Gallium oxide solar-blind ultraviolet detector based on selected area etching and preparation method thereof

Abstract

The invention discloses a gallium oxide solar-blind ultraviolet detector based on selective area etching and a preparation method thereof, and belongs to the technical field of semiconductor photoelectric detection. Comprises from bottom to top: a substrate; the first epitaxial layer is located on the substrate, and the first epitaxial layer is a highly doped n-Ga2O3 layer; the second epitaxial layer is located on the first epitaxial layer, and the second epitaxial layer is a lightly doped n-Ga2O3 layer; the third epitaxial layer is located on the second epitaxial layer, the third epitaxial layer is a highly-doped p-NiO layer, and the third epitaxial layer is distributed at intervals through selective area etching; and the first ohmic contact layer is located on the area where the third epitaxial layer is distributed at intervals. The detector adopts a PN junction structure working in a reverse bias state, and compared with a Schottky structure, the detector has the advantages that the built-in electric field intensity and the leakage current level of a device are less affected by high-energy photon irradiation and working environment temperature change, and the anti-irradiation performance of the device and the working capability under an extreme temperature condition are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor photoelectric detection technology, and to a gallium oxide solar-blind ultraviolet detector and its fabrication method, particularly to a gallium oxide solar-blind ultraviolet detector based on selected area etching and its fabrication method. Background Technology

[0002] Solar-blind ultraviolet detectors operate in the solar blind zone (240-280nm), exhibiting extremely low background noise. This results in ultra-high detection sensitivity and a very low false alarm rate even in complex environments, demonstrating significant application value in ultraviolet communication, high-voltage corona detection, missile early warning, and flame monitoring. From a device structure perspective, existing solar-blind ultraviolet detectors mainly face two key challenges: for back-incident structures, the strong absorption of incident photons by the substrate material significantly reduces quantum efficiency; while for front-incident structures, the heavily doped ohmic contact layer absorbs most photons. Although Schottky junction detectors can achieve an ideal surface barrier through metal-semiconductor contacts, they are prone to forming electro-vacancy defects under high-dose ultraviolet irradiation. This reduces the Schottky barrier height through the mirror potential effect, ultimately leading to a sharp increase in reverse leakage current. PN junctions are more stable than Schottky junctions, but traditional PN junction detectors suffer from extremely low detection efficiency in the ultraviolet band due to the strong absorption of ultraviolet photons by the non-active regions on the surface.

[0003] For the specific requirements of solar-blind ultraviolet (<280nm) detection, the ultrawide bandgap semiconductor Ga2O3 has become an ideal solution due to its unique material properties. This material has a bandgap of 4.4-5.1 eV, possesses intrinsic solar-blindness, and can completely avoid visible / near-infrared interference; simultaneously, its melting point exceeds 1800℃ and its breakdown field strength is as high as 8MV / cm, exhibiting environmental stability far exceeding that of silicon-based devices. However, due to its material properties, achieving p-type doping in Ga2O3 is relatively difficult. Nickel oxide (NiO), with its wide bandgap (~3.6-4.0 eV), natural p-type conductivity, and excellent chemical stability, has become an ideal material to match Ga2O3. NiO not only has high hole mobility, but its conductivity can also be further optimized through doping (such as Li, Cu, etc.). Furthermore, its high lattice matching with Ga2O3 can reduce interface defects and improve device performance. To this end, this invention proposes a gallium oxide solar-blind ultraviolet detector based on selected area etching, aiming to achieve high-efficiency solar-blind ultraviolet detection by optimizing the device structure and fabrication process. Summary of the Invention

[0004] The technical objective of this invention is to provide a gallium oxide solar-blind ultraviolet detector based on selected area etching and its fabrication method, so as to solve the problems of low detection efficiency, poor device stability and long-range reliability in the solar-blind ultraviolet band.

