A vertical structure ultraviolet photodetector and a preparation method thereof

Abstract

The application provides a vertical structure ultraviolet photodetector and a preparation method thereof. The ultraviolet photodetector is of a vertical structure, which is beneficial to the absorption of light by the ultraviolet photodetector, improves the light utilization rate of the ultraviolet photodetector, shortens the transmission distance compared with a horizontal structure, and is low in cost. The ultraviolet photodetector has a high light-dark current switching ratio and a small dark current, and has a fast response speed while keeping the light-dark current switching ratio and the dark current. A PN junction is formed between a nickel oxide hole transport layer and a beta phase gallium oxide single crystal, so that the ultraviolet photodetector has a self-driving performance. In the manufacturing process, a substrate is used as a support frame, and an electrode is packaged by using a conductive adhesive tape in one step, so that 3-5 photoetching steps of a traditional horizontal structure are omitted, the process is simplified, and the process manufacturing is simpler.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic device technology, and in particular to a vertical structure ultraviolet photodetector and its fabrication method. Background Technology

[0002] With the development of science and technology, solar-blind ultraviolet photodetectors have increasingly important application value in fields such as environmental monitoring and deep space exploration. However, due to the dual challenges of material performance and manufacturing cost, current mainstream photosensitive materials (such as AlGaN and SiC) each have their limitations: AlGaN requires a high Al content to achieve solar-blind ultraviolet response, but high-content AlGaN has more lattice defects, affecting device stability; SiC, although possessing certain ultraviolet detection capabilities, has insufficient bandgap, requiring the introduction of additional filtering structures to suppress visible light interference; while ultra-wide bandgap materials such as diamond, despite their superior performance, are difficult to scale up due to high cost and processing difficulty. Therefore, gallium oxide (GaO) is a suitable material for solar-blind ultraviolet detection due to its suitable bandgap (4.9 eV). However, GaO-based solar-blind ultraviolet photodetectors still suffer from drawbacks such as slow response speed, poor photoelectric performance, and inability to self-drive. Since GaO is an intrinsic n-type semiconductor and p-type doping is difficult, constructing a pn junction with GaO and other p-type materials is an effective solution for building self-driven solar-blind ultraviolet photodetectors. Furthermore, most current detectors employ a horizontal structure design, requiring multiple photolithography processes to fabricate electrode leads, resulting in complex and costly processes. Traditional vertical structures, due to heterojunction interface defects, struggle to balance high sensitivity with low dark current. Simultaneously, hole transport layers typically rely on expensive vacuum deposition techniques (such as magnetron sputtering of ITO), further hindering the industrialization of these devices. Therefore, how to simplify the manufacturing process while optimizing material and structural design to improve device performance has become a pressing technical challenge in this field. Summary of the Invention

[0003] In view of the above-mentioned shortcomings or improvement needs of the prior art, the present invention provides a vertical structure ultraviolet photodetector and its fabrication method.

[0004] The present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides a vertical structure ultraviolet photodetector, comprising, from bottom to top:

[0006] Substrate;

[0007] The bottom electrode is located on the surface of the substrate;

[0008] An absorption layer is located on the bottom electrode away from the substrate surface;

[0009] A hole transport layer is located away from the substrate surface of the absorption layer;

[0010] The top electrode is located in the hole transport layer away from the substrate surface;

[0011] The absorption layer is a β-phase gallium oxide single crystal, and the hole transport layer is a nickel oxide hole transport layer.

[0012] Preferably, the top electrode includes any one of a Bi electrode, a Pt electrode, an Au electrode, and an Al electrode;

[0013] The bottom electrode includes any one of a Pt electrode, an Au electrode, and an Al electrode.

[0014] The substrate includes any one of FTO conductive glass substrate, ITO conductive glass substrate, and Si substrate.

[0015] Preferably, the thickness of the bottom electrode is 80–150 nm;

[0016] The thickness of the absorption layer is 500–650 μm;

[0017] The thickness of the hole transport layer is 50–80 nm;

[0018] The thickness of the bottom electrode is 30–80 nm.

[0019] Secondly, the present invention also provides a method for fabricating the aforementioned vertical structure ultraviolet photodetector, comprising the following steps:

[0020] A bottom electrode, an absorption layer, a hole transport layer, and a top electrode are sequentially fabricated on a substrate.

