A solar-blind ultraviolet detector with enhanced suppression ratio and its fabrication method

Abstract

This invention provides a solar-blind ultraviolet detector with enhanced suppression ratio and its fabrication method, belonging to the technical field of semiconductor ultraviolet photodetector devices. It includes, from bottom to top, a sapphire substrate, an i-type AlN buffer layer, an i-type AlGaN transition layer, a heavily doped ohmic contact layer, a light-absorbing layer with low doping, and a p-type GaN ohmic contact layer. A p-type ohmic metal electrode is disposed above the p-type GaN ohmic contact layer, and an n-type ohmic contact electrode is also disposed on the heavily doped ohmic contact layer. A metal pad is disposed above the p-type ohmic metal electrode. A bandpass filter film is deposited at the bottom of the sapphire substrate, with the transmitting end of the bandpass filter film located in the UVC band. This solar-blind ultraviolet detector can improve the problems of poor suppression ratio and severe interference from sunlight in current AlGaN-based solar-blind detectors.

Description

Technical Field

[0001] This invention relates to the field of semiconductor ultraviolet photodetector technology, and in particular to a solar-blind ultraviolet detector with enhanced suppression ratio and its fabrication method. Background Technology

[0002] Ultraviolet radiation is the strongest form of radiation found in nature, with a wavelength range of 200nm to 400nm. Based on wavelength, it can be divided into three bands: UVA (400nm-320nm), UVB (320nm-290nm), and UVC (280nm-200nm). Sunlight is a major source of ultraviolet light on the Earth's surface. Due to absorption by the atmospheric ozone layer, there is a spectral blind zone of 240-280nm in the sunlight reaching the Earth's surface, known as the "solar blind zone." Ultraviolet detectors operating in this band are unaffected by solar background radiation and possess high sensitivity and signal-to-noise ratio, making them important for applications such as fire alarms and missile exhaust detection and tracking.

[0003] In related technologies, commonly used ultraviolet (UV) detectors can be divided into vacuum UV detectors and solid-state UV detectors. Solid-state UV detectors are mainly based on photodiodes using semiconductor materials. The semiconductor materials commonly used for UV detection are first-generation semiconductor Si and third-generation semiconductors GaN and SiC. Si has a bandgap of 1.12 eV and a wavelength response range covering the near-infrared-visible-ultraviolet range. It exhibits a strong response to visible light, requiring expensive and large-area UV filters for UV detection. Furthermore, Si has a strong absorption effect on ultraviolet light, resulting in extremely low quantum efficiency in the UV band. Therefore, the fabrication of UV detectors requires special UV-enhanced structural designs and modifications to the manufacturing process. AlGaN and SiC, as representative materials of third-generation semiconductors, have advantages such as large bandgap, high electron drift velocity, high critical breakdown field strength, high thermal conductivity, excellent chemical stability, and no response to visible light, making them ideal materials for fabricating ultraviolet detectors. Among them, (Al)GaN has advantages such as direct bandgap and tunable bandgap, making it the preferred material for fabricating solar-blind ultraviolet detectors.

[0004] However, among existing commercially available AlGaN and SiC ultraviolet detectors, AlGaN solar-blind ultraviolet detectors are mainly based on the technology of growing AlGaN materials on sapphire substrates. Although the crystal quality of AlGaN epitaxial materials has been greatly improved with the rapid development of UVC LED technology, the physical constraints of large lattice mismatch and thermal expansion coefficient mismatch between AlGaN materials and sapphire substrates, as well as the fact that Al atoms have a larger surface adhesion coefficient and lower surface mobility than Ga atoms, make it easy to generate a large number of through dislocations during the epitaxial growth of AlGaN on sapphire. AlGaN materials still have a high level of blue and yellow light band defects, resulting in weak responses in the UVB and UVA bands of current AlGaN solar-blind ultraviolet detectors, low solar-blind suppression ratio, and still being subject to interference from sunlight in practical applications, which seriously affects the signal-to-noise ratio of UVC monitoring. Summary of the Invention

[0005] This invention provides a solar-blind ultraviolet detector with enhanced suppression ratio and its fabrication method. It can improve the problems of poor suppression ratio and severe interference from sunlight in current AlGaN-based solar-blind detectors. The technical solution is as follows:

