A multi-band photodetector and a method for fabricating the same

Abstract

This invention belongs to the field of semiconductor optoelectronic device technology, specifically relating to a multi-band photodetector and its fabrication method. The multi-band photodetector provided by this invention includes, from bottom to top, a substrate, a buffer layer, a first N-type GaN layer, a first intrinsic GaN transition layer, a multi-quantum-well absorption layer, a second intrinsic GaN transition layer, and an Al... x Ga 1‑x N-component graded layer, third intrinsic GaN transition layer, second N-type GaN layer; Al x Ga 1‑x In the N-component graded layer, the Al component x decreases linearly from bottom to top; the first N-type GaN layer, Al x Ga 1‑x Ohmic electrodes are placed on the N-component gradient layer and the second N-type GaN layer. An overall N-P-N detection structure was constructed, consisting of a top P-I-N type ultraviolet light detection layer, a bottom P-I-N type visible-infrared light detection layer, and a general N-P-N type structure. This structure enables detection in the ultraviolet, visible, and ultraviolet-visible dual-band wavelengths, improving the device growth quality and stability.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic device technology, and specifically to a multi-band photodetector and its fabrication method. Background Technology

[0002] Photodetectors, by converting light signals into easily observable electrical signals, are widely used in various fields. Based on the detection wavelength, they can be classified into ultraviolet photodetectors, visible light photodetectors, infrared photodetectors, and far-infrared photodetectors. Ultraviolet photodetectors are commonly used in ultraviolet inspection, missile early warning and tracking, and medical diagnosis; visible light photodetectors are frequently used in lighting control, security monitoring, and machine vision; and infrared photodetectors have important applications in satellite remote sensing, infrared imaging, industrial temperature measurement, and security. In recent years, with the continuous development and improvement of semiconductor materials and their component fabrication processes, more and more researchers are dedicated to developing photodetector structures capable of multi-wavelength detection.

[0003] Currently, photodetector structures with dual-band detection (UV-IR, UV-Vis, and Visible-IR) and multi-band detection (UV-Vis-IR) have emerged. However, most photodetector structures achieve multi-band detection by combining various synthetic materials or organic chemical thin films with semiconductor materials. Chinese patent application CN114744122A, published on July 12, 2022, discloses a perovskite multi-band detector and its fabrication method. The detector structure consists of a transparent conductive substrate, an electron transport layer, a perovskite electrode, and a group 6 bismuth compound electrode. This type of detector structure typically requires complex fabrication processes and incurs high manufacturing costs.

[0004] There are also cases of dual-band detectors made solely from semiconductor materials. Chinese patent application CN101894831A, published on November 24, 2010, discloses an ultraviolet-infrared dual-band detector and its fabrication method. The raw material for the infrared detector is mainly InP, and the raw material for the ultraviolet detector is AlGaN. Since it is too difficult to stack and grow different types of material layers together, this invention uses a metal bonding process to flip-chip interconnect the infrared and ultraviolet detectors together. This detector structure also increases the manufacturing cost.

[0005] AlGaN material has a bandgap of 3.4 eV-6.2 eV, which corresponds to the wavelength range of the ultraviolet band. Therefore, it is often used as the preferred material for ultraviolet photodetectors. The bandgap of InGaN material can be continuously adjusted from 0.7 eV to 3.4 eV, and its corresponding wavelength range covers the ultraviolet band to the infrared band. Therefore, GaN material provides important support for the construction of dual-band photodetectors.

[0006] Chinese patent CN101626025B, authorized on June 1, 2011, discloses a gallium nitride-based multi-band detector and its fabrication method. This invention utilizes the continuous tunability of the bandgap of the GaN-based material system to grow AlN, GaN, InN and their ternary or multi-component compounds with different bandgap widths to meet different detection bands. However, its implementation mainly involves separating the device into different independent detection units through etching, stripping and electrode growth, resulting in relatively low integration. Summary of the Invention

[0007] The purpose of this invention is to provide a multi-band photodetector to solve the problem of low integration in existing multi-band photodetectors.

[0008] The second objective of this invention is to provide a method for fabricating a multi-band photodetector, thereby solving the problem of the complexity of existing multi-band photodetector fabrication methods.

