Algan-based deep ultraviolet led epitaxial wafer and preparation method

Abstract

This invention discloses an AlGaN-based deep ultraviolet (DUV) LED epitaxial wafer and its fabrication method. The AlGaN-based DUV LED epitaxial wafer comprises: a silicon carbide substrate, an Ag layer deposited on the silicon carbide substrate, an AlN buffer layer grown on the Ag layer, an AlGaN buffer layer grown on the AlN buffer layer, an undoped AlGaN layer grown on the AlGaN buffer layer, an n-type doped AlGaN layer grown on the undoped 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, and a p-type doped GaN thin film grown on the electron blocking layer. This invention eliminates the need for a stripping process, significantly improving external quantum efficiency; it reduces dislocation formation, increases carrier radiative recombination efficiency, and yields DUV LEDs with high thermal conductivity, high electrical conductivity, and high luminous efficacy; the DUV LED exhibits more uniform current distribution, improving light extraction efficiency, while also possessing good heat dissipation capabilities; the fabrication process is simple and reproducible.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to AlGaN-based deep ultraviolet LED epitaxial wafers and their preparation methods. Background Technology

[0002] Deep ultraviolet (DUV) light has broad application prospects in defense technology, information technology, biopharmaceuticals, environmental monitoring, public health, and sterilization. Currently used traditional UV light sources are gas lasers and mercury lamps, which suffer from drawbacks such as large size, high energy consumption, and pollution. AlGaN-based compound semiconductor UV light-emitting diodes (LEDs) are solid-state UV light sources with advantages such as small size, high efficiency, long lifespan, environmental friendliness, low energy consumption, and no pollution. High-Al content AlGaN materials are an irreplaceable material system for preparing high-performance DUV LEDs, with significant demand in both civilian and military applications. For example, in medical and health fields such as sterilization, cancer detection, and skin disease treatment, AlGaN-based UV light sources offer numerous advantages including no mercury pollution, tunable wavelength, small size, good integration, low energy consumption, and long lifespan.

[0003] However, the performance of AlGaN-based deep ultraviolet LED epitaxial wafers provided by existing technologies still needs to be improved. Summary of the Invention

[0004] The purpose of this invention is to provide an AlGaN-based deep ultraviolet LED epitaxial wafer and its preparation method, aiming to solve the problem that the quality of AlGaN-based deep ultraviolet LED epitaxial wafers needs to be improved in the prior art.

[0005] This invention provides an AlGaN-based deep ultraviolet LED epitaxial wafer based on a silicon carbide substrate, comprising: a silicon carbide substrate, an Ag layer deposited on the silicon carbide substrate, an AlN buffer layer grown on the Ag layer, an AlGaN buffer layer grown on the AlN buffer layer, an undoped AlGaN layer grown on the AlGaN buffer layer, an n-type doped AlGaN layer grown on the undoped 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, and a p-type doped GaN thin film grown on the electron blocking layer.

[0006] Furthermore, the thickness of the Ag layer is 500-1000 nm.

[0007] Furthermore, the thickness of the AlN buffer layer is 5–50 nm.

[0008] Furthermore, the thickness of the AlGaN buffer layer is 300–500 nm.

[0009] Furthermore, the thickness of the undoped AlGaN layer is 500–800 nm.

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

[0011] Furthermore, the AlGaN multi-quantum-well layer is an Al with 7 to 10 cycles. 0.3 Ga 0.7 N-well layer and Al 0.5 Ga 0.5 N-layer barrier, where Al 0.3 Ga 0.7 The thickness of the N-well layer is 2–3 nm, Al 0.5 Ga 0.5 The thickness of the N-barrier layer is 10–13 nm.

[0012] Furthermore, the electron blocking layer is Al. 0.4 Ga 0.6 The electron blocking layer has a thickness of 20–50 nm.

[0013] Furthermore, the thickness of the p-type doped GaN film is 300–350 nm.