[0005] Firstly, to achieve the above objectives, the technical solution adopted by this invention is a gallium oxide solar-blind ultraviolet detector based on selected area etching. This gallium oxide solar-blind ultraviolet detector is implemented using a p-NiO / n-Ga2O3 structure, providing a valid reference for next-generation ultraviolet photodetectors. The gallium oxide solar-blind ultraviolet detector includes, from bottom to top: Substrate; The first epitaxial layer is located on the substrate, and the first epitaxial layer is a highly doped n-Ga2O3 layer; The second epitaxial layer is located on the first epitaxial layer, and the second epitaxial layer is a lightly doped n-Ga2O3 layer; The third epitaxial layer is located on the second epitaxial layer. The third epitaxial layer is a highly doped p-NiO layer. The third epitaxial layer is distributed in an intermittent manner by selective etching. The first ohmic contact layer is located on the region where the third epitaxial layer is distributed at intervals.

[0006] Based on the first aspect, in a first possible implementation, the areas of the second epitaxial layer and the third epitaxial layer are smaller than the area of ​​the first epitaxial layer, and a portion of the first epitaxial layer forms an isolation platform with the second epitaxial layer and the third epitaxial layer; the portion of the platform refers to the area on the first epitaxial layer where the second epitaxial layer and the third epitaxial layer are located.

[0007] The gallium oxide solar-blind ultraviolet detector also includes a second ohmic contact layer, which is formed in the region outside the isolation mesa on the first epitaxial layer.

[0008] Based on the first aspect, in the second possible implementation, the substrate is a heavily doped n-type conductive substrate; the gallium oxide solar-blind ultraviolet detector further includes a second ohmic contact layer located on the other side of the substrate, which is opposite to the side of the substrate on which the first epitaxial layer is formed.

[0009] Optionally, the substrate can be any one of materials such as silicon, silicon carbide, gallium nitride, or gallium oxide; Optionally, the doping concentration of the first epitaxial layer is in the range of 1×10⁻⁶. 18 cm -3 Up to 1×10 21 cm -3 The doping concentration of the second epitaxial layer is no higher than that of the first epitaxial layer; the doping concentration of the third epitaxial layer is 1×10⁻⁶. 18 cm -3 Up to 1×10 21 cm -3 .

[0010] Optionally, the first epitaxial layer has a thickness of 0.210 μm, the second epitaxial layer has a thickness greater than 1 μm, the third epitaxial layer has a thickness range of 0.012 μm, and the thicknesses of the first ohmic contact layer and the second ohmic contact layer are greater than 0.1 μm.

[0011] Optionally, the first ohmic contact electrode is at least one of nickel or gold, preferably a nickel layer and a gold layer connected sequentially from bottom to top; the second ohmic contact electrode is at least one of titanium or gold, preferably a titanium layer and a gold layer connected sequentially from bottom to top.

[0012] Optionally, to further improve quantum efficiency, the third epitaxial layer is spaced out on the surface of the second epitaxial layer, with a fill factor (the fill factor being the ratio of the sum of the surface areas of all third epitaxial layer well regions to the surface area of ​​the third epitaxial layer before selective etching) of 10-90%; preferably, the fill factor is 60%. The third epitaxial layer well region formed by selective etching forms a lateral PN junction with the second epitaxial layer. Electron-hole pairs generated by incident ultraviolet photons separate under the combined action of the built-in electric field and the drift electric field of the PN junction, forming a photoresponse current, thereby realizing the detection of ultraviolet photons. More preferably, the third epitaxial layer region is in the form of a grid, mesh, or ring.

[0013] Optionally, the first ohmic contact layer is located entirely above the third epitaxial layer region, and its shape is grid-like, mesh-like, or annular, consistent with the shape of the third epitaxial layer region. The width of the electrode grid of the first ohmic contact layer is greater than 0.1 μm.

[0014] Optionally, the second ohmic contact layer is located entirely above the first epitaxial layer region, and its shape is square or annular, consistent with the shape of the third epitaxial layer region. The electrode width of the second ohmic contact layer is greater than 10 μm.

[0015] Unlike conventional PN junction detectors and Schottky detectors in the ultraviolet band, the gallium oxide solar-blind ultraviolet detector based on selected area etching (SITE) forms a lateral PN junction on the device surface. The active region of the device widens laterally in reverse bias mode, allowing incident ultraviolet photons to directly enter the active absorption region located between the device surface and the P-type or N-type well region. This effectively avoids the strong absorption of ultraviolet photons in the thick ohmic contact layer and transition layer of traditional devices, thus significantly improving the detection efficiency in the ultraviolet band, especially in the vacuum ultraviolet band. Furthermore, the detector uses a PN junction structure operating in reverse bias mode. Compared to Schottky structures, the built-in electric field strength and leakage current level are less affected by high-energy photon irradiation and changes in ambient temperature, effectively improving the device's radiation resistance and ability to operate under extreme temperature conditions.