[0021] Preferably, it includes the following steps:

[0022] β-phase gallium oxide single crystal is provided as the absorption layer;

[0023] Nickel oxide solution was spin-coated onto the surface of a β-phase gallium oxide single crystal to form a hole transport layer;

[0024] A bottom electrode was prepared on the surface of a β-phase gallium oxide single crystal far from the hole transport layer.

[0025] Apply conductive tape to the substrate surface;

[0026] The side of the β-phase gallium oxide single crystal with the bottom electrode is attached to the conductive tape.

[0027] A top electrode is fabricated on the surface of the hole transport layer.

[0028] Preferably, spin-coating a nickel oxide solution onto the surface of a β-phase gallium oxide single crystal to form a hole transport layer specifically includes the following steps:

[0029] NaOH solution is added dropwise to nickel nitrate solution. When the pH of nickel nitrate solution is 10-11, a solution containing Ni(OH)2 is prepared.

[0030] The solution containing Ni(OH)2 was centrifuged to obtain Ni(OH)2 colloid, which was dried and annealed to obtain nickel oxide powder.

[0031] Nickel oxide powder is added to water to obtain a nickel oxide solution;

[0032] A nickel oxide solution was dropped onto the surface of a β-phase gallium oxide single crystal, spin-coated, and annealed to obtain a nickel oxide hole transport layer.

[0033] Preferably, the solution containing Ni(OH)2 is centrifuged at 3000-3200 rpm to obtain Ni(OH)2 colloid, dried, and then annealed at 270-280℃ for 2-3 hours to obtain nickel oxide powder;

[0034] In the steps of adding nickel oxide solution dropwise onto the surface of β-phase gallium oxide single crystal, spin-coating, and annealing, the annealing temperature is 120-150℃ and the annealing time is 15-20min.

[0035] In the step of adding NaOH solution dropwise to nickel nitrate solution, the concentration of NaOH solution is 10-11 mol / L, the concentration of nickel nitrate solution is 0.5-1 mol / L, and the volume ratio of NaOH solution to nickel nitrate solution is 1:(2.5-3).

[0036] In the step of adding nickel oxide powder to water to obtain a nickel oxide solution, the concentration of the nickel oxide solution is 15-20 mg / mL.

[0037] Preferably, the bottom electrode is prepared on the surface of a β-phase gallium oxide single crystal by ion sputtering;

[0038] The top electrode was prepared on the surface of the hole transport layer by thermal evaporation.

[0039] Preferably, the bottom electrode is prepared on the surface of a β-phase gallium oxide single crystal by ion sputtering, wherein the controlled process parameters are: sputtering current of 30-35 mA, argon flow rate of 15-20 sccm, and sputtering chamber pressure of 0.1-0.3 Pa.

[0040] Preferably, the top electrode is prepared on the surface of the hole transport layer by thermal evaporation, wherein the thermal evaporation rate is 0.1 to 0.5 nm / s.

[0041] The vertical structure ultraviolet photodetector of the present invention has the following advantages over the prior art:

[0042] 1. The ultraviolet photodetector of this invention has a vertical structure and a high on / off current ratio, with an on / off ratio as high as 10. 5 And a relatively small dark current, where the dark current at 0V is 10. -13 A. While maintaining both conditions, it also has a very fast response speed, with a response time of approximately 100–300 ms. Since the hole transport layer is a nickel oxide hole transport layer, and nickel oxide is a P-type material, and the absorption layer is a β-phase gallium oxide (β-Ga2O3) single crystal, and the β-phase gallium oxide (β-Ga2O3) single crystal is an N-type material, a PN junction will be formed between the nickel oxide hole transport layer and the β-phase gallium oxide (β-Ga2O3) single crystal, giving the ultraviolet photodetector self-driving performance.

[0043] 2. The ultraviolet photodetector of the present invention adopts a vertical structure design, which is beneficial to the absorption of light by the ultraviolet photodetector. Compared with the horizontal structure, it shortens the transmission distance and reduces the cost. In terms of manufacturing process, a substrate is used as a support frame and the electrodes are brought out in one step by encapsulating them with conductive tape, which eliminates the 3 to 5 photolithography steps of the traditional horizontal structure, thus simplifying the process and making the manufacturing process simpler. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0045] Figure 1 This is a schematic diagram of the structure of a vertical structure ultraviolet photodetector prepared in one embodiment of the present invention;

[0046] Figure 2 The XRD pattern of the nickel oxide hole transport layer prepared in Example 1;

[0047] Figures 3-4 The images show SEM images of the nickel oxide hole transport layer prepared in Example 1 at different magnifications.

