AlGaN-based deep ultraviolet LED epitaxial wafer on Si substrate and preparation method thereof

Abstract

The present invention discloses an AlGaN-based deep ultraviolet LED epitaxial wafer on an Si substrate and a preparation method thereof. The AlGaN-based deep ultraviolet LED epitaxial wafer on the Si substrate includes: a low-temperature AlN layer grown on the Si substrate, a high-temperature AlN layer grown on the low-temperature AlN layer, a first AlGaN layer grown on the high-temperature AlN layer, a second AlGaN layer grown on the first AlGaN layer, an n-type doped AlGaN layer grown on the second AlGaN layer, an AlGaN multiple quantum well layer grown on the n-type doped AlGaN layer, an electron blocking layer grown on the AlGaN multiple quantum well layer, an Al composition step-graded p-type doped AlGaN layer grown on the electron blocking layer, and a p-type doped GaN layer grown on the Al composition step-graded p-type doped AlGaN layer.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and particularly to an AlGaN-based deep ultraviolet LED epitaxial wafer on an Si substrate and a preparation method thereof. Background Art

[0002] Deep ultraviolet light has broad application prospects in the fields of national defense technology, information technology, biopharmaceuticals, environmental monitoring, public health, sterilization and disinfection, etc. The traditional ultraviolet light sources currently used are gas lasers and mercury lamps, which have the disadvantages of large volume, high energy consumption and pollution. The AlGaN-based compound semiconductor ultraviolet light-emitting diode (LED) is a solid-state ultraviolet light source, which has the advantages of small volume, high efficiency, long life, environmental friendliness, low energy consumption and no pollution. The high-Al-component AlGaN material is an irreplaceable material system for preparing high-performance deep ultraviolet LEDs, and there is a great demand in both civilian and military aspects. For example, in the medical and health fields such as sterilization and disinfection, cancer detection, and skin disease treatment, the AlGaN-based ultraviolet light source has many advantages such as mercury-free pollution, wavelength tunability, small volume, good integration, low energy consumption, and long life.

[0003] In recent years, some progress has been made in the development of AlGaN-based deep ultraviolet LEDs, but performance problems such as low external quantum efficiency and low luminous power still hinder their commercialization, and high-quality epitaxial materials are the basis for preparing high-performance deep ultraviolet LEDs. Currently, high-quality AlGaN materials are generally fabricated by heteroepitaxial methods. At present, Si substrates are also used as the epitaxial substrates for AlGaN-based deep ultraviolet LEDs, but there is a large lattice mismatch between the Si substrate and the epitaxially grown AlGaN material. Therefore, to grow high-quality AlGaN materials and high-performance deep ultraviolet LED epitaxial wafers on Si substrates, major defects such as lattice mismatch, crystal dislocations, and stacking faults still need to be overcome. Summary of the Invention

[0004] The object of the present invention is an AlGaN-based deep ultraviolet LED epitaxial wafer on an Si substrate and a preparation method thereof, aiming to solve the problem that the performance of the AlGaN-based deep ultraviolet LED epitaxial wafer in the prior art needs to be improved.

[0005] An embodiment of the present invention provides an AlGaN-based deep ultraviolet LED epitaxial wafer on an Si substrate, which includes: a low-temperature AlN layer grown on the Si substrate, a high-temperature AlN layer grown on the low-temperature AlN layer, a first AlGaN layer grown on the high-temperature AlN layer, a second AlGaN layer grown on the first AlGaN layer, an n-type doped AlGaN layer grown on the second AlGaN layer, an AlGaN multiple quantum well layer grown on the n-type doped AlGaN layer, an electron blocking layer grown on the AlGaN multiple quantum well layer, an Al composition step-graded p-type doped AlGaN layer grown on the electron blocking layer, and a p-type doped GaN layer grown on the Al composition step-graded p-type doped AlGaN layer.

[0006] Preferably, the thickness of the low-temperature AlN layer is 50 - 100 nm.

[0007] Preferably, the thickness of the high-temperature AlN layer is 200 - 500 nm.

