Gallium oxide ultraviolet photoelectric detector and preparation method thereof

Abstract

The invention provides a gallium oxide ultraviolet photoelectric detector and a preparation method thereof. The detector of the present invention comprises: a substrate; the plurality of beta-gallium oxide table tops are arranged on the substrate in an array, and each beta-gallium oxide table top is an independent detection unit; the plurality of electrode pairs are arranged corresponding to the beta-gallium oxide table top; wherein each electrode pair comprises a first electrode and a second electrode which are arranged at an interval and electrically insulated from each other, for each beta-gallium oxide table top, the corresponding first electrode and second electrode respectively form a three-dimensional surrounding structure, and the three-dimensional surrounding structure covers the peripheral edge and the side wall of the top of the corresponding beta-gallium oxide table top. The beta-gallium oxide mesa is arranged on the substrate and extends to the surface of the substrate, and the top center area of the beta-gallium oxide mesa is not covered by an electrode to serve as a photosensitive window. According to the invention, high-density and microminiaturization integration of the beta-gallium oxide ultraviolet detector is realized.

Description

Technical Field

[0001] This application belongs to the field of ultraviolet photodetector. Specifically, this invention relates to a gallium oxide ultraviolet photodetector and its fabrication method. Background Technology

[0002] Ultraviolet photodetectors have important applications in fields such as space communication, environmental monitoring, biomedicine, and industrial inspection. The solar-blind ultraviolet band (wavelength approximately 200-280 nm) has become a research hotspot due to its extremely low background radiation, which can significantly improve the detection signal-to-noise ratio and sensitivity.

[0003] β-Gallium oxide (β-Ga₂O₃), as an emerging ultrawide bandgap semiconductor material, has an intrinsic absorption edge at approximately 260 nm corresponding to its bandgap width (approximately 4.9 eV), which falls precisely in the solar-blind ultraviolet band. This allows for a natural response to solar-blind ultraviolet light without the need for external filters. Furthermore, gallium oxide possesses advantages such as high breakdown electric field and good thermal stability, making it considered one of the ideal materials for fabricating high-performance solar-blind ultraviolet detectors.

[0004] Currently, most research on gallium oxide (GaO) ultraviolet detectors focuses on optimizing the performance of single-point or unit devices, such as improving responsivity and detectivity through heterojunctions and surface modification. However, for high-value-added applications such as imaging and multi-target sensing, it is essential to develop detector arrays with high uniformity and high spatial resolution. Existing GaO detector arrays typically have large individual pixel sizes (generally above 200 μm) and wide inter-pixel spacing. This large-size design stems primarily from the challenges faced by traditional processes in achieving micron-level fabrication precision, electrode lead layout, and controlling electrical crosstalk between units. The direct consequence is low spatial resolution and difficulty in high-density integration with existing silicon-based readout circuits, severely limiting the application of GaO detectors in miniaturized and intelligent systems (such as portable sensing devices and robot vision systems).

[0005] Therefore, how to break through the limitations of existing microfabrication processes and design and fabricate gallium oxide ultraviolet detector arrays with unit size and spacing reaching the micrometer level, as well as excellent photoelectric performance and high uniformity, has become a key technical problem that urgently needs to be solved to promote the material from laboratory material research to practical industrial applications. Summary of the Invention

[0006] One objective of this invention is to provide a gallium oxide ultraviolet photodetector with extremely small size and high density integration, so as to solve the problems of large size, low resolution and difficulty in large-scale integration of existing gallium oxide detector arrays.

[0007] Another objective of this invention is to provide a method for fabricating the gallium oxide ultraviolet photodetector of this invention. This method combines micro-nano fabrication techniques such as laser direct writing, inductively coupled plasma-reactive ion etching (ICP-RIE), and electron beam evaporation to achieve high-precision fabrication of devices with steep sidewalls, ensuring the consistency and repeatability of the array.

[0008] The above-mentioned objective of the present invention is achieved through the following technical solution.

[0009] On one hand, the present invention provides a gallium oxide ultraviolet photodetector, comprising:

[0010] Substrate;

[0011] A plurality of gallium β-oxide mesa arranged in an array on the substrate, each of the gallium β-oxide mesa being an independent detection unit; and

[0012] Multiple electrode pairs corresponding to the β-gallium oxide mesa;

[0013] Each electrode pair includes a first electrode and a second electrode that are spaced apart and electrically insulated from each other.

