Ultraviolet photodetector and preparation method thereof

Abstract

The present invention provides an ultraviolet photodetector and a preparation method thereof. The ultraviolet photodetector comprises: a silicon carbide substrate; a graphene channel, which is composed of a graphene material epitaxially grown on the silicon carbide substrate, wherein the intensity ratio of the D peak to the G peak of the graphene material in the Raman spectrum is not greater than 0.25; two metal electrodes, which are arranged on the silicon carbide substrate and respectively overlapped on both sides of the graphene channel; there is a work function difference between the graphene channel and the silicon carbide substrate, and a built-in electric field is formed at the contact interface between the graphene channel and the silicon carbide substrate. When external ultraviolet light irradiates the silicon carbide substrate, electron-hole pairs are formed in the silicon carbide substrate. Under the action of the built-in electric field, holes are injected from the silicon carbide substrate into the graphene channel, and the holes move from the graphene channel to the metal electrodes to form a photocurrent. Under the irradiation of external ultraviolet light, the ultraviolet photodetector can achieve 10 3 A / W magnitude response.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor photodetectors, and more particularly to an ultraviolet photodetector and a preparation method thereof. Background Art

[0002] In modern society, highly responsive ultraviolet photodetectors are needed to solve problems in related technical fields, especially in the fields of ultraviolet sterilization, treatment, and environmental pollution detection, where the requirements for detection accuracy are becoming increasingly stringent.

[0003] Graphene, with its excellent conductivity, wide spectral response, and low noise equivalent power, has broad application prospects in the field of ultrafast, wide-spectral-response photodetection. However, graphene's light absorption ability is weak, and the device response of the fabricated device is low, so it is necessary to compound the material or optimize the device. For example, the construction of heterojunctions with wide-bandgap materials (such as silicon carbide and gallium nitride), the preparation of graphene electrodes, chemical doping, gate modulation, and the use of nanoparticle modification can be used. Among these methods, the wide-bandgap material silicon carbide has excellent ultraviolet light absorption properties and can significantly improve optical gain. The graphene / silicon carbide heterostructure combines the advantages of both, effectively improving photoelectric performance.

[0004] Currently, high-responsivity Gr / 4H-SiC UV photodetectors achieve a responsivity of 254.1 A / W under 325nm light excitation, a source-drain voltage of -3V, and a gate voltage of 3V. However, applying large bias voltages and gate voltages increases energy consumption, and the gate fabrication process increases complexity, hindering industrial production. Summary of the Invention

[0005] To solve at least one of the technical problems in the prior art, an embodiment of the present invention provides an ultraviolet photodetector and a method for preparing the same, which has good cycle stability and can improve the sensitive response and sensitivity to ultraviolet rays.

[0006] The present invention provides an ultraviolet photodetector, comprising: a silicon carbide substrate; a graphene channel composed of a graphene material epitaxially grown on the silicon carbide substrate, wherein the intensity ratio of the D peak to the G peak of the graphene material in the Raman spectrum is not greater than 0.25; and two metal electrodes, arranged on the silicon carbide substrate and respectively overlapping two sides of the graphene channel; wherein there is a work function difference between the graphene channel and the silicon carbide substrate, and a built-in electric field is formed at the contact interface between the graphene channel and the silicon carbide substrate.

[0007] Optionally, the width of the graphene channel is 6µm~80µm, and the length of the graphene channel is 100µm~1200µm.

[0008] Optionally, the ratio of the length of the graphene channel to the width of the graphene channel ranges from length:width=100:20 to 600:6.

[0009] Optionally, the graphene channel is a single layer or a multilayer.

[0010] According to an embodiment of another aspect of the present invention, a method for preparing the above-mentioned ultraviolet photodetector is also provided, including: epitaxially growing a graphene material on a silicon carbide substrate; forming a patterned metal electrode on the above-mentioned graphene material, wherein the above-mentioned metal electrode includes a first metal electrode and a second metal electrode spaced apart from each other; and patterning the above-mentioned graphene material to form a graphene channel between the above-mentioned first metal electrode and the above-mentioned second metal electrode, which is connected to the above-mentioned first metal electrode and the above-mentioned second metal electrode, thereby obtaining the above-mentioned ultraviolet photodetector.

[0011] Optionally, the epitaxial growth of the graphene material on the silicon carbide substrate includes: placing the silicon carbide substrate in an inert gas atmosphere and performing a pyrolysis treatment on the surface of the silicon carbide substrate to form the graphene material.

[0012] Optionally, the above-mentioned placing the above-mentioned silicon carbide substrate in an inert gas atmosphere and performing pyrolysis treatment on the surface of the above-mentioned silicon carbide substrate to form the above-mentioned graphene material includes: preheating the above-mentioned silicon carbide substrate and then performing annealing treatment; placing the annealed silicon carbide substrate in the above-mentioned inert gas atmosphere and heating it to a preset temperature, and growing it in the above-mentioned inert gas atmosphere to form the above-mentioned graphene material.

[0013] Optionally, the temperature range of the annealing treatment is 1100° C. to 1200° C., the temperature range of the above-mentioned preset temperature is 1540° C. to 1640° C., and the time range for forming the above-mentioned graphene material is 18 minutes to 33 minutes.

[0014] Optionally, the above-mentioned formation of a patterned metal electrode on the above-mentioned graphene material includes: coating a first photoresist on the above-mentioned graphene material; patterning the above-mentioned first photoresist to obtain a patterned first photoresist and a first target area on the above-mentioned graphene material that is not covered by the above-mentioned first photoresist; forming a metal layer on the above-mentioned patterned first photoresist and on the above-mentioned first target area; removing the above-mentioned patterned first photoresist on the above-mentioned graphene material and the metal layer on the above-mentioned patterned first photoresist to obtain the above-mentioned patterned metal electrode.

[0015] Optionally, the above-mentioned graphene material is patterned to form a graphene channel connected to the first metal electrode and the second metal electrode between the first metal electrode and the second metal electrode, thereby obtaining the above-mentioned ultraviolet photodetector, including: coating a second photoresist on the above-mentioned graphene material; patterning the above-mentioned second photoresist to obtain a patterned second photoresist; removing the graphene material not covered by the above-mentioned patterned second photoresist to form a graphene channel connected to the first metal electrode and the second metal electrode between the above-mentioned first metal electrode and the second metal electrode, thereby obtaining the above-mentioned ultraviolet photodetector.