[0006] In a first aspect, embodiments of the present invention provide a solar-blind ultraviolet detector with enhanced suppression ratio, comprising, from bottom to top, a sapphire substrate, an i-type AlN buffer layer, an i-type AlGaN transition layer, a heavily doped ohmic contact layer, a light-absorbing layer with low doping, and a p-type GaN ohmic contact layer. The heavily doped ohmic contact layer has a patterned region, the light-absorbing layer with low doping and the p-type GaN ohmic contact layer are located in the patterned region, a p-type ohmic metal electrode is disposed above the p-type GaN ohmic contact layer, an n-type ohmic contact electrode is also disposed on the heavily doped ohmic contact layer surrounding the patterned region, a metal pad is disposed above the p-type ohmic metal electrode, and a passivation layer is disposed around the metal pad, the p-type ohmic metal electrode, the n-type ohmic contact electrode, the p-type GaN ohmic contact layer, the light-absorbing layer with low doping, and the heavily doped ohmic contact layer. A bandpass filter film is deposited at the bottom of the sapphire substrate, and the transmitting end of the bandpass filter film is located in the UVC band.

[0007] Optionally, the bandpass filter film includes a first metal layer, a dielectric layer, and a second metal layer that are alternately deposited from bottom to top. The first metal layer and the second metal layer are made of Al, Ag, Pt, or an alloy of the above metals, and the dielectric layer is made of silicon dioxide, silicon nitride, or aluminum oxide.

[0008] Optionally, the thickness of the first metal layer and the second metal layer ranges from 5 to 15 nm, and the thickness of the dielectric layer ranges from 40 to 70 nm.

[0009] Optionally, the doping concentration of the p-type GaN ohmic contact layer is in the range of 1×10⁻⁶. 18 -1×10 20 cm -3 The doping concentration range of the low-doped light-absorbing layer is 1×10⁻⁶. 14 -1×10 17 cm -3 The doping concentration range of the heavily doped ohmic contact layer is 1×10⁻⁶. 18 -3×10 19 cm -3 .

[0010] Optionally, the passivation layer has a thickness ranging from 50 to 1000 nm; the metal pad has a thickness ranging from 1 to 2 μm; the p-type ohmic metal electrode and the n-type ohmic contact electrode have a thickness ranging from 50 to 400 nm; the p-type GaN ohmic contact layer has a thickness ranging from 50 to 300 nm; the light-absorbing layer has a thickness ranging from 100 to 800 nm; the heavily doped ohmic contact layer has a thickness ranging from 300 to 1000 nm; the i-type AlGaN transition layer has a thickness ranging from 20 to 200 nm; the i-type AlN buffer layer has a thickness ranging from 0.20 to 3 μm; and the sapphire substrate has a thickness ranging from 100 to 500 μm.

[0011] Optionally, the p-type ohmic contact electrode is a single-layer or multi-layer composite structure made of Ni, Au, or Pt, and is circular or square in shape; the n-type ohmic contact electrode is a single-layer or multi-layer composite structure made of Ti, Al, Ni, Au, or Pt, and is ring-shaped.

[0012] Optionally, the metal pad is also provided above the n-type ohmic contact electrode.

[0013] Optionally, the metal pad is a single-layer or multi-layer composite structure made of Ti, Al, Ni, Au or Pt material.

[0014] Optionally, the passivation layer is made of at least one of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, or hafnium oxide.

[0015] In a second aspect, embodiments of the present invention provide a preparation method for fabricating the suppression ratio-enhanced solar-blind ultraviolet detector described in the first aspect, comprising:

[0016] The i-type AlN buffer layer, the i-type AlGaN transition layer, the heavily doped ohmic contact layer, the light-absorbing layer, and the p-type GaN ohmic contact layer are sequentially grown on the sapphire substrate.

[0017] An etching mask with a thickness of 300 nm was deposited on the solar-blind ultraviolet detector;

[0018] Remove the etching mask outside the active region mesa of the AlGaN solar-blind detector;

[0019] The active region mesas of the AlGaN solar-blind detector were etched out, with the etching depth extending to the heavily doped ohmic contact layer.