[0009] To solve the above-mentioned technical problems, the technical solution of the multi-band photodetector of the present invention is as follows: A multi-band photodetector includes, from bottom to top, a substrate, a buffer layer, a first N-type GaN layer, a first intrinsic GaN transition layer, a multi-quantum-well absorption layer, a second intrinsic GaN transition layer, and an Al2O3 layer. x Ga 1-x The layer consists of an N-component gradient layer, a third intrinsic GaN transition layer, and a second N-type GaN layer; the Al... x Ga 1-x In the N-component graded layer, the Al component x decreases linearly from bottom to top; the first N-type GaN layer, Al x Ga 1-x Ohmic electrodes are respectively provided on the N-component graded layer and the second N-type GaN layer.

[0010] This invention improves upon existing technology, providing a multi-band photodetector in which Al x Ga 1-x The structure of the PIN-type ultraviolet photodetector consists of an N-type graded layer, a third intrinsic GaN transition layer, and a second N-type GaN layer. Al x Ga 1-xThe N-component graded layer utilizes the polarization charge generated by the linearly decreasing aluminum composition in AlGaN material from bottom to top to achieve a P-type doping effect. This not only avoids the problem of reduced conductivity caused by the difficulty of P-type impurity doping and low acceptor ionization efficiency, but also reduces the Al content. x Ga 1-x The lattice mismatch between the N-component graded layer and the third intrinsic GaN transition layer, where Al x Ga 1-x The N-type graded-layer and the third intrinsic GaN transition layer form the main absorption region for ultraviolet light, enhancing the detection capability in the ultraviolet band. Specifically, the third intrinsic GaN transition layer acts as both a transition layer and an absorption layer. In a multi-band photodetector, the first N-type GaN layer, the first intrinsic GaN transition layer, the multi-quantum-well absorption layer, the second intrinsic GaN transition layer, and the Al... x Ga 1-x The N-component gradient layer constitutes a PIN-type visible-infrared photodetector structure. By controlling the composition and number of the multi-quantum-well absorption layer, the overall band structure of the active region can be changed, achieving tunability of the absorption band from visible light to infrared light. The photodetector as a whole presents an NPN-type structure, which can simultaneously achieve multi-band detection effects in ultraviolet and infrared.

[0011] The multi-band photodetector provided by this invention has a high degree of integration and can simultaneously realize ultraviolet light band detection, visible light-infrared band detection, and ultraviolet-infrared band detection. Moreover, the high degree of integration does not require the use of metal bonding to flip-chip interconnect the two detectors, which greatly reduces the integration complexity and cost of the multi-band detector.

[0012] To further reduce Al x Ga 1-x The lattice mismatch between the N-component graded layer and the third intrinsic GaN transition layer is preferably... x Ga 1-x In the N-component gradient layer, the Al component x decreases linearly from x1 to x2 from bottom to top, where 1>x1>x2≥0.

[0013] To further improve the detection effect, preferably, the thickness of the AlxGa1-xN composition gradient layer is 0.05 μm to 0.1 μm.

[0014] To further achieve tunability of the absorption band from visible light to infrared light, preferably, the multi-quantum-well absorption layer includes alternating quantum well layers and barrier layers, with the second intrinsic GaN transition layer, the first intrinsic GaN transition layer, and the barrier layer in contact, and the quantum well layers being In. x3 Ga 1-x3 N, where the barrier layer is In x4 Ga 1-x4N, where 0≤x3≤1, 0≤x4≤1, and x4≤x3.

[0015] To further improve the quantum efficiency of the multi-quantum-well absorption layer, preferably, the thickness of the quantum well layer is 0.001–0.005 μm, and the thickness of the barrier layer is 0.01–0.03 μm.

[0016] To further improve the detection effect, preferably, the dopant in the first N-type GaN layer and the second N-type GaN layer is Si or C, and the doping concentration is (1~4)×10⁻⁶. 18 cm -3 The thicknesses of the first N-type GaN layer and the second N-type GaN layer are 0.1–1.0 μm.

[0017] To further improve the stability of the detector, preferably, the buffer layer is AlN with a thickness of 0.01 μm to 2 μm; the thicknesses of the first intrinsic GaN transition layer, the second intrinsic GaN transition layer, and the third intrinsic GaN transition layer are all 0.01 to 0.05 μm.