[0016] According to an embodiment of the present invention, a UV photodetector and a method for preparing the same include a graphene channel formed of a graphene material epitaxially grown on a silicon carbide substrate, wherein the intensity ratio of the D peak to the G peak in the Raman spectrum of the graphene material is no greater than 0.25. Two metal electrodes are disposed on the silicon carbide substrate and overlap on either side of the graphene channel. There is a work function difference between the graphene channel and the silicon carbide substrate, and a built-in electric field is formed at the contact interface between the graphene channel and the silicon carbide substrate. When external UV light is irradiated on the silicon carbide substrate, the UV light excites the silicon carbide substrate to generate photogenerated carriers, forming electron-hole pairs in the silicon carbide substrate. Under the action of the built-in electric field, holes are injected from the silicon carbide substrate into the graphene channel, and the holes move from the graphene channel to the metal electrodes. At the same time, a potential barrier prevents the electron-hole pairs from recombination, thereby forming a photocurrent. The UV photodetector prepared in this way has good cyclic stability and can also improve the sensitive response and sensitivity to UV light. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a cross-sectional view of an ultraviolet photodetector according to an embodiment of the present invention;

[0018] Figure 2 is a Raman spectrum of a test graphene material according to an embodiment of the present invention;

[0019] Figure 3 is a Raman imaging test chart of the ratio of the D peak to the G peak intensity according to an embodiment of the present invention;

[0020] Figure 4 is a Raman imaging test chart of 2D peak half-maximum width according to an embodiment of the present invention;

[0021] Figure 5 This is an atomic force microscope test image of epitaxially grown graphene material on a silicon carbide substrate according to an embodiment of the present invention;

[0022] Figure 6 is a height topography image of a graphene material epitaxially grown on a silicon carbide substrate according to an embodiment of the present invention;

[0023] Figure 7 is a circuit diagram for preparing a Hall bar on a graphene material for testing mobility according to an embodiment of the present invention;

[0024] Figure 8 is a graph showing the potential difference and current at two locations on a graphene material according to an embodiment of the present invention;

[0025] Figure 9 is a graph showing resistance and magnetic field strength at two locations on a graphene material according to an embodiment of the present invention;

[0026] Figure 10 is a photoelectric performance test diagram of ultraviolet photodetectors with different graphene channel widths according to an embodiment of the present invention;

[0027] Figure 11 is a photoelectric performance test diagram of ultraviolet photodetectors with different graphene channel lengths according to an embodiment of the present invention;

[0028] Figure 12 is a scanning electron microscope image of an ultraviolet photodetector according to an embodiment of the present invention;

[0029] Figure 13 is a graph showing the aspect ratio of a graphene channel and the responsivity of an ultraviolet photodetector according to an embodiment of the present invention;

[0030] Figure 14 is a test result of an ultraviolet photodetector when the graphene channel is a single layer or a multilayer according to an embodiment of the present invention;

[0031] Figure 15 is a photoelectric performance test diagram of an ultraviolet photodetector under different bias voltages according to an embodiment of the present invention;

[0032] Figure 16 is a test diagram of the photoelectric performance of the ultraviolet photodetector under different ultraviolet light irradiation powers according to an embodiment of the present invention;

[0033] Figure 17 1 is a test diagram of the photoelectric performance of the ultraviolet photodetector under irradiation of irradiation light of different wavelengths according to an embodiment of the present invention;

[0034] Figure 18 is a response time test diagram of an ultraviolet photodetector according to an embodiment of the present invention;

[0035] Figure 19 is a stability test diagram of an ultraviolet photodetector according to an embodiment of the present invention;

[0036] Figure 20 is a repeatability test diagram of an ultraviolet photodetector according to an embodiment of the present invention;

[0037] Figure 21 is a flow chart of a method for preparing an ultraviolet photodetector according to an embodiment of the present invention;

[0038] Figure 22 is a schematic diagram of a manufacturing process of an ultraviolet photodetector according to an embodiment of the present invention;

[0039] Figure 23 is a flow chart of epitaxially growing a graphene material on a silicon carbide substrate according to an embodiment of the present invention;

[0040] Figure 24 is a flow chart of forming a patterned metal electrode on a graphene material according to an embodiment of the present invention;

[0041] Figure 25 The present invention is a flowchart of performing a patterning process on a graphene material to form a graphene channel between a first metal electrode and a second metal electrode according to an embodiment of the present invention.

[0042] In the drawings, the meanings of the reference numerals are as follows:

[0043] 1. Silicon carbide substrate;

[0044] 2. Graphene channel;

[0045] 3. Metal electrode. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0047] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the presence of the features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0048] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0049] When expressions such as “at least one of A, B, and C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, and C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.). When expressions such as “at least one of A, B, or C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, or C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.).

[0050] Existing ultraviolet photodetectors have the problem of low responsiveness. On the one hand, carrier mobility determines the transmission speed and efficiency of photogenerated carriers in the material. If the carrier mobility is low, the photogenerated carriers are easily scattered and recombined with impurities, lattice defects, etc. during the transmission process, resulting in a reduction in the number of carriers that can reach the electrode to form a photocurrent, thereby reducing the responsiveness. At the same time, a larger bias voltage may also be required to drive the movement of carriers, but applying a larger bias voltage will increase energy consumption. On the other hand, defects, dangling bonds, etc. on the surface and interface of the material will form surface states and interface states. These states will capture photogenerated carriers and cause them to recombine before reaching the electrode, reducing the effective photocurrent and thus reducing the responsiveness. Moreover, in order to overcome the obstacles of surface states and interface states to carrier transmission, it is often necessary to apply a larger bias voltage, which will also lead to increased energy consumption. At present, the high-responsivity Gr / 4H-SiC UV photodetector has a responsivity of 254.1A / W under 325nm light excitation, -3V source-drain voltage and 3V gate voltage. The existing graphene / silicon carbide UV photodetector has a maximum responsivity of 1298.38 cm due to the low mobility of graphene material. 2 / (V·s), the response is 10 2 A / W level, while applying a larger bias voltage and gate voltage increases energy consumption, and preparing the gate increases the process complexity, which is not conducive to industrial production.

[0051] In order to solve the problem of low responsiveness of ultraviolet photodetectors, according to an inventive concept of one aspect of the present invention, a graphene material is epitaxially grown on a silicon carbide substrate, and a graphene channel is formed by patterning the graphene material. The intensity ratio of the D peak to the G peak of the graphene material epitaxially grown on the silicon carbide substrate in the Raman spectrum is not greater than 0.25. Two metal electrodes are provided on the silicon carbide substrate and are respectively overlapped on both sides of the graphene channel. There is a work function difference between the graphene channel and the silicon carbide substrate. A built-in electric field is formed at the contact interface of the silicon carbide substrate. When external ultraviolet light is irradiated to the silicon carbide substrate, the ultraviolet light excites the silicon carbide substrate to generate photogenerated carriers, and electron-hole pairs are formed in the silicon carbide substrate. Under the action of the built-in electric field, holes are injected from the silicon carbide substrate into the graphene channel, and the holes move from the graphene channel to the metal electrode. At the same time, the potential barrier prevents the electron-hole pairs from recombining to form a photocurrent. The ultraviolet photodetector has good cycle stability and can improve the sensitive response and sensitivity to ultraviolet rays.

[0052] Figure 1 is a cross-sectional view of an ultraviolet photodetector according to an embodiment of the present invention.

[0053] According to an embodiment of the present invention, a UV photodetector is provided, such as Figure 1 As shown, the ultraviolet photodetector includes a silicon carbide substrate 1, a graphene channel 2, and two metal electrodes 3. The graphene channel 2 is formed by patterning graphene material epitaxially grown on the silicon carbide substrate 1. The intensity ratio of the D peak to the G peak of the graphene material epitaxially grown on the silicon carbide substrate 1 in the Raman spectrum is not greater than 0.25. The two metal electrodes 3 are arranged on the silicon carbide substrate 1 and overlap on both sides of the graphene channel 2. There is a work function difference between the graphene channel 2 and the silicon carbide substrate 1, and a built-in electric field is formed at the contact interface between the graphene channel 2 and the silicon carbide substrate 1. When external ultraviolet light is irradiated to the silicon carbide substrate 1, electron-hole pairs are formed in the silicon carbide substrate 1. Under the action of the built-in electric field, holes are injected from the silicon carbide substrate 1 into the graphene channel 2, and the holes move from the graphene channel 2 to the metal electrodes 3 to form a photocurrent.

