Graphene terahertz photoelectric detector based on element doping enhancement and preparation process

Abstract

The invention discloses a graphene terahertz photoelectric detector based on element doping enhancement and a preparation process, and belongs to the technical field of semiconductor devices and micro-nano processing and manufacturing, the graphene terahertz photoelectric detector comprises a substrate, a first electrode, a boron-doped graphene layer, a nitrogen-doped graphene layer and a second electrode; the first electrode and the boron-doped graphene layer are arranged on the substrate, and the side surface of the boron-doped graphene layer is in ohmic contact with the first electrode; the nitrogen-doped graphene layer is arranged on the boron-doped graphene layer; the second electrode is located on the nitrogen-doped graphene layer and forms ohmic contact with the nitrogen-doped graphene layer. According to the detector, on the basis of ensuring that the response time of a device is not shortened, photon-generated carrier recombination is effectively reduced, and the photoelectric response performance of the detector is improved; the preparation process is simple, the operation is easy, the operation is performed at room temperature, the sensitivity is high, and the important requirement of terahertz detection can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices and micro-nano processing and manufacturing, and particularly relates to a graphene terahertz photodetector enhanced by element doping and a preparation process thereof. Background Art

[0002] Terahertz (THz) waves are electromagnetic waves with a wavelength range between 3 millimeters and 30 micrometers, and their frequency band is located in the transition region between electronics and photonics. This unique position enables terahertz waves to possess the dual characteristics of low microwave photon energy and fast infrared wave frequency. In the field of imaging detection, terahertz waves exhibit significant application advantages: compared with microwaves, their shorter wavelength can achieve fast high-resolution imaging of objects; compared with infrared waves and visible light, terahertz waves have stronger penetration ability and can effectively penetrate non-polar materials such as plastics. These characteristics make terahertz waves have important application value in the detection of dangerous goods (such as the detection of explosives). However, terahertz detectors based on traditional materials such as silicon oxide and vanadium oxide have limitations such as large structural size, complex preparation process, high detection cost, and the need for a cooling system, which seriously restrict their practical applications.

[0003] Graphene is currently the most widely studied two-dimensional material. Its valence band and conduction band intersect near the Fermi level to form a Dirac cone, resulting in a zero bandgap for graphene. Therefore, it exhibits ultra-wide spectral absorption characteristics covering ultraviolet, visible light, infrared, and terahertz waves. In addition, graphene can achieve ballistic transport of carriers, and the theoretically achievable carrier mobility can reach 250000 cm 2 / V·s, and the average free path of carriers exceeds 22 μm. These excellent characteristics make graphene an ideal material for developing high-performance terahertz photodetectors.

[0004] However, the zero-bandgap energy band structure leads to a low lifetime of photo-generated carriers in graphene, which restricts its application in high-sensitivity terahertz photodetectors to a certain extent, and it is difficult to achieve efficient capture and conversion of terahertz signals. Although the response rate of graphene terahertz detectors can be improved through some technical means, compared with some traditional terahertz detectors, their response rate and detectivity need to be further improved. Therefore, exploring effective methods to regulate the energy band structure of graphene has important research significance. This can not only achieve directional regulation of the transmission performance of graphene, but also significantly improve the response characteristics of graphene terahertz detectors, thereby providing strong support for the in-depth development and wide application of terahertz technology. Summary of the Invention

[0005] The object of the present invention is to address the above deficiencies in the prior art and provide a graphene terahertz photodetector enhanced by element doping and a preparation process thereof, so as to solve the problem that it is difficult for existing graphene terahertz detectors to efficiently capture and convert terahertz signals.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect, the present invention provides a graphene terahertz photodetector enhanced by element doping, which includes a substrate, a first electrode, a boron-doped graphene layer, a nitrogen-doped graphene layer, and a second electrode;

[0008] The first electrode and the boron-doped graphene layer are both disposed on the substrate, and an ohmic contact is formed between the side surface of the boron-doped graphene layer and the first electrode; the nitrogen-doped graphene layer is disposed on the boron-doped graphene layer; the second electrode is located on the nitrogen-doped graphene layer and forms an ohmic contact with the nitrogen-doped graphene layer.