[0016] Secondly, to achieve the above objectives, the technical solution adopted by the present invention is a method for fabricating a gallium oxide solar-blind ultraviolet detector based on selected area etching, the method comprising: S1: Fabrication of a semiconductor epitaxial wafer. The semiconductor epitaxial wafer comprises, from bottom to top, a substrate, a first epitaxial layer, a second epitaxial layer, and a third epitaxial layer; wherein the first epitaxial layer is a highly doped n-Ga2O3 layer; the second epitaxial layer is a lightly doped n-Ga2O3 layer; and the third epitaxial layer is a highly doped p-NiO layer. S2: A mask is deposited on top of the third epitaxial layer, and the second and third epitaxial layers are etched downwards until the top of the first epitaxial layer is exposed to form a mesa.

[0017] S3: After coating a photoresist layer on top of the third epitaxial layer, exposure, development, and post-baking are performed to form a patterned dry-etched thick photoresist mask. Then, inductively coupled plasma etching (ICP) is used to selectively etch the third epitaxial layer downwards until the top of the second epitaxial layer is reached, forming spaced-apart patterned regions on the second epitaxial layer. Only the third epitaxial layer within the patterned regions is retained, forming spaced-apart well regions with the underlying second epitaxial layer. The photoresist is then removed.

[0018] S4: An electrode window is formed on top of the spaced-out third epitaxial layer using conventional photolithography, and then the first ohmic contact layer is deposited by electron beam evaporation.

[0019] S5: An electrode window is formed in the mesa region of the first epitaxial layer using conventional photolithography, and then the second ohmic contact layer is deposited by electron beam evaporation.

[0020] In a second possible implementation, the substrate is a heavily doped n-type conductive substrate; the second ohmic contact layer is located on the other side of the substrate, opposite to the side of the substrate where the first epitaxial layer is formed. The second ohmic contact layer is deposited using electron beam evaporation. The electrodes are fully covered. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the steps of growing a substrate, a first epitaxial layer, a second epitaxial layer, and a third epitaxial layer for a gallium oxide solar-blind ultraviolet detector based on selected area etching, as provided in an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram illustrating the steps of etching a mesa to form a gallium oxide solar-blind ultraviolet detector based on selected area etching, as provided in an embodiment of the present invention.

[0023] Figure 3This is a schematic diagram illustrating the steps of forming a patterned third epitaxial layer in a gallium oxide solar-blind ultraviolet detector based on selected area etching (SITE) according to an embodiment of the present invention.

[0024] Figure 4 Is Figure 3 A schematic diagram of the steps involved in depositing the first ohmic contact layer on the device.

[0025] Figure 5 It is real Figure 4 A schematic diagram illustrating the steps involved in depositing a second ohmic contact layer on the mesa of the device.

[0026] Figure 6 This is a schematic diagram of the deposition of another second ohmic contact layer provided in an embodiment of the present invention.

[0027] Figure 7 yes Figure 5 A top view of the structure.

[0028] Figure 8 yes Figure 5 Simulation diagram of local electric field distribution in the medium structure (based on SilvacoTCAD).

[0029] Figure 9 This is a flowchart of the fabrication method of the gallium oxide solar-blind ultraviolet detector based on selected area etching in Embodiment 1 of the present invention.

[0030] In the figure, 1 is the substrate; 2 is the first epitaxial layer; 3 is the second epitaxial layer; 4 is the third epitaxial layer; 5 is the first ohmic contact layer; and 6 is the second ohmic contact layer. Detailed Implementation

[0031] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0032] like Figures 1 to 7 As shown, this embodiment of the invention provides a gallium oxide solar-blind ultraviolet detector based on selected area etching, including a substrate 1, a first epitaxial layer 2, a second epitaxial layer 3, a third epitaxial layer 4, a first ohmic contact layer 5, and a second ohmic contact layer 6.

