Photovoltaic photoelectric detector and preparation method thereof

Abstract

The invention belongs to the field of photoelectric detectors, and discloses a photovoltaic photoelectric detector which adopts a two-dimensional molybdenum telluride / two-dimensional indium selenide horizontal heterojunction as a basic structure unit, is provided with a pair of symmetrical gold electrodes and is simple in device structure. According to the detector, electrodes are evaporated on a silicon substrate covered with silicon oxide, molybdenum telluride and indium selenide materials are transferred in sequence, and horizontal heterostructures are formed in a device channel and are only connected with the electrodes on one side respectively. The broadband absorption characteristic of narrow-band-gap molybdenum telluride and the anisotropic lattice structure of indium selenide are utilized to realize broadband and light polarization sensitive photoelectric detection at the same time on the device level; in combination with the characteristics of p-type doping and n-type doping of molybdenum telluride and indium selenide in air, a II-type heterostructure is constructed, dark current is inhibited by using a built-in electric field, and the separation and transport efficiency of photon-generated carriers is improved by cooperating with a bias electric field, so that high-performance photoelectric detection is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic photodetectors, and particularly relates to a high-performance, broadband, and light polarization-sensitive photovoltaic photodetector and a preparation method thereof. Background Art

[0002] Broadband and light polarization-sensitive photodetectors have great application potential in the fields of national defense, optical communication, low-light detection, medical and health, etc. Broadband and light polarization-sensitive detection and imaging technologies can be used for accurate and efficient target recognition in complex environments, meeting the development needs of the next-generation multi-dimensional photoelectric detection technology. Traditional polarization photodetectors usually require external optical elements and complex optical structures to achieve synchronous broadband and light polarization detection. The processing technology of van der Waals heterostructures integrated with two-dimensional materials with excellent optoelectronic properties is simple, and it has potential advantages in realizing synchronous broadband and light polarization detection and device miniaturization. Therefore, broadband and light polarization photodetectors based on van der Waals heterostructures have attracted much attention to explore the intrinsic properties of materials and use external fields to improve performance.

[0003] Two-dimensional materials have no dangling bonds, and there is no need to consider the lattice matching problem when constructing van der Waals heterostructures. In terms of performance, the constructed heterostructures can give play to the advantages of the constituent materials and are overall superior to any constituent material. When the constituent materials are isotropic materials, such as traditional silicon materials, new transition metal compounds, and carbon materials, etc., the heterostructure photodetectors can respond to a wide range of visible-infrared spectra. If such detectors do not have additional plasmonic structures and external light polarization elements to introduce anisotropy, it will be difficult to detect polarized light. When the constituent materials are anisotropic materials, such as germanium arsenide, rhenium sulfide, black phosphorus, and carbon nanotubes, etc., the heterostructures can have both broadband and light polarization-sensitive detection capabilities. Such detectors have become a research hotspot in recent years, but the detection performance is still insufficient. For example, germanium arsenide and rhenium sulfide have low carrier mobility and high photo-generated carrier recombination, and their dichroisms are 1.49 and 1.03. (Nano, 2018, 12, 12416-12423, ACS Photon, 2021, 8, 2650-2658.) Black phosphorus has a relatively high dichroism of 20.1, but it is very unstable in air. (Advanced Optical Materials, 2022, 10, 2102018.) In the patent with the publication number CN116799092A, Long Hao et al. prepared a detector based on gallium oxide, and the preparation of this invention is complex and requires controlling the interdigital spacing between the electrodes and the material. Although the device performance has been improved, polarization detection cannot be achieved.

[0004] Among various anisotropic materials, indium selenide (α-In2Se3) is relatively stable in air, usually n-type doped, and has a high of 488 cm 2 V-1 s -1 has a carrier mobility and a highly anisotropic lattice structure, and has a high absorption of polarized light. In addition, molybdenum telluride (2H-MoTe2) is usually p-type doped in air, has a high carrier mobility, a wide spectral absorption, and high stability. The two materials can construct a van der Waals heterostructure, which can realize synchronous broadband and polarization-sensitive photodetection. At the same time, by regulating the built-in electric field of the pn junction, the detection performance can be improved to achieve high-performance photodetection.