[0020] Remove the etching mask, repair the mesa etching damage using chemical modification, and then deposit the passivation layer;

[0021] Remove the passivation layer at the window of the n-type ohmic contact electrode, and deposit and fabricate the n-type ohmic contact electrode on the heavily doped ohmic contact layer;

[0022] Remove the passivation layer at the p-type ohmic metal electrode window, and deposit and fabricate the p-type ohmic metal electrode on the p-type GaN ohmic contact layer;

[0023] The metal pads are prepared on the surfaces of the p-type ohmic metal electrode and the n-type ohmic contact electrode;

[0024] The sapphire substrate is thinned and the bottom is polished. The bandpass filter film is then deposited, and the substrate is tested, sorted, and flip-chip packaged after laser cutting.

[0025] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0026] The solar-blind ultraviolet detector used in this embodiment of the invention, through the synergistic effect of a specially structured bandpass filter film and the properties of AlGaN material, can further suppress the response of AlGaN-based solar-blind ultraviolet detectors in the UVA and UVB bands while ensuring high quantum efficiency in the solar-blind band. This effectively improves the problems of poor suppression ratio and severe interference from sunlight in traditional AlGaN-based solar-blind detectors, and improves the signal-to-noise ratio and detection accuracy of the device in practical applications. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the solar-blind ultraviolet detector with enhanced suppression ratio provided in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the bandpass filter film provided in an embodiment of the present invention;

[0030] Figure 3 This is a theoretical calculation result of the transmittance of the bandpass filter film of the present invention in the ultraviolet band;

[0031] Figure 4 This is a flowchart of the preparation method provided in the embodiments of the present invention.

[0032] In the figure: 1-Sapphire substrate; 2-i-type AlN buffer layer; 3-i-type AlGaN transition layer; 4-Heavily doped ohmic contact layer; 5-Low-doped light absorption layer; 6-p-type GaN ohmic contact layer; 7-p-type ohmic metal electrode; 8-n-type ohmic contact electrode; 9-Bandpass filter film; 91-First metal layer; 92-Dielectric layer; 93-Second metal layer; m-Metal pad; n-Passivation layer. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0034] Figure 1 This is a schematic diagram of the structure of the solar-blind ultraviolet detector with enhanced suppression ratio provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the bandpass filter film provided in an embodiment of the present invention; Figure 3 This is a theoretical calculation result of the transmittance of the bandpass filter film of this invention in the ultraviolet band.

[0035] like Figures 1 to 3 As shown, based on the above-mentioned deficiencies, this embodiment of the invention provides a solar-blind ultraviolet detector with enhanced suppression ratio, based on a back-incidence structure design, where ultraviolet light is incident from the bottom of the sapphire substrate layer 1. The layer structure of this device, from bottom to top, includes:

[0036] The sapphire substrate 1 serves as the supporting base for the entire device, with a thickness ranging from 100 to 500 μm. A bandpass filter film 9 is deposited at the bottom of the thinned sapphire substrate 1 using vacuum deposition technology. This bandpass filter film 9 is the core innovation of this invention; its transmittance is located in the UVC band, specifically, its transmittance peak in the 240-280 nm band is higher than 40%, preferably higher than 50%, while its transmittance in the UVA and UVB bands is lower than 5%.

[0037] Above the sapphire substrate layer 1, an i-type AlN buffer layer 2 and an i-type AlGaN transition layer 3 are epitaxially grown sequentially. The thickness of the i-type AlN buffer layer 2 ranges from 0.20 to 3 μm and is used to alleviate the lattice mismatch between the sapphire substrate and the AlGaN material. The thickness of the i-type AlGaN transition layer 3 ranges from 20 to 200 nm and serves as a transition layer and stress relief layer.

[0038] Above the type-I AlGaN transition layer 3, a heavily doped ohmic contact layer 4 is provided, and its material is n-type Al y G a1-y N, with a doping concentration range of 1×10 18 -3×10 19 cm -3 , and a thickness range of 300 - 1000 nm. The heavily doped ohmic contact layer 4 has a special graphic area, which is formed by mesa etching process. In this graphic area, a low-doped light absorption layer 5 and a p-type GaN ohmic contact layer 6 are epitaxially grown.