[0033] A first epitaxial layer 2 is located on the substrate 1, and the first epitaxial layer is a highly doped n-Ga2O3 layer; a second epitaxial layer 3 is located on the first epitaxial layer 2, and the second epitaxial layer is a lightly doped n-Ga2O3 layer; a third epitaxial layer 4 is located on the second epitaxial layer 3, and the third epitaxial layer is a highly doped p-NiO layer. The areas of the second epitaxial layer 3 and the third epitaxial layer 4 are smaller than the area of ​​the first epitaxial layer 2, and a portion of the first epitaxial layer 2 forms an isolation platform with the second epitaxial layer 3 and the third epitaxial layer 4, wherein the portion of the platform refers to the area on the first epitaxial layer 2 where the second epitaxial layer 3 and the third epitaxial layer 4 are located. The third epitaxial layer 4 is patterned using selective etching. The first ohmic contact layer 5 located on the third epitaxial layer 4 is also a patterned ohmic contact layer. The area of ​​the first ohmic contact layer 5 is smaller than that of the third epitaxial layer 4, and its shape is grid-like, mesh-like, or ring-like. The ultraviolet detector further includes a second ohmic contact layer 6, which is formed in the region outside the isolation mesa on the first epitaxial layer. The second ohmic contact layer 6 is square or annular in shape. Another possible implementation of the second ohmic contact layer 6: when the substrate 1 is a heavily doped n-type conductive substrate; the second ohmic contact layer 6 is located on the other side of the substrate 1, which is opposite to the epitaxial direction of the substrate 1. In this case, the second ohmic contact layer 6 takes a full-coverage form.

[0034] In this embodiment of the invention, the gallium oxide solar-blind ultraviolet detector is fabricated with reference to... Figure 1 Using substrate 1 as the epitaxial substrate, a first epitaxial layer 2, a second epitaxial layer 3, and a third epitaxial layer 4 are sequentially grown on it. Exemplarily, in this embodiment of the invention, substrate 1 can be any of the materials such as silicon, gallium nitride, or silicon carbide. The first epitaxial layer 2 is an N-type doped gallium oxide layer with a thickness of 2 μm and a doping concentration of 1 × 10⁻⁶. 19 cm -3 The second epitaxial layer 3 above the first epitaxial layer 2 is an N-type doped gallium oxide layer with a thickness of 4 μm and a doping concentration of 1 × 10⁻⁶. 16 cm -3 The third epitaxial layer 4 above the second epitaxial layer 3 is a 0.1 μm thick P-type doped nickel oxide layer with a doping concentration of 1 × 10⁻⁶. 19 cm -3 .

[0035] Further, refer to Figure 2At the top of the device, above the third epitaxial layer 4, a Ni metal layer is deposited using physical vapor deposition (PVD) as a mask. Then, inductively coupled plasma etching (ICP) is used to etch downwards from the third epitaxial layer 4 and the second epitaxial layer 3 until the top of the first epitaxial layer 2 is exposed, forming a patterned region on the first epitaxial layer 2, retaining only the second epitaxial layer 3 and the third epitaxial layer 4 within the patterned region. A portion of the first epitaxial layer 2 forms an isolation mesa with the second epitaxial layer 3 and the third epitaxial layer 4, where the portion represents the area on the first epitaxial layer 2 containing the second epitaxial layer 3 and the third epitaxial layer 4. The etching depth from the third epitaxial layer 4 downwards is 4.1 μm, exposing the first epitaxial layer 2 before removing the metal mask. The use of a deposited metal mask as a pre-etching step is due to the difficulty in etching gallium oxide, as conventional photoresist as an etching mask is prone to insufficient blocking power.

