Amorphous gallium oxide nanosheets, UV-Vis-NIR broadband photodetectors and their fabrication methods

Abstract

This invention provides an amorphous gallium oxide nanosheet, its preparation method, and a UV-Vis-NIR broadband photodetector, comprising the following steps: mixing gallium acetylacetonate with KNO3 powder, calcining, and washing to obtain amorphous gallium oxide nanosheets. The amorphous gallium oxide nanosheets prepared by this method are nanosheets with a size of approximately several micrometers and a thickness of approximately 10-40 nm. These amorphous gallium oxide nanosheets are amorphous nanosheets with a low proportion of tetrahedral Ga centers, exhibiting advantages in broadband absorption and spin polarization. This invention assembles the above-mentioned amorphous gallium oxide nanosheets with conductive silicon wafers and graphene to form a vertically structured photodetector, forming a pair of back-to-back rectified junctions composed of a Schottky junction and a p-n junction connected in series, resulting in low dark current. The vertically structured photodetector based on this amorphous gallium oxide exhibits excellent UV-Vis-NIR broadband photodetector performance.

Description

Technical Field

[0001] This invention belongs to the field of advanced semiconductor materials and ultraviolet-visible-near-infrared broadband photodetector technology, and particularly relates to an amorphous gallium oxide nanosheet, a UV-Vis-NIR broadband photodetector and its preparation method. Background Technology

[0002] Broadband photodetectors in the ultraviolet-visible-near-infrared spectrum have wide applications in environmental monitoring, optical communication, and image sensing. Various semiconductor materials, such as sulfides, selenides, and tellurides, have been developed as optical response layers for broadband detectors. However, due to their individual drawbacks, such as environmental instability, complex fabrication processes, or toxicity, they struggle to achieve excellent overall performance. Wide bandgap metal-oxide semiconductors (MOS) offer a viable option for photodetectors due to their non-toxicity, low energy loss, high stability, and cost-effectiveness. However, the application of MOS in broadband photodetectors is typically limited by finite light absorption due to their inherently large bandgap. To overcome this limitation and achieve high-performance MOS broadband photodetectors, expanding the light absorption range and accelerating the separation of photogenerated carriers are crucial.

[0003] Therefore, it is of great significance to provide a metal oxide with a simple, non-toxic, and low-cost preparation process, and with a wide spectral response and efficient carrier separation, which can realize a UV-Vis-NIR broadband photodetector with high detectivity, low dark current and fast response speed. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an amorphous gallium oxide nanosheet, a UV-Vis-NIR broadband photodetector, and a preparation method thereof. The preparation method of the amorphous gallium oxide nanosheet has the advantages of being simple, non-toxic, and low-cost. The amorphous gallium oxide nanosheet of this invention has a wide absorption range and spin polarization properties. The photodetector based on the amorphous gallium oxide nanosheet of this invention has a wide spectral detection range, high detectivity, fast response speed, and low dark current.

[0005] This invention provides a method for preparing amorphous gallium oxide nanosheets, comprising the following steps:

[0006] Gallium acetylacetonate was mixed with KNO3 powder, calcined, and washed to obtain amorphous gallium oxide nanosheets.

[0007] Preferably, the mass ratio of gallium acetylacetonate to KNO3 is 1:(1.5-25).

[0008] Preferably, the calcination temperature is 190–260°C; the calcination atmosphere is air.

[0009] Heat to the required calcination temperature at a heating rate of 2–5 °C / min, and hold for 1–1.5 h.

[0010] This invention provides an amorphous gallium oxide nanosheet, prepared by the method described in the above technical solution;

[0011] The amorphous gallium oxide nanosheets have a size of 1–2 μm and a thickness of 10–40 nm.

[0012] Preferably, the proportion of Ga at the tetrahedral center of the amorphous gallium oxide nanosheet is lower than that of crystalline β-Ga2O3;

[0013] The amorphous gallium oxide nanosheets have a smaller band gap than crystalline β-Ga2O3 and exhibit increased gap states;

[0014] The amorphous gallium oxide nanosheets have a broadened light absorption range of 254–1064 nm.