[0014] For each of the β-gallium oxide mesa, the corresponding first electrode and second electrode each form a three-dimensional surrounding structure, which covers the top outer peripheral edge and sidewalls of the corresponding β-gallium oxide mesa and extends to the substrate surface, wherein the top mid-sized region of the β-gallium oxide mesa is uncovered by electrodes to serve as a photosensitive window.

[0015] Preferably, in the gallium oxide ultraviolet photodetector of the present invention, the maximum cross-sectional dimension of the β-gallium oxide mesa is 0.5 μm to 200 μm, more preferably 0.5 μm to 50 μm, and even more preferably 0.5 μm to 5 μm.

[0016] Preferably, in the gallium oxide ultraviolet photodetector of the present invention, the minimum spacing between the β-gallium oxide mesa is one-third of the maximum cross-sectional dimension of the β-gallium oxide mesa.

[0017] Preferably, in the gallium oxide ultraviolet photodetector of the present invention, the maximum spacing between the β-gallium oxide mesa is less than or equal to 200 μm.

[0018] Preferably, in the gallium oxide ultraviolet photodetector of the present invention, the thickness of the β-gallium oxide mesa is 180 nm to 400 nm.

[0019] Preferably, in the gallium oxide ultraviolet photodetector of the present invention, the thickness of the first electrode and the second electrode located on the substrate portion are each independently between 200 nm and 420 nm.

[0020] Preferably, in the gallium oxide ultraviolet photodetector of the present invention, the thickness of the first electrode and the second electrode located on the β-gallium oxide mesa portion are each independently between 200 nm and 420 nm.

[0021] Preferably, in the gallium oxide ultraviolet photodetector of the present invention, the substrate is a sapphire substrate or a silicon oxide substrate.

[0022] Preferably, in the gallium oxide ultraviolet photodetector of the present invention, the materials of the first electrode and the second electrode are independently selected from monolayer metals (such as Ag, In, Al, Pd, Pt or Au), transparent conductive oxides (such as ITO), graphene or a stacked structure composed of at least two metals.

[0023] Preferably, in the gallium oxide ultraviolet photodetector of the present invention, the stacked structure composed of at least two metals includes Ti / Au, Ti / Al / Ni / Au, Cr / Au or Ni / Au, where “ / ” indicates the stacking order from bottom to top.

[0024] The electrodes of the gallium oxide ultraviolet photodetector of the present invention have an in-plane structure, that is, a pair of electrodes of each detection unit are disposed on the same plane of the substrate, and are connected by means of... Figure 3 The three-dimensional surrounding structure shown achieves ohmic contact with the β-gallium oxide mesa.

[0025] On the other hand, the present invention provides a method for preparing the gallium oxide ultraviolet photodetector of the present invention, which includes the following steps:

[0026] (1) Forming a β-gallium oxide thin film on a substrate;

[0027] (2) A first patterned mask is formed on the β-gallium oxide thin film, the first patterned mask defining a plurality of spaced mesa windows;

[0028] (3) Using the first patterned mask as a mask, the β-gallium oxide thin film is etched to form a plurality of spaced β-gallium oxide mesa; then, the first patterned mask is removed;

[0029] (4) A second patterned mask is formed on a substrate having the β-gallium oxide mesa, the second patterned mask forming a pair of mutually isolated electrode patterns at positions corresponding to each β-gallium oxide mesa, each electrode pattern covering the top outer peripheral edge of the corresponding β-gallium oxide mesa and extending downward to the substrate surface; and

[0030] (5) Using the second patterned mask as a mask, deposit electrode material, and then remove the second patterned mask and the electrode material above it to form a plurality of first electrodes and second electrodes that are electrically insulated from each other.

[0031] Preferably, in the method described in this invention, the step of forming the first patterned mask in step (2) includes:

[0032] (i) Photoresist is coated on the β-gallium oxide film, and a photoresist window is formed by laser direct writing exposure and development;

[0033] (ii) Depositing metal within the window to form a metal hard mask; and

[0034] (iii) Remove the photoresist to obtain a first patterned mask composed of the metal hard mask.

[0035] Preferably, in the method described in this invention, the metal hard mask can be a material conventionally used in the art, such as Cr or Mo.

[0036] Preferably, in the method described in this invention, the etching of the β-gallium oxide thin film in step (3) is performed by inductively coupled plasma-reactive ion etching (ICP-RIE).

[0037] Preferably, in the method described in this invention, the electrode material in step (5) is deposited by electron beam evaporation deposition.