[0054] According to an embodiment of the present invention, a silicon carbide substrate 1, a graphene channel 2, and two metal electrodes 3 serve as the detector core of a UV photodetector. The silicon carbide substrate 1 serves as the absorption layer of the UV photodetector, and the graphene channel 2 serves as the transmission layer of the UV photodetector. The two metal electrodes 3 are attached to the silicon carbide substrate 1 and are in lateral contact with the graphene channel 2. When exposed to external UV light, the conductivity of the graphene channel 2 changes, thereby generating a change in the current signal. There is a work function difference between the graphene channel 2 and the silicon carbide substrate 1, and a built-in electric field forms at the interface between the graphene channel 2 and the silicon carbide substrate 1. When external ultraviolet light irradiates the silicon carbide substrate 1, the ultraviolet light excites the silicon carbide substrate 1 to generate photogenerated carriers, forming electron-hole pairs in the silicon carbide substrate 1. Under the action of the built-in electric field, holes are injected from the silicon carbide substrate 1 into the graphene channel 2, increasing the photogenerated current. The holes move from the graphene channel 2 to the metal electrode 3, and the potential barrier prevents the electron-hole pairs from recombination, forming a photocurrent. The two metal electrodes 3 are connected to an external signal acquisition device. The two metal electrodes 3 extract the signal from the graphene channel 2 and, by collecting changes in the current signal, output changes in the electrical signal to represent the sensitive response to ultraviolet light, thus achieving ultraviolet light detection.

[0055] Figure 2 is a Raman spectrum of a graphene material tested according to an embodiment of the present invention. Figure 3 is a Raman imaging test chart of the ratio of the D peak to the G peak intensity according to an embodiment of the present invention. Figure 4 This is a Raman imaging test chart of 2D peak half-maximum width according to an embodiment of the present invention. Figure 5 This is an atomic force microscope test image of epitaxially grown graphene material on a silicon carbide substrate according to an embodiment of the present invention. Figure 6 1 is a height topography diagram of epitaxially grown graphene material on a silicon carbide substrate 1 according to an embodiment of the present invention.

[0056] According to an embodiment of the present invention, Figure 2 As shown in the figure, the intensity ratio of the D peak to the G peak in the Raman spectrum indicates the degree of defects in the grown graphene material. The intensity ratio of the D peak to the G peak in the Raman spectrum of the graphene material epitaxially grown on the silicon carbide substrate 1 is in the range of 0.15 to 0.25. When the graphene channel 2 is a single layer, the half-maximum width (2D-FWHM) of the 2D peak in the Raman spectrum is in the range of 30 cm -1 ~40cm -1 In the case of multi-layer graphene channels 2, the full width at half maximum (2D-FWHM) of the 2D peak in the Raman spectrum is greater than 40 cm -1 .like Figure 3As shown, it is a Raman imaging test pattern about the ratio of the peak intensity of the D peak to the peak intensity of the G peak. The test size of the Raman imaging test pattern is 30μm×30μm, the step length is 3μm, and the ratio of the peak intensity of the D peak to the peak intensity of the G peak (I D / I G ) is between 0.15 and 0.25. Figure 4 As shown, it is a Raman imaging test diagram of the 2D peak half-height width. The range of the 2D peak half-height width is 30cm -1 ~40cm -1 Between. Figure 5 As shown, it is an atomic force microscope test image of epitaxial growth of graphene material on silicon carbide substrate 1, as shown in FIG. Figure 6 As shown, it is expressed as Figure 5 Height topography of epitaxially grown graphene material on silicon carbide substrate 1 at the same position.

[0057] Figure 7 is a circuit diagram for preparing a Hall bar on a graphene material for testing mobility according to an embodiment of the present invention. Figure 8 is a graph showing the potential difference and current at two locations on a graphene material according to an embodiment of the present invention. Figure 9 3 is a graph showing resistance and magnetic field strength at two locations on a graphene material according to an embodiment of the present invention.

[0058] According to an embodiment of the present invention, Figure 7 As shown in the figure, a mobility test is performed on a graphene material with a length L of 26µm and a width W of 24µm. The test environment is normal temperature and pressure, and the constant current I is 1µA. A Hall bar is prepared on the graphene material to test its mobility. Figure 7 Positions 1, 2, 3, 4, and 5 are the positions of the Hall bars. Current flows into position 4 and out of position 5. The potential difference between position 1 and position 2 is expressed as V xx , the potential difference between position 1 and position 3 is expressed as V xy , the graphene material prepared with the Hall bar is placed in magnetic fields of different intensities for measurement. Figure 8 As shown, it is expressed as the potential difference V between position 1 and position 2 xx The slope of the graph is the graph of the current I and the graphene resistance R xx , calculate the graphene resistance R according to the following formula (1) xx , graphene resistance R xx 4074Ω:

[0059] (1).

[0060] According to an embodiment of the present invention, the resistivity of graphene is calculated according to the following formula (2): , graphene resistivity is 3760.62Ω·cm:

[0061] (2).

[0062] According to an embodiment of the present invention, the test is performed at normal temperature and pressure, the constant current I is 1µA, and the resistance R between position 1 and position 3 is calculated according to the following formula (3): xy :

[0063] (3).

[0064] According to an embodiment of the present invention, Figure 9 As shown, it is represented by the resistance R between position 1 and position 3 xy The slope of the curve is the Hall coefficient R. H , calculate the Hall coefficient R according to the following formula (4) H , Hall coefficient R H 1135.91m 2 / C:

[0065] (4).

[0066] According to an embodiment of the present invention, Figure 8 and Figure 9 As shown in the figure, the graphene material obtained by epitaxial growth has high uniformity, few defects and high coverage of single-layer graphene. The carrier mobility is calculated according to the following formula (5): , its carrier mobility Can reach 3020.54 cm 2 / (V·s):

[0067] (5).

[0068] According to an embodiment of the present invention, a graphene material is epitaxially grown on a silicon carbide substrate 1, and a graphene channel 2 is patterned from the graphene material. Two metal electrodes 3 are arranged on the silicon carbide substrate 1 and are respectively overlapped on both sides of the graphene channel 2. There is a work function difference between the graphene channel 2 and the silicon carbide substrate 1. A built-in electric field is formed at the contact interface between the graphene channel 2 and the silicon carbide substrate 1. When external ultraviolet light is irradiated to the silicon carbide substrate 1, the ultraviolet light excites the silicon carbide substrate 1 to generate photogenerated carriers, and electron-hole pairs are formed in the silicon carbide substrate 1. Under the action of the built-in electric field, holes are injected from the silicon carbide substrate 1 into the graphene channel 2, and the holes move from the graphene channel 2 to the metal electrode 3. At the same time, the potential barrier prevents the electron-hole pairs from recombining to form a photocurrent. The ultraviolet photodetector has good cycle stability and can improve the sensitive response and sensitivity to ultraviolet rays.