[0018] To further improve the detection effect, preferably, a first N-type GaN layer, a second N-type GaN layer, and an Al layer are used. x Ga 1-x The ohmic electrode on the N-component graded layer is made of one or more of Ti, Al, and Au.

[0019] To further simplify the structure of the multi-band photodetector, preferably, the multi-band photodetector has a three-step structure that gradually decreases in size from bottom to top, exposing the surface of the first N-type GaN layer, Al, etc. x Ga 1-x The ohmic electrode is correspondingly disposed on the surface of the first N-type GaN layer and the surface of the second N-type GaN layer. x Ga 1-x The surface of the N-component gradient layer and the surface of the second N-type GaN layer.

[0020] The technical solution of the fabrication method of the multi-band photodetector of the present invention is as follows: A method for fabricating a multi-band photodetector includes the following steps: 1) Epitaxially grow the following layers on the substrate from bottom to top: a buffer layer, a first N-type GaN layer, a first intrinsic GaN transition layer, a multi-quantum-well absorber layer, a second intrinsic GaN transition layer, and an Al layer. x Ga 1-x N-component graded layer, third intrinsic GaN transition layer, second N-type GaN layer; 2) Etch the periphery of the third intrinsic GaN transition layer and the second N-type GaN layer to expose Al.x Ga 1-x N-component graded layer, for Al x Ga 1-x Etching is performed on the outer periphery of the N-type gradient layer, the second intrinsic GaN transition layer, the multi-quantum-well absorber layer, and the first intrinsic GaN transition layer to expose the first N-type GaN layer; etching is then performed on the second N-type GaN layer and the exposed Al... x Ga 1-x An ohmic electrode is deposited on an N-component gradient layer and a first N-type GaN layer.

[0021] The method for fabricating a multi-band photodetector provided by this invention can achieve the fabrication of the main structure of the photodetector simply through epitaxial growth. The fabricated multi-band photodetector can simultaneously achieve ultraviolet light band detection, visible light-infrared band detection, and ultraviolet-infrared band detection. The fabrication method provided by this invention does not require additional complex process steps such as coating or metal bonding, and has the characteristics of simple fabrication. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the multi-band photodetector in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the band structure of the multi-band photodetector in Embodiment 1 of the present invention; Figure 3 for Figure 1 A schematic diagram of the structure of the multi-quantum-well absorption layer in the image; Figure 4 This is a schematic diagram of the structure of the multi-band photodetector in Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of the band structure of the multi-band photodetector in Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of the structure after epitaxial growth on the substrate in the multi-band photodetector fabrication method of Embodiment 3 of the present invention; Figure 7 In order to be in Figure 6 A schematic diagram of the structure on which the edge of the AlxGa1-xN composition gradient layer is etched and exposed. Figure 8 In order to be in Figure 7 A schematic diagram of the structure of the first ohmic electrode and the second ohmic electrode deposited at the edge; Figure 9 In order to be in Figure 8 A schematic diagram of the structure on which the edge of the first N-type GaN layer is etched to expose the foundation; In the attached figures: 100, substrate; 200, AlN buffer layer; 300, first N-type GaN layer; 400, first intrinsic GaN transition layer; 500, multi-quantum-well absorber layer; 501, barrier layer; 502, quantum well layer; 600, second intrinsic GaN transition layer; 700, AlxGa1-xN composition gradient layer; 800, second intrinsic GaN transition layer; 900, second N-type GaN layer; 000, ohmic electrode; 001, first ohmic electrode; 002, second ohmic electrode; 003, third ohmic electrode. Detailed Implementation

[0023] The technical concept of the multi-band photodetector of this invention is as follows: Existing multi-band detectors are essentially different independent detection units, capable of detecting light in each band separately, resulting in poor monolithic integration. This invention, however, designs and constructs a top PIN-type ultraviolet detection structure and a lower PIN-type visible-infrared detection structure, forming an overall NPN structure. This achieves ultraviolet, visible-infrared, and ultraviolet-infrared band detection. Furthermore, it utilizes linear variations in Al composition to improve the P-type doping effect and lattice matching with the transition layer, enhancing device growth quality and stability. Finally, it employs multiple quantum well absorption layers to control the overall band structure of the active region, enabling tunability of the absorption band from visible to infrared light, thus improving the range and applicability of multi-band detection.