[0039] The low-doped light absorption layer 5 is made of n-type Al x Ga 1-x N material, with a doping concentration range of 1×10 14 -1×10 17 cm -3 , and a thickness range of 100 - 800 nm, which is the main light absorption area of the device. To ensure the solar-blind selectivity of the device, the aluminum components x and y of the AlGaN material need to satisfy a specific relationship: 0.70 < y and 0.35 < x < 0.6, so that the UVC wavelength light incident from the back of the substrate can pass through the heavily doped n-type Al y Ga 1-y N layer and be effectively absorbed by the n-type Al x Ga 1-x N light absorption layer with low doping concentration.

[0040] Above the low-doped light absorption layer 5, a p-type GaN ohmic contact layer 6 is provided, with a doping concentration range of 1×10 18 -1×10 20 cm -3 , and a thickness range of 50 - 300 nm. This layer is used to form a good p-type ohmic contact.

[0041] Above the p-type GaN ohmic contact layer 6, a p-type ohmic metal electrode 7 is provided, with a thickness range of 50 - 400 nm. In the exposed area of the heavily doped ohmic contact layer 4, that is, the periphery of the graphic area, an n-type ohmic contact electrode 8 is provided, and this electrode is distributed in a ring around the graphic area, with a thickness range of 50 - 400 nm as well.

[0042] Above the p-type ohmic metal electrode 7, a metal pad m is provided, with a thickness range of 1 - 2 μm, which is used for subsequent packaging and wire bonding. A passivation layer n is provided around the periphery of the metal pad m, p-type ohmic metal electrode 7, n-type ohmic contact electrode 8, p-type GaN ohmic contact layer 6, low-doped light absorption layer 5 and heavily doped ohmic contact layer 4. The thickness range of the passivation layer n is 50 - 1000 nm, which is used to protect the device surface and reduce surface leakage current.

[0043] The key innovation of the above structure lies in the introduction of the bandpass filter film 9. Traditional AlGaN-based solar-blind ultraviolet detectors exhibit weak responses in the UVA and UVB bands due to defects in the blue and yellow light bands present in the material, resulting in a low solar-blindness suppression ratio. This invention, by depositing a bandpass filter film 9 at the bottom of the sapphire substrate layer 1, utilizes its spectral selectivity—high transmittance (>40%) in the 240-280nm band and low transmittance (<5%) in the UVA and UVB bands—to pre-filter ultraviolet light in non-target wavelength bands before it enters the device.

[0044] Specifically, when ultraviolet light enters from the bottom of the sapphire substrate 1, it first passes through the bandpass filter 9 for spectral filtering. UVC light in the 240-280nm band, with a transmittance exceeding 40%, can effectively pass through the bandpass filter 9 and enter the sapphire substrate. However, UVA light in the 400nm-320nm and UVB light in the 320nm-290nm bands, with transmittance at the bandpass filter 9 below 5%, is largely blocked outside the device. This spectral pre-filtering mechanism, combined with the solar-blind selectivity of the AlGaN material itself, creates a dual suppression effect, significantly improving the solar-blind / visible suppression ratio of the device.

[0045] UVC-band ultraviolet light passing through the bandpass filter 9 continues to penetrate the sapphire substrate 1, the i-type AlN buffer layer 2, the i-type AlGaN transition layer 3, and the heavily doped ohmic contact layer 4. Since its bandgap is larger than that of the light-absorbing layer, it is transparent to UVC light and is ultimately absorbed in the light-absorbing layer 5, generating photogenerated carriers. Driven by the built-in electric field, these photogenerated carriers separate: electrons drift towards the heavily doped ohmic contact layer 4, and holes drift towards the p-type GaN ohmic contact layer 6. Finally, they are collected through their respective ohmic metal electrodes, forming a photocurrent signal.