[0014] This invention also provides a method for fabricating an AlGaN-based deep ultraviolet LED epitaxial wafer based on a silicon carbide substrate as described above, comprising:

[0015] Silicon carbide substrate selected;

[0016] An Ag layer is deposited on the silicon carbide substrate;

[0017] An AlN buffer layer is grown on the Ag layer;

[0018] An AlGaN buffer layer is grown on the AlN buffer layer;

[0019] An undoped AlGaN layer is grown on the AlGaN buffer layer;

[0020] An n-type doped AlGaN layer is epitaxially grown on the undoped AlGaN layer;

[0021] An AlGaN multiple quantum well layer is epitaxially grown on the n-type doped AlGaN layer;

[0022] An electron blocking layer is epitaxially grown on the AlGaN multi-quantum-well layer;

[0023] A p-type doped GaN thin film is epitaxially grown on the electron blocking layer.

[0024] This invention provides an AlGaN-based deep ultraviolet LED epitaxial wafer and its fabrication method. The AlGaN-based deep ultraviolet LED epitaxial wafer comprises: a silicon carbide substrate, an Ag layer deposited on the silicon carbide substrate, an AlN buffer layer grown on the Ag layer, an AlGaN buffer layer grown on the AlN buffer layer, an undoped AlGaN layer grown on the AlGaN buffer layer, an n-type doped AlGaN layer grown on the undoped 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, and a p-type doped GaN thin film grown on the electron blocking layer. This invention epitaxially grows an Ag layer as a reflective layer on a silicon carbide substrate, avoiding the absorption characteristics of ultraviolet light by the silicon carbide substrate itself. This eliminates the need for the substrate stripping process used in traditional deep ultraviolet LED growth on silicon carbide substrates, and significantly improves the external quantum efficiency of the device. The deep ultraviolet LED epitaxial wafer prepared by this invention effectively reduces dislocation formation, producing high-quality deep ultraviolet LED epitaxial wafers and improving carrier radiative recombination efficiency. This results in deep ultraviolet LEDs with high thermal conductivity, high electrical conductivity, and high luminous performance. Using an Ag layer as the reflective layer completely preserves the silicon carbide substrate as the base material and provides support, thus making the current distribution of the deep ultraviolet LED more uniform, improving light extraction efficiency, and providing good heat dissipation. The fabrication process of this invention is simple, reproducible, and can be used for large-scale production applications. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of an AlGaN-based deep ultraviolet LED epitaxial wafer based on a silicon carbide substrate provided in an embodiment of the present invention;

[0027] Figure 2 A schematic flowchart illustrating the fabrication method of AlGaN-based deep ultraviolet LED epitaxial wafers based on silicon carbide substrates provided in this embodiment of the invention;

[0028] Figure 3 Electroluminescence spectrum of AlGaN-based deep ultraviolet LED epitaxial wafers prepared on silicon carbide substrates in an embodiment of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

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

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

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

[0033] Please see Figure 1 This invention provides an AlGaN-based deep ultraviolet LED epitaxial wafer based on a silicon carbide substrate, comprising: a silicon carbide substrate 101, an Ag layer 102 deposited on the silicon carbide substrate 101, an AlN buffer layer 103 grown on the Ag layer 102, an AlGaN buffer layer 104 grown on the AlN buffer layer 103, an undoped AlGaN layer 105 grown on the AlGaN buffer layer 104, an n-type doped AlGaN layer 106 grown on the undoped 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, and a p-type doped GaN thin film 109 grown on the electron blocking layer 108.

[0034] The AlGaN-based deep ultraviolet LED epitaxial wafers prepared in the embodiments of the present invention have low defect density, good crystal quality, and good electrical and optical properties.

[0035] The silicon carbide substrate 101 can be a common commercial substrate.

[0036] Furthermore, the Ag layer 102 is deposited directly on the silicon carbide substrate 101. The thickness of the Ag layer 102 is preferably 500-1000 nm.