[0005] In view of the above analysis, the technical problems urgently needed to be solved in the prior art are as follows:

[0006] There is an urgent need to develop high-performance, broadband, and light polarization-sensitive photodetectors at present. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a high-performance, broadband, and light polarization-sensitive photovoltaic photodetector.

[0008] The technical solution of the present invention is as follows:

[0009] A photovoltaic photodetector, characterized by comprising:

[0010] A silicon substrate covered with silicon dioxide;

[0011] A pair of gold electrodes symmetrically arranged on the silicon substrate;

[0012] A two-dimensional molybdenum telluride material and a two-dimensional indium selenide material arranged on the silicon substrate and located between a pair of gold electrodes, and the two-dimensional molybdenum telluride material and the two-dimensional indium selenide material form a horizontal heterojunction structure in the channel region between the electrodes;

[0013] One end of the two-dimensional molybdenum telluride material is connected to one side electrode, and the other end extends to the middle of the channel region;

[0014] One end of the two-dimensional indium selenide material is connected to the other side electrode, and the other end forms a heterojunction interface with the two-dimensional molybdenum telluride material;

[0015] The heterojunction is a type-II energy band structure, which suppresses the dark current through the built-in electric field and cooperates with the external bias electric field to achieve a wide spectral response and light polarization-sensitive detection in the wavelength range of 520 nm to 1550 nm.

[0016] The anisotropy ratio (PR) of the photocurrent is 1.40 ± 0.05 (@638 nm); the responsivity is 0.005 A / W to 4.6 A / W; the specific detectivity is 0.006×10^9 Jones to 6.7×10^9 Jones.

[0017] The thickness of the silicon substrate covered with silicon dioxide is 0.5 mm to 0.6 mm.

[0018] The thickness of the two-dimensional molybdenum telluride material is 78 nm ± 5 nm, and the thickness of the two-dimensional indium selenide material is 68 nm ± 5 nm.

[0019] The thickness of the gold electrode is 50 nm to 70 nm.

[0020] The two-dimensional molybdenum telluride material is p-type doped, and the two-dimensional indium selenide material is n-type doped. When they are in contact, a pn junction structure is formed, and the direction of the built-in electric field of the pn junction points from indium selenide to molybdenum telluride.

[0021] The present invention also provides a method for preparing a photovoltaic photodetector, which is characterized by including the following steps:

[0022] S1: Clean the silicon substrate covered with silicon dioxide;

[0023] S2: Prepare symmetric gold electrodes on the silicon substrate through ultraviolet lithography, electron beam evaporation and lift-off processes;

[0024] S3: Transfer the two-dimensional molybdenum telluride material onto the silicon substrate by mechanical cleavage technology, control its thickness to be 78 nm ± 5 nm, and connect one end of the material to one side electrode, and the other end extends to the middle of the channel region;

[0025] S4: Transfer the two-dimensional indium selenide material onto the silicon substrate by mechanical cleavage technology, control its thickness to be 68 nm ± 5 nm, and connect one end of the material to the other side electrode, and the other end forms a heterojunction interface with the two-dimensional molybdenum telluride material.

[0026] Further, in the step S2, the thickness of the gold electrode is controlled to be 50 nm to 70 nm by electron beam evaporation process.

[0027] Further, in the steps S3 and S4, the mechanical cleavage technology includes controlling the number of layers of the two-dimensional material and flattening the edges.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] Both the two-dimensional molybdenum telluride and the two-dimensional indium selenide selected in the present invention are narrow-bandgap materials, which respectively have broadband absorption characteristics and anisotropic crystal structures, and can simultaneously achieve photoelectric detection of broadband (520 nm–1550 nm) and light polarization sensitivity (PR = 1.40).

