Ultraviolet photoelectric detector with vertical structure and preparation method thereof

Abstract

The invention provides a vertical structure ultraviolet photoelectric detector and a preparation method thereof. The ultraviolet photoelectric detector is of a vertical structure, the design facilitates light absorption of the ultraviolet photoelectric detector, the light utilization rate of the ultraviolet photoelectric detector is improved, and compared with a horizontal structure, the transmission distance is shortened, and the cost is low; the ultraviolet photoelectric detector provided by the invention has a relatively high switching ratio of light and dark current and relatively small dark current, and also has a very high response speed under the condition of keeping the switching ratio of light and dark current and the dark current; a PN junction is formed between the nickel oxide hole transport layer and the beta-phase gallium oxide single crystal, so that the ultraviolet photoelectric detector has self-driving performance; in the manufacturing process, the substrate is used as a supporting frame, and the extraction electrode is packaged in one step through the conductive adhesive tape, 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] The present invention relates to the technical field of semiconductor photoelectric devices, and in particular to a vertical structure ultraviolet photodetector and a preparation method thereof. Background Art

[0002] With the advancement of science and technology, solar-blind ultraviolet (UV) photodetectors are gaining increasing importance in fields such as environmental monitoring and deep space exploration. However, they face the dual challenges of material performance and fabrication cost. Currently, mainstream photosensitive materials (such as AlGaN and SiC) each have limitations. AlGaN requires a high Al content to achieve solar-blind UV response, but high-content AlGaN has numerous lattice defects, which affect device stability. While SiC has some UV detection capabilities, its bandgap is insufficient, requiring additional filtering structures to suppress visible light interference. Ultra-wide bandgap materials such as diamond, despite their superior performance, are difficult to scale due to their high cost and processing difficulties. Therefore, gallium oxide (GaO) has emerged as a suitable material for solar-blind UV detection due to its suitable bandgap (4.9 eV). However, GaO-based solar-blind UV photodetectors still suffer from slow response speed, poor photoelectric performance, and the inability to self-power. Because GaO is an intrinsic n-type semiconductor and difficult to dop-type, forming a pn junction with other p-type materials has become an effective approach for constructing self-powered solar-blind UV photodetectors. Furthermore, most current detectors utilize a horizontal structure, requiring multiple photolithography processes to fabricate electrode leads, resulting in complex and costly processes. Traditional vertical structures, however, struggle to achieve both high sensitivity and low dark current due to defects at the heterojunction interface. Furthermore, the hole transport layer typically relies on costly vacuum coating techniques (such as magnetron sputtering of ITO), further hindering the device's industrialization. Therefore, optimizing material and structural design while streamlining the process to enhance device performance has become a pressing technical challenge in this field. Summary of the Invention

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

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

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

[0006] substrate;

[0007] a bottom electrode, located on the surface of the substrate;

[0008] an absorption layer, located on the bottom electrode away from the substrate surface;

[0009] a hole transport layer, located on the absorption layer away from the substrate surface;

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

[0011] Wherein, 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 an FTO conductive glass substrate, an ITO conductive glass substrate, and a Si substrate.

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

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

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

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

[0019] In a second aspect, the present invention further provides a method for preparing the vertical structure ultraviolet photodetector, comprising the following steps:

[0020] A bottom electrode, an absorption layer, a hole transport layer and a top electrode are prepared in sequence on the substrate.

[0021] Preferably, the method comprises the following steps:

[0022] providing a β-phase gallium oxide single crystal as an absorption layer;

[0023] Spin coating a nickel oxide solution on the surface of a β-phase gallium oxide single crystal to form a hole transport layer;

[0024] A bottom electrode is prepared on the surface of the β-phase gallium oxide single crystal away from the hole transport layer;

[0025] Pasting a conductive tape on the surface of the substrate;

[0026] Pasting the side of the β-phase gallium oxide single crystal with the bottom electrode on a conductive tape;

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

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

[0029] Adding NaOH solution dropwise to nickel nitrate solution, when the pH of nickel nitrate solution is 10-11, a solution containing Ni(OH)2 is obtained;

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

[0031] adding nickel oxide powder to water to obtain a nickel oxide solution;

[0032] The nickel oxide solution is dropped onto the surface of the beta-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, which is then dried and annealed at 270-280°C for 2-3 hours to obtain nickel oxide powder;

[0034] The nickel oxide solution is dropped onto the surface of the β-phase gallium oxide single crystal, and spin-coated, and annealed at a temperature of 120 to 150° C. for 15 to 20 minutes.