[0036] Further, refer to Figure 3 A uniform layer of photoresist is spin-coated on top of the device, above the third epitaxial layer 4. After exposure, development, and post-baking, a dry etching photoresist mask is formed. Then, inductively coupled plasma etching (ICP) is used to etch the third epitaxial layer 4 downwards at intervals until the top of the second epitaxial layer 3 is exposed, forming a gate region on the second epitaxial layer 3. Only the third epitaxial layer 4 within the gate pattern is retained, forming an interspersed gate structure with the lower second epitaxial layer 3. The etching depth from the third epitaxial layer 4 downwards is 0.1 μm. After exposing the second epitaxial layer 3, the photoresist is removed. The width, spacing, and well depth of the interspersed gate-shaped third epitaxial layer 4 are 1 μm, 2 μm, and 0.1 μm, respectively. The fill factor (the ratio of the sum of the surface areas of all well regions of the third epitaxial layer 4 to the total surface area of ​​the third epitaxial layer 4 before selected area etching) is 60%. Further, refer to Figure 4 A layer of photoresist is uniformly spin-coated on the top of the device, that is, above the top region of the third epitaxial layer 4. After exposure, development and post-baking, a patterned ohmic contact photoresist mask is formed. Then, metal Ni / Au is deposited sequentially by physical vapor deposition (PVD) to form the first ohmic contact layer 5.

[0037] Further, refer to Figure 5 A layer of photoresist is uniformly spin-coated over the non-mesa region of the first epitaxial layer 2. After exposure, development, and post-baking, a patterned ohmic contact photoresist mask is formed. Then, Ti / Au metal is sequentially deposited using physical vapor deposition (PVD) to form the second ohmic contact layer 6. The first ohmic contact layer 5 is a grid-like structure composed of strip electrodes, with a strip electrode width of 0.6 μm and a strip electrode spacing of 2.4 μm. The second ohmic contact layer 6 is a rectangular shape with a frame width of 100 μm. Figure 7 Showing Figure 5 A top-view schematic diagram of the structure. The first ohmic contact layer 5, in the shape of grids, and the second ohmic contact layer 6, in the shape of a square frame, can be clearly seen.

[0038] In another possible implementation of this invention, reference is made to... Figure 6 When the substrate is a heavily doped n-type conductive substrate, the second ohmic contact layer 6 is deposited sequentially with metal Ti / Au on the back side of the substrate 1 by physical vapor deposition (PVD) in a full-coverage manner.

[0039] This invention provides a gallium oxide solar-blind ultraviolet detector based on selected area etching. Both the first ohmic contact layer and the third epitaxial layer of this detector employ patterned grid structures, effectively avoiding energy loss caused by ultraviolet photons penetrating passive regions such as the ohmic contact layer and passivation layer on the surface of traditional PN junction detectors, thereby significantly improving the device's detection efficiency in the ultraviolet band.

[0040] On the other hand, such as Figure 8 As shown, the third epitaxial layer, with its intermittently distributed grid-like structure, has an opposite conductivity type to the second epitaxial layer. This design not only forms a longitudinally distributed depletion region at the interface between the second and third epitaxial layers but also a laterally distributed surface depletion region in the well region above the second epitaxial layer, which is not covered by the third epitaxial layer. Incident ultraviolet photons can be directly absorbed by this lateral depletion region on the surface. This mechanism further improves the detector's detection efficiency in the ultraviolet band. Furthermore, under reverse bias conditions, the depletion region on the surface of the device's well region expands further laterally, increasing the electric field strength and enlarging the effective photon collection area. It is predicted that the device will have even higher quantum efficiency under high bias voltage.

[0041] Compared to the shortcomings of traditional Schottky junction ultraviolet detectors, whose detection performance is easily affected by changes in the Schottky barrier height, the gallium oxide solar-blind ultraviolet detector based on selected area etching exhibits good temperature stability and strong radiation resistance, and has the potential to operate stably for extended periods in high-radiation and high-temperature environments. Furthermore, this detector can effectively avoid device performance fluctuations caused by lattice damage during ion implantation, has a wider process window, and is beneficial for industrial production.

[0042] like Figure 9 As shown, the fabrication process of the above-mentioned device is as follows: S1: Using substrate 1 as the epitaxial substrate, the first epitaxial layer 2, the second epitaxial layer 3 and the third epitaxial layer 4 are grown sequentially on it.