[0008] Preferably, the thickness of the first AlGaN layer is 2 - 10 nm.

[0009] Preferably, the thickness of the second AlGaN layer is 800 - 2000 nm.

[0010] Preferably, the thickness of the n-type doped AlGaN layer is 3 - 5 μm.

[0011] Preferably, the AlGaN multiple quantum well layer is composed of 7 - 10 periods of Al 0.3 Ga 0.7 N well layers and Al 0.5 Ga 0.5 N barrier layers.

[0012] Preferably, the thickness of the Al 0.3 Ga 0.7 N well layer is 2 - 3 nm, and the thickness of the Al 0.5 Ga 0.5 N barrier layer is 10 - 13 nm.

[0013] Preferably, in the direction from near the Si substrate to far from the Si substrate, the content of Al in the Al composition step-graded p-type doped AlGaN layer gradually decreases from 0.4 to 0, and the thickness of the Al composition step-graded p-type doped AlGaN layer is 300 - 350 nm.

[0014] An embodiment of the present invention provides a method for preparing the above-mentioned AlGaN-based deep ultraviolet LED epitaxial wafer, which includes:

[0015] Select an Si substrate;

[0016] Grow a low-temperature AlN layer on the Si substrate;

[0017] Grow a high-temperature AlN layer on the low-temperature AlN layer;

[0018] Grow a first AlGaN layer on the high-temperature AlN layer;

[0019] Grow a second AlGaN layer on the first AlGaN layer;

[0020] Grow an n-type doped AlGaN layer on the second AlGaN layer;

[0021] Grow an AlGaN multi-quantum well layer on the n-type doped AlGaN layer;

[0022] Grow an electron blocking layer on the AlGaN multi-quantum well layer;

[0023] Grow an Al composition step-graded p-type doped AlGaN layer on the electron blocking layer;

[0024] Grow a p-type doped GaN layer on the Al composition step-graded p-type doped AlGaN layer.

[0025] The embodiment of the present invention provides an AlGaN-based deep ultraviolet LED epitaxial wafer on a Si substrate and a preparation method. The AlGaN-based deep ultraviolet LED epitaxial wafer on the Si substrate includes: a low-temperature AlN layer grown on the Si substrate, a high-temperature AlN layer grown on the low-temperature AlN layer, a first AlGaN layer grown on the high-temperature AlN layer, a second AlGaN layer grown on the first AlGaN layer, an n-type doped AlGaN layer grown on the second AlGaN layer, an AlGaN multi-quantum well layer grown on the n-type doped AlGaN layer, an electron blocking layer grown on the AlGaN multi-quantum well layer, an Al composition step-graded p-type doped AlGaN layer grown on the electron blocking layer, and a p-type doped GaN layer grown on the Al composition step-graded p-type doped AlGaN layer. The present invention adopts a combination of a low-temperature AlN layer and a high-temperature AlN layer, as well as an amorphous buffer layer technology, to reduce the stress between Si and AlGaN; and adopts an Al composition step-graded p-type AlGaN structure to overcome the deficiencies of the prior art and obtain a high-performance AlGaN-based deep ultraviolet LED. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 This is a schematic structural diagram of an AlGaN-based deep ultraviolet LED epitaxial wafer on an Si substrate provided by an embodiment of the present invention;

[0028] Figure 2 This is a schematic flow diagram of a method for preparing an AlGaN-based deep ultraviolet LED epitaxial wafer on an Si substrate provided by an embodiment of the present invention. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] It should be understood that when used in this specification and the appended claims, the terms "comprises" and "comprising" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0031] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in this specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0032] It should be further understood that the term " / and / " used in this specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0033] An embodiment of the present invention provides an AlGaN-based deep ultraviolet LED epitaxial wafer on an Si substrate, as Figure 1As shown, it includes: a low-temperature AlN layer 102 grown on a Si substrate 101, a high-temperature AlN layer 103 grown on the low-temperature AlN layer 102, a first AlGaN layer 104 grown on the high-temperature AlN layer 103, a second AlGaN layer 105 grown on the first AlGaN layer 104, an n-type doped AlGaN layer 106 grown on the second AlGaN layer 105, an AlGaN multiple quantum well layer 107 grown on the n-type doped AlGaN layer 106, an electron blocking layer 108 grown on the AlGaN multiple quantum well layer 107, an Al composition step-graded p-type doped AlGaN layer 109 grown on the electron blocking layer 108, and a p-type doped GaN layer 110 grown on the Al composition step-graded p-type doped AlGaN layer 109.