[0069] According to an embodiment of the present invention, the width of the graphene channel 2 is 6µm to 80µm, and the length of the graphene channel 2 is 100µm to 1200µm.

[0070] Figure 10 1 is a photoelectric performance test diagram of an ultraviolet photodetector with different widths of the graphene channel 2 according to an embodiment of the present invention.

[0071] According to an embodiment of the present invention, the width and length of the graphene channel 2 are adjusted and photoelectric tests are performed respectively. The performance tests are performed on ultraviolet photodetectors with a length of 600 μm and widths of 6 μm, 10 μm, 20 μm, 40 μm, 60 μm, and 80 μm, respectively. The test results are as follows: Figure 10 shown. Figure 10 Figure (a) shows the curve of response R and width. Figure 10 Figure (b) shows the curve of external quantum efficiency EQE and width. Figure 10 Figure (c) in the figure shows a graph of normalized detection D* and width. Figure 10 Figure (d) in the figure plots the noise equivalent power (NEP) versus width. As the width increases from 6µm to 20µm, the responsivity (R) and external quantum efficiency (EQE) increase significantly. As the width increases from 20µm to 80µm, the responsivity (R) and external quantum efficiency (EQE) decrease gradually. As the width increases from 6µm to 10µm, the normalized detectivity (D*) increases significantly, while the noise equivalent power (NEP) decreases significantly. As the width increases from 10µm to 40µm, the normalized detectivity (D*) decreases gradually, while the noise equivalent power (NEP) increases gradually. As the width increases from 40µm to 80µm, the normalized detectivity (D*) decreases rapidly, while the noise equivalent power (NEP) increases rapidly. Taking into account the responsivity R, external quantum efficiency EQE, normalized detectivity D* and noise equivalent power NEP, the photoelectric performance of the UV photodetector is optimal when the width of the graphene channel 2 is 20µm, with a responsivity R of 533 A / W and an external quantum efficiency EQE of 2.40×10 5 %, and the normalized detection D* is 1.60×10 12 Jones, the noise equivalent power NEP is 3.74×10 -15 .

[0072] According to embodiments of the present invention, as the width of the graphene channel 2 increases, the effective area for UV light absorption increases, generating more photogenerated carriers, increasing photocurrent and improving photoelectric performance. When the width of the graphene channel 2 exceeds a certain value (for example, 20µm), carriers become excessively dispersed, and the efficiency of collecting photogenerated carriers decreases, leading to a decrease in photocurrent, responsivity R, and external quantum efficiency (EQE). Furthermore, when the width of the graphene channel 2 exceeds 40µm, the resistance of the UV photodetector decreases, while the dark current increases, resulting in a significant decrease in the normalized detectivity (D*) and a significant increase in the noise equivalent power (NEP).

[0073] Figure 11 1 is a photoelectric performance test diagram of an ultraviolet photodetector with different lengths of the graphene channel 2 according to an embodiment of the present invention.

[0074] According to an embodiment of the present invention, a performance test was conducted on ultraviolet photodetectors with a graphene channel 2 width of 20 μm and a graphene channel 2 length of 100 μm, 150 μm, 200 μm, 400 μm, 600 μm, and 1200 μm, respectively. The test results are as follows: Figure 11 shown. Figure 11 Figure (a) shows the curve of response R and length. Figure 11 Figure (b) shows the curve of external quantum efficiency EQE and length. Figure 11 Figure (c) in the figure shows the normalized detection degree D* and length curve, Figure 11 Figure (d) in the figure shows a curve of noise equivalent power NEP and length. As the length increases from 100µm to 200µm, the responsivity R, external quantum efficiency EQE and normalized detection D* gradually increase, and the noise equivalent power NEP gradually decreases. As the length increases from 200µm to 1200µm, the responsivity R, external quantum efficiency EQE and normalized detection D* decrease significantly, and the noise equivalent power NEP increases significantly. Taking into account the responsivity R, external quantum efficiency EQE, normalized detection D* and noise equivalent power NEP, when the length of graphene channel 2 is 200µm, the photoelectric performance of the ultraviolet photodetector is optimal, with a responsivity R of 3900 A / W and an external quantum efficiency EQE of 1.76×10 6 %, and the normalized detection D* is 8.31×10 12 Jones, the noise equivalent power NEP is 7.22×10 -16 .

[0075] According to embodiments of the present invention, as the length of the graphene channel 2 decreases, the carrier transit time decreases, the probability of recombination and scattering of photogenerated carriers decreases, carrier generation exceeds recombination, photocurrent increases, and the photoelectric performance of the UV photodetector improves. When the length of the graphene channel 2 is less than a certain value (for example, 200 µm), carriers become too concentrated. As the length decreases, the probability of recombination of photogenerated carriers increases, carrier generation becomes less than recombination, photocurrent decreases, and the photoelectric performance of the UV photodetector degrades.

[0076] Figure 12 is a scanning electron microscope image of an ultraviolet photodetector according to an embodiment of the present invention.

[0077] According to an embodiment of the present invention, Figure 12 As shown in the figure, a high-performance UV photodetector with a graphene channel 2 of 200µm in length and 20µm in width was fabricated using a single-layer graphene material with few defects and good uniformity. Comprehensive performance testing and analysis were then conducted. When the length of the graphene channel 2 was 200µm and the width of the graphene channel 2 was 20µm, the photoelectric performance of the UV photodetector reached its optimum, with a responsivity R of 5375A / W and an external quantum efficiency EQE of 2.4×10 6 %, and the normalized detection D* is 1.11×10 13 Jones, the noise equivalent power NEP is 5.68×10 -16 .

[0078] According to an embodiment of the present invention, the responsivity of a fabricated UV photodetector is enhanced by improving the quality of epitaxial growth of graphene materials and optimizing the size of the graphene channel 2, rather than modification. Using a single-layer graphene material with few defects and good uniformity, a high-performance UV photodetector with a graphene channel 2 measuring 200µm x 20µm was fabricated.

[0079] Figure 13 3 is a graph showing the aspect ratio of the graphene channel 2 and the responsivity of the ultraviolet photodetector according to an embodiment of the present invention.

[0080] According to an embodiment of the present invention, Figure 13 As shown, the ratio of the length of the graphene channel 2 to the width of the graphene channel 2 ranges from length:width=100:20 to 600:6.

[0081] According to an embodiment of the present invention, the ratio of the length of the graphene channel 2 to the width of the graphene channel 2 is preferably 200:20. When the aspect ratio of the graphene channel 2 decreases, the width of the graphene channel 2 increases relatively. Under the condition of ultraviolet light irradiation, the photogenerated carriers generated by photon excitation are more easily transmitted and collected in the wider graphene channel 2, thereby increasing the number of photogenerated carriers reaching the metal electrode 3, thereby improving the responsivity of the ultraviolet photodetector. However, if the length of the graphene channel 2 is excessively reduced, the recombination probability of the carriers in the graphene channel 2 will increase. In the process from generation to collection, the carriers are more likely to meet and recombine in the shorter graphene channel 2, resulting in a reduction in the number of carriers that can reach the metal electrode 3 to form a photocurrent, thereby reducing the responsivity of the ultraviolet photodetector.