[0015] This invention provides a broadband photodetector for UV-Vis-NIR, including a bottom electrode;

[0016] A photoresponsive layer disposed on the bottom electrode;

[0017] Top electrode covering the photoresponse layer;

[0018] The photoresponsive layer is an amorphous gallium oxide nanosheet prepared by the preparation method described in the above technical solution or an amorphous gallium oxide nanosheet described in the above technical solution.

[0019] Preferably, the bottom electrode is a P-type silicon wafer with a thickness of 200–500 μm and a wafer size of (0.4 × 0.4) cm to (2 × 2) cm.

[0020] The top electrode is made of graphene with a thickness of 0.340–0.350 nm;

[0021] The thickness of the photoresponse layer is 0.020–3 μm.

[0022] Preferably, the broadband photodetector has the ability to detect light in the UV-Vis-NIR range of 254–1064 nm;

[0023] It exhibits a dark current as low as 63pA under forward bias.

[0024] It has a fast response speed: τ 上升 <30ms,τ 下降 <50ms.

[0025] Preferably, a Schottky junction and a pn junction are formed at the contact interface between the amorphous gallium oxide nanosheets and graphene and p-type silicon, respectively;

[0026] The Schottky junction and pn junction are connected in series to form a back-to-back rectifier junction.

[0027] This invention provides a method for fabricating the broadband photodetector described in the above technical solution, comprising the following steps:

[0028] An ethanol suspension of amorphous gallium oxide nanosheets with a concentration of 2–15 mg / mL was spin-coated onto the bottom electrode to form a photoresponsive layer.

[0029] By covering the photoresponse layer with the top electrode, a broadband photodetector is obtained.

[0030] This invention provides a method for preparing amorphous gallium oxide nanosheets, comprising the following steps: mixing gallium acetylacetonate with KNO3 powder, calcining, and washing to obtain amorphous gallium oxide nanosheets. The amorphous gallium oxide nanosheets prepared by this method are nanosheets with a size of approximately several micrometers and a thickness of approximately 10-40 nm. These amorphous gallium oxide nanosheets are amorphous nanosheets with a low proportion of tetrahedral Ga centers, exhibiting advantages in broad-spectrum absorption and spin polarization. This invention assembles the above-mentioned amorphous gallium oxide nanosheets with conductive silicon wafers and graphene to form a vertically structured photodetector, forming a pair of back-to-back rectified junctions composed of a Schottky junction and a pn junction connected in series, resulting in low dark current. The vertically structured photodetector based on this amorphous gallium oxide exhibits excellent UV-Vis-NIR broad-spectrum photodetector performance. Attached Figure Description

[0031] Figure 1 X-ray diffraction pattern of the amorphous gallium oxide nanosheets prepared in this invention;

[0032] Figure 2 Transmission electron microscope image of amorphous gallium oxide nanosheets prepared at 200℃ in this invention;

[0033] Figure 3 An atomic force microscope image of the amorphous gallium oxide nanosheets prepared in this invention;

[0034] Figure 4 High-angle annular dark-field scanning transmission electron microscope image of the amorphous gallium oxide nanosheets prepared in this invention;

[0035] Figure 5 Extended X-ray absorption fine structure (EXAFS) spectra of amorphous gallium oxide nanosheets and β-Ga2O3 prepared in this invention;

[0036] Figure 6 The ultraviolet-visible light near-infrared diffuse reflectance absorption spectra of amorphous gallium oxide nanosheets and β-Ga2O3 prepared in this invention;

[0037] Figure 7 The band gap diagrams are for the amorphous gallium oxide nanosheets and β-Ga2O3 prepared in this invention.

[0038] Figure 8 The density of states diagrams of amorphous gallium oxide nanosheets and β-Ga2O3 prepared in this invention are shown.

[0039] Figure 9 Hysteresis loop diagrams of amorphous gallium oxide nanosheets and β-Ga2O3 prepared in this invention;

[0040] Figure 10 The fluorescence spectra of amorphous gallium oxide nanosheets and β-Ga2O3 prepared in this invention are shown.