[0034] Due to the large lattice mismatch between Si and AlGaN, the present invention adopts a low-temperature combined with a high-temperature AlN buffer layer, as well as an amorphous buffer layer technology to reduce the stress between Si and AlGaN; and adopts an Al composition step-graded p-type AlGaN structure to overcome the deficiencies of the prior art and obtain a high-performance AlGaN-based deep ultraviolet LED.

[0035] In one embodiment, the thickness of the low-temperature AlN layer 102 is 50 - 100 nm, such as 75 nm. The low-temperature AlN layer 102 can prevent the back-melting etching reaction of Ga and Si at high temperatures. The low-temperature grown AlN buffer layer (i.e., the low-temperature AlN layer 102) has a high defect density and can reduce the dislocation extending into the high-temperature grown AlN buffer layer (i.e., the high-temperature AlN layer 103).

[0036] In one embodiment, the thickness of the high-temperature AlN layer 103 is 200 - 500 nm, such as 350 nm. Both the low-temperature AlN layer 102 and the high-temperature AlN layer 103 are buffer layers, providing a high-quality template for the growth of the subsequent first AlGaN layer 104 and second AlGaN layer 105.

[0037] In one embodiment, the thickness of the first AlGaN layer 104 is 2 - 10 nm, such as 5 nm. The first AlGaN layer 104 is an amorphous buffer layer AlGaN. In the embodiment of the present invention, a thin amorphous buffer layer AlGaN is adopted. The amorphous material can have a large number of vacancy defects, and dislocations are easy to nucleate in this layer of material. At the same time, the vacancy defects can promote the slip of dislocations in the buffer layer and prevent the dislocations from penetrating into the subsequent epitaxial layer. Therefore, this large-mismatch buffer layer can play a role in stress release. The Al composition in the first AlGaN layer 104 is 0.7 (the meaning of this component is the proportion of Al in the total content of Al and Ga), that is, the first AlGaN layer 104 is Al 0.7 Ga0.3 N layer.

[0038] In one embodiment, the thickness of the second AlGaN layer 105 is 800 - 2000 nm, such as 1500 nm. The Al component in the second AlGaN layer 105 is 0.5, that is, the second AlGaN layer 105 is Al 0.5 Ga 0.5 N layer. The first AlGaN layer 104 and the second AlGaN layer 105 can provide a high-quality material template for the growth of the subsequent n-type doped AlGaN layer 106.

[0039] In one embodiment, the thickness of the n-type doped AlGaN layer 106 is 3 - 5 μm, such as 4 μm. The function of the n-type doped AlGaN layer 106 is to provide electrons for the multi-quantum well layer.

[0040] In one embodiment, the AlGaN multi-quantum well layer 107 is composed of 7 - 10 periods of Al 0.3 Ga 0.7 N well layer and Al 0.5 Ga 0.5 N barrier layer (such as 8 periods). The AlGaN multi-quantum well layer 107 is the active light-emitting layer of the LED. Electrons and holes perform radiative recombination in this layer to emit light of a specific wavelength. One period is composed of one layer of Al 0.3 Ga 0.7 N well layer and one layer of Al 0.5 Ga 0.5 N barrier layer. In this way, one layer of Al 0.3 Ga 0.7 N well layer and one layer of Al 0.5 Ga 0.5 N barrier layer are repeatedly stacked alternately to form multiple periods of Al 0.3 Ga 0.7 N well layer and Al 0.5 Ga 0.5 N barrier layer.