[0046] Through the synergistic effect of the bandpass filter film 9 and the properties of AlGaN material, this invention can further suppress the response of AlGaN-based solar-blind ultraviolet detectors in the UVA and UVB bands while ensuring high quantum efficiency in the solar-blind band. This effectively improves the problems of poor suppression ratio and severe interference from sunlight in traditional AlGaN-based solar-blind detectors, and improves the signal-to-noise ratio and detection accuracy of the device in practical applications.

[0047] Optionally, the bandpass filter film 9 includes a first metal layer 91, a dielectric layer 92, and a second metal layer 93 alternately deposited from bottom to top. The first metal layer 91 and the second metal layer 93 are made of Al, Ag, Pt, or an alloy of the above metals, and the dielectric layer 92 is made of silicon dioxide, silicon nitride, or aluminum oxide. To achieve the above-mentioned spectral selectivity, the bandpass filter film 9 adopts a metal-dielectric-metal sandwich composite structure, specifically including a first metal layer 91, a dielectric layer 92, and a second metal layer 93 alternately deposited from bottom to top. The first metal layer 91 and the second metal layer 93 can be made of Al, Ag, Pt, or an alloy of the above metals, with a thickness ranging from 5 to 15 nm. In a preferred embodiment, aluminum (Al) is used as the metal layer material, with a thickness of 15 nm. The dielectric layer 92 can be made of silicon dioxide, silicon nitride, or aluminum oxide, with a thickness ranging from 40 to 70 nm. In a preferred embodiment, silicon dioxide (SiO2) is used as the dielectric layer material, with a thickness of 55 nm.

[0048] For electromagnetic waves with frequencies lower than those of metallic plasma, including visible light and some ultraviolet light, the metal layer exhibits strong reflection and absorption. The penetration depth of light waves within the metal is extremely short, typically only tens of nanometers. Therefore, the first metal layer 91 and the second metal layer 93 can effectively block UVA, UVB, and visible light radiation. When the metal layer thickness is relatively thin (5-15 nm) and a dielectric layer is sandwiched between the two metal layers, a Fabry-Perot resonant cavity structure is formed. At a specific resonant wavelength, constructive interference occurs between the incident and reflected light waves, allowing light of that wavelength to pass through the entire sandwich structure with high transmittance.

[0049] The thickness (5-15 nm) of the first metal layer 91 and the second metal layer 93, along with their material selection, affects the quality factor (Q) of the resonance peak, and consequently, the full width at half maximum (FWHM) of the transmittance curve. Thinner metal layers and high-reflectivity metal materials such as Al and Ag contribute to the formation of a high-Q resonant cavity, thereby achieving a narrow-bandwidth, high-transmittance spectral response. (Reference) Figure 3 Experiments show that the transmittance of this structure can reach 47% at 260nm, and the passband half width at half maximum is about 38nm. In the wavelength band above 300nm, the transmittance is less than 5%.

[0050] By rationally designing the material and thickness parameters of the first metal layer 91, the dielectric layer 92, and the second metal layer 93, high transmittance in the UVC band and strong suppression of the UVA and UVB bands can be precisely achieved, thus providing ideal spectral filtering characteristics for solar-blind ultraviolet detectors. The fabrication process of this bandpass filter film 9 is mature and can be achieved using conventional vacuum deposition techniques such as electron beam evaporation or magnetron sputtering. It is fully compatible with existing AlGaN-based solar-blind detector fabrication processes and will not increase process difficulty or cost.

[0051] Furthermore, the doping concentration of the p-type GaN ohmic contact layer 6 ranges from 1 × 10⁻⁶. 18 -1×10 20 cm -3 This ensures the formation of a good p-type ohmic contact and reduces contact resistance; the doping concentration of the low-doped light-absorbing layer 5 ranges from 1×10⁻⁶. 14 -1×10 17 cm -3 This low doping concentration is beneficial for forming a wider depletion region, improving the collection efficiency of photogenerated carriers, and reducing dark current; the doping concentration range of the heavily doped ohmic contact layer 4 is 1×10⁻⁶. 18 -1×10 20 cm -3 This ensures that the n-type ohmic contact electrode 8 can form a low-resistance ohmic contact.