[0024] Understandably, in the fabrication process of multi-band photodetectors, after epitaxial growth on the substrate, the outer periphery of the third intrinsic GaN transition layer and the second N-type GaN layer can be etched first to expose Al. x Ga 1-x N-component graded layer, then the second N-type GaN layer, exposed Al x Ga 1-x An ohmic electrode is deposited on an N-component graded layer; then an Al electrode is deposited. x Ga 1-x The outer periphery of the N-component gradient layer, the second intrinsic GaN transition layer, the multi-quantum-well absorber layer, and the first intrinsic GaN transition layer is etched to expose the first N-type GaN layer, and then an ohmic electrode is deposited on the exposed first N-type GaN layer. Alternatively, the outer periphery of the third intrinsic GaN transition layer and the second N-type GaN layer can be etched first to expose Al. x Ga 1-x N-component graded layer, then Al x Ga 1-x Etching is performed on the periphery of the N-type gradient layer, the second intrinsic GaN transition layer, the multi-quantum-well absorber layer, and the first intrinsic GaN transition layer to expose the first N-type GaN layer; then etching is performed on the second N-type GaN layer and the exposed Al x Ga1-x An ohmic electrode is deposited on an N-component gradient layer and a first N-type GaN layer.

[0025] In a specific implementation, the number of quantum well layers in the multi-quantum-well absorption layer is 8 to 12.

[0026] In a specific embodiment, the thickness of the first N-type GaN layer is 0.2~0.5μm, and the doping concentration of the dopant in the first N-type GaN layer is (3.5~4)×10⁻⁶. 18 cm -3 The thickness of the second N-type GaN layer is 0.1~0.2μm, and the doping concentration of the dopant in the second N-type GaN layer is (1~3.5)×10⁻⁶. 18 cm -3 .

[0027] The embodiments of the present invention will be further described below with reference to specific examples.

[0028] I. Specific Embodiments of the Multi-Band Photodetector of the Present Invention Example 1 The multi-band photodetector in this embodiment is as follows: Figure 1-3 As shown, the structure includes, from bottom to top, a substrate 100, an AlN buffer layer 200, a first N-type GaN layer 300, a first intrinsic GaN transition layer 400, a multi-quantum-well absorption layer 500, a second intrinsic GaN transition layer 600, an AlxGa1-xN composition gradient layer 700, a third intrinsic GaN transition layer 800, and a second N-type GaN layer 900.

[0029] The substrate 100 is sapphire; the AlN buffer layer 200 has a thickness of 0.2 μm; the first N-type GaN layer 300 is N-type doped GaN, with Si as the dopant and a doping concentration of 3.5 × 10⁻⁶. 18 cm -3 The thickness of the first N-type GaN layer 300 is 0.2 μm; the thickness of the first intrinsic GaN transition layer 400 is 0.02 μm, which is unintentionally doped GaN.

[0030] The multi-quantum-well absorber layer 500 includes eight alternating quantum well layers 502 and nine barrier layers 501. The second intrinsic GaN transition layer 600 and the first intrinsic GaN transition layer 400 are both in contact with the barrier layers 501. The quantum well layers 502 are made of In. x3 Ga 1-x3 N, barrier layer 501 is In x4 Ga 1-x4N, both material layers are unintentionally intrinsically doped, where x3=0.15 and x4=0, meaning the band gap of barrier layer 501 is greater than that of quantum well layer 502; the thickness of quantum well layer 502 is 0.005 μm and the thickness of barrier layer 501 is 0.025 μm.

[0031] The second intrinsic GaN transition layer 600 is unintentionally doped GaN, and the thickness of the second intrinsic GaN transition layer 600 is 0.02 μm; In the AlxGa1-xN graded layer 700, the Al composition x decreases linearly from x1 to x2 from bottom to top, where x1=0.2 and x2=0. The thickness of the AlxGa1-xN graded layer 700 is 0.05μm.