[0041] In one embodiment, the thickness of the Al 0.3 Ga 0.7 N well layer is 2 - 3 nm, such as 2.5 nm. The thickness of the Al 0.5 Ga 0.5 N barrier layer is 10 - 13 nm, such as 12 nm.

[0042] The electron blocking layer 108 can prevent electrons from overflowing when current is injected, so that electrons cannot be completely confined in the quantum well for radiative recombination. The electron blocking layer 108 can be Al 0.4 Ga 0.6N electron blocking layer. The thickness of the electron blocking layer 108 is 20 - 50 nm, such as 30 nm.

[0043] In one embodiment, in the direction from close to the Si substrate to far from the Si substrate, the content of the Al component in the Al component segmented gradient p-type doped AlGaN layer 109 gradually decreases from 0.4 to 0 (i.e., from Al 0.4 Ga 0.6 N to Al0Ga1N), the thickness of the Al component segmented gradient p-type doped AlGaN layer 109 is 300 - 350 nm, such as 325 nm. The Al component segmented gradient p-type doped AlGaN layer 109 provides holes for the multi-quantum well active layer. In the deep ultraviolet LED device structure, electrons are injected from the n-type layer into the multi-quantum well region and recombine with holes injected from the p-type region. Therefore, the electron current density in the material growth direction gradually decreases, and the additional current generated by the electron current overflowing into the p-type layer is defined as the electron leakage current. Due to the polarization electric field in the multi-quantum well and the electron blocking layer causing the energy band to bend, the quantum barrier and the traditional electron blocking layer cannot effectively block the electrons in the quantum well, resulting in obvious electron leakage in the traditional deep ultraviolet LED structure. The electrons injected by the Al component segmented gradient p-type doped AlGaN layer 109 are more effectively confined in the multi-quantum well, and more holes are effectively injected into the active region, thereby effectively improving the radiative recombination efficiency of the deep ultraviolet LED with the Al component segmented gradient p-type doped AlGaN layer 109.

[0044] The p-type doped GaN layer 110 can provide holes for the multi-quantum well layer and is conducive to forming a good ohmic contact with the metal electrode. The thickness of the p-type doped GaN layer 110 is 300 - 350 nm, such as 325 nm. In the p-type doped GaN layer 110, the doping element is Mg, and the doping concentration of Mg is 1×10 17 ~5×10 18 .

[0045] The embodiment of the present invention provides a preparation method of the AlGaN-based deep ultraviolet LED epitaxial wafer as described above, as Figure 2 shown, which includes steps S201 - S210:

[0046] S201. Select a Si substrate;

[0047] S202. Grow a low-temperature AlN layer on the Si substrate;

[0048] S203. Grow a high-temperature AlN layer on the low-temperature AlN layer;

[0049] S204. Grow a first AlGaN layer on the high-temperature AlN layer;

[0050] S205. Grow a second AlGaN layer on the first AlGaN layer;

[0051] S206. Grow an n-type doped AlGaN layer on the second AlGaN layer;

[0052] S207. Grow an AlGaN multi-quantum well layer on the n-type doped AlGaN layer;

[0053] S208. Grow an electron blocking layer on the AlGaN multi-quantum well layer;

[0054] S209. Grow an Al composition step-graded p-type doped AlGaN layer on the electron blocking layer;

[0055] S210. Grow a p-type doped GaN layer on the Al composition step-graded p-type doped AlGaN layer. In the step S201, a commercially available ordinary Si substrate can be selected.

[0056] In the step S202, in the low-temperature AlN layer growth step, grow the low-temperature AlN layer by metalorganic chemical vapor deposition. The process conditions are: trimethylaluminum as the Al source, ammonia as the N source, hydrogen as the carrier gas, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 900 - 1000 °C, the beam ratio V / III is 3000 - 5000, and the growth rate is 1 - 2 μm / h.

[0057] In the step S203, in the high-temperature AlN layer growth step, grow the high-temperature AlN layer on the low-temperature AlN layer by metalorganic chemical vapor deposition. The process conditions are: trimethylaluminum as the Al source, ammonia as the N source, hydrogen as the carrier gas, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam ratio V / III is 3000 - 5000, and the growth rate is 1 - 2 μm / h.