[0052] Optionally, the passivation layer n has a thickness ranging from 50 to 1000 nm, ensuring sufficient passivation protection while avoiding stress problems caused by excessive thickness; the metal pad m has a thickness ranging from 1 to 2 μm, ensuring bonding strength and conductivity; the p-type ohmic metal electrode 7 and the n-type ohmic contact electrode 8 have a thickness ranging from 50 to 400 nm, ensuring good electrical contact; the p-type GaN ohmic contact layer 6 has a thickness ranging from 50 to 300 nm; the light-absorbing layer 5 has a thickness ranging from 100 to 800 nm; the heavily doped ohmic contact layer 4 has a thickness ranging from 300 to 1000 nm; the i-type AlGaN transition layer 3 has a thickness ranging from 20 to 200 nm; the i-type AlN buffer layer 2 has a thickness ranging from 0.20 to 3 μm; and the sapphire substrate has a thickness ranging from 100 to 500 μm. As mentioned above, the thickness of each semiconductor functional layer needs to be optimized by balancing factors such as light absorption efficiency, carrier transport, and stress control.

[0053] Optionally, the p-type ohmic contact electrode is a single-layer or multi-layer composite structure made of Ni, Au, or Pt, in a circular or square shape, preferably a Ni / Au double-layer structure with a thickness of 50 / 50 nm; the n-type ohmic contact electrode 8 is a single-layer or multi-layer composite structure made of Ti, Al, Ni, Au, or Pt, in a ring shape to allow light to enter from the central region, preferably a Ni / Ti / Al / Au four-layer structure with a thickness of 20 / 20 / 60 / 50 nm. Different metal combinations and thickness ratios can be adjusted according to specific ohmic contact requirements.

[0054] Optionally, a metal pad m is also provided above the n-type ohmic contact electrode 8. The metal pad m is a single-layer or multi-layer composite structure made of Ti, Al, Ni, Au, or Pt. In practical applications, to facilitate packaging and wire bonding, a metal pad m can also be provided above the n-type ohmic contact electrode 8. This metal pad m can be a single-layer or multi-layer composite structure made of Ti, Al, Ni, Au, or Pt, preferably a Ti / Au double-layer structure with a thickness of 50 / 1000 nm to provide a good bonding interface.

[0055] Optionally, the passivation layer n is made of at least one of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, or hafnium oxide. Different passivation materials have different dielectric constants, passivation effects, and thermal stability, and can be selected according to the operating environment and performance requirements of the device. In a preferred embodiment, silicon dioxide (SiO2) is used as the passivation layer material, with a thickness of 300 nm, and is prepared by plasma-enhanced chemical vapor deposition (pECVD).

[0056] Figure 4 This is a flowchart of the preparation method provided in the embodiments of the present invention. For example... Figure 4 As shown, embodiments of the present invention also provide a preparation method for producing such... Figures 1 to 2 The method for the solar-blind ultraviolet detector with enhanced suppression ratio shown includes the following steps:

[0057] S1. On a sapphire substrate 1, an i-type AlN buffer layer 2, an i-type AlGaN transition layer 3, a heavily doped ohmic contact layer 4, a lightly doped light absorption layer 5, and a p-type GaN ohmic contact layer 6 are grown sequentially.

[0058] S2. Deposit an etch mask with a thickness of 300 nm on a solar-blind ultraviolet detector.

[0059] Specifically, pECVD was used to deposit SiO2 with a thickness of 300 nm on the epitaxial wafer of the solar blind detector.

[0060] S3. Remove the etching mask outside the active region mesa of the AlGaN solar-blind detector.

[0061] Specifically, a combination of photolithography and ICp / RIE etching or wet etching techniques is used to remove SiO2 outside the active region mesa of the solar-blind detector.

[0062] S4. Etch out the active region mesa of the AlGaN solar-blind detector, with the mesa etching depth extending to the heavily doped ohmic contact layer 4.

[0063] Specifically, ICP etching technology is used to etch out the active region mesa of the solar-blind detector, with the etching depth of the mesa extending to the heavily doped ohmic contact layer 4.

[0064] S5. Remove the etching mask, repair the mesa etching damage using chemical modification, and deposit a passivation layer n.