[0032] The third intrinsic GaN transition layer 800 is unintentionally doped GaN, and its thickness is 0.02 μm; the second N-type GaN layer 900 is N-type doped GaN with Si as the dopant and a doping concentration of 3.5 × 10⁻⁶. 18 cm -3 The second N-type GaN layer has a thickness of 0.1 μm. Each layer is coaxially arranged. The area of ​​the third intrinsic GaN transition layer 800 and the second N-type GaN layer 900 in the direction parallel to the substrate is smaller than that of the first intrinsic GaN transition layer 400, the multi-quantum-well absorber layer 500, the second intrinsic transition layer 600, and the AlxGa1-xN composition gradient layer 700, so as to expose the edge of the AlxGa1-xN composition gradient layer 700. Similarly, referring to the above arrangement, the edge of the first N-type GaN layer 300 is exposed. A three-step structure that gradually decreases in size from bottom to top is formed, exposing the surface of the first N-type GaN layer 300, AlxGa1-xN composition gradient layer 700, and AlxGa1-xN composition gradient layer 900, respectively. x Ga 1-x The surface of the N-component graded layer 700 and the surface of the second N-type GaN layer 900.

[0033] The first exposed N-type GaN layer 300, Al x Ga 1-x Ohmic electrodes 000 are respectively provided at the edges of the N-component graded layer 700 and the second N-type GaN layer 900. A first ohmic electrode 001 is provided at the edge of the second N-type GaN layer 900. Al x Ga 1-xA second ohmic electrode 002 is provided at the edge of the N-component gradient layer 700, and a third ohmic electrode 003 is provided at the edge of the first N-type GaN layer 300. The first ohmic electrode 001, the second ohmic electrode 002, and the third ohmic electrode 003 are all made of Ti / Al / Ti / Au. The first ohmic electrode 001, the second ohmic electrode 002, and the third ohmic electrode 003 are all annular metal electrodes. The overall structure of the multi-band photodetector of this invention is as follows: Figure 1 As shown.

[0034] Figure 2 A schematic diagram of the band structure of the multi-band photodetector of Embodiment 1 of the present invention is shown. The ultraviolet absorption is mainly composed of the middle region between the second N-type GaN layer 900 and the composition-gradient layer 700. The material of this region is mainly GaN-Al0.2Ga0.8N, with a band gap of 3.4 eV-4 eV, corresponding to an absorption band cutoff wavelength of 310 nm-365 nm, belonging to the ultraviolet band. The material of the multiple quantum well layer is In0.15Ga0.85N-GaN, with a material band gap of 2.89 eV-3.4 eV, corresponding to an absorption band cutoff wavelength of 365 nm-429 nm, covering the ultraviolet-visible light band. Furthermore, quantum effects exist in the multiple quantum well region; quantum states are generated in the quantum wells, and transitions between different quantum energy levels also increase the absorption wavelength, expanding the absorption range of the visible light band.

[0035] It is understood that the cross-sectional shape of each layer of the present invention in the direction parallel to the substrate can be polygonal or circular, such as square, rectangular or circular. The multi-band photodetector of the present invention can be a micrometer-scale or millimeter-scale device.

[0036] Example 2 The multi-band photodetector in this embodiment is as follows: Figure 4-5 As shown, the structure includes, from bottom to top, a substrate 100, an AlN buffer layer 200, a first N-type GaN layer 300, a first intrinsic GaN transition layer 400, a multi-quantum-well absorption layer 500, a second intrinsic GaN transition layer 600, an AlxGa1-xN composition gradient layer 700, a third intrinsic GaN transition layer 800, and a second N-type GaN layer 900.

[0037] The substrate 100 is sapphire; the AlN buffer layer 200 has a thickness of 0.2 μm; the first N-type GaN layer 300 is N-type doped GaN, with Si as the dopant and a doping concentration of 4 × 10⁻⁶. 18 cm -3 The thickness of the first N-type GaN layer 300 is 0.5 μm; the thickness of the first intrinsic GaN transition layer 400 is 0.02 μm, which is unintentionally doped GaN.