[0009] Further, the substrate is a silicon oxide wafer with a thickness of 100 nm - 500 nm.

[0010] Further, the thicknesses of both the boron-doped graphene layer and the nitrogen-doped graphene layer are 0.05 - 0.5 μm.

[0011] Further, the first electrode includes a 1 nm - 3 nm metal Cr as a transition layer and a 10 nm - 40 nm metal Au; the second electrode is a 10 - 40 nm metal Ni.

[0012] Further, the lateral distance between the first electrode and the second electrode is 100 - 500 μm.

[0013] In the second aspect, the present invention provides a preparation process for a graphene terahertz photodetector enhanced by element doping, which includes the following steps:

[0014] S1. Use a silicon oxide wafer as the substrate and perform ultrasonic cleaning on the substrate;

[0015] S2. Use a patterned metal mask template to deposit the first electrode on the substrate;

[0016] S3. Synthesize a boron-doped graphene dispersion by a hydrothermal method;

[0017] S4. Perform ultraviolet ozone treatment on the surface of the substrate;

[0018] S5. Spin-coat the boron-doped graphene dispersion on the surface of the substrate to obtain a boron-doped graphene layer;

[0019] S6. Synthesize a nitrogen-doped graphene dispersion by a hydrothermal method;

[0020] S7. Spin-coat the nitrogen-doped graphene dispersion on the surface of the boron-doped graphene layer to obtain a nitrogen-doped graphene layer;

[0021] S8. Deposit a second electrode on the surface of the nitrogen-doped graphene film using a patterned metal mask;

[0022] S9. Remove the boron-doped graphene layer and the nitrogen-doped graphene layer on the first electrode to expose the first electrode.

[0023] Further, in S2, cover the patterned metal mask on the surface of the silicon oxide wafer, and use thermal evaporation to deposit 1 nm - 3 nm of metal Cr and 10 nm - 40 nm of metal Au on the surface of the silicon oxide wafer at a rate of 0.1 nm / s - 10 nm / s in a vacuum environment to obtain the first electrode.

[0024] Further, in S5, ultrasonically treat the boron-doped graphene dispersion, and spin-coat the boron-doped graphene dispersion uniformly on the surface of the silicon oxide to obtain a boron-doped graphene layer with a thickness of 0.05 - 0.5 μm; the boron-doped graphene layer completely covers the surface of the first electrode.

[0025] Further, in S7, ultrasonically treat the nitrogen-doped graphene dispersion, and spin-coat the graphene dispersion on the surface of the boron-doped graphene layer supported by the silicon oxide substrate to obtain a nitrogen-doped graphene layer with a thickness of 0.05 - 0.5 μm.

[0026] Further, in S8, cover the patterned metal mask on the surface of the nitrogen-doped graphene thin layer, and use physical vapor deposition technology to deposit 10 - 40 nm of metal Ni on the surface of the nitrogen-doped graphene thin layer at a rate of 0.1 nm / s - 10 nm / s in a vacuum environment to obtain the second electrode.

[0027] The graphene terahertz photodetector and preparation process based on element doping enhancement provided by the present invention have the following beneficial effects:

[0028] 1. The present invention uses a homojunction formed by boron-doped graphene and nitrogen-doped graphene as a photosensitive layer and a carrier transport layer to construct a terahertz wave detector. When terahertz waves irradiate on the homojunction, a large number of carriers (including electrons and holes) are generated through the photovoltaic process and the photothermal process. Among them, boron-doped graphene is P-type doped, and nitrogen-doped graphene is N-type doped. Due to the different energy band structures, the electrons and holes generated in the photovoltaic process and the photothermal process can be effectively separated. Combining with the high carrier mobility of graphene itself, boron-doped graphene can quickly transport photo-generated holes, and nitrogen-doped graphene can quickly transport photo-generated carriers, thereby effectively reducing the recombination of photo-generated carriers and improving the optoelectronic response performance of the detector on the basis of ensuring that the response time of the device is not reduced. Moreover, using a homostructure to construct the detector can reduce the device processing difficulty and maintain the device stability.

