C. lower than the lowest growth temperature of the quantum well active layer.

6. A method for preparing a deep ultraviolet LED having an injection efficiency improvement layer structure according to any one of claims 1 to 5, characterized in that: The steps include: (1) Growing an AlN intrinsic layer: growing a buffer layer in the AlN intrinsic layer on a sapphire substrate at 400-800°C, with a thickness of 10-50 nm, then raising the temperature to 1200-1400°C, and growing an AlN intrinsic layer on the buffer layer in the AlN intrinsic layer, with a total thickness of 500-4000 nm; (2) Growing an n-type AlGaN electron injection layer: cooling the temperature to 800-1200°C, and growing an n-type AlGaN electron injection layer on the AlN intrinsic layer, wherein the Al component percentage is 20-90% and the thickness is 500-4000 nm; (3) Growing a current spreading layer: cooling the temperature to 700-1100° C. and growing a current spreading layer on one side of the n-type AlGaN electron injection layer; (4) Growing a quantum well active layer: maintaining a temperature of 700-1100° C. and growing a quantum well active layer on one side of the current spreading layer; (5) Growing a first carrier injection efficiency improvement layer: maintaining a temperature of 700-1100° C., growing a first carrier injection efficiency improvement layer on the quantum well active layer with a thickness of 1-50 nm; (6) Growing a second carrier injection efficiency improvement layer: cooling the temperature to 500° C. to 1050° C., and growing a second carrier injection efficiency improvement layer on the first carrier injection efficiency improvement layer; (7) Growing an electron blocking layer: heating the temperature to 700°C to 1100°C, and growing an electron blocking layer on the second carrier injection efficiency improvement layer, wherein the electron blocking layer is a single-layer AlGaN structure or an AlGaN / AlGaN superlattice structure, wherein the average Al composition is 50% to 100% and the thickness is 0.1 nm to 200 nm; (8) Growing a p-type AlGaN hole injection layer: growing a p-type AlGaN hole injection layer on the electron blocking layer at 700-1100°C, wherein the Al component percentage is 10%-100%, the thickness is 1-50 nm, and Mg is used as a p-type dopant; (9) Growth of a p-type GaN contact layer: Growing a p-type GaN contact layer on the p-type AlGaN hole injection layer at 400-900° C. with a thickness of 1-20 nm, and using Mg as a p-type dopant.

Images