[0035] In the step of dripping a NaOH solution into a nickel nitrate solution, the concentration of the NaOH solution is 10-11 mol / L, the concentration of the nickel nitrate solution is 0.5-1 mol / L, and the volume ratio of the NaOH solution to the 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 to 20 mg / mL.

[0037] Preferably, the bottom electrode is prepared on the surface of the 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 the 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 a thermal evaporation method, 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 UV photodetector of the present invention has a vertical structure and a high light-dark current switching ratio, with a switching ratio of up to 10 5 , and a smaller dark current, where the dark current at 0V is 10 -13 A. While maintaining the two conditions, it also has a very fast response speed, with a response time of about 100 to 300ms. Since the hole transport layer is a nickel oxide hole transport layer, nickel oxide is a P-type material, and the absorption layer is a β-Ga2O3 single crystal, which is an N material, a PN junction is formed between the nickel oxide hole transport layer and the β-Ga2O3 single crystal, making the ultraviolet photodetector have self-driven performance.

[0043] 2. The ultraviolet photodetector of the present invention adopts a vertical structure design, which is conducive to the absorption of light by the ultraviolet photodetector. Compared with the horizontal structure, it shortens the transmission distance and has low cost. In terms of manufacturing process, the substrate is used as a supporting frame and the lead-out electrode is packaged in one step through conductive tape, which eliminates the 3 to 5 photolithography steps of the traditional horizontal structure, realizes process simplification, and makes the process manufacturing simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0045] Figure 1 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 These are SEM images of the nickel oxide hole transport layer prepared in Example 1 at different magnifications.

[0048] Figure 5 The vertical structure UV photodetector prepared in Example 1 was tested without 254 nm UV light and with 80 μW / cm 2 Comparison of IV curves under 254nm UV light;

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

[0050] Figure 7 This is a graph showing the IT characteristic curve of the vertical structure UV photodetector prepared in Example 1 during the first 50 seconds;

[0051] Figure 8 This is a graph showing the IT characteristic of the vertical structure UV photodetector prepared in Example 1 after 50 seconds;

[0052] Figure 9 The UV photodetector prepared in Comparative Example 1 was tested without adding 254 nm UV light and with adding 80 μW / cm 2 Comparison of IV curves under 254nm UV light;

[0053] Figure 10 This is the XRD pattern of the β-phase gallium oxide single crystal in Example 1. DETAILED DESCRIPTION

[0054] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0055] In the description of the present invention, it should be understood that the directions or positions indicated by “upper” and the like are based on the directions or positions shown in the accompanying drawings, or are the directions or positions in which the product of the invention is usually placed when in use, or are the directions or positions commonly understood by those skilled in the art. These directions or positions are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0056] The order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of this application, the term "including" means "including but not limited to". Various embodiments of the present invention may be presented 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 understood 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 the range. For example, the range description from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0057] The present invention provides a vertical structure ultraviolet photodetector, which includes, from bottom to top:

[0058] substrate;

[0059] a bottom electrode, located on the substrate surface;

[0060] an absorption layer located away from the substrate surface and away from the bottom electrode;

[0061] A hole transport layer is located on the absorption layer away from the substrate surface;

[0062] A top electrode located on 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. Its core feature 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 in sequence 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 in sequence. 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 the present invention has a vertical structure, has a high light-dark current switching ratio and a small dark current, and has a fast response speed while maintaining the two conditions; since the hole transport layer 5 is a nickel oxide hole transport layer, 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 material, a PN junction is formed between the nickel oxide hole transport layer and the β-phase gallium oxide (β-Ga2O3) single crystal, so that the ultraviolet photodetector has self-driven performance.

[0066] In some embodiments, for ease of preparation, the ultraviolet photodetector of the present invention is a vertical structure, such as Figure 1 As shown, a conductive tape 2 is provided between the substrate 1 and the bottom electrode 3; specifically, the conductive tape 2 is pasted on the substrate 1, mainly used to lead out the bottom electrode 3, and after the bottom electrode and the nickel oxide hole transport layer are respectively 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, and then the top electrode is prepared on the surface of the nickel oxide hole transport layer, thereby 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 an FTO conductive glass substrate, an ITO conductive glass substrate, and a Si substrate, preferably an FTO conductive glass substrate.

[0071] In some embodiments, the bottom electrode has a thickness of 80-150 nm.

[0072] In some embodiments, the thickness of the absorption 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 preparing the vertical structure ultraviolet photodetector, comprising the following steps:

[0076] A bottom electrode, an absorption layer, a hole transport layer and a top electrode are prepared in sequence on the substrate.