[0030] The present invention uses a two-dimensional indium selenide / two-dimensional molybdenum telluride horizontal heterostructure as the basic structural unit, which has a pair of symmetric gold electrodes and a simple device structure. By constructing a type-II heterostructure and utilizing the anisotropy of indium selenide and the wide-spectrum light absorption characteristics of molybdenum telluride, synchronous broadband and light polarization-sensitive photoelectric detection can be achieved; the built-in electric field is used to suppress the dark current, and it cooperates with the bias electric field to improve the separation and transport efficiency of photo-generated carriers, thereby achieving high-performance photoelectric detection.

[0031] Photoelectric detectors are key components for realizing optoelectronic conversion in information systems and can be used in applications such as photoelectric detection, communication, and imaging. Broadband and polarization-sensitive photoelectric detection and imaging technologies can accurately and efficiently identify targets in complex environments, meeting the development needs of the next-generation multi-dimensional photoelectric detection. Traditional polarization light detectors usually require external optical elements and complex optical structures to achieve synchronous broadband and polarization-sensitive photoelectric detection. Currently, broadband and polarization-sensitive photoelectric detection technologies have become international frontier hotspots.

[0032] Van der Waals heterostructures integrate two-dimensional materials with excellent optoelectronic properties and have potential advantages in realizing broadband and polarization detection. Based on traditional heterostructure photoelectric detectors such as silicon materials, new transition metal compounds, and carbon materials, visible-infrared broadband detection can be achieved. However, due to the isotropy of the crystal structures of these materials, these devices are usually insensitive to polarization. For anisotropic materials such as germanium arsenide, rhenium sulfide, black phosphorus, and carbon nanotubes, heterostructure photoelectric detectors with both multi-color and polarization detection capabilities can be constructed, but they still face limitations in terms of high performance. For example, the dichroism of germanium arsenide and rhenium sulfide is average, being 1.49 and 1.56 respectively; the dichroism of black phosphorus is relatively high, being 20.1, but it is very unstable in air; single-walled carbon nanotubes have high anisotropy in molecular structure and electrical and optoelectronic properties, but due to their nanoscale tube diameters, they are difficult to locate and process in micro-nano processing. Although ordered carbon nanotube arrays are convenient for positioning and processing, they usually require complex growth, impurity removal, and assembly processes.

[0033] As a kind of anisotropic material, indium selenide is stable in air, usually n-type doped, has a carrier mobility as high as 488 cm 2 V -1 s -1 and has an anisotropic lattice structure, which can be used for light polarization detection. In addition, molybdenum telluride is usually p-type doped in air, has high carrier mobility, wide-spectrum absorption, and high stability. The two materials can be used to construct a van der Waals heterostructure. While synchronously achieving broadband and polarization-sensitive photoelectric detection, the detection performance can be improved by regulating the built-in electric field of the pn junction, and high-performance photoelectric detection can be realized.

[0034] The technical solution of the present invention provides an example and a feasible development strategy for high-performance broadband and polarization-sensitive photodetectors in industrial applications. By constructing a two-dimensional indium selenide and two-dimensional molybdenum telluride heterostructure, based on a simple symmetric electrode device design, the intrinsic characteristics of each constituent material are innovatively utilized, such as the broad-spectrum light absorption, high carrier mobility, and high stability of molybdenum telluride, combined with the anisotropic lattice structure, high carrier mobility, and high stability of indium selenide, to achieve synchronous broadband and polarization-sensitive photodetection.

[0035] First, by using narrow-bandgap two-dimensional molybdenum telluride as the photosensitive material, the present invention can achieve photodetection in a wider spectral range, including the visible light and near-infrared regions, ensuring the broadband photoelectric response of the heterostructure photodetector. Second, by utilizing the anisotropic crystal structure of indium selenide, the polarization light response of the heterojunction photodetector can be ensured. Finally, synchronous broadband and light polarization-sensitive photodetection are achieved at the device level.

