Ultraviolet photoelectric detector and preparation method thereof

Abstract

The invention provides an ultraviolet photoelectric detector and a preparation method thereof. The ultraviolet photoelectric detector comprises a silicon carbide substrate; the graphene channel is formed by a graphene material epitaxially growing on the silicon carbide substrate, and the intensity ratio of a D peak to a G peak of the graphene material in a Raman spectrum is not greater than 0.25; the two metal electrodes are arranged on the silicon carbide substrate and are in lap joint with the two sides of the graphene channel respectively; a graphene channel is formed in the silicon carbide substrate, a work function difference exists between the graphene channel and the silicon carbide substrate, a built-in electric field is formed on a contact interface of 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 into the graphene channel from the silicon carbide substrate, and the graphene channel is formed. Holes move to the metal electrode from the graphene channel to form light current, and the ultraviolet photoelectric detector can realize 103A / W magnitude response under the irradiation of external ultraviolet light.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor photoelectric detectors, and more specifically, to an ultraviolet photoelectric detector 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 has broad application prospects in the field of ultrafast wide-spectrum response photoelectric detection due to its excellent conductivity, wide spectral response, and low noise equivalent power. However, graphene has weak light absorption ability and the device response is low, so it is necessary to composite the material or optimize the device, such as constructing a heterojunction with wide-bandgap materials (silicon carbide, gallium nitride, etc.), preparing graphene electrodes, chemically doping, implementing gate modulation, and using nanoparticle modification. Among these methods, wide-bandgap material silicon carbide has good ultraviolet light absorption characteristics and can significantly improve light gain. The graphene / silicon carbide heterostructure combines the advantages of both and effectively improves the photoelectric performance.

[0004] 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. However, applying a large bias voltage and gate voltage increases energy consumption, and the gate preparation increases process complexity, which is not conducive to industrial production. Summary of the invention

[0005] In order 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 photoelectric detector, comprising: 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 are respectively overlapped on both 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, comprising: 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 comprises 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 connected to the above-mentioned first metal electrode and the above-mentioned second metal electrode between 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, 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 includes: preheating the silicon carbide substrate and then performing an annealing treatment; placing the annealed silicon carbide substrate in the inert gas atmosphere and heating it to a preset temperature, and growing it in the inert gas atmosphere to form the 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 min to 33 min.

[0014] Optionally, the formation of a patterned metal electrode on the graphene material includes: coating a first photoresist on the graphene material; patterning 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 the first target area; removing the patterned first photoresist on the graphene material and the metal layer on the patterned first photoresist to obtain the 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 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 first metal electrode and the second metal electrode, thereby obtaining the above-mentioned ultraviolet photodetector.

[0016] According to an ultraviolet photodetector and a preparation method thereof of an embodiment of the present invention, a graphene channel is formed by a graphene material epitaxially grown on a silicon carbide substrate, 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 are arranged on the silicon carbide substrate and overlapped on both sides of the graphene channel respectively, 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 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, and at the same time, a potential barrier prevents the electron-hole pairs from recombining to form a photocurrent. The ultraviolet photodetector prepared in this way has good cycle stability and can improve the sensitive response and sensitivity to ultraviolet rays. 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 peak intensities of the D peak to the G peak according to an embodiment of the present invention;

[0020] Figure 4 is a Raman imaging test chart of a 2D peak half-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 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 of potential difference and current at two locations on a graphene material according to an embodiment of the present invention;

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

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

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

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

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

[0030] Fig.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] Fig.15 is a test diagram of the photoelectric performance of the ultraviolet photodetector under different bias voltages according to an embodiment of the present invention;

[0032] Fig.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] Fig.17 This is a test diagram of the photoelectric performance of the ultraviolet photodetector under the irradiation of irradiation lights of different wavelengths according to an embodiment of the present invention;