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

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

[0079] S2, spin coating a nickel oxide solution on the surface of the β-phase gallium oxide single crystal to form a hole transport layer;

[0080] S3, preparing a bottom electrode on the surface of the β-phase gallium oxide single crystal away from the hole transport layer;

[0081] S4, pasting a conductive tape on the surface of the substrate;

[0082] S5, pasting the side of the β-phase gallium oxide single crystal with the bottom electrode on a 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 on the surface of a β-phase gallium oxide single crystal to form a hole transport layer specifically includes the following steps:

[0085] Adding NaOH solution dropwise to nickel nitrate solution, when the pH of nickel nitrate solution is 10-11, a solution containing Ni(OH)2 is obtained;

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

[0087] adding nickel oxide powder to water to obtain a nickel oxide solution;

[0088] The nickel oxide solution is dropped onto the surface of the beta-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, which is then dried and annealed at 270-280°C for 2-3 h to obtain nickel oxide powder;

[0090] The nickel oxide solution is dropped onto the surface of the β-phase gallium oxide single crystal, and spin-coated, and annealed at a temperature of 120 to 150° C. for 15 to 20 minutes.

[0091] In the step of dripping a NaOH solution into a nickel nitrate solution, the concentration of the NaOH solution is 10-11 mol / L, the concentration of the nickel nitrate solution is 0.5-1 mol / L, and the volume ratio of the NaOH solution to the 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 to 20 mg / mL.

[0093] In some embodiments, the bottom electrode is prepared on the surface of the 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, an ion sputtering method is used to prepare a bottom electrode on the surface of a β-phase gallium oxide single crystal, 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 a thermal evaporation method, wherein the thermal evaporation rate is 0.1 to 0.5 nm / s.

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

[0100] The ultraviolet photodetector of the present invention adopts a vertical structure design, which facilitates its light absorption and improves its light utilization rate. Compared with horizontal structures, it shortens the transmission distance and is low-cost. The nickel oxide hole transport layer is prepared by a chemical method. In terms of manufacturing process, the substrate is used as a support frame and the lead electrodes are packaged in one step using conductive tape, eliminating the three to five photolithography steps of the traditional horizontal structure, achieving a simplified process and making the manufacturing process simpler. In terms of performance, the ultraviolet photodetector of the present invention has a high light-dark current switching ratio and a low dark current. While maintaining these two conditions, it also has a fast response speed. Because 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 the two, which has self-driven performance.

[0101] The vertical structure ultraviolet photodetector and its preparation method of the present application are further described below with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

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

[0103] Example 1

[0104] The present invention provides a method for preparing a vertical structure ultraviolet photodetector, comprising the following steps:

[0105] S1. Place FTO conductive glass substrates with a length, width and height of 20 mm, 20 mm and 2 mm respectively in deionized water, acetone and anhydrous ethanol for ultrasonic cleaning for 30 min each to remove surface dirt, and then dry them for later use;

[0106] S2. A β-Ga2O3 single crystal is used as an absorption layer. The thickness of the β-Ga2O3 single crystal is 600 μm.

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

[0108] S31, taking out NaOH powder and nickel nitrate hexahydrate, and adding them to water to prepare 10 mol / L NaOH solution and 0.5 mol / L nickel nitrate solution respectively;

[0109] A 10 mol mol / L NaOH solution is added dropwise to a 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 and the pH value of the solution is 10-11, a solution containing Ni(OH)2 is obtained.

[0110] S32, centrifuging the solution containing Ni(OH)2 at 3000 rpm to obtain Ni(OH)2 colloid, drying to obtain nickel hydroxide (Ni(OH)2 powder), and then annealing at 270°C for 2h to obtain nickel oxide powder;

[0111] S33, adding nickel oxide powder to water to obtain a 15 mg / mL nickel oxide solution;

[0112] S34, dropping nickel oxide solution onto the surface of a 600 μm thick β-phase gallium oxide single crystal, and spin coating it at a speed of 3000 rpm. After the spin coating is completed, annealing is carried out on a constant temperature table at 120° C. for 15 minutes 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 a surface of a 600 μm thick β-phase gallium oxide single crystal 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 an ion sputtering method. The process parameters controlled are: a sputtering current of 30 mA, an argon gas flow rate of 15 sccm, and a sputtering chamber pressure of 0.2 Pa.