[0038] Preferably, in the method described in this invention, the step of forming the second patterned mask in step (4) includes:

[0039] (a) Coating photoresist on the substrate having β-gallium oxide mesa;

[0040] (b) The photoresist is exposed using a laser direct writing system in an overlay alignment manner to form an electrode pattern corresponding to the gallium oxide mesa;

[0041] (c) Develop the exposed photoresist to form the second patterned mask.

[0042] In one specific embodiment of the present invention, the method for preparing the gallium oxide ultraviolet photodetector of the present invention includes the following steps:

[0043] (1) Photoresist is coated on the surface of a β-Ga2O3 epitaxial wafer slice on a sapphire substrate, and optical exposure and development are performed by a laser direct writing system;

[0044] (2) A hard mask Cr is deposited on the β-Ga2O3 pattern, and then the photoresist is removed by dissolution;

[0045] (3) Gallium oxide structure was obtained by ICP-RIE etching, and then the hard mask Cr was removed by chemical etching solution cleaning;

[0046] (4) Apply photoresist to the sample again and expose and develop the electrode pattern on the sample by laser direct writing overlay.

[0047] (5) Cr / Au metal electrodes are deposited on the electrode pattern by electron beam evaporation deposition;

[0048] (6) The device with deposited electrodes is placed in acetone for desolvation to obtain a complete device.

[0049] The technical solution of this invention has the following beneficial effects:

[0050] (1) High-density, miniaturized integration of β-gallium oxide ultraviolet detectors was achieved: Through innovative three-dimensional surround electrode structure design and high-precision overlay process, the size of the detector unit and the unit spacing were successfully reduced to the micrometer level (up to 1 μm). This breaks through the limitation that the size of existing gallium oxide array units is usually greater than 200 μm, significantly improves the spatial resolution of the array, and lays the foundation for gallium oxide materials in applications requiring high-precision imaging or dense sensing nodes.

[0051] (2) Excellent photoelectric detection performance was achieved: The unique electrode structure effectively increased the contact area between the electrode and gallium oxide, optimizing the carrier collection path. Simultaneously, the design without metal obstruction in the central region maximized the retention of the photosensitive area. These factors combined to enable the device to exhibit outstanding overall performance at the micrometer scale, including extremely low dark current (as low as 10⁻⁶ ppm). -12 (A-level), high on / off ratio (up to 10) 7 High response speed (up to 20ms), high responsiveness (10) 4 A / W ratio and high specific detectivity (1.62×10⁻⁶) 14 Jones or cm·Hz 1 / 2 ·W -1 Its external quantum efficiency can reach 10. 7 Its overall electrical performance far exceeds that of conventional devices.

[0052] (3) Improved device process compatibility and reliability: The micro-nano fabrication processes used, such as laser direct writing, ICP-RIE etching, and electron beam evaporation, are mature and controllable. The three-dimensional surrounding electrode structure itself provides good mechanical anchoring, enhancing the adhesion and long-term stability of the electrodes. The entire fabrication process has high repeatability and uniformity, making it suitable for large-area, large-scale production.

[0053] (4) Expanding the application scenarios of gallium oxide devices: The micron-level high-density array structure makes it easy to integrate heterogeneously with existing silicon-based readout circuits (ROICs) or other functional modules. This has greatly promoted the leap of gallium oxide ultraviolet detectors from single components to system-level applications (such as compact ultraviolet imaging chips, robot vision sensors, wearable monitoring devices, etc.), and accelerated its process from laboratory research to practical industrial applications.

[0054] In summary, this invention solves the key bottleneck in the micro-nano scale integration of gallium oxide ultraviolet detectors through the synergy of "structural innovation" and "process innovation," not only achieving a significant improvement in device performance but also providing a practical technical solution for its large-scale application in high-value-added fields. Attached Figure Description

[0055] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein:

[0056] Figure 1 A flowchart illustrating the fabrication process of a gallium oxide ultraviolet photodetector according to a specific embodiment of the present invention is provided, wherein the gallium oxide ultraviolet photodetector has a detection unit arranged in an 8×8 array.