[0029] 2. The present invention makes different changes to the energy band structure of graphene by improving the doping type of graphene, so that photo-generated carriers are effectively separated, and the response performance of the detector to terahertz waves is improved. And by changing the doping degree and doping area, the device performance can be adjusted. The detector of the present invention has a simple preparation process, is easy to operate, works at room temperature, and has high sensitivity, which can meet the major requirements of terahertz detection. Brief Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of the graphene terahertz optoelectronic detector based on element doping enhancement in Embodiment 1 of the present invention.

[0031] Among them, 1. Substrate; 2. First electrode; 3. Boron-doped graphene layer; 4. Nitrogen-doped graphene layer; 5. Second electrode.

[0032] Figure 2 It is a schematic diagram of boron-doped graphene in Embodiment 2 of the present invention.

[0033] Figure 3 It is the Fourier infrared spectrum of boron-doped graphene in Embodiment 2 of the present invention.

[0034] Figure 4 It is a schematic diagram of nitrogen-doped graphene in Embodiment 3 of the present invention.

[0035] Figure 5 It is the Fourier infrared spectrum of nitrogen-doped graphene in Embodiment 3 of the present invention.

[0036] Figure 6 It is a terahertz optoelectronic detection system

[0037] Figure 7 It is the test result of the current response of the element-doped enhanced graphene terahertz detector to 0.22 THz terahertz waves with a power of 0.1 mW in Embodiment 4 of the present invention.

[0038] Figure 8 This is the test result of the current response of the nitrogen-doped graphene terahertz detector in Comparative Example 1 of the present invention to a 0.22 THz terahertz wave with a power of 0.1 mW.

[0039] Figure 9 This is the test result of the response time of the boron-doped graphene terahertz detector in Comparative Example 2 of the present invention to a 0.22 THz terahertz wave with a power of 0.1 mW. Detailed implementation manners

[0040] The following describes the detailed implementation manners of the present invention to facilitate those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the detailed implementation manners. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions created using the concept of the present invention are within the scope of protection.

[0041] Example 1

[0042] This example provides a graphene terahertz photodetector enhanced by element doping, which can effectively reduce the recombination of photo-generated carriers and improve the optoelectronic response performance of the detector on the basis of ensuring that the response time of the device is not reduced. Refer to Figure 1 , and it specifically includes:

[0043] Substrate 1, first electrode 2, boron-doped graphene layer 3, nitrogen-doped graphene layer 4, and second electrode 5;

[0044] Among them, the first electrode 2 and the boron-doped graphene layer 3 are both disposed on the substrate 1, and an ohmic contact is formed between the side surface of the boron-doped graphene layer 3 and the first electrode 2. The nitrogen-doped graphene layer 4 is disposed on the boron-doped graphene layer 3, and the second electrode 5 is located on the nitrogen-doped graphene layer 4 and forms an ohmic contact with the nitrogen-doped graphene layer 4.

[0045] Specifically, as a preference of this example, the substrate 1 uses a silicon oxide wafer with a thickness of 100 nm - 500 nm. Among them, the thickness of the photo-oxidized silicon layer on the surface of the silicon oxide substrate 1 is greater than 100 nm.

[0046] As a preference of this example, the thicknesses of both the boron-doped graphene layer 3 and the nitrogen-doped graphene layer 4 are 0.05 - 0.5 μm. Among them, the boron element concentration in the boron-doped graphene layer 3 is ≥ 3%; the nitrogen element concentration in the nitrogen-doped graphene layer 4 is ≥ 4%.