[0043] Specifically, in this step, substrate 1 is a semi-insulating gallium oxide substrate. The first epitaxial layer 2 is an N-type doped gallium oxide layer with a thickness of 2 μm and a doping concentration of 1 × 10⁻⁶. 19 cm-3 The second epitaxial layer 3 above the first epitaxial layer 2 is an N-type doped gallium oxide layer with a thickness of 4 μm and a doping concentration of 1 × 10⁻⁶. 16 cm -3 The third epitaxial layer 4 above the second epitaxial layer 3 is a 0.1 μm thick P-type doped nickel oxide layer with a doping concentration of 1 × 10⁻⁶. 19 cm -3 .

[0044] S2: A mask is deposited on top of the third epitaxial layer 4, and the third epitaxial layer 4 and the second epitaxial layer 3 are etched downwards until the top of the first epitaxial layer 2 is exposed to form a mesa.

[0045] Specifically, in this step, a Ni metal layer is deposited as a mask by evaporation on the top of the device, that is, above the third epitaxial layer 4. Then, the third epitaxial layer 4 and the second epitaxial layer 3 are etched downwards using inductively coupled plasma etching (ICP) until the top of the first epitaxial layer 2 is exposed, so as to form a patterned area on the first epitaxial layer 2. Only the third epitaxial layer 4 and the second epitaxial layer 3 in the patterned area are retained, forming the first stepped mesa structure with the first epitaxial layer 2 below.

[0046] S3: A dry etching photoresist mask is formed on the top of the third epitaxial layer 4 by photolithography. Then, the third epitaxial layer 4 is etched downwards using selective etching technology until the top of the second epitaxial layer 3 is reached, forming a gate-shaped third epitaxial layer.

[0047] Specifically, in this step, the top of the third epitaxial layer 4 is coated with photoresist, which is then exposed, developed, and baked to form a patterned dry-etched thick photoresist mask. Then, inductively coupled plasma etching (ICP) is used to etch the third epitaxial layer downwards until it reaches the top of the second epitaxial layer, forming spaced-apart patterned regions on the second epitaxial layer. Only the third epitaxial layer within these patterned regions is retained, forming spaced-apart well regions with the underlying second epitaxial layer. Afterwards, the photoresist is removed.

[0048] S4: An electrode window is formed on the top of the spaced-out third epitaxial layer 4 using conventional photolithography, and then the first ohmic contact layer 5 is deposited by electron beam evaporation.

[0049] Specifically, in this step, photoresist is coated on top of the spaced-out third epitaxial layer 4, followed by exposure, development, and post-baking to form a patterned electrode window. Subsequently, the spaced-out first ohmic contact layer 5 is deposited using electron beam evaporation. The deposited multilayer metal is Ni / Au.

[0050] S5: An electrode window is formed on the top of the mesa region of the first epitaxial layer 2 using conventional photolithography, and then the second ohmic contact layer 6 is deposited by electron beam evaporation.

[0051] Specifically, in this step, photoresist is coated on top of the mesa region of the first epitaxial layer 2, and then exposed, developed, and baked to form a patterned electrode window. Subsequently, the second ohmic contact layer 6 is deposited by electron beam evaporation. The deposited multilayer metal is Ti / Au.

[0052] Based on the first aspect, in a second possible implementation, the substrate is a heavily doped n-type conductive substrate; the second ohmic contact layer is located on the other side of the substrate, which is opposite to the side of the substrate on which the first epitaxial layer is formed.

[0053] Specifically, a second ohmic contact layer 6 is directly deposited on the opposite side of the substrate using electron beam evaporation. The electrodes are fully covered. The deposited multilayer metals are all / Ti / Au.

Claims

1. A gallium oxide solar-blind ultraviolet detector based on selected area etching, characterized in that: Bottom-up including Substrate; The first epitaxial layer is located on the substrate, and the first epitaxial layer is a highly doped n-Ga2O3 layer; The second epitaxial layer is located on the first epitaxial layer, and the second epitaxial layer is a lightly doped n-Ga2O3 layer; The third epitaxial layer is located on the second epitaxial layer. The third epitaxial layer is a highly doped p-NiO layer. The third epitaxial layer is distributed in an intermittent manner by selective etching. The first ohmic contact layer is located on the region where the third epitaxial layer is distributed at intervals.