[0057] Figure 2 The layout design of the gallium oxide ultraviolet photodetector of Embodiment 1 of the present invention is shown, wherein the gallium oxide ultraviolet photodetector has a detection unit arranged in an 8×8 array;

[0058] Figure 3 A schematic diagram of the structure of a single detection unit of the gallium oxide ultraviolet photodetector according to Embodiment 1 of the present invention is shown;

[0059] Figure 4 The diagram shows a physical image of the gallium oxide ultraviolet photodetector according to Embodiment 1 of the present invention, wherein the gallium oxide ultraviolet photodetector has a detection unit arranged in an 8×8 array;

[0060] Figure 5 The image shown is a SEM image of the gallium oxide ultraviolet photodetector of Embodiment 2 of the present invention;

[0061] Figure 6 The IV characteristic curve of the ultraviolet photodetector prepared in Example 1;

[0062] Figure 7 This is a response graph of the IT curve of the ultraviolet photodetector prepared in Example 1 as a function of light intensity;

[0063] Figure 8 The responsivity and specific detectivity curves of the ultraviolet photodetector prepared in Example 1 at different voltages (-5V to 5V);

[0064] Figure 9 The photocurrent variation curves of the ultraviolet photodetector prepared in Example 1 under different light intensities are shown.

[0065] Figure 10 The diagram shows the external quantum efficiency of the ultraviolet photodetector prepared in Example 1 at different voltages (-5V to 5V). Detailed Implementation

[0066] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0067] Figure 1 A flowchart illustrating the fabrication process of a gallium oxide ultraviolet photodetector according to a specific embodiment of the present invention is provided, wherein the gallium oxide ultraviolet photodetector has a detection unit arranged in an 8×8 array.

[0068] Figure 1 The process is illustrated below. First, ultraviolet photoresist is spin-coated onto a β-Ga2O3 sapphire epitaxial wafer. The substrate is sapphire, and the epitaxial layer is β-Ga2O3. After coating, the sample is baked, then exposed using a laser direct-write system, and subsequently developed and fixed in an organic developer to obtain the photoresist pattern. Next, a suitable thickness of metallic Cr is deposited on the surface via electron beam evaporation, and then excess photoresist is removed with an organic solvent to obtain a Cr metal mask layer, as shown below. Figure 1 As shown in (c). Subsequently, a dry etching process was performed using a mixed reactive gas in the ICP-RIE system. After etching, the residual Cr mask was removed using a Cr etchant, as shown in [reference needed]. Figure 1 (e). Subsequently, the photoresist was spin-coated again and dried. The Cr / Au circuit pattern was etched using a laser direct writing system. After the circuit pattern was developed and fixed, the Cr / Au electrode was deposited using an electron beam evaporation deposition system. Finally, the excess metal on the surface was removed by solvent acetone to obtain the final sample, as shown in Figure (f).

[0069] Example 1

[0070] (1) A β-gallium oxide film with a thickness of 200 nm was grown on sapphire by MOCVD technology. The specific growth conditions were as follows: triethylgallium (60 sccm) and O2 (60 sccm) were used as precursors, Ar (1200 sccm) was used as carrier gas, the reaction chamber pressure was 40 Torr, and the reaction temperature was 800℃.

[0071] (2) A first patterned mask is formed on the β-gallium oxide thin film, the first patterned mask defining a plurality of spaced mesa windows;

[0072] The steps of forming the first patterned mask include: (i) coating a 1 μm thick AZ1500 photoresist on the β-gallium oxide thin film, exposing it by laser direct writing and developing it with AZ300MIF developer to form a photoresist window; wherein the photoresist window is a rectangular pit array with a length of 10 μm and a width of 10 μm, the array being arranged in 8×8, and the spacing between the pits being 5 μm; (ii) depositing Cr metal in the window to form a metal hard mask; and (iii) removing the photoresist to obtain the first patterned mask composed of the metal hard mask Cr.

[0073] (3) Using the first patterned mask as a shield, the β-gallium oxide thin film is etched by inductively coupled plasma-reactive ion etching (ICP-REI) to form multiple spaced β-gallium oxide mesa. The specific process parameters of the ICP-REI process are: etching gases are BCl3 and Ar, BCl3 flow rate is 25 sccm, Ar flow rate is 15 sccm, pressure is 8 mTorr, ICP power is 900W, RIE bias power is 90W, and etching temperature is 20℃. Then, the sample is treated with GCT ECR100 Cr etching solution for 5 min to remove the first patterned mask.

[0074] (4) A second patterned mask is formed on the substrate having the β-gallium oxide mesa, the second patterned mask forming a pair of mutually isolated electrode patterns at the position corresponding to each β-gallium oxide mesa, each electrode pattern covering the top outer peripheral edge of the corresponding β-gallium oxide mesa and extending downward to the surface of the substrate.