[0048] Figure 5 The vertical structure ultraviolet photodetector prepared in Example 1 was tested without 254 nm ultraviolet light and with an external 80 μW / cm² light. 2 A comparison of IV curves under 254nm ultraviolet light;

[0049] Figure 6 This is an IT curve of the vertical structure ultraviolet photodetector prepared in Example 1 after long-term storage during testing.

[0050] Figure 7 The image shows the IT characteristics of the vertical structure ultraviolet photodetector prepared in Example 1 during the first 50 seconds.

[0051] Figure 8 The image shows the IT characteristics of the vertical structure ultraviolet photodetector prepared in Example 1 after 50 seconds.

[0052] Figure 9 The ultraviolet photodetector prepared in Comparative Example 1 was tested under conditions of no 254 nm ultraviolet light and an external 80 μW / cm² light. 2 A comparison of IV curves under 254nm ultraviolet light;

[0053] Figure 10 The XRD pattern of the β-phase gallium oxide single crystal in Case 1 is shown. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0055] In the description of this invention, it should be understood that the orientation or positional relationship indicated by terms such as "above" is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use, or the orientation or positional relationship in which those skilled in the art are usually understood. It is only for the convenience of describing this invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0056] The order in which the embodiments are described below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0057] This application provides a vertical structure ultraviolet photodetector, comprising, from bottom to top:

[0058] Substrate;

[0059] The bottom electrode is located on the substrate surface;

[0060] The absorption layer is located at the bottom electrode away from the substrate surface;

[0061] Hole transport layer, located away from the substrate surface of the absorption layer;

[0062] The top electrode is located in the hole transport layer away from the substrate surface;

[0063] The absorption layer is a β-phase gallium oxide single crystal, and the hole transport layer is a nickel oxide hole transport layer.

[0064] The ultraviolet photodetector of the present invention has a vertical structure, the core feature of which is that the light incident direction and the current transmission direction are perpendicular to each other. In the vertical structure ultraviolet photodetector, each functional layer (such as the bottom electrode, absorption layer, hole transport layer and top electrode of the present invention) is stacked sequentially along a direction perpendicular to the light incident direction. Specifically, the vertical structure ultraviolet photodetector of the present invention includes a substrate 1, a bottom electrode 3, an absorption layer 4, a hole transport layer 5 and a top electrode 6 stacked sequentially; wherein, the absorption layer 4 is a β-phase gallium oxide (β-Ga2O3) single crystal absorption layer, and the hole transport layer 5 is a nickel oxide hole transport layer 5.

[0065] The ultraviolet photodetector of this invention has a vertical structure, a high on / off current ratio and a small dark current, and a fast response speed while maintaining both. Since the hole transport layer 5 is a nickel oxide hole transport layer, and nickel oxide is a P-type material, and the absorption layer 4 is a β-phase gallium oxide (β-Ga2O3) single crystal, and the β-phase gallium oxide (β-Ga2O3) single crystal is an N-type material, a PN junction is formed between the nickel oxide hole transport layer and the β-phase gallium oxide (β-Ga2O3) single crystal, giving the ultraviolet photodetector self-driving performance.

[0066] In some embodiments, for ease of fabrication, the ultraviolet photodetector of the present invention has a vertical structure, such as... Figure 1 As shown, a conductive tape 2 is placed between the substrate 1 and the bottom electrode 3. Specifically, the conductive tape 2 is pasted on the substrate 1, mainly for leading out the bottom electrode 3. After the bottom electrode and the nickel oxide hole transport layer are prepared on the upper and lower surfaces of the β-phase gallium oxide (β-Ga2O3) single crystal, the side of the β-phase gallium oxide (β-Ga2O3) single crystal with the bottom electrode is pasted on the conductive tape. Then, the top electrode is prepared on the surface of the nickel oxide hole transport layer, thus obtaining a vertical structure ultraviolet photodetector.

[0067] In some embodiments, the top electrode 6 includes any one of a Bi electrode, a Pt electrode, an Au electrode, and an Al electrode, preferably a bismuth (Bi) electrode.

[0068] In some embodiments, the bottom electrode includes any one of a Pt electrode, an Au electrode, and an Al electrode, preferably a Pt electrode.

[0069] In some embodiments, the top electrodes 6 are arranged in an array on the surface of the hole transport layer 5, and a gap is formed between two adjacent top electrodes 6.