[0041] Figure 11 The fluorescence lifetime diagrams of the amorphous gallium oxide nanosheets and β-Ga2O3 prepared in this invention are shown.

[0042] Figure 12 This is a schematic diagram of a photodetector device with a vertical structure made of amorphous gallium oxide nanosheets prepared based on the present invention (graphene / a-GaO). x NSs / p-Si devices);

[0043] Figure 13 Graphene / a-GaO x IV curves of NSs / p-Si devices under UV-Vis-NIR light irradiation;

[0044] Figure 14 Graphene / a-GaO x The curve of detectivity D of NSs / p-Si device calculated under UV-Vis-NIR light irradiation;

[0045] Figure 15 Graphene / a-GaO x IV curves of NSs / p-Si devices under dark conditions;

[0046] Figure 16 Graphene / a-GaO x Band structure diagram of NSs / p-Si device under forward bias when illuminated;

[0047] Figure 17 Graphene / a-GaO x The response time curve of NSs / p-Si device under 254nm light illumination;

[0048] Figure 18 Graphene / a-GaO xIt curves of NSs / p-Si and graphene / β-Ga2O3 / p-Si devices under 254nm light irradiation;

[0049] Figure 19 a-GaO x A schematic diagram illustrating the mechanism by which NSs spin polarization promotes carrier separation;

[0050] Figure 20 This is a transmission electron microscope image of amorphous gallium oxide nanosheets prepared at 220℃ according to the present invention.

[0051] Figure 21 A diagram showing the Ga-O tetrahedral proportions of amorphous gallium oxide and crystalline β-Ga₂O₃ prepared in this invention;

[0052] Figure 22 a-GaO x NSs transient optical response It curve. Detailed Implementation

[0053] This invention provides a method for preparing amorphous gallium oxide nanosheets, comprising the following steps:

[0054] Gallium acetylacetonate was mixed with KNO3 powder, calcined, and washed to obtain amorphous gallium oxide nanosheets.

[0055] The amorphous nanosheet preparation process provided by this invention is simple, non-toxic, and low in cost. The amorphous gallium oxide nanosheets prepared by this method have a low tetrahedral center Ga and a low band gap, as well as gapped state and spin polarization properties, exhibiting a broad UV-Vis-NIR response and fast carrier separation.

[0056] In this invention, the KNO3 powder is an inorganic salt template agent; the mass ratio of gallium acetylacetonate to KNO3 is 1:(1.5-25).

[0057] This invention involves grinding and mixing gallium acetylacetonate with inorganic salt KNO3 powder until homogeneous; the grinding time is 10–40 min. The ground mixture is then spread evenly in a ceramic boat and placed in a tube furnace for calcination; preferably, the temperature is raised to 190–260°C in an air atmosphere at a heating rate of 2–5°C / min, and held for 1–1.5 h. After calcination, the furnace is cooled to room temperature.

[0058] In this invention, the calcined product is washed with deionized water and anhydrous ethanol 3 to 4 times. After drying, amorphous gallium oxide nanosheets are obtained.

[0059] This invention provides an amorphous gallium oxide nanosheet, prepared by the method described in the above technical solution;

[0060] The amorphous gallium oxide nanosheets have a size of 1–2 μm and a thickness of 10–40 nm.

[0061] The UV-Vis-NIR broadband photodetector fabricated based on the aforementioned amorphous gallium oxide nanosheets exhibits advantages such as high detectivity, low dark current, and fast response speed. This amorphous gallium oxide-based UV-Vis-NIR broadband photodetector shows promising applications in environmental monitoring, optical communication, and image sensing.

[0062] The amorphous gallium oxide nanosheets provided by this invention have a significantly lower proportion of tetrahedral Ga at their centers compared to crystalline β-Ga₂O₃. The preferred ratio of tetrahedral Ga to octahedral Ga in the amorphous gallium oxide nanosheets is 1 / 10 to 3 / 10. These amorphous gallium oxide nanosheets exhibit low tetrahedral GaO₄ coordination. The amorphous gallium oxide nanosheets possess advantages in broad-spectrum absorption and spin polarization. The band gap of the amorphous gallium oxide nanosheets is smaller than that of crystalline β-Ga₂O₃, and they exhibit increased gap states. The amorphous gallium oxide nanosheets also possess a broadened light absorption range of 254–1064 nm.