[0065] Specifically, wet etching was used to remove the SiO2 etching mask, chemical modification was used to repair the mesa etching damage, and a 300nm thick SiO2 layer was deposited on the surface.

[0066] S6. Remove the passivation layer n at the window of the n-type ohmic contact electrode 8, and deposit and prepare the n-type ohmic contact electrode 8 on the heavily doped ohmic contact layer 4.

[0067] Specifically, photolithography and wet etching techniques were used to remove the passivation layer n at the 8-window of the n-type ohmic contact electrode; Ti / Al / Ni / Au alloy layers with thicknesses of 20 / 20 / 60 / 50 nm were sequentially deposited on the mesa surface using electron beam evaporation; after metal stripping, the metal was rapidly thermally annealed at 800°C for 2 minutes in a nitrogen atmosphere.

[0068] S7. Remove the passivation layer n at the window of the p-type ohmic metal electrode 7, and deposit and prepare the p-type ohmic metal electrode on the p-type GaN ohmic contact layer 6.

[0069] Specifically, photolithography and wet etching techniques were used to remove the passivation layer at the window of the p-type ohmic metal electrode 7; Ni / Au alloy layers with a thickness of 50 / 50 nm were sequentially deposited on the mesa surface by electron beam evaporation; after metal stripping, the metal was rapidly thermally annealed at 500°C for 1 minute in a nitrogen / oxygen (3:1) mixed atmosphere.

[0070] S8. Prepare metal pads m on the surfaces of p-type ohmic metal electrode 7 and n-type ohmic contact electrode 8.

[0071] Specifically, Ti / Au composite metal pads with a thickness of 50 / 1000 nm are evaporated on the surfaces of the p-type ohmic metal electrode 7 and the n-type ohmic contact electrode 8 using photolithography and electron beam evaporation.

[0072] S9. Thin the sapphire substrate 1 and polish the bottom, then deposit the bandpass filter film 9 by evaporation, and perform testing, sorting, and flip packaging after laser cutting.

[0073] Specifically, the sapphire substrate 1 is thinned to 200 μm using chemical mechanical thinning and polished to a mirror finish. A bandpass filter film 9 is deposited on the back of the sapphire substrate 1 using vacuum deposition, employing an Al / SiO2 / Al sandwich resonant cavity structure with a thickness of 15 / 55 / 15 nm. The entire structure is then cut using laser scribing, tested, sorted, and flip-chip packaged.

[0074] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0075] The above description is merely an optional embodiment of the present invention and is not intended to limit the present invention. 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 solar-blind ultraviolet detector with enhanced suppression ratio, characterized in that, The system comprises, from bottom to top, a sapphire substrate (1), an i-type AlN buffer layer (2), an i-type AlGaN transition layer (3), a heavily doped ohmic contact layer (4), a light-absorbing light layer (5), and a p-type GaN ohmic contact layer (6). The heavily doped ohmic contact layer (4) has a patterned region. The light-absorbing light layer (5) and the p-type GaN ohmic contact layer (6) are located within the patterned region. A p-type ohmic metal electrode (7) is disposed above the p-type GaN ohmic contact layer (6). An n-type ohmic contact electrode (8) is also disposed on the heavily doped ohmic contact layer (4) surrounding the patterned region. A metal pad (m) is disposed above the p-type ohmic metal electrode (7). m), the p-type ohmic metal electrode (7), the n-type ohmic contact electrode (8), the p-type GaN ohmic contact layer (6), the low-doped light absorption layer (5) and the heavily doped ohmic contact layer (4) are surrounded by a passivation layer (n), the bottom of the sapphire substrate layer (1) is coated with a bandpass filter film (9), the transmitting end of the bandpass filter film (9) is located in the UVC band, the bandpass filter film (9) includes a first metal layer (91), a dielectric layer (92) and a second metal layer (93) alternately deposited from bottom to top, the first metal layer (91) and the second metal layer (93) are made of Al, Ag, Pt or alloys of the above metals, and the dielectric layer (92) is made of silicon dioxide, silicon nitride or aluminum oxide; The transmittance of ultraviolet light in the 240-280nm band to the bandpass filter film (9) is higher than 40%, while the transmittance of ultraviolet light in the 400-320nm and 320-290nm bands to the bandpass filter film (9) is lower than 5%.