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

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

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

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

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

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

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

[0041] Fig.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] Below, 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 concepts 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 existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0048] All terms (including technical and scientific terms) used herein 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] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally 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 a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally 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 a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0050] Existing ultraviolet photodetectors have the problem of low responsivity. 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 responsivity. At the same time, a larger bias voltage may be required to drive the movement of carriers, but applying a larger bias voltage will increase energy consumption. On the other hand, defects and dangling bonds on the surface and interface of the material will form surface states and interface states, which will capture photogenerated carriers and cause them to recombine before reaching the electrode, reducing the effective photocurrent and thus reducing the responsivity. 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 increase 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 materials. 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 responsivity 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, 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 arranged on the silicon carbide substrate and overlapped on both sides of the graphene channel respectively, there is a work function difference between the graphene channel and the silicon carbide substrate, and the graphene channel and the carbon are A built-in electric field is formed at the contact interface of the silicon carbide substrate. When external ultraviolet light irradiates 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 the graphene material epitaxially grown on the silicon carbide substrate 1. 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 not greater than 0.25. The two metal electrodes 3 are arranged on the silicon carbide substrate 1 and overlapped on both sides of the graphene channel 2 respectively. There is a work function difference between the graphene channel 2 and the silicon carbide substrate 1, and the contact interface between the graphene channel 2 and the silicon carbide substrate 1 forms a built-in electric field. When external ultraviolet light irradiates 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, the silicon carbide substrate 1, the graphene channel 2 and the two metal electrodes 3 serve as the detector core of the ultraviolet photodetector, the silicon carbide substrate 1 serves as the absorption layer of the ultraviolet photodetector, the graphene channel 2 serves as the transmission layer of the ultraviolet photodetector, and the two metal electrodes 3 are attached to the silicon carbide substrate 1 and are respectively laterally overlapped and contacted on both sides of the graphene channel 2. The graphene channel 2 changes its conductivity under external ultraviolet light irradiation, 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. The contact interface between the graphene channel 2 and the silicon carbide substrate 1 forms a built-in electric field. When external ultraviolet light irradiates 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, 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 pair from recombining to form a photocurrent. The two metal electrodes 3 are connected to an external signal acquisition device. The two metal electrodes 3 lead out the signal of the graphene channel 2, and by collecting the change of the current signal, the change of the output electrical signal represents the sensitive response to the ultraviolet light, thereby realizing the detection of the ultraviolet light.

[0055] Figure 2 is a Raman spectrum of a test graphene material according to an embodiment of the present invention, Figure 3 is a Raman imaging test chart of the ratio of the peak intensity of the D peak to the peak intensity of the G peak according to an embodiment of the present invention. Figure 4 is a Raman imaging test chart of a 2D peak half-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 profile of a graphene material epitaxially grown 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, the intensity ratio of the D peak to the G peak in the Raman spectrum characterizes 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-width (2D-FWHM) of the 2D peak in the Raman spectrum is in the range of 30 cm -1 ~40cm -1 In the case where the graphene channel 2 is multilayered, the half-width (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 chart 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 chart is 30µm×30µm, the step length is 3µm, and the ratio of the peak intensity of the D peak to 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 half-height width of the 2D peak ranges from 30cm -1 ~40cm -1 Between. Figure 5 As shown, it is an atomic force microscope test image of epitaxially grown graphene material on silicon carbide substrate 1, as shown in 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 of potential difference and current at two locations on a graphene material according to an embodiment of the present invention, Fig. 9 is a graph of 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, a graphene material with a length L of 26µm and a width W of 24µm is tested for mobility. 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 Position 1, position 2, position 3, position 4 and position 5 are the positions of the Hall bars. The current flows in from position 4 and flows out from 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 denoted as V xy , the graphene material prepared with the Hall bar is placed in magnetic fields of different strengths for measurement. Figure 8 As shown, it is represented by 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 For 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 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 1 μA, 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, Fig. 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 Fig. 9 As shown, the graphene material obtained by epitaxial growth has high uniformity, few defects and high coverage. 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 overlapped on both sides of the graphene channel 2, respectively. 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, 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, a 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-80µm, and the length of the graphene channel 2 is 100µm-1200µm.