[0082] According to an embodiment of the present invention, the graphene channel 2 is a single layer or multiple layers.

[0083] Figure 14 This is a test result of an ultraviolet photodetector when the graphene channel 2 is a single layer or a multilayer according to an embodiment of the present invention.

[0084] According to an embodiment of the present invention, the growth quality of the graphene material is closely related to the photoelectric performance of the ultraviolet photodetector. Figure 14 As shown in the figure, under UV irradiation of the same wavelength and a bias voltage of 1.0V, the responsivity of the multilayer graphene (MLG) channel is 2250A / W, while the responsivity of the single-layer graphene (SLG) channel reaches 5025A / W. The UV photodetector fabricated using the single-layer graphene (SLG) channel has a higher responsivity than the multilayer graphene (MLG) channel. The interaction between graphene layers and the large number of defects lead to increased electron scattering, resulting in a lower electron scattering probability in the single-layer graphene channel compared to the multilayer graphene channel. The generated photogenerated carriers can effectively participate in current generation, improving the responsivity of the fabricated UV photodetector.

[0085] According to an embodiment of the present invention, the thickness of the two metal electrodes 3 is 40 nm.

[0086] According to the embodiment of the present invention, the length of the two metal electrodes 3 is 100 μm, and the width of the two metal electrodes 3 is 100 μm.

[0087] Figure 15 1 is a photoelectric performance test diagram of an ultraviolet photodetector under different bias voltages according to an embodiment of the present invention.

[0088] According to the embodiments of the present invention, adjusting the bias voltage can effectively improve the photoelectric performance of the ultraviolet photodetector, such as Figure 15 As shown, Figure 15Figure (a) shows the curve of response R and bias voltage. Figure 15 Figure (b) shows the curve of external quantum efficiency EQE and bias voltage. Figure 15 Figure (c) shows the normalized detection D* versus bias voltage. Figure 15 Figure (d) in the figure shows a curve diagram of noise equivalent power NEP and bias voltage. Figure 15 Figure (a) in Figure 15 Figure (b) in Figure 15 Figure (c) and Figure 15 As shown in Figure (d), the test results show that the responsivity R, external quantum efficiency EQE and normalized detectivity D* increase with the increase of bias voltage, while the noise equivalent power NEP decreases with the increase of bias voltage. -5 When V increases to 1.0 V, the responsivity R increases from 0.08 A / W to 5375 A / W, and the external quantum efficiency EQE increases from 36.07% to 2.4×10 6 %, the normalized detection D* increased from 2.49×10 10 Jones rose to 1.11×10 13 Jones, the noise equivalent power NEP is from 2.54×10 -13 Down to 5.68×10 -16 As the applied bias voltage increases, the electric field between the electrodes is enhanced, the carrier migration speed is improved, and the photoelectric performance of the UV photodetector is optimized.

[0089] According to an embodiment of the present invention, Figure 15 Figure (e) shows the relationship between the bias voltage and the average responsivity of the UV photodetector. Figure 15 Figure (f) shows the relationship between the current and the average responsivity of the UV photodetector. Figure 15 Figure (e) and Figure 15 The lightning position in Figure (f) is shown as a circuit breaker. Figure 15 Figure (e) and Figure 15 As shown in Figure (f), when a bias voltage of 1.1V is applied, a current of 56.4μA flows. At this current, the UV photodetector is prone to short circuiting. At a bias voltage of 1.1V, the UV photodetector experienced short circuiting after 52 tests. At a bias voltage of 1.0V, no short circuiting occurred after 500 tests. To ensure the usability of the UV photodetector, the maximum bias voltage applied during testing was 1.0V.

[0090] Figure 16This is a test diagram of the photoelectric performance of an ultraviolet photodetector under different ultraviolet light irradiation powers according to an embodiment of the present invention.

[0091] According to the embodiment of the present invention, different irradiation powers of ultraviolet light also have an impact on the performance of the ultraviolet photodetector. Figure 16 As shown, Figure 16 Figure (a) shows the curve of responsivity R and irradiation power P. Figure 16 Figure (b) shows the curve of external quantum efficiency EQE and irradiation power P. Figure 16 Figure (c) shows the curve of normalized detection D* and irradiation power P. Figure 16 Figure (d) in the figure shows a curve diagram of noise equivalent power NEP and irradiation power P. Figure 16 Figure (a) in Figure 16 Figure (b) in Figure 16 Figure (c) and Figure 16 As shown in Figure (d), the test results show that the responsivity R, external quantum efficiency EQE and normalized detectivity D* first increase and then decrease with the increase of ultraviolet light irradiation power P, and the noise equivalent power NEP first decreases and then increases with the increase of irradiation power P. When the irradiation power P is 0.002μW, the responsivity R is 4400A / W, the external quantum efficiency EQE is 2.0×10 6 %, and the normalized detection D* is 6.45×10 12 Jones, the noise equivalent power NEP is 6.94×10 -16 As the irradiation power P increases, the responsivity R, external quantum efficiency EQE and normalized detectivity D* increase, while the noise equivalent power NEP decreases. When the irradiation power P is 0.004μW, the photoelectric performance of the UV photodetector is optimal. The responsivity R reaches 5375A / W, and the external quantum efficiency EQE reaches 2.4×10 6 %, and the normalized detection D* reached 1.11×10 13 Jones, the noise equivalent power NEP is 5.68×10 -16 When the irradiation power P increases from 0.004μW to 0.2μW, the photoelectric performance of the UV photodetector decreases rapidly. The responsivity R decreases from 5375A / W to 209A / W, and the external quantum efficiency EQE decreases from 2.4×10 6 % dropped to 9.4×10 4 %, the normalized detection D* increased from 1.11×10 13 Jones first rose to a maximum of 1.30×10 13 Jones dropped to 3.06×10 12Jones (although the normalized detectivity D* is the largest under the irradiation power P of 0.008μW, the other photoelectric properties are lower than those under the irradiation power P of 0.004μW. Therefore, the photoelectric performance of the UV photodetector is the best under the irradiation power P of 0.004μW). The noise equivalent power NEP increases from 5.68×10 -16 Increased to 1.46×10 -14 (The above-mentioned irradiation power P is the product of the incident light power density and the effective light absorption area of the ultraviolet photodetector).

[0092] According to an embodiment of the present invention, within a specific range of irradiation power P (irradiation power P less than 0.004 μW), the operating state of the ultraviolet photodetector is in the linear enhancement region. At this time, an increase in irradiation power P can effectively excite more carriers to participate in conduction, thereby improving the responsivity of the ultraviolet photodetector. Due to physical limitations, at higher irradiation power P (irradiation power P greater than 0.004 μW), the output signal of the ultraviolet photodetector may saturate, and the current has a nonlinear relationship with the input optical power until it gradually approaches the saturation value. In addition, as the irradiation power P increases (irradiation power P greater than 0.01 μW), the self-heating phenomenon associated with high optical power causes a sharp increase in the probability of carrier recombination and scattering. The carrier recombination and scattering are greater than the generation, and the generated photocurrent decreases, resulting in a decrease in the performance of the ultraviolet photodetector.