[0114] S5, pasting a conductive tape on the surface of the FTO conductive glass substrate;

[0115] S6, pasting the side of the β-phase gallium oxide single crystal with the bottom electrode on a conductive tape;

[0116] S7. Prepare a top electrode on the surface of the hole transport layer, where the top electrode is a Bi electrode; use a thermal evaporation method to prepare a Bi top electrode with a thickness of 50 nm on the surface of the hole transport layer, wherein the thermal evaporation rate is 0.2 nm / s.

[0117] Comparative Example 1

[0118] This comparative example provides a method for preparing an ultraviolet photodetector, which is the same as Example 1 except that the nickel oxide hole transport layer is not included. The specific preparation process includes the following steps:

[0119] S1. Place FTO conductive glass substrates with a length, width and height of 20 mm, 20 mm and 2 mm respectively in deionized water, acetone and anhydrous ethanol for ultrasonic cleaning for 30 min each to remove surface dirt, and then dry them for later use;

[0120] S2. A β-Ga2O3 single crystal is used as an absorption layer; the thickness of the β-Ga2O3 single crystal is 600 μm;

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

[0122] S4, pasting a conductive tape on the surface of the FTO conductive glass substrate;

[0123] S5, pasting the side of the β-phase gallium oxide single crystal with the bottom electrode on a 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, wherein 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] From the XRD spectrum, it can be seen that the nickel oxide (NiO x ) content, where the three peaks in the figure correspond to the (111), (200), and (220) crystal planes, indicating that nickel oxide (NiO x )The hole transport layer was successfully added.

[0128] Figures 3-4These are 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 that in Figure 3 In this image, the high magnification allows for microscopic observation of the particle morphology on the surface of the nickel oxide film. It can be seen that the particles are mostly spherical, which is consistent with the sol-gel preparation process, which tends to form spherical nanoparticles during solvent evaporation and precursor gelation.

[0130] and Figure 4 This image, taken at a lower magnification, shows the overall structure of the nickel oxide film. From a macroscopic perspective, the film is relatively continuous and has good coverage.

[0131] Figure 5 The vertical structure ultraviolet photodetector prepared in Example 1 is not subjected to 254nm ultraviolet light (i.e. Figure 5 dark current) and an external 80 μW / cm 2 254nm ultraviolet light (ie Figure 5 Comparison of IV curves under medium photocurrent.

[0132] Figure 9 The UV photodetector prepared in Comparative Example 1 is not subjected to 254 nm UV light (i.e. Figure 9 dark current) and an external 80 μW / cm 2 254nm ultraviolet light (ie Figure 9 Comparison of IV curves under medium photocurrent.

[0133] The IV curve was tested using a Keithley 4200A-SCS semiconductor parameter analyzer. A linear voltage sweep was used from -5V to +5V to observe the device's current response under positive and negative bias conditions.

[0134] from Figure 5 It can be seen that the dark current of the vertical structure UV photodetector prepared in Example 1 is significantly lower than Figure 9 The dark current of the vertical structure ultraviolet photodetector prepared in Comparative Example 1 is as low as 10 -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 light-to-dark current ratio (i.e., the ratio of photocurrent to dark current, on-off ratio) of the vertical structure UV photodetector prepared in Example 1 is also significantly better than Figure 9 The vertical structure ultraviolet photodetector prepared in comparative example 1 and the vertical structure ultraviolet photodetector prepared in example 1 have a light-to-dark current ratio of up to 10 5 , while the light-to-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 the illuminated and non-illuminated 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 UV photodetector prepared in Example 1 (tested using Keithley KEITHLEY4200A-SCS semiconductor parameter analyzer) is used to evaluate the photoelectric response characteristics of the device under periodic light switching conditions. During the experiment, the device was operated in a 0V bias (zero bias) state. The specific test method was: manually switch the light source, that is, manually turn on or off the light source at regular intervals (the light source is 80μW / cm 2 By observing the periodic changes in current in the IT curve, key device parameters such as response speed, on / off ratio, and stability can be further extracted.

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

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

[0140] Specifically, Figures 7-8 This is the IT characteristic curve of the vertical structure UV photodetector prepared in Example 1 under 0V bias during testing. Figure 7 is the IT characteristic curve for the first 50s, and Figure 8 It is the IT characteristic curve after the last 50s test.

[0141] from Figures 7-8 It can be seen from Figures 7 to 8 that the vertical structure ultraviolet photodetector prepared in Example 1 has stable performance after testing for a period of time and has self-driving performance; and it can be seen from Figures 7 to 8 that the response time of the vertical structure ultraviolet photodetector prepared in Example 1 is approximately 100 to 300 ms.