[0063] The amorphous gallium oxide nanosheets of this invention exhibit weak ferromagnetism; the fluorescence intensity of the amorphous gallium oxide nanosheets of this invention is relatively weak; the photogenerated carrier lifetime of the amorphous gallium oxide nanosheets of this invention is relatively long (approximately 12.36 ns).

[0064] This invention provides a broadband photodetector for UV-Vis-NIR, including a bottom electrode;

[0065] A photoresponsive layer disposed on the bottom electrode;

[0066] Top electrode covering the photoresponse layer;

[0067] The photoresponsive layer is an amorphous gallium oxide nanosheet prepared by the preparation method described in the above technical solution or an amorphous gallium oxide nanosheet described in the above technical solution.

[0068] The UV-Vis-NIR broadband photodetector provided by this invention is a graphene / a-GaO with a vertical structure prepared from amorphous gallium oxide according to this invention. x NSs / p-Si photodetectors are used for UV-Vis-NIR photodetection. These detectors feature high detectivity, fast response speed, and low dark current, which helps advance the application of metal oxides in broadband photodetectors.

[0069] The broadband photodetector provided by the present invention includes a bottom electrode, which is a conductive P-type silicon wafer with a thickness of 200-550 μm; the preferred size of the silicon wafer is (0.4×0.4) cm to (2×2) cm.

[0070] The broadband photodetector provided by this invention includes a photoresponse layer disposed on the bottom electrode; the photoresponse layer is an amorphous gallium oxide nanosheet prepared by the preparation method described in the above technical solution or an amorphous gallium oxide nanosheet described in the above technical solution. The thickness of the photoresponse layer is 0.020–3 μm.

[0071] The broadband photodetector provided by the present invention includes a top electrode made of graphene with a thickness of 0.340–0.350 nm.

[0072] The broadband photodetector provided by this invention has the ability to detect UV-Vis-NIR light in the range of 254–1064 nm, exhibiting a performance of 7.2 × 10⁻⁶ nm. 12 ~5.8×10 13 Jones's detectivity; low dark current down to 63 pA under forward bias; fast response speed: τ 上升 <30ms, τ 下降 <50ms.

[0073] Schottky junctions and pn junctions are formed at the contact interfaces between amorphous gallium oxide nanosheets and graphene and p-type silicon, respectively; the Schottky junctions and pn junctions are connected in series to form a pair of back-to-back rectifier junctions, which can effectively suppress the dark current of the detector.

[0074] This invention provides a method for fabricating the broadband photodetector described in the above technical solution, comprising the following steps:

[0075] An ethanol suspension of amorphous gallium oxide nanosheets with a concentration of 2–15 mg / mL was spin-coated onto the bottom electrode to form a photoresponsive layer.

[0076] By covering the photoresponse layer with the top electrode, a broadband photodetector is obtained.

[0077] Specifically, in this invention, the amorphous gallium oxide nanosheets are dissolved in anhydrous ethanol, with a preferred concentration of 2–15 mg / ml; the mixture is thoroughly ultrasonically mixed to obtain an ethanol suspension of amorphous gallium oxide nanosheets; the ethanol suspension of amorphous gallium oxide nanosheets is spin-coated onto a P-type silicon wafer to form a photoresponse layer; and a single layer of graphene, cut to a size slightly smaller than that of the P-type silicon wafer, is transferred onto the photoresponse layer using a liquid phase transfer method to obtain a broadband photodetector.

[0078] In this invention, the composite material after graphene transfer is preferably bonded to a PCB board with copper tape using silver paste, with P-type silicon in contact with copper, and silver wires are led out from the copper tape using silver paste; similarly, silver wires are led out from the top electrode graphene using silver paste.