[0093] Figure 17 This is a test diagram of the photoelectric performance of an ultraviolet photodetector under irradiation of irradiation light of different wavelengths according to an embodiment of the present invention.

[0094] According to an embodiment of the present invention, Figure 17 As shown, Figure 17 Figure (a) shows the curve of responsivity R and irradiation wavelength. Figure 17 Figure (b) shows the curve of external quantum efficiency EQE and irradiation wavelength. Figure 17 Figure (c) shows the normalized detection D* versus the wavelength of the irradiated light. Figure 17 Figure (d) shows the curve of noise equivalent power NEP and irradiation light wavelength. Figure 17 Figure (a) in Figure 17 Figure (b) in Figure 17 Figure (c) and Figure 17As shown in Figure (d), when the wavelength of the irradiated light is 240nm, the responsivity R of the ultraviolet photodetector is 4766.7A / W. As the wavelength increases, the responsivity R slowly increases. When the wavelength of the irradiated light is 320nm, the responsivity R of the ultraviolet photodetector reaches a maximum value of 5349.5A / W. In the ultraviolet light band within the range of 320nm~400nm, the responsivity R of the ultraviolet photodetector shows a downward trend, but the responsivity value remains above 4395.3A / W. In other spectral ranges, the responsivity R drops rapidly. The external quantum efficiency EQE shows a downward trend with the increase of the wavelength of the irradiated light. There is a peak when the wavelength of the irradiated light is 320nm, and the external quantum efficiency EQE is 2.1×10 6 %. The normalized detection D* first increases and then decreases with the increase of the wavelength of the irradiated light. When the wavelength of the irradiated light is 320nm, the normalized detection D* reaches a maximum value of 1.2×10 13 Jones. The noise equivalent power (NEP) first decreases and then increases with the increase of the wavelength of the irradiated light. When the wavelength of the irradiated light is 320nm, the noise equivalent power (NEP) reaches a minimum value of 5.2×10 -16 .

[0095] Figure 18 This is a response time test diagram of an ultraviolet photodetector according to an embodiment of the present invention.

[0096] According to an embodiment of the present invention, the response time is divided into rise time and relaxation time (i.e., fall time). The rise time refers to the time required for the photocurrent signal to rise from 0 to 63.2% of the peak value (i.e., 1-1 / e), and the relaxation time refers to the time required for the photocurrent signal to fall from the peak value to 36.8% of the peak value (i.e., 1 / e). Figure 18 As shown in Figure (a), as the external UV light is turned on, the photocurrent reaches a peak of 262.4nA. When the external UV light is turned off, the photocurrent drops to zero. At a bias voltage of 0.01V, the UV photodetector exhibits a rise time of 0.98s and a relaxation time of 2.51s. The transient photocurrent response waveform is basically the same after 19 consecutive cycles of on / off irradiation from the UV light source, as shown in Figure 1. Figure 18 As shown in Figure (b), the UV photodetector has good repeatability.

[0097] Figure 19 This is a stability test diagram of an ultraviolet photodetector according to an embodiment of the present invention.

[0098] According to an embodiment of the present invention, the curves of the responsivity of the UV photodetector after the first test and after storage in air for 30 days and 90 days as a function of bias voltage are compared. Figure 19 As shown, the data are basically consistent, all maintained at 4×103 A / W or above, indicating that the ultraviolet photodetector has quite stable photoelectric performance.

[0099] Figure 20 This is a repeatability test diagram of an ultraviolet photodetector according to an embodiment of the present invention.

[0100] According to an embodiment of the present invention, Figure 20 As shown in the figure, 18 UV photodetector arrays of the same size were prepared to test the reliability of the device's photoelectric performance, and the performance tests were carried out under the same conditions. Figure 20 Figure (a) shows the responsivity R of all UV photodetectors. Figure 20 Figure (b) shows the external quantum efficiency EQE of all UV photodetectors, Figure 20 Figure (c) shows the normalized detectivity D* of all UV photodetectors. Figure 20 Figure (d) shows the noise equivalent power NEP of all UV photodetectors. Under 0.004μW UV irradiation and 1.0V bias voltage, all UV photodetectors show 2×10 1 μA-level photocurrent, 5×10 3 A / W level responsivity R, 2×10 4 Optical gain of the order of 2×10 6 % level external quantum efficiency EQE, 1×10 13 The normalized detectivity D* of Jones magnitude and 6×10 -16 The performance of all UV photodetectors is maintained at the same level, and the test results have a high degree of credibility.

[0101] According to the embodiment of the present invention, the number of epitaxially grown graphene material layers is controllable, the quality is high, and the area is large. The mobility of a single-layer graphene material reaches 3020.54 cm 2 / (V·s), the prepared UV photodetector exhibits excellent performance, mainly due to the following four reasons: 1. The two-dimensional structure of the UV photodetector facilitates the rapid separation and transport of carriers. The probability of electron scattering in a single-layer graphene channel is lower than that in a multilayer graphene channel (interactions between layers and the possible presence of more defects will lead to increased electron scattering), allowing the generated photogenerated carriers to effectively participate in the generation of current, thereby improving the photoelectric conversion efficiency. 2. Graphene's excellent carrier mobility allows photogenerated holes to quickly move in the graphene channel 2 to the metal electrode 3 for collection, significantly enhancing the photogenerated current flowing through the external circuit. 3. The epitaxial growth of graphene material on the silicon carbide substrate 1 has good contact and few defects, further ensuring high performance and stability. 4. The high transparency and excellent conductivity of the graphene material enable it to conduct electrons quickly and efficiently without significantly hindering light transmission.

[0102] According to an embodiment of the present invention, the reasonable design of the size of the ultraviolet photodetector improves the efficiency of collecting photogenerated carriers and reduces the probability of carrier recombination before reaching the metal electrode 3. As the width of the graphene channel 2 increases, the path for photogenerated carriers to reach the metal electrode 3 through the graphene channel 2 becomes relatively wider, and the transmission of photogenerated carriers is less likely to be congested or accumulated, and the obstruction is relatively less. The resistance of the ultraviolet photodetector decreases, which is beneficial to the transmission of photogenerated carriers and improves the conductivity. The increase in effective light area is accompanied by an increase in the concentration of photogenerated carriers, which optimizes the photoelectric performance. However, when the width of the graphene channel 2 is greater than a certain value, it will lead to a decrease in some photoelectric performance, mainly for the following five reasons: 1. Carriers are excessively dispersed, and the efficiency of collecting photogenerated carriers decreases. 2. Edge effects are generated, which is not conducive to the transmission and collection of photogenerated carriers. 3. The parasitic capacitance becomes larger, which is not conducive to the transmission and processing of photogenerated carrier signals. 4. It generates a space charge effect, accumulates charges in local locations, changes the electric field distribution, affects the movement of photogenerated carriers, and may bring negative effects and reduce photoelectric performance. 5. The resistance of the ultraviolet photodetector decreases, the dark current increases sharply, and some photoelectric performance decreases. As the length of the graphene channel 2 decreases, the photogenerated carriers are transmitted to the metal electrode 3 more quickly, reducing the loss caused by recombination and improving the responsivity and response time. However, when the length of the graphene channel 2 is less than a certain value, the photoelectric performance will decrease. There are four main reasons: 1. Carriers are too concentrated in a short distance, increasing the probability of recombination. 2. Quantum confinement effect occurs, which restricts the movement of carriers in these directions and makes the fluctuation more significant. 3. It increases process requirements, making it easy to have problems such as non-uniformity and defects, reducing the stability and accuracy of the ultraviolet photodetector. 4. Abnormal changes in resistance occur, which is not conducive to the transmission and collection of photogenerated carriers.