[0047] As a preference of this example, the first electrode 2 includes a 1 nm - 3 nm metal Cr as a transition layer and a 10 nm - 40 nm metal Au; the second electrode 5 is a 10 - 40 nm metal Ni.

[0048] As a preference of this embodiment, the lateral distance between the first electrode 2 and the second electrode 5 is 100 - 500 μm.

[0049] This embodiment also provides a preparation process of a graphene terahertz photodetector enhanced by element doping, which specifically includes the following steps:

[0050] S1. Use a silicon oxide wafer as the substrate 1 and ultrasonically clean the substrate 1.

[0051] Specifically, take a silicon oxide wafer with an area of 10 mm × 10 mm, and ultrasonically clean the silicon oxide wafer with acetone, alcohol, and deionized water in sequence, and then dry it for standby.

[0052] S2. Use a patterned metal mask to deposit the first electrode 2 on the substrate 1.

[0053] Specifically, cover the patterned metal mask on the surface of the clean silicon oxide wafer, and use the thermal evaporation method. In a vacuum environment, deposit 1 nm - 3 nm of metal Cr and 10 nm - 40 nm of metal Au on the surface of the silicon oxide wafer at a rate of 0.1 nm / s - 10 nm / s; after the evaporation is completed, remove the metal mask covering the surface of the silicon oxide wafer to obtain a patterned gold electrode, that is, deposit the first electrode 2 on the substrate 1.

[0054] S3. Synthesize boron-doped graphene dispersion by hydrothermal method.

[0055] Specifically, mix the graphene oxide dispersion (1 - 5 mg / mL) and boric acid in a mass ratio of 1:5 - 1:20 (such as 10 mg GO: 50 - 200 mg H3BO3), and ultrasonically process the mixture for 30 - 60 minutes to make it uniform.

[0056] Transfer the mixture to a stainless steel hydrothermal reaction kettle lined with polytetrafluoroethylene, seal it and place it in an oven, react at 180 - 220 °C for 6 - 24 hours, cool to room temperature, centrifuge at 8000 - 12000 rpm for 10 minutes, wash with deionized water and ethanol for 3 - 5 times, and vacuum dry at 60 - 80 °C for 6 - 12 hours to obtain boron-doped graphene powder.

[0057] Add the boron-doped graphene powder to deionized water to prepare a boron-doped graphene dispersion with a concentration of 10 - 100 mg / ml.

[0058] S4. Perform ultraviolet ozone treatment on the surface of the substrate 1, and the treatment time is 10 - 20 min.

[0059] S5. Spin-coat the boron-doped graphene dispersion on the surface of the substrate to obtain the boron-doped graphene layer 3.

[0060] Specifically, the graphene dispersion is ultrasonically treated for 30 minutes.

[0061] Take 20 μL of the aqueous dispersion of boron-doped graphene, drop it onto the surface of silicon oxide, and spin-coat it at 3000 rpm for 30 seconds. Repeat this step 3 - 10 times.

[0062] The obtained film is left standing at room temperature or in an environment below 60°C for more than 8 hours to dry and obtain the boron-doped graphene layer 3.

[0063] As a preference of this embodiment, the boron doping amount in the boron-doped graphene is ≥ 3%.

[0064] S6. Synthesize the nitrogen-doped graphene dispersion by the hydrothermal method;

[0065] Specifically, mix the graphene oxide dispersion (1 - 5 mg / mL) and urea in a mass ratio of 1:10 - 1:50, and ultrasonically treat for 30 - 60 minutes to make the mixture uniform.

[0066] Transfer the mixture to a stainless-steel hydrothermal reaction kettle lined with polytetrafluoroethylene, seal it and place it in an oven, react at 60 - 200°C for 6 - 24 hours, cool to room temperature, remove the liquid, and centrifuge it at a speed of 8000 - 12000 rpm for 10 minutes, and wash it 3 - 5 times with deionized water and ethanol.

[0067] Vacuum dry at 60 - 80°C for 6 - 12 hours to obtain the nitrogen-doped graphene powder.