[0079] This invention utilizes the graphene / a-GaO with a vertical structure prepared above.x NSs / p-Si photodetectors were used for UV-Vis-NIR photodetection. Their photoelectric performance was tested using monochromatic light at wavelengths of 254 / 365 / 404 / 520 / 640 / 780 / 808 / 980 / 1064 nm. Experimental results show that this graphene / a-GaO… x The NSs / p-Si photodetector exhibits good photoresponse in the light range of 254–1064 nm.

[0080] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of an amorphous gallium oxide nanosheet, a UV-Vis-NIR broadband photodetector, and a preparation method provided by the present invention, should not be construed as limiting the scope of protection of the present invention.

[0081] Example 1

[0082] 1. A method for preparing amorphous gallium oxide nanosheets, comprising the following steps:

[0083] Weigh 7g of gallium acetylacetonate and 14g of KNO3 powder separately, and grind them for 20 minutes to mix them evenly. Spread the evenly mixed powder evenly in a ceramic boat to form a thin layer, cover it and place it in a tube furnace for calcination. The heating rate is 5℃ / min, and the temperature is raised to 200℃ and held for 1 hour. After cooling to room temperature in the furnace, wash it three times with deionized water and anhydrous ethanol respectively, and then dry it in an oven for later use.

[0084] The structural morphology of the amorphous gallium oxide nanosheets obtained in this invention was characterized, and the results are as follows: Figures 1-5 As shown. Figure 1 X-ray diffraction patterns of amorphous gallium oxide nanosheets and β-Ga2O3; Figure 2 , Figure 3 These are transmission electron microscope and atomic force microscope images of amorphous gallium oxide nanosheets, respectively. Figure 4 This is a high-angle annular dark-field scanning transmission electron microscope image; Figure 5 The extended X-ray absorption fine structure (EXAFS) spectra of amorphous gallium oxide nanosheets and β-Ga2O3 are shown.

[0085] As can be seen from the above characteristics:

[0086] The amorphous gallium oxide nanosheets of this invention have a size of approximately 1–2 μm and a thickness of approximately 11 nm.

[0087] The amorphous gallium oxide nanosheets of this invention have a much lower tetrahedral center Ga than crystalline β-Ga₂O₃;

[0088] In this invention, the Ga content at the tetrahedral center of the amorphous gallium oxide nanosheet is 1 / 10.

[0089] The optical properties, electronic structure, and magnetic properties of the amorphous gallium oxide nanosheets of this invention were characterized and theoretically calculated, and the results are attached. Figures 6-11 As shown. Figure 6 The ultraviolet-to-near-infrared diffuse reflectance absorption spectrum of amorphous gallium oxide nanosheets and β-Ga2O3; Figure 7 The band gap diagrams are for amorphous gallium oxide nanosheets and β-Ga2O3. Figure 8 Density of states diagrams for amorphous gallium oxide nanosheets and β-Ga2O3; Figure 9 Hysteresis loop diagrams of amorphous gallium oxide nanosheets and β-Ga2O3; Figure 10 Fluorescence spectra of amorphous gallium oxide nanosheets and β-Ga2O3; Figure 11 The fluorescence lifetime diagrams are for amorphous gallium oxide nanosheets and β-Ga2O3.

[0090] The above characterization results show that:

[0091] The amorphous gallium oxide nanosheets of this invention have a broadened light absorption range (UV-Vis-NIR: 254-1064nm);

[0092] The amorphous gallium oxide nanosheets of the present invention have a reduced band gap (3.6 eV) and an increased number of gap states;

[0093] The amorphous gallium oxide nanosheets of this invention have spin polarization characteristics;

[0094] The amorphous gallium oxide nanosheets of this invention exhibit weak ferromagnetism;

[0095] The amorphous gallium oxide nanosheets of this invention exhibit weak fluorescence intensity.

[0096] The amorphous gallium oxide nanosheets of this invention have a long photogenerated carrier lifetime (approximately 12.36 ns);

[0097] The recombination of photogenerated electrons and holes in amorphous gallium oxide nanosheets of the present invention is effectively suppressed.