[0103] Figure 21is a flow chart of a method for preparing an ultraviolet photodetector according to an embodiment of the present invention, Figure 22 Schematic diagram of the manufacturing process of an ultraviolet photodetector according to an embodiment of the present invention.

[0104] According to another embodiment of the present invention, Figure 21 and Figure 22 As shown, a method for preparing the above-mentioned ultraviolet photodetector is provided, including the following steps S1 to S3.

[0105] Step S1: epitaxially growing graphene material on a silicon carbide substrate 1 .

[0106] Figure 23 FIG. 4 is a flow chart of epitaxially growing a graphene material on a silicon carbide substrate 1 according to an embodiment of the present invention.

[0107] According to an embodiment of the present invention, Figure 23 As shown, before step S1, the semi-insulating 4H-SiC single crystal substrate is cut into 3.5×4.5 mm pieces using an STX-202A diamond wire saw. 2 The size (such as Figure 23 Ⅰ process), ultrasonic treatment in acetone, isopropanol and deionized water for 30 min respectively (such as Figure 23 Ⅱ process in the process) to remove organic impurities on the surface of the silicon carbide substrate 1 to obtain a pretreated silicon carbide substrate 1, and finally put the pretreated silicon carbide substrate 1 into a graphite crucible (such as Figure 23 III process in the process).

[0108] Step S2: forming a patterned metal electrode 3 on the graphene material, wherein the metal electrode 3 includes a first metal electrode and a second metal electrode spaced apart from each other.

[0109] Step S3: performing a patterning process on the graphene material to form a graphene channel 2 between the first metal electrode and the second metal electrode, which is connected to the first metal electrode and the second metal electrode, thereby obtaining an ultraviolet photodetector.

[0110] According to an embodiment of the present invention, the UV photodetector prepared using the above method has a simple metal-graphene-metal planar structure, with the graphene channel 2 serving as the UV photodetector's transmission layer and the silicon carbide substrate 1 serving as the UV photodetector's absorption layer. This UV photodetector's fabrication process eliminates the need for substrate transfer and subsequent modification, simplifying the fabrication process and achieving high responsivity to weak UV light. The UV photodetector maintains a simple and efficient structure, is compatible with semiconductor processes, and is highly practical.

[0111] According to an embodiment of the present invention, epitaxially growing a graphene material on a silicon carbide substrate 1 includes placing the silicon carbide substrate 1 in an inert gas atmosphere and performing a pyrolysis treatment on a surface of the silicon carbide substrate 1 to form the graphene material.

[0112] According to an embodiment of the present invention, a graphene material is grown by epitaxially pyrolyzing a silicon carbide substrate 1. Silicon atoms sublime and escape from the surface of the silicon carbide substrate 1 before carbon atoms. In an inert gas atmosphere (for example, argon, 400 sccm to 550 sccm), the enriched carbon atoms are reconstructed on the surface into graphene material (such as Figure 23 IV process in the process).

[0113] According to an embodiment of the present invention, placing a silicon carbide substrate 1 in an inert gas atmosphere and performing a pyrolysis treatment on the surface of the silicon carbide substrate 1 to form a graphene material includes: preheating the silicon carbide substrate 1 and then performing an annealing treatment, then placing the annealed silicon carbide substrate 1 in an inert gas atmosphere and heating it to a preset temperature, and growing it in the inert gas atmosphere to form a graphene material.

[0114] According to an embodiment of the present invention, the temperature for preheating silicon carbide substrate 1 is approximately 800°C.

[0115] According to an embodiment of the present invention, the temperature range of the annealing treatment is 1100° C. to 1200° C., the temperature range of the preset temperature is 1540° C. to 1640° C., and the time range for forming the graphene material is 18 min to 33 min.

[0116] In one embodiment, the silicon carbide substrate 1 is preheated and placed in an argon atmosphere to be heated to 1200°C, annealed in the argon atmosphere for 20 minutes, and then the annealed silicon carbide substrate 1 is placed in an argon atmosphere and heated, the temperature is controlled at 1540°C~1640°C, and the time is 18min~33min. In the argon atmosphere, the enriched carbon atoms are reconstructed into graphene materials on the surface, and the graphene is combined with the carbon atoms. Figure 22 The graph of growth temperature and growth time is shown in Table 1 below. The Raman test data of graphene material epitaxially grown on silicon carbide substrate 1 under different conditions are shown in Table 1 below.

[0117] Table 1 Raman test data of graphene material epitaxially grown on silicon carbide substrate 1 under different conditions

[0118]

[0119] According to the embodiment of the present invention, it can be seen from Table 1 that the optimal growth conditions are a growth temperature of 1640°C and a growth time of 1400s. Under the conditions of a growth temperature of 1640°C and a growth time of 1400s, a 3.5×4.5mm 2A single-layer graphene material with high uniformity, fewer defects and higher coverage is obtained on a semi-insulating silicon carbide substrate of a certain size.

[0120] According to an embodiment of the present invention, in the initial stage of growth of the graphene material, the junction of the defect and the step clustering has a high surface free energy, and the silicon atoms at the location sublime rapidly. As the growth temperature increases, the number of graphene nucleation points gradually increases, making graphene more inclined to form in the smooth step area with uniform surface energy distribution, promoting the growth of graphene materials with high coverage and good uniformity. The appropriate growth temperature and time allow the silicon atoms on the surface of the silicon carbide substrate 1 to sublimate at a suitable speed and provide sufficient energy to cause silicon carbide decomposition and epitaxial growth of graphene materials in the uniform and flat area of the surface of the silicon carbide substrate 1. At the same time, the silicon vapor pressure in the graphite crucible chamber reaches a saturated state in a short time to inhibit the formation of graphene material, so that the growth of the graphene material is in a balanced state.

[0121] According to an embodiment of the present invention, the size design of the graphite crucible affects the growth of the graphene material. The rapidly sublimated silicon atoms cause the silicon vapor pressure in the graphite crucible to rise, inhibiting the subsequent growth rate of the graphene material and reducing the number of nucleation points in areas with low surface free energy. The reasonable design of the graphite crucible body and the graphite crucible cap helps to regulate the growth of the graphene material.

[0122] Figure 24 4 is a flow chart of forming a patterned metal electrode 3 on a graphene material according to an embodiment of the present invention.

[0123] According to an embodiment of the present invention, Figure 24 As shown, forming a patterned metal electrode 3 on the graphene material includes the following steps S20 to S23.

[0124] Step S20: coating a first photoresist on the graphene material.

[0125] According to an embodiment of the present invention, a first photoresist is spin-coated on the surface of the graphene material using a coating machine, and the first photoresist is a thin film S1805.