[0068] Add the nitrogen-doped graphene powder to deionized water to prepare a nitrogen-doped graphene dispersion with a concentration of 10 - 100 mg / ml.

[0069] S7. Spin-coat the nitrogen-doped graphene dispersion on the surface of the boron-doped graphene layer 3 to obtain the nitrogen-doped graphene layer 4;

[0070] Specifically, ultrasonically treat the nitrogen-doped graphene dispersion for 30 minutes.

[0071] Take 20 μL of the aqueous dispersion of nitrogen-doped graphene, drop it onto the surface of the boron-doped graphene film supported by the silicon oxide substrate 1, and spin-coat it at 3000 rpm for 30 seconds. Repeat this step 3 - 10 times.

[0072] The obtained film is left standing at room temperature or in an environment below 60°C for more than 8 hours to dry and obtain the nitrogen-doped graphene layer 4.

[0073] As a preference of this embodiment, the boron doping amount in the nitrogen-doped graphene is ≥ 4%.

[0074] S8. Deposit the second electrode 5 on the surface of the nitrogen-doped graphene film using a patterned metal mask;

[0075] Specifically, cover the surface of the nitrogen-doped graphene film supported by the silicon oxide substrate 1 with the patterned metal mask. Using physical vapor deposition technology, in a vacuum environment, deposit 10 - 40 nm of metal Ni on the surface of the nitrogen-doped graphene film at a rate of 0.1 nm / s - 10 nm / s. After the evaporation is completed, remove the metal mask covering the surface of the nitrogen-doped graphene film to obtain a patterned Ni electrode, that is, the second electrode 5.

[0076] S9. Use acetone to remove the boron-doped graphene layer 3 and the nitrogen-doped graphene layer 4 on the upper surface of the first electrode 2, while keeping the contact between the first electrode 2 and the boron-doped graphene layer 3 when the first electrode 2 is exposed.

[0077] Example 2

[0078] In this example, boron-doped graphene is prepared using the method in Example 1, and the Fourier transform infrared spectrum of the boron-doped graphene is tested.

[0079] Figure 2 is a schematic diagram of boron-doped graphene, Figure 3 is the Fourier transform infrared spectrum of boron-doped graphene. Figure 3 The 1066 cm in -1 corresponds to the B-C bond, 1436 cm -1 corresponds to the B-O bond, 1633 cm -1 corresponds to the C=O bond. This result shows that the method in Example 1 of the present invention can synthesize boron-doped graphene.

[0080] Example 3

[0081] In this example, nitrogen-doped graphene is prepared using the method in Example 1, and the Fourier transform infrared spectrum of the nitrogen-doped graphene is tested.

[0082] Figure 4 is a schematic diagram of nitrogen-doped graphene, Figure 5 is the Fourier transform infrared spectrum of nitrogen-doped graphene. Figure 5 is the Fourier transform infrared spectrum of nitrogen-doped graphene, 1177 cm -1 corresponds to the C-N bond, 1545 cm -1 corresponds to the C=N bond, 1619 cm -1 corresponds to the C=O bond. This result shows that the method in Example 1 of the present invention can synthesize nitrogen-doped graphene.

[0083] Example 4

[0084] Reference Figure 6, the terahertz detector prepared in Example 1 was placed in a terahertz optoelectronic detection system. An arbitrary waveform generator was used to modulate a terahertz wave of 0.22 THz to output a terahertz wave with a periodically varying optical power, and then the terahertz wave was perpendicularly projected onto the surface of the element-doped enhanced graphene terahertz detector. A digital source meter was connected to the two electrodes of the detector to extract and output an effective optoelectronic response signal. As Figure 7 shown, with the periodic change of the terahertz optical power, the element-doped enhanced graphene terahertz detector can output an electrically signal with a periodic change, and for a terahertz wave of 0.1 mW, the response photocurrent of the detector is 0.85 μA.