[0070] In some embodiments, the substrate includes any one of FTO conductive glass substrate, ITO conductive glass substrate, and Si substrate, preferably an FTO conductive glass substrate.

[0071] In some embodiments, the thickness of the bottom electrode is 80–150 nm.

[0072] In some embodiments, the thickness of the absorbent layer is 500–650 μm.

[0073] In some embodiments, the thickness of the hole transport layer is 50–80 nm.

[0074] In some embodiments, the thickness of the top electrode is 30–80 nm.

[0075] Based on the same inventive concept, the present invention also provides a method for fabricating the above-mentioned vertical structure ultraviolet photodetector, comprising the following steps:

[0076] A bottom electrode, an absorption layer, a hole transport layer, and a top electrode are sequentially fabricated on a substrate.

[0077] In some embodiments, the fabrication method of a vertical structure ultraviolet photodetector includes the following steps:

[0078] S1. Provide a β-phase gallium oxide single crystal as the absorption layer;

[0079] S2. Spin-coat a nickel oxide solution onto the surface of a β-phase gallium oxide single crystal to form a hole transport layer;

[0080] S3. A bottom electrode is prepared on the surface of a β-phase gallium oxide single crystal far from the hole transport layer.

[0081] S4. Adhere conductive tape to the substrate surface;

[0082] S5. Attach the side of the β-phase gallium oxide single crystal with the bottom electrode to the conductive tape.

[0083] S6. Prepare a top electrode on the surface of the hole transport layer.

[0084] In some embodiments, spin-coating a nickel oxide solution onto the surface of a β-phase gallium oxide single crystal to form a hole transport layer specifically includes the following steps:

[0085] NaOH solution is added dropwise to nickel nitrate solution. When the pH of nickel nitrate solution is 10-11, a solution containing Ni(OH)2 is prepared.

[0086] The solution containing Ni(OH)2 was centrifuged to obtain Ni(OH)2 colloid, which was dried and annealed to obtain nickel oxide powder.

[0087] Nickel oxide powder is added to water to obtain a nickel oxide solution;

[0088] A nickel oxide solution was dropped onto the surface of a β-phase gallium oxide single crystal, spin-coated, and annealed to obtain a nickel oxide hole transport layer.

[0089] In some embodiments, a solution containing Ni(OH)2 is centrifuged at 3000-3200 rpm to obtain Ni(OH)2 colloid, dried, and then annealed at 270-280°C for 2-3 hours to obtain nickel oxide powder;

[0090] In the steps of adding nickel oxide solution dropwise onto the surface of β-phase gallium oxide single crystal, spin-coating, and annealing, the annealing temperature is 120-150℃ and the annealing time is 15-20min.

[0091] In the step of adding NaOH solution dropwise to nickel nitrate solution, the concentration of NaOH solution is 10-11 mol / L, the concentration of nickel nitrate solution is 0.5-1 mol / L, and the volume ratio of NaOH solution to nickel nitrate solution is 1:(2.5-3).

[0092] In the step of adding nickel oxide powder to water to obtain a nickel oxide solution, the concentration of the nickel oxide solution is 15-20 mg / mL.

[0093] In some embodiments, the bottom electrode is prepared on the surface of a β-phase gallium oxide single crystal by ion sputtering.

[0094] The top electrode was prepared on the surface of the hole transport layer by thermal evaporation.

[0095] Specifically, NaOH is added to water to obtain a NaOH solution, and nickel nitrate hexahydrate is added to water to obtain a nickel nitrate solution.

[0096] In some embodiments, a bottom electrode is prepared on the surface of a β-phase gallium oxide single crystal by ion sputtering, wherein the controlled process parameters are: sputtering current of 30-35 mA, argon flow rate of 15-20 sccm, and sputtering chamber pressure of 0.1-0.3 Pa.

[0097] In some embodiments, the conductive tape is a conductive carbon tape.

[0098] In some embodiments, a top electrode is prepared on the surface of the hole transport layer by thermal evaporation, wherein the thermal evaporation rate is 0.1–0.5 nm / s.

[0099] In some embodiments, the substrate is further cleaned before preparation. Specifically, the substrate is ultrasonically cleaned in deionized water, acetone, and anhydrous ethanol for 30 minutes each to remove surface contaminants.