[0037] Furthermore, the thickness of the AlN buffer layer 103 is preferably 5–50 nm. The AlN buffer layer 103 is used to reduce the lattice mismatch between the silicon carbide substrate 101 and the AlGaN material.

[0038] Furthermore, the thickness of the AlGaN buffer layer 104 is preferably 300–500 nm. The AlGaN buffer layer 104 serves as a template for the growth of AlGaN materials.

[0039] Furthermore, the thickness of the undoped AlGaN layer 105 is preferably 500–800 nm. Because the AlGaN buffer layer 104 has a high defect density, an undoped AlGaN layer 105 is grown before the active layer (i.e., n-type, multiple quantum well, or p-type layer). The AlGaN buffer layer 104 and the undoped AlGaN layer 105 are made of the same material, AlGaN. This is because growing AlGaN with a lattice mismatch with AlN on AlN would result in a large number of defects. Therefore, an AlGaN layer is grown as a buffer layer, and then an undoped AlGaN layer is grown to prepare for the next n-type AlGaN layer. This layer is called the undoped AlGaN layer mainly to distinguish it from the n-type AlGaN layer.

[0040] Furthermore, the thickness of the n-type doped AlGaN layer 106 is preferably 3–5 μm. The n-type doped AlGaN layer 106 may be doped with Si, with a Si doping concentration of 1 × 10⁻⁶. 17 ~1×10 20 cm -3 .

[0041] Furthermore, the AlGaN multi-quantum-well layer 107 is an Al with 7 to 10 cycles. 0.3 Ga 0.7 N-well layer and Al 0.5 Ga 0.5 N-layer barrier, where Al 0.3 Ga 0.7 The thickness of the N-well layer is preferably 2–3 nm, Al 0.5 Ga 0.5 The thickness of the N-barrier layer is preferably 10–13 nm. The total thickness of the AlGaN multi-quantum-well layer 107 is 80–160 nm. Here, the period refers to a single Al layer. 0.3 Ga 0.7 N-well layer and one layer of Al 0.5 Ga 0.5The N-layers are alternately arranged to form a cycle, and a total of 7 to 10 cycles are set.

[0042] Furthermore, the electron blocking layer 108 is Al. 0.4 Ga 0.6 The electron blocking layer 108 has a thickness of 20–50 nm. An n-type doped AlGaN, an AlGaN multi-quantum-well layer, and a p-type doped GaN constitute the light-emitting layer. To prevent injected electrons from inefficiently radiatively recombinizing in the active region, the electron blocking layer is inserted between the p-type GaN and the quantum barrier.

[0043] Furthermore, the thickness of the p-type doped GaN thin film 109 is preferably 300–350 nm.

[0044] Please see Figure 2 The present invention also provides a method for preparing an AlGaN-based deep ultraviolet LED epitaxial wafer based on a silicon carbide substrate as described above. Figure 2 As shown, the preparation method includes steps S201 to S209:

[0045] S201. Select a silicon carbide substrate;

[0046] S202, Deposit an Ag layer on the silicon carbide substrate;

[0047] S203. An AlN buffer layer is grown on the Ag layer;

[0048] S204. An AlGaN buffer layer is grown on the AlN buffer layer;

[0049] S205. An undoped AlGaN layer is grown on the AlGaN buffer layer;

[0050] S206. An n-type doped AlGaN layer is epitaxially grown on the undoped AlGaN layer;

[0051] S207. Epitaxially grow an AlGaN multiple quantum well layer on the n-type doped AlGaN layer;

[0052] S208. An electron blocking layer is epitaxially grown on the AlGaN multi-quantum-well layer;

[0053] S209. Epitaxially grow a p-type doped GaN thin film on the electron blocking layer.

[0054] The preparation method provided in this invention effectively solves the problem of silicon carbide absorbing ultraviolet light by depositing an Ag layer on a silicon carbide substrate as a mirror. At the same time, the Ag layer can also serve as a conductive layer, avoiding the need for electrode deposition during chip fabrication and effectively simplifying the LED chip manufacturing process.