[0085] Comparative Example 1

[0086] Comparative Example 1 was a nitrogen-doped graphene terahertz detector without the boron-doped graphene layer 3 in Example 1. The preparation process of Comparative Example 1 included the following steps:

[0087] A1. Take a silicon oxide wafer with an area of 10 mm × 10 mm, and ultrasonically clean the silicon oxide wafer with acetone, alcohol, and deionized water in sequence, and dry it for standby.

[0088] A2. Cover the surface of the clean silicon oxide wafer with a patterned metal mask. Using the thermal evaporation method, in a vacuum environment, deposit 1 nm - 3 nm of metal Cr and 10 nm - 40 nm of metal Au on the surface of the silicon oxide wafer at a rate of 0.1 nm / s - 10 nm / s. After the evaporation is completed, remove the metal mask covering the surface of the silicon oxide wafer to obtain a patterned gold electrode; that is, deposit the first electrode on the substrate.

[0089] A3. Synthesize nitrogen-doped graphene by the hydrothermal method: Mix the graphene oxide dispersion (1 - 5 mg / mL) and urea in a mass ratio of 1:10 - 1:50, and ultrasonically process for 30 - 60 minutes to make the mixture uniform. Transfer the mixture to a stainless-steel hydrothermal reaction kettle with a polytetrafluoroethylene inner liner, seal it and place it in an oven, and react at 60 - 200 °C for 6 - 24 hours. After cooling to room temperature, remove the liquid, and centrifuge it at a speed of 8000 - 12000 rpm for 10 minutes, and wash it with deionized water and ethanol 3 - 5 times. Vacuum dry it at 60 - 80 °C for 6 - 12 hours to obtain nitrogen-doped graphene powder. Add the nitrogen-doped graphene powder to deionized water to prepare a nitrogen-doped graphene dispersion with a concentration of 10 - 100 mg / ml.

[0090] A4. Perform ultraviolet ozone treatment on the silicon oxide wafer with a gold electrode on its surface for 10 - 20 min.

[0091] A5. Ultrasonically treat the nitrogen-doped graphene dispersion for 30 minutes. Take 20 μL of the nitrogen-doped graphene dispersion and drop it onto the surface of the silicon oxide substrate, then spin-coat it at 3000 rpm for 30 seconds. Repeat this step 3 - 10 times. Let the obtained thin film stand at room temperature or in an environment below 60 °C for more than 8 hours to dry it and obtain the nitrogen-doped graphene layer.

[0092] A6. Cover the surface of the nitrogen-doped graphene thin film supported by the silicon oxide substrate with the patterned metal mask. Using physical vapor deposition technology, in a vacuum environment, deposit 10 - 40 nm of metal Ni on the surface of the nitrogen-doped graphene thin film at a rate of 0.1 nm / s - 10 nm / s. After the evaporation is completed, remove the metal mask covering the surface of the nitrogen-doped graphene thin film to obtain the patterned Ni electrode, that is, the second electrode.

[0093] A7. Use acetone to remove the nitrogen-doped graphene layer on the upper surface of the first electrode to partially expose it.

[0094] Place the terahertz detector prepared in this example into the terahertz optoelectronic detection system. As Figure 6 shown, use an arbitrary waveform generator to modulate a terahertz wave of 0.22 THz to output a terahertz wave with a periodically varying optical power, and then vertically project the terahertz wave onto the surface of the detector. Connect the digital source meter to the two electrodes of this detector to extract and output the effective optoelectronic response signal. As Figure 8 shown, with the periodic change of the terahertz optical power, this detector can output a periodically varying electrical signal. And for a terahertz wave of 0.1 mW, the response photocurrent of the detector is 0.061 μA. Since the device only contains boron-doped graphene, which is only a P-type semiconductor and cannot effectively separate photo-generated carriers, the response performance of the device is significantly lower than that of the example.