[0038] The multi-quantum-well absorber layer 500 includes 12 alternating quantum well layers 502 and 13 barrier layers 501. The second intrinsic GaN transition layer 600 and the first intrinsic GaN transition layer 400 are both in contact with the barrier layers 501. The quantum well layers 502 are made of In. x3 Ga 1-x3 N, barrier layer 501 is In x4 Ga 1-x4 N, both material layers are unintentionally intrinsically doped, where x3=0.55 and x4=0.4, that is, the band gap of the barrier layer 501 is greater than that of the quantum well layer 502; the thickness of the quantum well layer 502 is 0.003 μm and the thickness of the barrier layer 501 is 0.012 μm.

[0039] The second intrinsic GaN transition layer 600 is unintentionally doped GaN, and the thickness of the second intrinsic GaN transition layer 600 is 0.02 μm; In the AlxGa1-xN graded layer 700, the Al composition x decreases linearly from x1 to x2 from bottom to top, where x1=0.2 and x2=0. The thickness of the AlxGa1-xN graded layer 700 is 0.05μm.

[0040] The third intrinsic GaN transition layer 800 is unintentionally doped GaN, and its thickness is 0.02 μm; the second N-type GaN layer 900 is N-type doped GaN, with Si as the dopant and a doping concentration of 1×10⁻⁶. 18 cm -3 The second N-type GaN layer has a thickness of 0.1 μm. The arrangement of each layer and the ohmic electrode is the same as in Embodiment 1. The overall structure of the multi-band photodetector in Embodiment 2 is as follows: Figure 3 As shown.

[0041] Figure 4 This is a schematic diagram of the band structure of the multi-band photodetector in Example 2. Due to the reduced doping concentration of the second N-type GaN layer, the built-in electric field of the ultraviolet absorption layer decreases, and the band tilt also decreases accordingly. The material remains AlGaN / GaN, corresponding to ultraviolet light absorption. The doping concentration of the first N-type GaN layer is slightly increased, and the materials for the quantum well and quantum barrier are In0.55Ga0.45N and In0.4Ga0.6N, respectively. The band gap of these materials is 1.92 eV-2.32 eV, corresponding to an absorption band cutoff wavelength of 534 nm-646 nm. Furthermore, as the thickness of the quantum well decreases, the energy levels of the quantum states become closer, and the maximum wavelength of the actual absorption band in this example will be further extended to the infrared band.

[0042] The operating mode of the multi-band photodetector of this invention is as follows: Mode 1: Apply bias voltage to 001 and 002 to achieve detection only in the ultraviolet band; Mode 2: Apply a bias voltage to 002 and 003 to achieve visible light-infrared band detection; Mode 3: Apply bias voltages simultaneously to 001, 002, and 003 to achieve ultraviolet-infrared band detection.

[0043] II. Specific Embodiments of the Fabrication Method of the Multi-band Photodetector of the Present Invention Example 3 This embodiment describes the fabrication method of the multi-band photodetector in Example 1, such as... Figure 6-9 As shown, specifically: 1) An AlN buffer layer 200, a first N-type GaN layer 300, a first intrinsic GaN transition layer 400, a multi-quantum-well absorber layer 500, a second intrinsic GaN transition layer 600, an AlxGa1-xN composition gradient layer 700, a third intrinsic GaN transition layer 800, and a second N-type GaN layer 900 are epitaxially grown sequentially from bottom to top on a substrate 100, as follows: Figure 6 As shown; 2) After epitaxial growth is completed, with the central axis of the substrate 100 parallel to the epitaxial growth direction as the center, photolithography and plasma etching are performed on the outer periphery of the third intrinsic GaN transition layer 800 and the second N-type GaN layer 900 to expose the edge of the AlxGa1-xN composition gradient layer 700, such as... Figure 7 As shown, a first ohmic electrode 001 and a second ohmic electrode 002 are deposited at the edge of the second N-type GaN layer 900 and on the AlxGa1-xN composition gradient layer 700, respectively, using photolithography and electron beam evaporation. Figure 8 As shown; 3) Continuing with the central axis of substrate 100 as the center, etch the outer periphery of the AlxGa1-xN composition gradient layer 700, the second intrinsic transition layer 600, the multi-quantum-well absorber layer 500, and the first intrinsic GaN transition layer 400 to expose the edge of the first N-type GaN layer 300, such as... Figure 9 As shown, a third ohmic electrode 003 is deposited at the edge of the first N-type GaN layer 300 using photolithography and electron beam evaporation to obtain the multi-band photodetector of Example 1. Figure 1 As shown.