2. The solar-blind ultraviolet detector with enhanced suppression ratio according to claim 1, characterized in that, The thickness of the first metal layer (91) and the second metal layer (93) ranges from 5 to 15 nm, and the thickness of the dielectric layer (92) ranges from 40 to 70 nm.

3. The solar-blind ultraviolet detector with enhanced suppression ratio according to claim 1, characterized in that, The doping concentration range of the p-type GaN ohmic contact layer (6) is 1×10⁻⁶. 18 -1×10 20 cm -3 The doping concentration range of the low-doped light-absorbing layer (5) is 1×10⁻⁶. 14 -1×10 17 cm -3 The doping concentration range of the heavily doped ohmic contact layer (4) is 1×10⁻⁶. 18 -3×10 19 cm -3 .

4. The solar-blind ultraviolet detector with enhanced suppression ratio according to claim 1, characterized in that, The passivation layer (n) has a thickness range of 50-1000 nm; the metal pad (m) has a thickness range of 1-2 μm; the p-type ohmic metal electrode (7) and the n-type ohmic contact electrode (8) have a thickness range of 50-400 nm; the p-type GaN ohmic contact layer (6) has a thickness range of 50-300 nm; the low-doped light absorption layer (5) has a thickness range of 100-800 nm; the heavily doped ohmic contact layer (4) has a thickness range of 300-1000 nm; the i-type AlGaN transition layer (3) has a thickness range of 20-200 nm; the i-type AlN buffer layer (2) has a thickness range of 0.20-3 μm; and the sapphire substrate has a thickness range of 100-500 μm.

5. The solar-blind ultraviolet detector with enhanced suppression ratio according to claim 1, characterized in that, The p-type ohmic contact electrode is a single-layer or multi-layer composite structure made of Ni, Au or Pt material, and is circular or square in shape; the n-type ohmic contact electrode (8) is a single-layer or multi-layer composite structure made of Ti, Al, Ni, Au or Pt material, and is ring-shaped.

6. The solar-blind ultraviolet detector with enhanced suppression ratio according to any one of claims 1 to 5, characterized in that, The metal pad (m) is also provided above the n-type ohmic contact electrode (8).

7. The solar-blind ultraviolet detector with enhanced suppression ratio according to claim 6, characterized in that, The metal pad (m) is a single-layer or multi-layer composite structure made of Ti, Al, Ni, Au or Pt.

8. The solar-blind ultraviolet detector with enhanced suppression ratio according to any one of claims 1 to 5, characterized in that, The passivation layer (n) is made of at least one of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, or hafnium oxide.

9. A method for fabricating a solar-blind ultraviolet detector with enhanced suppression ratio as described in any one of claims 1 to 8, characterized in that, include: The i-type AlN buffer layer (2), the i-type AlGaN transition layer (3), the heavily doped ohmic contact layer (4), the light-absorbing layer (5) and the p-type GaN ohmic contact layer (6) are sequentially grown on the sapphire substrate layer (1). An etching mask with a thickness of 300 nm was deposited on the solar-blind ultraviolet detector; Remove the etching mask outside the active region mesa of the AlGaN solar-blind detector; The active region mesa of the AlGaN solar-blind detector was etched out, and the etching depth of the mesa reached the heavily doped ohmic contact layer (4). Remove the etching mask, repair the mesa etching damage using chemical modification, and then deposit the passivation layer (n). Remove the passivation layer (n) at the window of the n-type ohmic contact electrode (8), and deposit and fabricate the n-type ohmic contact electrode (8) on the heavily doped ohmic contact layer (4); Remove the passivation layer (n) at the window of the p-type ohmic metal electrode (7), and deposit and prepare the p-type ohmic metal electrode (7) on the p-type GaN ohmic contact layer (6). The metal pads (m) are prepared on the surfaces of the p-type ohmic metal electrode (7) and the n-type ohmic contact electrode (8); The sapphire substrate (1) is thinned and the bottom is polished, and the bandpass filter film (9) is deposited by vapor deposition. After laser cutting, it is tested, sorted and flip-chip packaged.

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