[0098] 2. Assemble the amorphous gallium oxide nanosheets prepared above into a photodetector with a vertical structure for UV-Vis-NIR photodetection. This specifically includes the following steps:

[0099] 1) Dissolve the amorphous gallium oxide nanosheets prepared in this invention in anhydrous ethanol to prepare a 5 mg / mL turbid solution, and mix it evenly by ultrasonication;

[0100] 2) Cut 500nm thick P-type silicon into 0.8×0.8cm squares, and ultrasonically clean them sequentially with water, ethanol, and acetone for 3 minutes each to keep the surface clean. Place them on a spin coater for later use;

[0101] 3) Drop the uniform turbid liquid from 1) onto the silicon wafer from 2), about 2 drops, to obtain a spin coating with a thickness of about 300nm;

[0102] 4) Attach insulating tape to one end of the spin coating layer, and use wet transfer to transfer graphene onto the spin coating layer, ensuring that the graphene portion covers the insulating tape;

[0103] 5) The silicon wafer of the composite material obtained in 4) is attached to a PCB board with copper tape using silver paste. Then, the bottom electrode and top electrode are led out with silver wires using silver paste. This will produce a photodetector with a vertical structure for UV-Vis-NIR photoelectric testing.

[0104] The photoelectric performance of the photodetector with a vertical structure prepared according to this invention was tested. The results are as follows: Figures 12-19 As shown.

[0105] Figure 12 This is a schematic diagram of a photodetector device with a vertical structure made of amorphous gallium oxide nanosheets prepared based on the present invention (graphene / a-GaO). x NSs / p-Si devices).

[0106] Figure 13 Graphene / a-GaO x IV curves of NSs / p-Si devices under UV-Vis-NIR light irradiation; Figure 14 Graphene / a-GaO x The detectivity D of NSs / p-Si devices under UV-Vis-NIR illumination. * The curve illustrates the graphene / a-GaO nanosheets prepared in this invention used as the photoresponse layer. x NSs / p-Si devices exhibit good photoresponse in the UV-Vis-NIR range. They show a light response of 7.2 × 10⁻⁶ for the 1064-254 nm wavelength range. 12 ~5.8×10 13 Jones' detection rate.

[0107] Figure 15 Graphene / a-GaO x The IV curves of the NSs / p-Si device under dark conditions illustrate the graphene / a-GaO of this invention. x NSs / p-Si devices have a dark current as low as 63pA.

[0108] Figure 16 Graphene / a-GaO xThe band structure diagram of the NSs / p-Si device under forward bias when illuminated shows the carrier flow direction. This indicates the formation of a Schottky barrier at the graphene-amorphous gallium oxide interface and a pn junction at the interface between amorphous gallium oxide and p-type silicon. The Schottky barrier and the pn junction are connected in series to form a back-to-back rectifier junction, effectively reducing the device's dark current.

[0109] Figure 17 Graphene / a-GaO x The response time curve of the NSs / p-Si device under 254nm light irradiation; illustrating the graphene / a-GaO of the present invention. x NSs / p-Si devices have a faster response time (τ). 上升 <30ms,τ 下降 <50ms)

[0110] Figure 18 Graphene / a-GaO x The It curves of NSs / p-Si and graphene / β-Ga2O3 / p-Si devices under 254nm light illumination; illustrating the graphene / α-GaO x The higher optical response of NSs / p-Si indicates that spin polarization effectively suppresses carrier recombination.

[0111] Figure 19 a-GaO x A diagram illustrating the mechanism by which NSs spin polarization promotes carrier separation. When photoinduced electrons in a spin state are excited to the conduction band, their original spin state disappears due to ultrafine interactions and spin-orbit coupling during electron transfer. Holes, however, retain their spin direction, thereby suppressing the recombination rate of electron-hole pairs.

[0112] Example 2

[0113] 1. A method for preparing amorphous gallium oxide nanosheets, comprising the following steps:

[0114] Weigh 7g of gallium acetylacetonate and 14g of KNO3 powder separately, and grind them for 20 minutes to mix them evenly. Spread the evenly mixed powder evenly in a ceramic boat to form a thin layer, cover it and place it in a tube furnace for calcination. The heating rate is 5℃ / min, and the temperature is raised to 220℃ and held for 1.5 hours. After cooling to room temperature in the furnace, wash it three times with deionized water and anhydrous ethanol respectively, and then dry it in an oven for later use.