[0058] In the step S204, in the first AlGaN layer growth step, grow the first AlGaN layer on the high-temperature AlN layer by metalorganic chemical vapor deposition. The process conditions are: trimethylaluminum as the Al source, trimethylgallium as the Ga source, ammonia as the N source, hydrogen as the carrier gas, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 600 - 900 °C, the beam ratio V / III is 3000 - 5000, and the growth rate is 1 - 2 μm / h.

[0059] In the step S205, in the second AlGaN layer growth step, the second AlGaN layer is grown on the first AlGaN layer by metal organic chemical vapor deposition. The process conditions are as follows: trimethylaluminum is used as the Al source, trimethylgallium is used as the Ga source, ammonia is used as the N source, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 1 - 2 μm / h.

[0060] In the step S206, in the n-type doped AlGaN layer epitaxial growth step, the n-type doped AlGaN layer is grown on the second AlGaN layer by metal organic chemical vapor deposition. The process conditions are as follows: trimethylaluminum is used as the Al source, trimethylgallium is used as the Ga source, ammonia is used as the N source, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 2 - 4 μm / h; the n-type doped AlGaN layer is doped with Si, and the Si doping concentration is 1×10 17 ~1×10 20 cm -3 .

[0061] In the step S207, in the AlGaN multiple quantum well layer epitaxial growth step, 7 - 10 cycles of Al 0.3 Ga 0.7 N well layer / Al 0.5 Ga 0.5 N barrier layer are grown on the n-type doped AlGaN layer by metal organic chemical vapor deposition. The process conditions are as follows: trimethylaluminum is used as the Al source, trimethylgallium is used as the Ga source, ammonia is used as the N source, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 2 - 4 μm / h.

[0062] In the step S208, in the electron blocking layer epitaxial growth step, an Al 0.4 Ga 0.6 N electron blocking layer is grown on the AlGaN multiple quantum well layer by metal organic chemical vapor deposition. The process conditions are as follows: trimethylaluminum is used as the Al source, trimethylgallium is used as the Ga source, ammonia is used as the N source, the reaction chamber pressure is 50 - 300 torr, the substrate temperature is 1000 - 1260 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 2 - 4 μm / h.

[0063] In the step S209, in the epitaxial growth step of the Al component segmented gradient p-type doped AlGaN layer, the metal organic chemical vapor deposition method is used to grow the Al component segmented gradient p-type doped AlGaN layer on the electron blocking layer. The process conditions are as follows: trimethylaluminum is used as the Al source, trimethylgallium is used as the Ga source, ammonia is used as the N source, the reaction chamber pressure is 50 - 300 torr, the Si substrate temperature is 1000 - 1260 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 2 - 4 μm / h.

[0064] In the step S210, in the epitaxial growth step of the p-type doped GaN layer, the metal organic chemical vapor deposition method is used to grow the p-type doped GaN layer on the Al component segmented gradient p-type doped AlGaN layer. The process conditions are as follows: trimethylgallium is used as the Ga source, ammonia is used as the N source, the reaction chamber pressure is 50 - 300 torr, the Si substrate temperature is 1000 - 1060 °C, the beam flux ratio V / III is 3000 - 5000, and the growth rate is 2 - 4 μm / h.

[0065] The AlGaN-based deep ultraviolet LED grown on the Si substrate prepared in one embodiment of the present invention is fabricated into a chip: electrodes are electron beam evaporated and annealed on the AlGaN-based deep ultraviolet LED epitaxial wafer grown in this embodiment to form ohmic contacts. For the AlGaN-based deep ultraviolet LED device prepared on the Si substrate, at a working current of 50 mA, the light output power of the LED device is 3.3 mW, and the turn-on voltage value is 5.18 V. The AlGaN-based deep ultraviolet LED grown on the Si substrate prepared in another embodiment of the present invention is fabricated into a chip: electrodes are electron beam evaporated and annealed on the AlGaN-based deep ultraviolet LED epitaxial wafer grown in this embodiment to form ohmic contacts. For the AlGaN-based deep ultraviolet LED device prepared on the Si substrate, at a working current of 50 mA, the light output power of the LED device is 3.5 mW, and the turn-on voltage value is 5.5 V.