[0095] Comparative Example 2

[0096] Comparative Example 2 is a boron-doped graphene terahertz detector without a nitrogen-doped graphene layer in Example 1. The preparation process of Comparative Example 2 includes the following steps:

[0097] B1. Take a silicon oxide wafer with an area of 10 mm × 10 mm, and ultrasonically clean the silicon oxide wafer with acetone, alcohol, and deionized water in sequence, then dry it for standby.

[0098] B2. Cover the surface of the clean silicon oxide wafer with the patterned metal mask. Using thermal evaporation, in a vacuum environment, deposit 1 nm - 3 nm of metal Cr and 10 nm - 40 nm of metal Au on the surface of the silicon oxide wafer at a rate of 0.1 nm / s - 10 nm / s. After the evaporation is completed, remove the metal mask covering the surface of the silicon oxide wafer to obtain the patterned gold electrode;; that is, deposit the first electrode on the substrate.

[0099] B3. Synthesize boron-doped graphene using the hydrothermal method: Mix the graphene oxide dispersion (1 - 5 mg / mL) and boric acid in a mass ratio of 1:5 to 1:20 (such as 10 mg GO: 50 - 200 mg H3BO3), and ultrasonically treat for 30 - 60 minutes to make the mixture uniform. Transfer the mixture to a stainless-steel hydrothermal reactor lined with polytetrafluoroethylene, seal it, and place it in an oven. React at 180 - 220 °C for 6 - 24 hours. After cooling to room temperature, centrifuge at 8000 - 12000 rpm for 10 minutes, and wash with deionized water and ethanol 3 - 5 times. Vacuum dry at 60 - 80 °C for 6 - 12 hours to obtain boron-doped graphene powder. Add the boron-doped graphene powder to deionized water to prepare a boron-doped graphene dispersion with a concentration of 10 - 100 mg / ml.

[0100] B4. Ultraviolet ozone treat the silicon oxide wafer with gold electrodes on its surface for 10 - 20 min.

[0101] B5. Ultrasonically treat the boron-doped graphene dispersion for 30 minutes. Take 20 μL of the boron-doped graphene dispersion, drop it onto the silicon oxide surface, and spin-coat at 3000 rpm for 30 seconds. Repeat this step 3 - 10 times. Let the obtained film stand at room temperature or in an environment below 60 °C for more than 8 hours to dry it, and obtain the boron-doped graphene layer 3.

[0102] B6. Cover the surface of the boron-doped graphene film supported by the silicon oxide substrate with a patterned metal mask. Using physical vapor deposition technology, deposit 10 - 40 nm of metal Ni on the surface of the boron-doped graphene film in a vacuum environment at a rate of 0.1 nm / s - 10 nm / s. After evaporation is completed, remove the metal mask covering the surface of the boron-doped graphene film to obtain a patterned second electrode;

[0103] B7. Use acetone to remove the boron-doped graphene layer on the upper surface of the gold electrode to partially expose it.

[0104] Place the terahertz detector prepared in this embodiment in a terahertz optoelectronic detection system, as Figure 6 shown. Modulate the terahertz wave of 0.22 THz using an arbitrary waveform generator to make it output a terahertz wave with a periodically changing optical power, and then vertically project the terahertz wave onto the detector surface. Connect the digital source meter to the two electrodes of the detector to extract and output an effective optoelectronic response signal. As Figure 9 shown, with the periodic change of the terahertz optical power, this detector can output a periodically changing electrical signal, and for a terahertz wave of 0.1 mW, the response photocurrent of the detector is 0.04 μA. Since the device only contains boron-doped graphene, which is only a P-type semiconductor and cannot effectively separate photo-generated carriers, the response performance of the device is significantly lower than that of Example 1.

[0105] Although the specific embodiments of the invention have been described in detail with reference to the accompanying drawings, it should not be construed as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative efforts still fall within the scope of protection of this patent.