[0070] Fig.10 It 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 of ultraviolet photodetectors with a length of 600 µm and widths of 6 µm, 10 µm, 20 µm, 40 µm, 60 µm, and 80 µm are tested. The test results are as follows: Fig.10 shown. Fig.10 Figure (a) shows a curve of responsivity R and width. Fig.10 Figure (b) shows the curve of external quantum efficiency EQE and width. Fig.10 Figure (c) in the figure shows a graph of normalized detection D* versus width. Fig.10 Figure (d) in the figure is a graph of noise equivalent power NEP and 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 gradually decrease. As the width increases from 6µm to 10µm, the normalized detection D* increases significantly, and the noise equivalent power NEP decreases significantly. As the width increases from 10µm to 40µm, the normalized detection D* decreases gradually, and the noise equivalent power NEP increases gradually. As the width increases from 40µm to 80µm, the normalized detection D* decreases rapidly, and 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, when the width of the graphene channel 2 is 20µm, the photoelectric performance of the UV photodetector is optimal, 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 an embodiment of the present invention, as the width of the graphene channel 2 increases, the effective area for absorbing ultraviolet light increases, the number of photogenerated carriers generated increases, the photocurrent increases, and the photoelectric performance is improved. When the width of the graphene channel 2 is greater than a certain value (for example, 20µm), the carriers are excessively dispersed, and the efficiency of collecting photogenerated carriers decreases, resulting in a decrease in photocurrent, responsivity R, and external quantum efficiency EQE. In addition, when the width of the graphene channel 2 is greater than 40µm, the resistance of the ultraviolet photodetector decreases and the dark current increases, resulting in a significant decrease in the normalized detection D* and a significant increase in the noise equivalent power NEP.

[0073] Fig.11 It is a test diagram of the photoelectric performance of ultraviolet photodetectors 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 is performed 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: Fig.11 shown. Fig.11 Figure (a) shows a curve of response R and length. Fig.11 Figure (b) shows the curve of external quantum efficiency EQE and length. Fig.11 Figure (c) in the figure shows a graph of normalized detection D* versus length. Fig.11 Figure (d) in the figure is a graph 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. Considering the responsivity R, external quantum efficiency EQE, normalized detection D* and noise equivalent power NEP comprehensively, 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 the embodiment 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, the carrier generation is greater than the recombination, the photocurrent increases, and the photoelectric performance of the ultraviolet photodetector is improved. When the length of the graphene channel 2 is less than a certain value (for example, 200 μm), the carriers are too concentrated, and as the length decreases, the probability of recombination of photogenerated carriers increases, the carrier generation is less than the recombination, the photocurrent decreases, and the photoelectric performance of the ultraviolet photodetector decreases.

[0076] Fig.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, Fig.12 As shown in the figure, a high-performance ultraviolet photodetector with a graphene channel 2 of 200µm in length and 20µm in width was prepared using a single-layer graphene material with fewer defects and better uniformity, and a comprehensive performance test and analysis was performed. When the length of the graphene channel 2 is 200µm and the width of the graphene channel 2 is 20µm, the photoelectric performance of the ultraviolet photodetector reaches the best, 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 the prepared ultraviolet photodetector is improved by improving the quality of epitaxial growth of graphene materials and optimizing the size of the graphene channel 2 instead of modification. A high-performance ultraviolet photodetector with a graphene channel 2 size of 200µm×20µm is prepared using a single-layer graphene material with fewer defects and better uniformity.

[0079] Fig.13 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, Fig.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 responsiveness 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 responsiveness of the ultraviolet photodetector.