[0126] Step S21: performing patterning on the first photoresist to obtain a patterned first photoresist and a first target area on the graphene material that is not covered by the first photoresist.

[0127] According to an embodiment of the present invention, a silicon carbide substrate coated with a first photoresist is pre-baked using a hot plate machine, and then exposed using a photolithography machine. The silicon carbide substrate is then placed in a developer solution for development and hardened using a hot plate machine. The silicon carbide substrate is then etched using a reactive etcher. After etching, residual developer residue is removed.

[0128] Step S22: forming a metal layer on the patterned first photoresist and on the first target area.

[0129] In one embodiment, an electron beam evaporation device is used to deposit the metal layer. The material of the metal layer may be chromium gold. The process parameters are controlled so that the thickness of the evaporated metal layer is 40 nm.

[0130] Step S23 : removing the patterned first photoresist on the graphene material and the metal layer on the patterned first photoresist to obtain a patterned metal electrode 3 .

[0131] According to an embodiment of the present invention, after the metal layer is deposited, the silicon carbide substrate is placed in an acetone solution to clean the first photoresist, thereby obtaining a metal electrode 3 with a specific pattern on the silicon carbide substrate.

[0132] Figure 25 4 is a flow chart of performing a patterning process on a graphene material to form a graphene channel 2 between a first metal electrode and a second metal electrode according to an embodiment of the present invention.

[0133] According to an embodiment of the present invention, Figure 25 As shown, the graphene material is patterned to form a graphene channel 2 between the first metal electrode and the second metal electrode, thereby obtaining an ultraviolet photodetector, including the following steps S30 to S32.

[0134] Step S30: coating a second photoresist on the graphene material.

[0135] According to an embodiment of the present invention, a second photoresist is spin-coated on the graphene material, and the second photoresist is thick photoresist S1813.

[0136] Step S31: performing patterning processing on the second photoresist to obtain a patterned second photoresist.

[0137] According to an embodiment of the present invention, the second photoresist is photolithographically processed to retain the second photoresist between the first metal electrode and the second metal electrode as a mask for the graphene material, thereby protecting the graphene material between the first metal electrode and the second metal electrode.

[0138] Step S32: removing the graphene material not covered by the patterned second photoresist to form a graphene channel 2 between the first metal electrode and the second metal electrode, thereby obtaining an ultraviolet photodetector.

[0139] According to an embodiment of the present invention, a reactive ion etcher is used to etch away the graphene material not covered by the patterned second photoresist, the second photoresist mask is washed away with acetone, and a graphene channel 2 connected to the first metal electrode and the second metal electrode is prepared between the first metal electrode and the second metal electrode, thereby obtaining an ultraviolet photodetector.

[0140] According to an embodiment of the present invention, after the ultraviolet photodetector is completed, the metal electrode 3 on the silicon carbide substrate is connected to the base with an aluminum wire by spot-coating silver glue. After being connected to the external circuit, the test is carried out. During the test, the ultraviolet lamp is placed above the graphene channel 2 and irradiated with a 275nm ultraviolet lamp. The light power density of the ultraviolet lamp is required to be stable during the test.

[0141] According to an embodiment of the present invention, the ultraviolet photodetector prepared by the above method does not require the aid of complex modification and doping methods. The graphene channel 2 of the prepared ultraviolet photodetector is a high-quality single-layer graphene material, which has a sensitive response to weak ultraviolet light, simplifies the preparation steps of the ultraviolet photodetector, saves the cost of preparing the ultraviolet photodetector, is conducive to industrial production, and at the same time reduces the variables in the processing process, so that the ultraviolet photodetector has relatively stable repeatability, which is conducive to promoting the practical application of ultraviolet photodetectors.

[0142] According to the embodiment of the present invention, 10 3 It has an A / W magnitude response and good cycle stability and repeatability, and can be applied to fields such as environmental monitoring, ultraviolet sterilization treatment, and communications-related fields.

[0143] The above describes embodiments of the present invention. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be advantageously used in combination. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which are intended to fall within the scope of the present invention.

Claims

1. An ultraviolet photodetector, characterized in that: include: Silicon carbide substrate; A graphene channel, comprising a graphene material epitaxially grown by pyrolyzing the silicon carbide substrate in a graphite crucible in an inert gas atmosphere, wherein the graphene channel is a single layer and the intensity ratio of the D peak to the G peak of the graphene material in a Raman spectrum is no greater than 0.25; Two metal electrodes are provided on the silicon carbide substrate and are respectively connected to two sides of the graphene channel; There is a work function difference between the graphene channel and the silicon carbide substrate, and a built-in electric field is formed at the contact interface between the graphene channel and the silicon carbide substrate.

2. The ultraviolet photodetector according to claim 1, characterized in that The width of the graphene channel is 6µm~80µm, and the length of the graphene channel is 100µm~1200µm.

3. The ultraviolet photodetector according to claim 2, characterized in that: The ratio of the length of the graphene channel to the width of the graphene channel is in the range of length:width=100:20 to 600:

6.

4. A method for preparing the ultraviolet photodetector according to any one of claims 1 to 3, characterized in that: include: placing a silicon carbide substrate in a graphite crucible for pyrolysis treatment in an inert gas atmosphere, and epitaxially growing a graphene material on the silicon carbide substrate; forming a patterned metal electrode on the graphene material, wherein the metal electrode comprises a first metal electrode and a second metal electrode spaced apart from each other; The graphene material is patterned to form a graphene channel between the first metal electrode and the second metal electrode, which is connected to the first metal electrode and the second metal electrode, thereby obtaining the ultraviolet photodetector.

5. The method according to claim 4, characterized in that Placing the silicon carbide substrate in a graphite crucible in an inert gas atmosphere for pyrolysis treatment, and epitaxially growing a graphene material on the silicon carbide substrate comprises: preheating the silicon carbide substrate and then performing an annealing treatment; The annealed silicon carbide substrate is placed in a graphite crucible and heated to a preset temperature in the inert gas atmosphere, and then grown in the inert gas atmosphere to form the graphene material.

6. The method according to claim 5, characterized in that The temperature range of the annealing treatment is 1100° C. to 1200° C., the temperature range of the preset temperature is 1540° C. to 1640° C., and the time range for forming the graphene material is 18 minutes to 33 minutes.

7. The method according to claim 4, characterized in that The step of forming a patterned metal electrode on the graphene material comprises: coating a first photoresist on the graphene material; performing a patterning process on the first photoresist to obtain a patterned first photoresist and a first target area on the graphene material that is not covered by the first photoresist; forming a metal layer on the patterned first photoresist and on the first target area; The patterned first photoresist on the graphene material and the metal layer on the patterned first photoresist are removed to obtain the patterned metal electrode.

8. The method according to claim 4, characterized in that The graphene material is patterned to form a graphene channel between the first metal electrode and the second metal electrode, which is connected to the first metal electrode and the second metal electrode, thereby obtaining the ultraviolet photodetector, comprising: coating a second photoresist on the graphene material; performing patterning on the second photoresist to obtain a patterned second photoresist; The graphene material not covered by the patterned second photoresist is removed to form a graphene channel between the first metal electrode and the second metal electrode, which is connected to the first metal electrode and the second metal electrode, thereby obtaining the ultraviolet photodetector.

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