[0100] The ultraviolet photodetector of this invention adopts a vertical structure design, which is beneficial for the absorption of light by the ultraviolet photodetector and improves its light utilization rate. Compared with the horizontal structure, it shortens the transmission distance and reduces costs. The hole transport layer of nickel oxide is prepared by chemical method. In terms of fabrication process, a substrate is used as a support frame and the electrodes are led out in one step by encapsulating them with conductive tape, eliminating the 3-5 photolithography steps of the traditional horizontal structure, thus simplifying the process and making the fabrication process simpler. In terms of performance, the ultraviolet photodetector of this invention has a high on / off current ratio and a low dark current. While maintaining these two properties, it also has a fast response speed. Furthermore, since the prepared nickel oxide is a p-type material and the β-phase gallium oxide (Ga2O3) single crystal is an n-type material, a PN junction is formed between them, which has self-driving performance.

[0101] The following detailed embodiments further illustrate the vertical structure ultraviolet photodetector and its fabrication method of this application. This section further explains the invention in conjunction with specific embodiments, but should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in the art.

[0102] The β-phase gallium oxide (β-Ga2O3) single crystals used in the following examples were obtained by mechanically exfoliating β-Ga2O3 seed crystals (from Jiufengshan Laboratory; the XRD diffraction pattern of the single crystal is shown below). Figure 10 The single-crystal gallium oxide described in this invention is not limited to that obtained by mechanically peeling off β-Ga2O3 seed crystals, but also includes other commercial gallium oxide single-crystal products and gallium oxide single-crystal epitaxial wafers (such as epitaxial wafers produced by companies such as Fujia Technology Co., Ltd.).

[0103] Example 1

[0104] This application provides a method for fabricating a vertical structure ultraviolet photodetector, including the following steps:

[0105] S1. Place the FTO conductive glass substrate with a length, width and height of 20mm, 20mm and 2mm respectively into deionized water, acetone and anhydrous ethanol for ultrasonic cleaning for 30 minutes each to remove the dirt on the surface, and dry it for later use.

[0106] S2. Take a β-phase gallium oxide (β-Ga2O3) single crystal as the absorption layer. The thickness of the β-phase gallium oxide (β-Ga2O3) single crystal is 600μm.

[0107] S3. Spin-coating a nickel oxide solution onto the surface of a β-phase gallium oxide single crystal to form a nickel oxide hole transport layer, specifically including the following steps:

[0108] S31. Take out NaOH powder and nickel nitrate hexahydrate, and add them to water to prepare a 10 mol / L NaOH solution and a 0.5 mol / L nickel nitrate solution, respectively.

[0109] A solution containing Ni(OH)₂ is prepared by adding 10 mol / L NaOH solution dropwise to 0.5 mol / L nickel nitrate solution. When the volume ratio of the added NaOH solution to the nickel nitrate solution is 1:2.5, the pH value of the solution is 10-11.

[0110] S32. Centrifuge the solution containing Ni(OH)2 at 3000 rpm to obtain Ni(OH)2 colloid, dry it to obtain nickel hydroxide (Ni(OH)2 powder), and then anneal it at 270℃ for 2 h to obtain nickel oxide powder.

[0111] S33. Add nickel oxide powder to water to obtain a nickel oxide solution with a concentration of 15 mg / mL;

[0112] S34. A nickel oxide solution is dropped onto the surface of a β-phase gallium oxide single crystal with a thickness of 600 μm and spin-coated at a speed of 3000 rpm. After spin-coating, the film is placed on a constant temperature table at 120℃ and annealed for 15 min to obtain a nickel oxide film with a thickness of 80 nm, which is the hole transport layer.

[0113] S4. A bottom electrode is prepared on the surface of a β-phase gallium oxide single crystal with a thickness of 600 μm, away from the hole transport layer. The bottom electrode is a Pt bottom electrode with a thickness of 100 nm. Specifically, the Pt bottom electrode is prepared on the surface of the β-phase gallium oxide single crystal by ion sputtering. The controlled process parameters are: sputtering current of 30 mA, argon flow rate of 15 sccm, and sputtering chamber pressure of 0.2 Pa.

[0114] S5. Adhere conductive tape to the surface of the FTO conductive glass substrate;

[0115] S6. Attach the side of the β-phase gallium oxide single crystal with the bottom electrode to the conductive tape.

[0116] S7. A top electrode is prepared on the surface of the hole transport layer. The top electrode is a Bi electrode. A Bi top electrode with a thickness of 50 nm is prepared on the surface of the hole transport layer by thermal evaporation, wherein the thermal evaporation rate is 0.2 nm / s.