[0115] The structure, morphology and optical properties of the amorphous gallium oxide nanosheets obtained in this invention were characterized, and the results are shown in the figure. Figure 1 X-ray diffraction pattern of amorphous gallium oxide nanosheets prepared under these conditions; Figure 20 This is a transmission electron microscope image of the amorphous gallium oxide nanosheet. Figure 21This is a diagram showing the Ga-O tetrahedral proportions of Examples 1 and 2, and crystalline gallium oxide; Figure 6 The ultraviolet-to-near-infrared diffuse reflectance absorption spectrum of amorphous gallium oxide nanosheets and β-Ga2O3; Figure 7 This is a bandgap diagram of amorphous gallium oxide nanosheets. Figure 10 Fluorescence spectra of amorphous gallium oxide nanosheets and crystalline β-Ga2O3; Figure 11 The fluorescence lifetime diagrams are for amorphous gallium oxide nanosheets and crystalline β-Ga2O3.

[0116] As can be seen from the above characteristics:

[0117] The gallium oxide nanosheets in this embodiment are amorphous and have a size of approximately 1–2 μm.

[0118] The amorphous gallium oxide nanosheets in this embodiment have a much lower tetrahedral center Ga (β-Ga2O3: ~50%; α-GaO) than crystalline β-Ga2O3. x -220℃: ~24%; α-GaO x -220℃: ~10%);

[0119] The amorphous gallium oxide nanosheets in this embodiment have a broadened light absorption range (254-1064 nm);

[0120] The amorphous gallium oxide nanosheets in this embodiment have a reduced band gap (3.9 eV) and an increased number of gap states;

[0121] The amorphous gallium oxide nanosheets in this embodiment exhibit weak ferromagnetism;

[0122] The fluorescence intensity of the amorphous gallium oxide nanosheets in this embodiment is relatively weak.

[0123] The amorphous gallium oxide nanosheets in this embodiment have a relatively long photogenerated carrier lifetime (11.58 ns);

[0124] In this embodiment, the recombination of photogenerated electrons and holes in amorphous gallium oxide nanosheets is effectively suppressed.

[0125] 2. Assemble the amorphous gallium oxide nanosheets prepared above into a photodetector with a vertical structure for UV-Vis-NIR photodetection. This specifically includes the following steps:

[0126] 1) Dissolve the amorphous gallium oxide nanosheets prepared in this invention in anhydrous ethanol to prepare a 5 mg / mL turbid solution, and mix it evenly by ultrasonication;

[0127] 2) Cut 500nm thick P-type silicon into 0.8×0.8cm squares, and ultrasonically clean them sequentially with water, ethanol, and acetone for 3 minutes each to keep the surface clean. Place them on a spin coater for later use;

[0128] 3) Drop the uniform turbid liquid from 1) onto the silicon wafer from 2), about 2 drops, and the resulting spin coating thickness is about 300nm;

[0129] 4) Attach insulating tape to one end of the spin coating layer, and use wet transfer to transfer graphene onto the spin coating layer, ensuring that the graphene portion covers the insulating tape;

[0130] 5) The silicon wafer of the composite material obtained in 4) is attached to a PCB board with copper tape using silver paste. Then, the bottom electrode and top electrode are led out with silver wires using silver paste. This will produce a photodetector with a vertical structure for UV-Vis-NIR photoelectric testing.

[0131] The photoelectric performance of the photodetector with a vertical structure prepared according to this invention was tested. The results are as follows: Figure 22 As shown.

[0132] Figure 22 Graphene / a-GaO x The instantaneous photoresponse (It) curve of the NSs / p-Si device under UV-Vis-NIR light irradiation. This illustrates the graphene / a-GaO nanosheets prepared in this invention used as the photoresponse layer. x NSs / p-Si devices exhibit high photoresponse current and fast photoresponse speed in the UV-Vis-NIR (254-1064nm) range.