[0075] The steps for forming the second patterned mask include: (a) coating a 1 μm thick AZ1500 photoresist on the substrate having a β-gallium oxide mesa; (b) exposing the photoresist using a laser direct writing system in an overlay alignment manner to form an electrode pattern corresponding to the gallium oxide mesa; and (c) developing the exposed photoresist using AZ300MIF developer to form the second patterned mask.

[0076] (5) Using the second patterned mask as a shield, Cr / Au electrode material is deposited by electron beam evaporation deposition, wherein the thickness of the Cr layer is 60 nm and the thickness of the Au layer is 180 nm. Subsequently, the second patterned mask and the electrode material above it are removed to form a plurality of electrically insulated first electrodes (Cr / Au) and second electrodes (Cr / Au). The thickness of the first and second electrodes located on the substrate portion is 240 nm. The thickness of the first and second electrodes located on the β-gallium oxide mesa portion is 240 nm.

[0077] Figure 2The diagram illustrates the layout design of a gallium oxide ultraviolet photodetector according to Embodiment 1 of the present invention, wherein the gallium oxide ultraviolet photodetector has an 8×8 array of detection units. The electrode wiring endpoints can also be square, circular, or polygonal electrodes, etc.

[0078] Figure 3 This diagram illustrates the structure of a single detection unit in the gallium oxide ultraviolet photodetector of Embodiment 1 of the present invention. Figure 3 As shown, the epitaxial layer on substrate 1 is a β-gallium oxide functional layer 2, and the thickness of the β-gallium oxide functional layer 2 is 200 nm. Figure 3 Further shown, an electrode layer 3 is staggered with the substrate 1 and β-gallium oxide 2, and the metal electrode layer 3 forms an ohmic contact with β-gallium oxide 2. The thickness of the metal electrode layer located on the substrate portion can be 240 nm. The thickness of the metal electrode layer located on the β-gallium oxide mesa portion is 240 nm.

[0079] Figure 4 The diagram shows a physical image of the gallium oxide ultraviolet photodetector according to Embodiment 1 of the present invention, wherein the gallium oxide ultraviolet photodetector has a detection unit arranged in an 8×8 array.

[0080] Example 2

[0081] The preparation process of this embodiment is similar to that of Embodiment 1, except that the process of forming the first patterned mask in step (2) is changed. Specifically, the step of forming the first patterned mask includes: (i) coating 1 μm of photoresist AZ1500 on the β-gallium oxide thin film, exposing it by laser direct writing and developing it with AZ300MIF developer to form a photoresist window; wherein the photoresist window is a rectangular pit array with a length of 10 μm and a width of 10 μm, the array can be arranged in 50×50, and the spacing between the pits is 5 μm; (ii) depositing metal Cr in the window to form a metal hard mask; and (iii) removing the photoresist to obtain the first patterned mask composed of the metal hard mask Cr.

[0082] Figure 5 The image shows an SEM image of the gallium oxide ultraviolet photodetector of Embodiment 2 of the present invention.

[0083] Performance testing

[0084] Specifically, Figure 6 The test method is as follows: under different light intensities (0.3 mW, 0.85 mW, 1.67 mW, 2.5 mW, etc.) of a 254nm light source in darkness and under different light intensities, the current-voltage (IV) curves under each condition were measured using a Keithley 4200 test system. Figure 6The ultraviolet photodetector prepared in Example 1 has an on / off ratio of up to 10. 7 .

[0085] Figure 7 The testing method is as follows: using 254nm (2.5mw / cm) 2 The device was irradiated with a pulsed light source signal, and its IT response curve under a 5V bias voltage was measured using a Keithley 4200 test system, showing the change in light intensity (0.2 mW, 0.53 mW, 0.96 mW, 1.4 mW, etc.). Figure 7 The response speed of the ultraviolet photodetector prepared in Example 1 can reach 20ms.

[0086] Figure 8 The responsivity and detectivity curves of the detector at different voltages (-5V to 5V) are obtained based on the Keithley 4200 test system. Figure 8 The responsivity of the ultraviolet photodetector prepared in Example 1 is shown to be approximately 10. 4 A / W, specific detectivity 1.62 × 10 14 Jones.

[0087] Figure 9 The photocurrent changes of the detector under different light intensities (0.3mW, 0.85mW, 1.67mW, 2.5mW, etc.) were measured using the Keithley 4200 testing system. Figure 9 The response current of the ultraviolet photodetector prepared in Example 1 shows that the change in light intensity initially increases rapidly, but then tends to saturate as the light intensity increases.