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

[0083] Fig.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. Fig.14 As shown in the figure, under the irradiation of ultraviolet light of the same wavelength, a bias voltage of 1.0V is applied, the responsivity of the multilayer graphene (MLG) channel is 2250A / W, and the responsivity of the single-layer graphene (SLG) channel reaches 5025A / W. The ultraviolet photodetector prepared by the single-layer graphene (SLG) channel has a higher responsivity than that of the multilayer graphene (MLG) channel. The interaction between graphene layers and more defects will lead to increased electron scattering, resulting in a lower probability of electron scattering in the single-layer graphene channel relative to the multilayer graphene channel. The generated photogenerated carriers can effectively participate in the generation of current, thereby improving the responsivity of the prepared ultraviolet photodetector.

[0085] According to the 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] Fig.15 This is a test diagram of the photoelectric performance 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 Fig.15 As shown, Fig.15Figure (a) shows the curve of responsivity R and bias voltage. Fig.15 Figure (b) shows the curve of external quantum efficiency EQE and bias voltage. Fig.15 Figure (c) in the figure shows a graph of normalized detection D* versus bias voltage. Fig.15 Figure (d) in the figure shows a curve diagram of noise equivalent power NEP and bias voltage. Fig.15 Figure (a) in Fig.15 Figure (b) Fig.15 Figure (c) and Fig.15 As shown in Figure (d) in the figure, the test results show that the responsivity R, external quantum efficiency EQE and normalized detection 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 increases, the carrier migration speed increases, and the photoelectric performance of the UV photodetector is optimized.

[0089] According to an embodiment of the present invention, Fig.15 Figure (e) shows the relationship between the bias voltage and the average responsivity of the UV photodetector. Fig.15 Figure (f) shows the relationship between the current and the average responsivity of the UV photodetector. Fig.15 Figure (e) and Fig.15 The lightning position in Figure (f) indicates that a circuit breaker has occurred. Fig.15 Figure (e) and Fig.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 circuit. The UV photodetector was short-circuited after 52 tests at a bias voltage of 1.1V. At a bias voltage of 1.0V, there was no short circuit after 500 tests. To ensure the use of the UV photodetector, the maximum bias voltage applied during the test was 1.0V.

[0090] Fig.16The diagram 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.

[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. Fig.16 As shown, Fig.16 Figure (a) shows the curve of responsivity R and irradiation power P. Fig.16 Figure (b) shows the curve of external quantum efficiency EQE and irradiation power P. Fig.16 Figure (c) shows the normalized detection D* versus irradiation power P. Fig.16 Figure (d) in the figure shows a curve diagram of noise equivalent power NEP and irradiation power P. Fig.16 Figure (a) in Fig.16 Figure (b) Fig.16 Figure (c) and Fig.16 As shown in Figure (d), the test results show that the responsivity R, external quantum efficiency EQE and normalized detection D* first increase and then decrease with the increase of the irradiation power P of ultraviolet light, and the noise equivalent power NEP first decreases and then increases with the increase of the 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 detection D* increase, and 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 %, 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 % decreased 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 detection 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 optimal 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 is less than 0.004 μW), the working state of the ultraviolet photodetector is in a linear enhancement region, and the increase in irradiation power P can effectively excite more carriers to participate in conduction, so that the responsiveness of the ultraviolet photodetector is improved accordingly. Due to physical limitations, the output signal of the ultraviolet photodetector may be saturated at a higher irradiation power P (irradiation power P is greater than 0.004 μW), and the current is nonlinearly related to the input optical power until it gradually approaches the saturation value. In addition, as the irradiation power P increases (irradiation power P is 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, and the carrier recombination and scattering are greater than the generation, and the generated photocurrent is reduced, resulting in a decrease in the performance of the ultraviolet photodetector.

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

[0094] According to an embodiment of the present invention, Fig.17 As shown, Fig.17 Figure (a) shows the curve of responsivity R and irradiation light wavelength. Fig.17 Figure (b) shows the curve of external quantum efficiency EQE and irradiation light wavelength. Fig.17 Figure (c) shows the normalized detection D* versus the wavelength of the irradiated light. Fig.17 Figure (d) in the figure shows a curve of noise equivalent power NEP and irradiated light wavelength. Fig.17 Figure (a) in Fig.17 Figure (b) Fig.17 Figure (c) and Fig.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 decreases first 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 the minimum value of 5.2×10 -16 .