[0133] As shown in the above embodiments, this invention provides a method for preparing amorphous gallium oxide nanosheets, comprising the following steps: mixing gallium acetylacetonate with KNO3 powder, calcining, and washing to obtain amorphous gallium oxide nanosheets. The amorphous gallium oxide nanosheets prepared by this method are nanosheets with a size of approximately several micrometers and a thickness of approximately 10-40 nm. These amorphous gallium oxide nanosheets are amorphous nanosheets with a low proportion of tetrahedral Ga centers, exhibiting advantages in broad-spectrum absorption and spin polarization. This invention assembles the above-mentioned amorphous gallium oxide nanosheets with conductive silicon wafers and graphene to form a photodetector with a vertical structure, forming a pair of back-to-back rectified junctions composed of a Schottky junction and a pn junction connected in series, resulting in a low dark current. The photodetector with a vertical structure based on this amorphous gallium oxide exhibits excellent UV-Vis-NIR broad-spectrum photodetector performance.

[0134] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing amorphous gallium oxide nanosheets, comprising the following steps: Gallium acetylacetonate was mixed with KNO3 powder, calcined, and washed to obtain amorphous gallium oxide nanosheets. The proportion of Ga in the tetrahedral center of the amorphous gallium oxide nanosheet is lower than that in crystalline β-Ga2O3; The amorphous gallium oxide nanosheets have a smaller band gap than crystalline β-Ga2O3 and exhibit increased gap states; The amorphous gallium oxide nanosheets have a broadened light absorption range of 254~1064 nm.

2. The preparation method according to claim 1, characterized in that, The mass ratio of gallium acetylacetonate to KNO3 is 1:(1.5~25).

3. The preparation method according to claim 1, characterized in that, The calcination temperature is 190~260 ℃; the calcination atmosphere is air; Heat to the required calcination temperature at a heating rate of 2~5 ℃ / min, and hold for 1~1.5 h.

4. An amorphous gallium oxide nanosheet, characterized in that, Prepared by the preparation method according to any one of claims 1 to 3; The amorphous gallium oxide nanosheets have a size of 1~2 μm and a thickness of 10~40 nm; The proportion of Ga in the tetrahedral center of the amorphous gallium oxide nanosheet is lower than that in crystalline β-Ga2O3; The amorphous gallium oxide nanosheets have a smaller band gap than crystalline β-Ga2O3 and exhibit increased gap states; The amorphous gallium oxide nanosheets have a broadened light absorption range of 254~1064 nm.

5. A UV-Vis-NIR broadband photodetector, comprising a bottom electrode; A photoresponsive layer disposed on the bottom electrode; Top electrode covering the photoresponse layer; The photoresponsive layer is an amorphous gallium oxide nanosheet prepared by the preparation method of any one of claims 1 to 3 or an amorphous gallium oxide nanosheet as described in claim 4.

6. The UV-Vis-NIR broadband photodetector according to claim 5, characterized in that, The bottom electrode is a P-type silicon wafer with a thickness of 200~500 μm and a wafer size of (0.4×0.4) cm~(2×2) cm; The top electrode is made of graphene with a thickness of 0.340~0.350 nm; The thickness of the photoresponse layer is 0.020~3 μm.

7. The UV-Vis-NIR broadband photodetector according to claim 5, characterized in that, The broadband photodetector has the ability to detect light in the UV-Vis-NIR 254~1064 nm range; It exhibits a dark current as low as 63 pA under forward bias. It has a fast response speed: τ 上升 <30 ms, τ 下降 <50 ms.

8. The UV-Vis-NIR broadband photodetector according to claim 5, characterized in that, Schottky junctions and pn junctions are formed at the interfaces between amorphous gallium oxide nanosheets and graphene and p-type silicon, respectively. The Schottky junction and pn junction are connected in series to form a back-to-back rectifier junction.

9. A method for fabricating a UV-Vis-NIR broadband photodetector according to any one of claims 5 to 8, comprising the following steps: An ethanol suspension of amorphous gallium oxide nanosheets with a concentration of 2-15 mg / mL was spin-coated onto the bottom electrode to form a photoresponsive layer. By covering the photoresponse layer with the top electrode, a broadband photodetector is obtained.

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