[0066] The embodiments of the present invention adopt a low-temperature combined with a high-temperature AlN buffer layer and an amorphous buffer layer technology to reduce the lattice mismatch between Si and AlGaN; relieve the defect density in the thin film, thereby realizing the growth of high-crystalline-quality AlGaN thin films and AlGaN-based deep ultraviolet LED epitaxial wafers; in the preparation method of the present invention, an Al component segmented and gradually changed p-type AlGaN structure is adopted, which is beneficial to overcoming the problem of low light extraction efficiency caused by the polarization effect of AlGaN-based deep ultraviolet LEDs and obtaining high-performance AlGaN-based deep ultraviolet LEDs; the present invention uses Si as a substrate, which is easy to obtain and inexpensive, and is beneficial to reducing production costs; the growth process of the present invention is unique and simple to implement and has repeatability; the present invention can obtain an epitaxial layer thin film with high quality and a smooth interface, and further prepare high-performance and high-light-emitting-efficiency AlGaN-based optoelectronic devices. This method is simple to implement, has remarkable effects and is inexpensive.

[0067] The various embodiments in the specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0068] It should also be noted that in this specification, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

Claims

1. An AlGaN-based deep ultraviolet LED epitaxial wafer on an Si substrate, characterized in that, Comprising: A low-temperature AlN layer grown on a Si substrate, a high-temperature AlN layer grown on the low-temperature AlN layer, a first AlGaN layer grown on the high-temperature AlN layer, a second AlGaN layer grown on the first AlGaN layer, an n-type doped AlGaN layer grown on the second AlGaN layer, an AlGaN multi-quantum well layer grown on the n-type doped AlGaN layer, an electron blocking layer grown on the AlGaN multi-quantum well layer, an Al composition step-graded p-type doped AlGaN layer grown on the electron blocking layer, and a p-type doped GaN layer grown on the Al composition step-graded p-type doped AlGaN layer; The thickness of the low-temperature AlN layer is 50 - 100 nm; The thickness of the high-temperature AlN layer is 200 - 500 nm; The thickness of the first AlGaN layer is 2 - 10 nm; The thickness of the second AlGaN layer is 800 - 2000 nm; The thickness of the n-type doped AlGaN layer is 3 - 5 μm; The AlGaN multi-quantum well layer consists of 7 to 10 periods of Al 0.3 Ga 0.7 N well layers and Al 0.5 Ga 0.5 N barrier layers; The Al 0.3 Ga 0.7 N well layer has a thickness of 2 to 3 nm, and the Al 0.5 Ga 0.5 N barrier layer has a thickness of 10 to 13 nm; In the direction from near the Si substrate to far from the Si substrate, the content of Al component in the Al composition step-graded p-type doped AlGaN layer gradually decreases from 0.4 to 0, and the thickness of the Al composition step-graded p-type doped AlGaN layer is 300 - 350 nm.

2. A method for preparing an AlGaN-based deep ultraviolet LED epitaxial wafer according to claim 1, characterized in that, Comprising: Select a Si substrate; Grow a low-temperature AlN layer on the Si substrate; Grow a high-temperature AlN layer on the low-temperature AlN layer; Grow a first AlGaN layer on the high-temperature AlN layer; Grow a second AlGaN layer on the first AlGaN layer; Grow an n-type doped AlGaN layer on the second AlGaN layer; Grow an AlGaN multi-quantum well layer on the n-type doped AlGaN layer; Grow an electron blocking layer on the AlGaN multi-quantum well layer; Grow an Al composition step-graded p-type doped AlGaN layer on the electron blocking layer; Grow a p-type doped GaN layer on the Al composition step-graded p-type doped AlGaN layer.

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