Claims

1. A graphene terahertz photodetector enhanced by element doping, characterized in that: It includes a substrate, a first electrode, a boron-doped graphene layer, a nitrogen-doped graphene layer, and a second electrode; The first electrode and the boron-doped graphene layer are both disposed on the substrate, and an ohmic contact is formed between the side surface of the boron-doped graphene layer and the first electrode; the nitrogen-doped graphene layer is disposed on the boron-doped graphene layer; the second electrode is located on the nitrogen-doped graphene layer and forms an ohmic contact with the nitrogen-doped graphene layer.

2. The graphene terahertz photodetector based on element doping enhancement according to claim 1, wherein: The substrate is a silicon oxide wafer with a thickness of 100 nm - 500 nm.

3. The graphene terahertz photodetector based on element doping enhancement according to claim 1, wherein: The thicknesses of both the boron-doped graphene layer and the nitrogen-doped graphene layer are 0.05 - 0.5 μm.

4. The graphene terahertz photodetector based on element doping enhancement according to claim 1, characterized in that: The first electrode includes a 1 nm - 3 nm metal Cr as a transition layer and 10 nm - 40 nm of metal Au; the second electrode is 10 - 40 nm of metal Ni.

5. The graphene terahertz photodetector based on element doping enhancement according to claim 1, characterized in that: The lateral distance between the first electrode and the second electrode is 100 - 500 μm.

6. A preparation process for the graphene terahertz photodetector based on element doping enhancement according to any one of claims 1 to 5, characterized in that, It includes the following steps: S1. Use a silicon oxide wafer as the substrate and perform ultrasonic cleaning on the substrate; S2. Use a patterned metal mask template to deposit the first electrode on the substrate; S3. Synthesize a boron-doped graphene dispersion by a hydrothermal method; S4. Perform ultraviolet ozone treatment on the substrate surface; S5. Spin-coat the boron-doped graphene dispersion on the substrate surface to obtain a boron-doped graphene layer; S6. Synthesize a nitrogen-doped graphene dispersion by a hydrothermal method; S7. Spin-coat the nitrogen-doped graphene dispersion on the surface of the boron-doped graphene layer to obtain a nitrogen-doped graphene layer; S8. Use a patterned metal mask template to deposit the second electrode on the surface of the nitrogen-doped graphene thin film; S9. Remove the boron-doped graphene layer and the nitrogen-doped graphene layer on the first electrode to expose the first electrode.

7. The preparation process of the graphene terahertz photodetector based on element doping enhancement according to claim 6, characterized in that: In S2, cover the patterned metal mask template on the surface of the silicon oxide wafer, and use thermal evaporation to deposit 1 nm - 3 nm of metal Cr and 10 nm - 40 nm of metal Au on the surface of the silicon oxide wafer at a rate of 0.1 nm / s - 10 nm / s in a vacuum environment, thereby obtaining the first electrode.

8. The manufacturing process of the graphene terahertz photodetector based on element doping enhancement according to claim 6, characterized in that: In S5, perform ultrasonic treatment on the boron-doped graphene dispersion, and use the spin-coating method to uniformly drop the boron-doped graphene dispersion onto the silicon oxide surface to obtain a boron-doped graphene layer with a thickness of 0.05 - 0.5 μm; the boron-doped graphene layer completely covers the surface of the first electrode.

9. The preparation process of the graphene terahertz photodetector based on element doping enhancement according to claim 6, characterized in that: In S7, perform ultrasonic treatment on the nitrogen-doped graphene dispersion, and use the spin-coating method to drop the graphene dispersion onto the surface of the boron-doped graphene layer supported by the silicon oxide substrate to obtain a nitrogen-doped graphene layer with a thickness of 0.05 - 0.5 μm.

10. The manufacturing process of the graphene terahertz photodetector based on element doping enhancement according to claim 6, characterized in that: In S8, cover the patterned metal mask template on the surface of the nitrogen-doped graphene thin layer, and use physical vapor deposition technology to deposit 10 - 40 nm of metal Ni on the surface of the nitrogen-doped graphene thin layer at a rate of 0.1 nm / s - 10 nm / s in a vacuum environment, thereby obtaining the second electrode.

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