[0095] Fig.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). Fig.18 As shown in Figure (a), as the external UV light is turned on, the photocurrent is generated until the peak value is 262.4nA. When the external UV light is turned off, the photocurrent drops to zero. Under 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 by the UV light source, as shown in Figure (a). Fig.18 As shown in Figure (b), the UV photodetector has good repeatability.

[0097] Fig.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 the bias voltage are compared. Fig.19 As shown, the data are basically consistent, all maintained at 4×103 A / W and above, indicating that the ultraviolet photodetector has quite stable photoelectric performance.

[0099] Fig. 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, Fig. 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 was tested under the same conditions. Fig. 20 Figure (a) shows the responsivity R of all UV photodetectors. Fig. 20 Figure (b) shows the external quantum efficiency EQE of all UV photodetectors, Fig. 20 Figure (c) shows the normalized detectivity D* of all UV photodetectors. Fig. 20 Figure (d) shows the noise equivalent power NEP of all UV photodetectors. Under 0.004 μW UV irradiation and 1.0 V bias voltage, all UV photodetectors exhibit 2×10 1 μA photocurrent, 5×10 3 A / W level responsivity R, 2×10 4 Optical gain of the order of magnitude, 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 materials is controllable, the quality is high, the area is large, and the mobility of a single-layer graphene material reaches 3020.54cm 2 / (V·s), the prepared UV photodetector exhibits excellent performance, mainly for the following four reasons: 1. The two-dimensional structure of the UV photodetector facilitates the rapid separation and transmission 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 possible more defects will lead to increased electron scattering), so that the generated photogenerated carriers can effectively participate in the generation of current, improving the photoelectric conversion efficiency. 2. The excellent carrier mobility of graphene allows photogenerated holes to quickly move in the graphene channel 2 to the metal electrode 3 to be collected, significantly enhancing the photogenerated current flowing through the external circuit. 3. The epitaxial growth of graphene materials on the silicon carbide substrate 1 has good contact and fewer defects, further ensuring high performance and stability. 4. The high transparency and excellent conductivity of graphene materials enable it to quickly and effectively conduct electrons 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 recombination of carriers 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 is relatively wider, and the transmission of photogenerated carriers is not prone to congestion and accumulation, 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 cause some photoelectric performance to decrease, 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. Generate space charge effect, accumulate charge in local position, change electric field distribution, affect the movement of photogenerated carriers, 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 faster, 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 be reduced. There are mainly four reasons: 1. The carriers are too concentrated in a short distance, increasing the probability of recombination. 2. The quantum confinement effect is generated, the movement of carriers in these directions is restricted, and the volatility becomes more significant. 3. Increase process requirements, prone to problems such as non-uniformity and defects, and reduce the stability and accuracy of ultraviolet photodetectors. 4. Abnormal changes in resistance occur, which is not conducive to the transmission and collection of photogenerated carriers.

[0103] Fig.21is a flow chart of a method for preparing an ultraviolet photodetector according to an embodiment of the present invention, Fig. 22 It is a 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, Fig.21 and Fig. 22 As shown, a method for preparing the above-mentioned ultraviolet photodetector is provided, comprising the following steps S1 to S3.

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

[0106] Fig.23 1 is a flow chart of epitaxially growing 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, Fig.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 Fig.23 In process I), ultrasonic treatment was performed in acetone, isopropanol and deionized water for 30 min respectively (e.g. Fig.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 Fig.23 III process in the process).

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

[0109] Step S3: performing a graphene material patterning process 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 ultraviolet photodetector prepared by the above method has a simple metal-graphene-metal plane structure, the graphene channel 2 serves as the transmission layer of the ultraviolet photodetector, and the silicon carbide substrate 1 serves as the absorption layer of the ultraviolet photodetector. The preparation process of the ultraviolet photodetector does not require substrate transfer and subsequent modification, simplifies the preparation process, achieves high responsiveness to weak ultraviolet light, and ensures the simplicity and efficiency of the structure of the ultraviolet photodetector, and is compatible with semiconductor processes and has strong practicality.