[0088] Figure 10 The image shows the quantum efficiency (EQE) curves of the detector at different voltages (-5V to 5V) under a 5V bias, measured using the Keithley 4200 test system. Figure 10 The ultraviolet photodetector prepared in Example 1 shows an external quantum efficiency of up to 10. 7 .

Claims

1. A gallium oxide ultraviolet photodetector, comprising: Substrate; Multiple β-gallium oxide mesas arranged in an array on the substrate, each of the β-gallium oxide mesas being an independent detection unit; as well as Multiple electrode pairs corresponding to the β-gallium oxide mesa; Each electrode pair includes a first electrode and a second electrode that are spaced apart and electrically insulated from each other. For each of the β-gallium oxide mesa, the corresponding first electrode and second electrode each form a three-dimensional surrounding structure, which covers the top outer peripheral edge and sidewalls of the corresponding β-gallium oxide mesa and extends to the substrate surface, wherein the top central region of the β-gallium oxide mesa is uncovered by electrodes to serve as a photosensitive window.

2. The gallium oxide ultraviolet photodetector according to claim 1, wherein, The maximum cross-sectional dimension of the β-gallium oxide mesa is 0.5 μm to 200 μm, preferably 0.5 μm to 50 μm, and more preferably 0.5 μm to 5 μm.

3. The gallium oxide ultraviolet photodetector according to claim 1, wherein, The minimum spacing between the β-gallium oxide mesa is one-third of the maximum cross-sectional dimension of the β-gallium oxide mesa; Preferably, the maximum spacing between the β-gallium oxide mesa is less than or equal to 200 μm.

4. The gallium oxide ultraviolet photodetector according to claim 1, wherein, The thickness of the β-gallium oxide mesa is 180 nm to 400 nm.

5. The gallium oxide ultraviolet photodetector according to claim 1, wherein, The thickness of the first electrode and the second electrode located on the substrate portion are each independently between 200 nm and 420 nm; Preferably, the thickness of the first electrode and the second electrode located on the β-gallium oxide mesa portion is each independently between 200 nm and 420 nm.

6. The gallium oxide ultraviolet photodetector according to claim 1, wherein, The substrate is a sapphire substrate or a silicon oxide substrate; Preferably, the materials of the first electrode and the second electrode are independently selected from single-layer metal, transparent conductive oxide, graphene, or a stacked structure composed of at least two metals. More preferably, the stacked structure composed of at least two metals includes Ti / Au, Ti / Al / Ni / Au, Cr / Au, or Ni / Au, where " / " indicates the stacking order from bottom to top.

7. A method for preparing a gallium oxide ultraviolet photodetector according to any one of claims 1 to 6, comprising the following steps: (1) Forming a β-gallium oxide thin film on a substrate; (2) A first patterned mask is formed on the β-gallium oxide thin film, the first patterned mask defining a plurality of spaced mesa windows; (3) Using the first patterned mask as a mask, the β-gallium oxide thin film is etched to form a plurality of spaced β-gallium oxide mesa; (4) A second patterned mask is formed on the substrate having the β-gallium oxide mesa, the second patterned mask forming a pair of mutually isolated electrode patterns at the position corresponding to each β-gallium oxide mesa, each electrode pattern covering the top outer peripheral edge of the corresponding β-gallium oxide mesa and extending downward to the surface of the substrate. as well as (5) Using the second patterned mask as a mask, deposit electrode material, and then remove the second patterned mask and the electrode material above it to form a plurality of first electrodes and second electrodes that are electrically insulated from each other.

8. The method according to claim 7, wherein, The steps in step (2) for forming the first patterned mask include: (i) Photoresist is coated on the β-gallium oxide film, and a photoresist window is formed by laser direct writing exposure and development; (ii) Depositing metal within the window to form a metal hard mask; and (iii) Remove the photoresist to obtain a first patterned mask composed of the metal hard mask.

9. The method according to claim 7, wherein, The etching of the β-gallium oxide film in step (3) is performed by inductively coupled plasma-reactive ion etching. Preferably, the electrode material in step (5) is deposited by electron beam evaporation deposition.

10. The method according to claim 7, wherein, The step of forming the second patterned mask in step (4) includes: (a) Coating photoresist on the substrate having β-gallium oxide mesa; (b) The photoresist is exposed using a laser direct writing system in an overlay alignment manner to form an electrode pattern corresponding to the gallium oxide mesa; (c) Develop the exposed photoresist to form the second patterned mask.

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