[0044] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-band photodetector, characterized in that, The structure, arranged from bottom to top, includes a substrate, a buffer layer, a first N-type GaN layer, a first intrinsic GaN transition layer, a multiple quantum well absorber layer, a second intrinsic GaN transition layer, and an Al layer. x Ga 1-x The layer consists of an N-component gradient layer, a third intrinsic GaN transition layer, and a second N-type GaN layer; the Al... x Ga 1-x In the N-component graded layer, the Al component x decreases linearly from bottom to top; the first N-type GaN layer, Al x Ga 1-x Ohmic electrodes are respectively provided on the N-component graded layer and the second N-type GaN layer.

2. The multi-band photodetector as described in claim 1, characterized in that, The Al x Ga 1-x In the N-component gradient layer, the Al component x decreases linearly from x1 to x2 from bottom to top, where 1>x1>x2≥0.

3. The multi-band photodetector as described in claim 1 or 2, characterized in that, The thickness of the AlxGa1-xN graded layer is 0.05 μm to 0.1 μm.

4. The multi-band photodetector as described in claim 1, characterized in that, The multi-quantum-well absorber layer comprises alternating quantum well layers and barrier layers. The second intrinsic GaN transition layer, the first intrinsic GaN transition layer, and the barrier layer are in contact. The quantum well layers are made of In. x3 Ga 1-x3 N, where the barrier layer is In x4 Ga 1-x4 N, where 0≤x3≤1, 0≤x4≤1, and x4≤x3.

5. The multi-band photodetector as described in claim 4, characterized in that, The thickness of the quantum well layer is 0.001–0.005 μm, and the thickness of the barrier layer is 0.01–0.03 μm.

6. The multi-band photodetector as described in claim 1, characterized in that, The first and second N-type GaN layers are doped with Si or C, with a doping concentration of (1~4)×10⁻⁶. 18 cm -3 The thicknesses of the first N-type GaN layer and the second N-type GaN layer are 0.1–1.0 μm.

7. The multi-band photodetector as described in claim 1, characterized in that, The buffer layer is AlN with a thickness of 0.01 μm to 2 μm; the thicknesses of the first intrinsic GaN transition layer, the second intrinsic GaN transition layer, and the third intrinsic GaN transition layer are all 0.01 to 0.05 μm.

8. The multi-band photodetector as described in claim 1, characterized in that, First N-type GaN layer, second N-type GaN layer, Al x Ga 1-x The ohmic electrode on the N-component graded layer is made of one or more of Ti, Al, and Au.

9. The multi-band photodetector as described in claim 1, characterized in that, The multi-band photodetector has a three-step structure that gradually decreases in size from bottom to top, exposing the surface of the first N-type GaN layer, Al, etc. x Ga 1-x The ohmic electrode is correspondingly disposed on the surface of the first N-type GaN layer and the surface of the second N-type GaN layer. x Ga 1-x The surface of the N-component gradient layer and the surface of the second N-type GaN layer.

10. A method for fabricating a multi-band photodetector as described in any one of claims 1-9, characterized in that, Includes the following steps: 1) Epitaxially grow the following layers on the substrate from bottom to top: a buffer layer, a first N-type GaN layer, a first intrinsic GaN transition layer, a multi-quantum-well absorber layer, a second intrinsic GaN transition layer, and an Al layer. x Ga 1-x N-component graded layer, third intrinsic GaN transition layer, second N-type GaN layer; 2) Etch the periphery of the third intrinsic GaN transition layer and the second N-type GaN layer to expose Al. x Ga 1-x N-component graded layer, for Al x Ga 1-x Etching is performed on the outer periphery of the N-type gradient layer, the second intrinsic GaN transition layer, the multi-quantum-well absorber layer, and the first intrinsic GaN transition layer to expose the first N-type GaN layer; etching is then performed on the second N-type GaN layer and the exposed Al... x Ga 1-x An ohmic electrode is deposited on an N-component gradient layer and a first N-type GaN layer.

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