[0117] Comparative Example 1

[0118] This comparative example provides a method for fabricating an ultraviolet photodetector, similar to Example 1, except that it does not contain a nickel oxide hole transport layer. The specific fabrication process includes the following steps:

[0119] S1. Place the FTO conductive glass substrate with a length, width and height of 20mm, 20mm and 2mm respectively into deionized water, acetone and anhydrous ethanol for ultrasonic cleaning for 30 minutes each to remove the dirt on the surface, and dry it for later use.

[0120] S2. Use a β-phase gallium oxide (β-Ga2O3) single crystal as the absorption layer; the thickness of the β-phase gallium oxide (β-Ga2O3) single crystal is 600μm;

[0121] S3. A bottom electrode is prepared on the surface of a β-phase gallium oxide single crystal. The bottom electrode is a Pt bottom electrode. Specifically, the Pt bottom electrode is prepared on the surface of a β-phase gallium oxide single crystal by ion sputtering, with a thickness of 100 nm. The controlled process parameters are: sputtering current of 30 mA, argon flow rate of 15 sccm, and sputtering chamber pressure of 0.2 Pa.

[0122] S4. Adhere conductive tape to the surface of the FTO conductive glass substrate;

[0123] S5. Attach the side of the β-phase gallium oxide single crystal with the bottom electrode to the conductive tape.

[0124] S6. A top electrode is formed on the surface of the β-phase gallium oxide single crystal away from the bottom electrode. The top electrode is a Bi electrode. A Bi top electrode with a thickness of 50 nm is prepared on the β-phase gallium oxide single crystal by thermal evaporation, wherein the thermal evaporation rate is 0.2 nm / s.

[0125] Performance testing

[0126] Figure 2 The XRD pattern of the nickel oxide hole transport layer prepared in Example 1;

[0127] The XRD pattern shows that the nickel oxide (NiO) in this invention... x The content of ) is shown in the figure, where the three peaks correspond to the (111), (200), and (220) crystal planes, respectively, indicating that nickel oxide (NiO) contains ) x The hole transport layer has been successfully added.

[0128] Figures 3-4The images show SEM images of the nickel oxide hole transport layer prepared in Example 1 at different magnifications.

[0129] from Figures 3-4 It can be seen from this that, Figure 3 Due to the use of a large magnification, the particle morphology of the nickel oxide film surface can be observed at a microscopic scale. It can be seen that most of the particles are spherical, which is consistent with the characteristics of the sol-gel method, which easily forms spherical nanoparticles during solvent evaporation and precursor gelation.

[0130] and Figure 4 The image shown is at a relatively low magnification, revealing the overall structure of the nickel oxide film. From a macroscopic perspective, the film appears to be relatively continuous and has good coverage.

[0131] Figure 5 The vertical structure ultraviolet photodetector prepared in Example 1 was used without 254nm ultraviolet light (i.e., Figure 5 (dark current) and applied 80μW / cm 2 254nm ultraviolet light (i.e. Figure 5 Comparison of IV curves under photocurrent.

[0132] Figure 9 The ultraviolet photodetector prepared in Comparative Example 1 was tested without 254nm ultraviolet light (i.e., Figure 9 (dark current) and applied 80μW / cm 2 254nm ultraviolet light (i.e. Figure 9 Comparison of IV curves under photocurrent.

[0133] The specific test method for the IV curve is as follows: The test is conducted using a Keithley 4200A-SCS semiconductor parameter analyzer. During the test, a linear voltage scan method is used, with the scan voltage range from -5V to +5V, to observe the current response behavior of the device under positive and negative bias voltages.

[0134] from Figure 5 It can be seen that the dark current of the vertical structure ultraviolet photodetector prepared in Example 1 is significantly lower than that of the standard ultraviolet photodetector. Figure 9 The dark current of the vertical structure ultraviolet photodetector prepared in Comparative Example 1; the dark current of the vertical structure ultraviolet photodetector prepared in Example 1 is as low as 10 ohms at 0V bias. -13 A is much smaller than the dark current of the ultraviolet photodetector prepared in Comparative Example 1. The smaller the dark current, the lower the noise current of the detector itself, which helps to improve the sensitivity and signal-to-noise ratio of photodetection.