2. The gallium oxide solar-blind ultraviolet detector based on selected area etching according to claim 1, characterized in that: The areas of the second epitaxial layer and the third epitaxial layer are smaller than the area of ​​the first epitaxial layer, and a portion of the first epitaxial layer forms an isolation platform with the second epitaxial layer and the third epitaxial layer; the portion of the platform refers to the area on the first epitaxial layer that has the second epitaxial layer and the third epitaxial layer.

3. A gallium oxide solar-blind ultraviolet detector based on selected area etching according to claim 2, characterized in that: The gallium oxide solar-blind ultraviolet detector also includes a second ohmic contact layer, which is formed in the region outside the isolation mesa on the first epitaxial layer.

4. A gallium oxide solar-blind ultraviolet detector based on selected area etching according to claim 1, characterized in that: The substrate is a heavily doped n-type conductive substrate; the gallium oxide solar-blind ultraviolet detector further includes a second ohmic contact layer, which is located on the other side of the substrate, opposite to the side of the substrate on which the first epitaxial layer is formed.

5. A gallium oxide solar-blind ultraviolet detector based on selected area etching according to claim 1, characterized in that: The substrate is any one of silicon, silicon carbide, gallium nitride, or gallium oxide.

6. A gallium oxide solar-blind ultraviolet detector based on selected area etching according to claim 1, characterized in that: The doping concentration range of the first epitaxial layer is 1×10⁻⁶. 18 cm -3 Up to 1×10 21 cm -3 The doping concentration of the second epitaxial layer is no higher than that of the first epitaxial layer; the doping concentration of the third epitaxial layer is 1×10⁻⁶. 18 cm -3 Up to 1×10 21 cm -3 .

7. A gallium oxide solar-blind ultraviolet detector based on selected area etching according to claim 1, characterized in that: The first epitaxial layer has a thickness of 0.210 μm, the second epitaxial layer has a thickness greater than 1 μm, the third epitaxial layer has a thickness range of 0.012 μm, and the thicknesses of the first ohmic contact layer and the second ohmic contact layer are greater than 0.1 μm.

8. A gallium oxide solar-blind ultraviolet detector based on selected area etching according to claim 1, characterized in that: The first ohmic contact electrode is at least one of nickel or gold; the second ohmic contact electrode is at least one of titanium or gold.

9. A gallium oxide solar-blind ultraviolet detector based on selected area etching according to claim 1, characterized in that: The first ohmic contact layer is located entirely above the third epitaxial layer region, and its shape is grid-like, mesh-like, or ring-like, consistent with the shape of the third epitaxial layer region; the width of the electrode grid of the first ohmic contact layer is greater than 0.1 μm.

10. A method for fabricating a gallium oxide solar-blind ultraviolet detector based on selected area etching as described in any one of claims 1-9, characterized in that: The preparation method includes: S1: Fabrication of a semiconductor epitaxial wafer; wherein, the semiconductor epitaxial wafer comprises, from bottom to top, a substrate, a first epitaxial layer, a second epitaxial layer and a third epitaxial layer; wherein, the first epitaxial layer is a highly doped n-Ga2O3 layer; the second epitaxial layer is a lightly doped n-Ga2O3 layer, and the third epitaxial layer is a highly doped p-NiO layer; S2: Deposit a mask on top of the third epitaxial layer and etch the second and third epitaxial layers downwards until the top of the first epitaxial layer is exposed to form a mesa; S3: Photoresist is coated on the third epitaxial layer, and after exposure, development, and post-baking, a patterned dry-etched thick photoresist mask is formed. Then, the third epitaxial layer is selectively etched downwards to the top of the second epitaxial layer using inductively coupled plasma (ICP) etching, so as to form a patterned region with intervals on the second epitaxial layer. Only the third epitaxial layer within the patterned region is retained, forming an intervald well region with the second epitaxial layer below. After that, the photoresist is removed. S4: An electrode window is formed on the top of the spaced-out third epitaxial layer using conventional photolithography, and then the first ohmic contact layer is deposited by electron beam evaporation. S5: An electrode window is formed in the mesa region of the first epitaxial layer using conventional photolithography, and then the second ohmic contact layer is deposited by electron beam evaporation.

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