[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 a 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 sublimate and escape from the surface of the silicon carbide substrate 1 before carbon atoms do. In an inert gas atmosphere (for example, an inert gas such as argon, 400 sccm to 550 sccm), the enriched carbon atoms are reconstructed on the surface into a graphene material (such as Fig.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 to be 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 material is combined with the carbon atoms. Fig. 22 The curve diagram of growth temperature and growth time in FIG. 1 is shown in Table 1 below, and the Raman test data of graphene material epitaxially grown on silicon carbide substrate 1 under different conditions.

[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 growth temperature of 1640°C and the growth time of 1400s are the optimal growth conditions. Under the conditions of the growth temperature of 1640°C and the growth time of 1400s, it is possible to grow a 3.5×4.5mm 2A single-layer graphene material with higher 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 graphene materials, the junction between defects and step bunching has a high surface free energy, and the silicon atoms at the location sublimate rapidly. As the growth temperature increases, the number of graphene nucleation points gradually increases, making graphene more inclined to form in a smooth step area with uniform surface energy distribution, promoting the growth of graphene materials with high coverage and good uniformity. Appropriate growth temperature and time allow silicon atoms on the surface of silicon carbide substrate 1 to sublimate at a suitable speed, and provide sufficient energy, so that silicon carbide decomposition and epitaxial growth of graphene materials occur in the uniform and flat area of ​​the surface of 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 materials, so that the growth of graphene materials 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, thereby inhibiting the subsequent growth rate of the graphene material and reducing the number of nucleation points in areas with lower 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] Fig.24 It 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, Fig.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 processing on the first photoresist to obtain the 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 a photolithography machine is used to expose the silicon carbide substrate. The silicon carbide substrate is placed in a developer for development, and a hot plate machine is used for hardening the film. A reactive etcher is used to etch the silicon carbide substrate. After etching, the residual glue 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 a metal layer. The material of the metal layer may be chrome 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 the 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] Fig.25 It 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, Fig.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 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 to protect 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, which is connected to 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, and the connection method is to apply silver glue. After connecting to the external circuit, the test is carried out. During the test, the ultraviolet lamp is placed above the graphene channel 2, and a 275nm ultraviolet lamp is used for irradiation. The optical 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 need to resort to complicated modification and doping methods. The prepared ultraviolet photodetector has a graphene channel 2 of 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 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 A / W magnitude response, good cycle stability and repeatability, and can be applied to environmental monitoring, ultraviolet sterilization treatment and communication-related fields.

[0143] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination. The scope of the present invention is defined by the attached 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 should all fall within the scope of the present invention.

Claims

1. An ultraviolet photoelectric detector, characterized in that: include: 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; Two metal electrodes are disposed on the silicon carbide substrate and are respectively overlapped on 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=100:20~600:

6.

4. The ultraviolet photodetector according to claim 1, characterized in that: The graphene channel is a single layer or a multi-layer.

5. A method for preparing an ultraviolet photodetector as claimed in any one of claims 1 to 4, characterized in that: include: epitaxially growing graphene material on a 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.

6. The method according to claim 5, characterized in that The epitaxial growth of graphene material on the silicon carbide substrate comprises: The silicon carbide substrate is placed in an inert gas atmosphere and a surface of the silicon carbide substrate is pyrolyzed to form the graphene material.

7. The method according to claim 6, characterized in that 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 comprises: Preheating the silicon carbide substrate and then performing an annealing treatment; The annealed silicon carbide substrate is placed in the inert gas atmosphere and heated to a preset temperature, and then grown in the inert gas atmosphere to form the graphene material.

8. The method according to claim 7, 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 min to 33 min.

9. The method according to claim 5, 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.

10. The method according to claim 5, 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, including: 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 and connected to the first metal electrode and the second metal electrode, thereby obtaining the ultraviolet photodetector.

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