[0055] Specifically, in step S202, an Ag layer is deposited using a thermal evaporation method at a deposition temperature of 200–300°C, and the thickness of the Ag layer is 500–1000 nm.

[0056] Preferably, in step S203, the AlN buffer layer is grown by magnetron sputtering at a growth temperature of 400–500°C, and the thickness of the AlN buffer layer is 5–50 nm.

[0057] Preferably, in step S204, an AlGaN buffer layer is grown on the AlN buffer layer using metal-organic chemical vapor deposition. The process conditions are: reaction chamber pressure of 50–300 torr, Si substrate temperature of 1000–1260°C, beam current ratio V / III of 3000–5000, and growth rate of 2–4 μm / h.

[0058] Preferably, in step S205, an undoped AlGaN layer is grown on the AlGaN buffer layer using metal-organic chemical vapor deposition. The process conditions are: reaction chamber pressure of 50–300 torr, Si substrate temperature of 1000–1260°C, beam current ratio V / III of 3000–5000, and growth rate of 2–4 μm / h.

[0059] Preferably, in step S206, an n-type doped AlGaN layer is grown on the undoped AlGaN layer using metal-organic chemical vapor deposition (MOCVD). The process conditions are: reaction chamber pressure of 50–300 torr, Si substrate temperature of 1000–1260°C, beam current ratio V / III of 3000–5000, and growth rate of 2–4 μm / h. The n-type doped AlGaN layer is doped with Si, and the Si doping concentration is 1 × 10⁻⁶. 17 ~1×10 20 cm -3 .

[0060] Preferably, in step S207, 7 to 10 cycles of Al are grown on the n-type doped AlGaN layer using metal-organic chemical vapor deposition. 0.3 Ga 0.7 N-well layer / Al 0.5 Ga 0.5 The N-barrier layer was fabricated under the following conditions: reaction chamber pressure of 50–300 torr, Si substrate temperature of 1000–1260℃, beam current ratio V / III of 3000–5000, and growth rate of 2–4 μm / h.

[0061] Preferably, in step S208, Al is grown on the AlGaN multiple quantum well layer using metal-organic chemical vapor deposition. 0.4 Ga 0.6The N electron blocking layer was fabricated under the following conditions: reaction chamber pressure of 50–300 torr, Si substrate temperature of 1000–1260℃, beam current ratio V / III of 3000–5000, and growth rate of 2–4 μm / h.

[0062] Preferably, in step S209, a p-type doped GaN thin film is grown on the electron blocking layer using metal-organic chemical vapor deposition. The process conditions are: reaction chamber pressure of 50–300 torr, Si substrate temperature of 1000–1060°C, beam current ratio V / III of 3000–5000, and growth rate of 2–4 μm / h.

[0063] The electroluminescence (EL) spectrum of the AlGaN-based deep ultraviolet LED epitaxial wafer prepared according to the embodiments of the present invention is as follows: Figure 3 As shown.

[0064] In existing technologies, a reflective electrode, such as Ag, is deposited on the p-type GaN contact surface, followed by substrate transfer bonding, removal of the previously grown silicon substrate, and the deposition of an n-type electrode, such as Ag, on an n-type Al. z Ga 1-z The final LED chip fabricated on an N-layer surface has a vertical structure with p-layer electrodes at the bottom and n-type electrodes at the top. This typically involves the deposition of reflective electrodes and substrate transfer bonding, making the process complex and cumbersome. This invention addresses the drawback of silicon carbide substrates absorbing deep ultraviolet light by employing an Ag layer. It avoids the need for multiple reflective electrode depositions and silicon carbide substrate removal processes during chip fabrication. After obtaining the epitaxial wafer, p-type electrodes are directly deposited on the p-type GaN surface, resulting in a vertical LED chip with n-type electrodes at the bottom and p-type electrodes at the top.