[0135] also, Figure 5The photocurrent to dark current ratio (i.e., the ratio of photocurrent to dark current, or the on / off ratio) of the vertical structure ultraviolet photodetector prepared in Example 1 is also significantly better than that of the traditional method. Figure 9 The vertical structure ultraviolet photodetector prepared in Comparative Example 1; the vertical structure ultraviolet photodetector prepared in Example 1 has a photo-dark current ratio as high as 10. 5 In contrast, the light-dark current ratio of the ultraviolet photodetector prepared in Comparative Example 1 is less than one order of magnitude (<10), indicating that the vertical structure ultraviolet photodetector prepared in Example 1 has a greater current difference between illuminated and unilluminated states, and has a stronger light response resolution capability.

[0136] In summary, the photoelectric performance (including low dark current and high light-to-dark ratio) of the vertical structure ultraviolet photodetector prepared in Example 1 is significantly better than that of the ultraviolet photodetector prepared in Comparative Example 1.

[0137] Figures 6-8 The IT response curve of the vertical structure ultraviolet photodetector prepared in Example 1 (tested using a Keithley 4200A-SCS semiconductor parameter analyzer) was used to evaluate the photoelectric response characteristics of the device under periodic illumination switching conditions. During the experiment, the device operated at 0V bias (zero bias). The specific testing method was as follows: the light source was manually switched on and off at regular intervals (the light source was 80 μW / cm²). 2 The device uses 254nm ultraviolet light to simulate a periodic illumination environment. By observing the periodic changes in current in the IT curve, key parameters such as the device's response speed, on / off ratio, and stability can be further extracted.

[0138] Specifically, Figure 6 This is an IT curve of the vertical structure ultraviolet photodetector prepared in Example 1 after long-term storage during testing.

[0139] from Figure 6 As can be seen, the IT curve is relatively stable from beginning to end.

[0140] Specifically, Figures 7-8 The image shows the IT characteristic curve of the vertical structure ultraviolet photodetector prepared in Example 1 under a 0V bias voltage during testing. Figure 7 It is the IT characteristic curve for the first 50 seconds, and Figure 8 This is the IT characteristic curve after the last 50 seconds of testing.

[0141] from Figures 7-8 As can be seen from the data, the vertical structure ultraviolet photodetector prepared in Example 1 still maintains stable performance after a period of testing and has self-driving capabilities; and as can be seen from 7 to 8, the response time of the vertical structure ultraviolet photodetector prepared in Example 1 is approximately 100 to 300 ms.

[0142] Figure 10 The image shows the XRD pattern of the β-phase gallium oxide (β-Ga2O3) single crystal in Example 1.

[0143] from Figure 10 As can be seen from the data, the diffraction peaks are located at 2Theda = 24.187, 30.059, 37.386, 44.732, 49.544, 49.560, and 60.888, which correspond to the (201), (400), (401), (112), (402), (-602), and (020) crystal plane diffraction of β-phase gallium oxide (β-Ga2O3), respectively. Among them, the (020) diffraction peak is sharp and has a high intensity, which means that the β-Ga2O3 used has a (020) preferred orientation and excellent crystallinity.

[0144] The above description is only a preferred 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 vertical structure ultraviolet photodetector, characterized in that, From bottom to top, including: Substrate; The bottom electrode is located on the surface of the substrate; An absorption layer is located on the bottom electrode away from the substrate surface; A hole transport layer is located in the absorption layer away from the substrate surface; The top electrode is located in the hole transport layer away from the substrate surface; The absorption layer is a β-phase gallium oxide single crystal, and the hole transport layer is a nickel oxide hole transport layer. The top electrode includes any one of Bi electrode, Pt electrode, Au electrode, and Al electrode; The bottom electrode includes any one of a Pt electrode, an Au electrode, and an Al electrode. The thickness of the absorption layer is 500~650μm; The thickness of the hole transport layer is 50~80nm; The thickness of the bottom electrode is 30~80nm; The method for fabricating the vertical structure ultraviolet photodetector includes the following steps: β-phase gallium oxide single crystal is provided as the absorption layer; Nickel oxide solution was spin-coated onto the surface of a β-phase gallium oxide single crystal to form a hole transport layer; A bottom electrode was prepared on the surface of a β-phase gallium oxide single crystal far from the hole transport layer. Apply conductive tape to the substrate surface; The side of the β-phase gallium oxide single crystal with the bottom electrode is attached to the conductive tape. A top electrode is fabricated on the surface of the hole transport layer; Spin-coating a nickel oxide solution onto the surface of a β-phase gallium oxide single crystal to form a hole transport layer specifically includes the following steps: NaOH solution is added dropwise to nickel nitrate solution. When the pH of nickel nitrate solution is 10-11, a solution containing Ni(OH)2 is prepared. The solution containing Ni(OH)2 was centrifuged to obtain Ni(OH)2 colloid, which was dried and annealed to obtain nickel oxide powder. Nickel oxide powder is added to water to obtain a nickel oxide solution; A nickel oxide solution was dropped onto the surface of a β-phase gallium oxide single crystal, spin-coated, and annealed to obtain a nickel oxide hole transport layer. The solution containing Ni(OH)2 was centrifuged at 3000~3200 rpm to obtain Ni(OH)2 colloid, dried, and then annealed at 270~280℃ for 2~3 h to obtain nickel oxide powder; In the steps of adding nickel oxide solution dropwise onto the surface of β-phase gallium oxide single crystal, spin-coating, and annealing, the annealing temperature is 120~150℃ and the annealing time is 15~20min. In the step of adding NaOH solution dropwise to nickel nitrate solution, the concentration of NaOH solution is 10~11 mol / L, the concentration of nickel nitrate solution is 0.5~1 mol / L, and the volume ratio of NaOH solution to nickel nitrate solution is 1:(2.5~3). In the step of adding nickel oxide powder to water to obtain a nickel oxide solution, the concentration of the nickel oxide solution is 15~20 mg / mL.