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

[0143] from Figure 10 It can be seen that the diffraction peaks are located at 2Theda=24.187, 30.059, 37.386, 44.732, 49.544, 49.560, and 60.888, corresponding 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 intense, 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 in the scope of protection of the present invention.

Claims

1. A vertical structure ultraviolet photodetector, characterized in that: From bottom to top, it includes: substrate; a bottom electrode, located on the surface of the substrate; an absorption layer, located on the bottom electrode away from the substrate surface; a hole transport layer, located on the absorption layer away from the substrate surface; A top electrode is located on the hole transport layer away from the substrate surface; Wherein, the absorption layer is a β-phase gallium oxide single crystal, and the hole transport layer is a nickel oxide hole transport layer.

2. The vertical structure ultraviolet photodetector according to claim 1, characterized in that: The top electrode includes any one of a Bi electrode, a Pt electrode, an Au electrode, and an Al electrode; The bottom electrode includes any one of a Pt electrode, an Au electrode, and an Al electrode; The substrate includes any one of an FTO conductive glass substrate, an ITO conductive glass substrate, and a Si substrate.

3. The vertical structure ultraviolet photodetector according to claim 1, characterized in that: The thickness of the bottom electrode is 80 to 150 nm; The thickness of the absorption layer is 500 to 650 μm; The thickness of the hole transport layer is 50 to 80 nm; The thickness of the bottom electrode is 30-80 nm.

4. A method for preparing a vertical structure ultraviolet photodetector according to any one of claims 1 to 3, characterized in that: The following steps are involved: A bottom electrode, an absorption layer, a hole transport layer and a top electrode are prepared in sequence on the substrate.

5. The method for preparing a vertical structure ultraviolet photodetector according to claim 4, wherein: The following steps are involved: providing a β-phase gallium oxide single crystal as an absorption layer; Spin coating a nickel oxide solution on the surface of a β-phase gallium oxide single crystal to form a hole transport layer; A bottom electrode is prepared on the surface of the β-phase gallium oxide single crystal away from the hole transport layer; Pasting a conductive tape on the surface of the substrate; Pasting the side of the β-phase gallium oxide single crystal with the bottom electrode on a conductive tape; A top electrode is prepared on the surface of the hole transport layer.

6. The method for preparing a vertical structure ultraviolet photodetector according to claim 4, wherein: Spin coating a nickel oxide solution on the surface of a β-phase gallium oxide single crystal to form a hole transport layer specifically includes the following steps: Adding NaOH solution dropwise to nickel nitrate solution, when the pH of nickel nitrate solution is 10-11, a solution containing Ni(OH)2 is obtained; The solution containing Ni(OH)2 is centrifuged to obtain Ni(OH)2 colloid, which is then dried and annealed to obtain nickel oxide powder; adding nickel oxide powder to water to obtain a nickel oxide solution; The nickel oxide solution is dropped onto the surface of the beta-phase gallium oxide single crystal, spin-coated, and annealed to obtain a nickel oxide hole transport layer.

7. The method for preparing a vertical structure ultraviolet photodetector according to claim 6, wherein: The solution containing Ni(OH)2 was centrifuged at 3000-3200 rpm to obtain Ni(OH)2 colloid, which was then dried and annealed at 270-280°C for 2-3 hours to obtain nickel oxide powder; The nickel oxide solution is dropped onto the surface of the β-phase gallium oxide single crystal, and spin-coated, and annealed at a temperature of 120 to 150° C. for 15 to 20 minutes. In the step of dripping a NaOH solution into a nickel nitrate solution, the concentration of the NaOH solution is 10-11 mol / L, the concentration of the nickel nitrate solution is 0.5-1 mol / L, and the volume ratio of the NaOH solution to the 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 to 20 mg / mL.

8. The method for preparing a vertical structure ultraviolet photodetector according to claim 7, wherein: The bottom electrode is prepared on the surface of β-phase gallium oxide single crystal by ion sputtering method; The top electrode was prepared on the surface of the hole transport layer by thermal evaporation.

9. The method for preparing a vertical structure ultraviolet photodetector according to claim 8, wherein: The bottom electrode was prepared on the surface of a β-phase gallium oxide single crystal by ion sputtering, wherein the controlled process parameters were: sputtering current of 30-35 mA, argon gas flow of 15-20 sccm, and sputtering chamber pressure of 0.1-0.3 Pa.

10. The method for preparing a vertical structure ultraviolet photodetector according to claim 8, wherein: The top electrode is prepared on the surface of the hole transport layer by adopting a thermal evaporation method, wherein the thermal evaporation rate is 0.1-0.5 nm / s.

Images