[0065] Furthermore, the fabrication of deep ultraviolet (DUV) LEDs requires high-Al content AlGaN epitaxial layers to achieve the required bandgap. However, traditional epitaxial substrates such as sapphire and silicon do not perform satisfactorily in DUV LED epitaxial processes. For example, the lattice mismatch between sapphire and silicon and the AlN buffer layer is significant, and the resulting stress can cause cracks in the epitaxial layer. While silicon carbide substrates have a clear advantage over sapphire substrates in terms of lattice mismatch and are suitable for growing high-Al content GaN materials, due to the inherent absorption characteristics of ultraviolet light on silicon carbide substrates, it is generally necessary to peel off the silicon carbide substrate and transfer the AlGaN active layer to a substrate such as silicon to complete the fabrication of the DUV LED chip. This complex fabrication process greatly limits its application in related fields. This invention uses silicon carbide as the substrate for deep ultraviolet (DUV) LEDs and pre-epitaxially grows an Ag layer on the silicon carbide substrate as a reflective layer. This avoids the absorption characteristics of ultraviolet light by the silicon carbide substrate itself, eliminating the need for the substrate stripping process used in traditional DUV LED growth on silicon carbide substrates. It also significantly improves the external quantum efficiency of the device. This invention is a proprietary DUV LED epitaxial wafer that effectively reduces dislocation formation, producing high-quality DUV LED epitaxial wafers and improving carrier radiative recombination efficiency. It can produce DUV LEDs with high thermal conductivity, high electrical conductivity, and high luminous performance. Using an Ag layer as the reflective layer completely preserves the silicon carbide substrate as a base and provides support, resulting in a more uniform current distribution in the DUV LED, improving light extraction efficiency, and providing good heat dissipation. The fabrication method of this invention is simple, repeatable, and can be used for large-scale production applications.

[0066] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

[0067] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. An AlGaN-based deep ultraviolet LED epitaxial wafer based on a silicon carbide substrate, characterized in that, include: A silicon carbide substrate, an Ag layer deposited on the silicon carbide substrate, an AlN buffer layer grown on the Ag layer, an AlGaN buffer layer grown on the AlN buffer layer, an undoped AlGaN layer grown on the AlGaN buffer layer, an n-type doped AlGaN layer grown on the undoped 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, and a p-type doped GaN thin film grown on the electron blocking layer; The thickness of the Ag layer is 500-1000 nm; The thickness of the AlN buffer layer is 5–50 nm; The thickness of the AlGaN buffer layer is 300–500 nm; The thickness of the undoped AlGaN layer is 500–800 nm; The thickness of the n-type doped AlGaN layer is 3–5 μm; The AlGaN multi-quantum-well layer has 7-10 periods of Al. 0.3 Ga 0.7 N-well layer and Al 0.5 Ga 0.5 N-layer barrier, where Al 0.3 Ga 0.7 The thickness of the N-well layer is 2–3 nm, Al 0.5 Ga 0.5 The thickness of the N-barrier layer is 10–13 nm; The electron blocking layer is Al. 0.4 Ga 0.6 N electron blocking layer, wherein the thickness of the electron blocking layer is 20-50 nm; The thickness of the p-type doped GaN film is 300–350 nm.

2. A method for preparing an AlGaN-based deep ultraviolet LED epitaxial wafer based on a silicon carbide substrate as described in claim 1, characterized in that, include: Silicon carbide substrate selected; An Ag layer is deposited on the silicon carbide substrate; An AlN buffer layer is grown on the Ag layer; An AlGaN buffer layer is grown on the AlN buffer layer; An undoped AlGaN layer is grown on the AlGaN buffer layer; An n-type doped AlGaN layer is epitaxially grown on the undoped AlGaN layer; An AlGaN multiple quantum well layer is epitaxially grown on the n-type doped AlGaN layer; An electron blocking layer is epitaxially grown on the AlGaN multi-quantum-well layer; A p-type doped GaN thin film is epitaxially grown on the electron blocking layer.

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