2. The vertical structure ultraviolet photodetector as described in claim 1, characterized in that, The substrate includes any one of FTO conductive glass substrate, ITO conductive glass substrate, and Si substrate.

3. The vertical structure UV photodetector of claim 1, wherein, The thickness of the bottom electrode is 80~150nm.

4. A method for fabricating a vertical structure UV photodetector as claimed in any one of claims 1 to 3, characterized in that, Includes the following steps: β-phase gallium oxide single crystal is provided as the absorption layer; Nickel oxide solution was spin-coated onto the surface of a β-phase gallium oxide single crystal to form a hole transport layer; A bottom electrode was prepared on the surface of a β-phase gallium oxide single crystal far from the hole transport layer. Apply conductive tape to the substrate surface; The side of the β-phase gallium oxide single crystal with the bottom electrode is attached to the conductive tape. A top electrode is fabricated on the surface of the hole transport layer; Spin-coating a nickel oxide solution onto the surface of a β-phase gallium oxide single crystal to form a hole transport layer specifically includes the following steps: NaOH solution is added dropwise to nickel nitrate solution. When the pH of nickel nitrate solution is 10-11, a solution containing Ni(OH)2 is prepared. The solution containing Ni(OH)2 was centrifuged to obtain Ni(OH)2 colloid, which was dried and annealed to obtain nickel oxide powder. Nickel oxide powder is added to water to obtain a nickel oxide solution; A nickel oxide solution was dropped onto the surface of a β-phase gallium oxide single crystal, spin-coated, and annealed to obtain a nickel oxide hole transport layer. The solution containing Ni(OH)2 was centrifuged at 3000~3200 rpm to obtain Ni(OH)2 colloid, dried, and then annealed at 270~280℃ for 2~3 h to obtain nickel oxide powder; In the steps of adding nickel oxide solution dropwise onto the surface of β-phase gallium oxide single crystal, spin-coating, and annealing, the annealing temperature is 120~150℃ and the annealing time is 15~20min. In the step of adding NaOH solution dropwise to nickel nitrate solution, the concentration of NaOH solution is 10~11 mol / L, the concentration of nickel nitrate solution is 0.5~1 mol / L, and the volume ratio of NaOH solution to nickel nitrate solution is 1:(2.5~3). In the step of adding nickel oxide powder to water to obtain a nickel oxide solution, the concentration of the nickel oxide solution is 15~20 mg / mL.

5. The method for fabricating a vertical structure ultraviolet photodetector as described in claim 4, characterized in that, The bottom electrode was prepared on the surface of a β-phase gallium oxide single crystal by ion sputtering. The top electrode was prepared on the surface of the hole transport layer by thermal evaporation.

6. The method of fabricating a vertical structure UV photodetector of claim 4, wherein, The bottom electrode was prepared on the surface of a β-phase gallium oxide single crystal by ion sputtering. The controlled process parameters were: sputtering current of 30~35mA, argon flow rate of 15~20 sccm, and sputtering chamber pressure of 0.1~0.3 Pa.

7. The method of fabricating a vertical structure UV photodetector of claim 5, wherein, The top electrode was prepared on the surface of the hole transport layer by thermal evaporation, wherein the thermal evaporation rate was 0.1~0.5 nm / s.

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