[0036] Second, molybdenum telluride and indium selenide are p-type and n-type doped in air respectively. When they are in contact, a type-II heterostructure can be formed due to band bending. The built-in electric field generated can suppress the dark current and cooperate with the bias electric field to enhance the separation and transport efficiency of photo-generated carriers, achieving high-performance photodetection.

[0037] Generally speaking, by designing a van der Waals heterostructure and utilizing the intrinsic electrical and optoelectronic characteristics of various constituent materials, the present invention realizes multi-dimensional photodetection that is broadband based on wavelength and polarization-sensitive based on the light polarization angle; at the same time, by utilizing the synergistic effect of the built-in electric field and the bias electric field of the heterostructure, the improvement of photodetection performance is achieved, providing an example and a feasible solution for the next-generation high-performance and multi-dimensional photodetection, with strong industrial application prospects, especially in the fields of photoelectric sensing, imaging, and optical communication, and can promote the technological progress of related industries. Description of the Drawings

[0038] Figure 1 is a front-side schematic view of the structure of a high-performance, broadband, and light polarization-sensitive photovoltaic photodetector provided by an embodiment of the present invention.

[0039] Figure 2 is a left-side schematic view of the structure of a high-performance, broadband, and light polarization-sensitive photovoltaic photodetector provided by an embodiment of the present invention.

[0040] Figure 3 is a top-view schematic view of the structure of a high-performance, broadband, and light polarization-sensitive photovoltaic photodetector provided by an embodiment of the present invention.

[0041] Figure 4 is the light response of a high-performance, broadband, and light polarization-sensitive photovoltaic photodetector provided by an embodiment of the present invention at different wavelengths.

[0042] Figure 5 It is the polarization-sensitive response of the high-performance, broadband, and light polarization-sensitive photovoltaic photodetector provided by the embodiments of the present invention at different wavelength bands.

[0043] Figure 6 It is the comparison of the responsivity and specific detectivity of the high-performance, broadband, and light polarization-sensitive photovoltaic photodetector provided by the embodiments of the present invention in the visible-near infrared broadband.

[0044] Figure 7 It is the imaging and optical communication applications of the high-performance, broadband, and light polarization-sensitive photovoltaic photodetector provided by the embodiments of the present invention. Figure 7 Parts a and b in it are the display of imaging results; Figure 7 Part c in it is the comparison of the input and output results of optical communication coding.

[0045] In the figure: 1. Two-dimensional molybdenum telluride material, 2. Two-dimensional indium selenide material, 3. Electrode, 4. Silicon substrate covered with silicon dioxide. Detailed implementation manners

[0046] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0047] As Figure 1 , Figure 2 , Figure 3 shown, the embodiments of the present invention provide a high-performance, broadband, and light polarization-sensitive photovoltaic photodetector. Based on a symmetric electrode device structure, an indium selenide / molybdenum telluride horizontal heterojunction is constructed as the basic structural unit. The detector has a pair of symmetric gold electrodes. By using the broadband absorption characteristics of narrow-bandgap molybdenum telluride and the anisotropic lattice structure of indium selenide, broadband and light polarization-sensitive photoelectric detection are simultaneously realized at the device level.

[0048] For the detector, first, two end electrodes 3 are evaporated on the silicon substrate 4 covered with silicon dioxide, and then the two-dimensional molybdenum telluride material 1 and the two-dimensional indium selenide material 2 are transferred successively. The two materials form a horizontal heterostructure in the channel between the electrodes and are respectively connected to only one side electrode. Combining the characteristics of p-type and n-type doping of molybdenum telluride and indium selenide in the air, by constructing a type-II heterostructure, the built-in electric field is used to suppress the dark current, and it cooperates with the bias electric field to improve the separation and transport efficiency of photo-generated carriers, realizing high-performance photoelectric detection.

[0049] The thickness of the silicon substrate 4 covered with silicon dioxide is 0.5 - 0.6 mm.

[0050] The thickness of the two-dimensional molybdenum telluride material 1 is about 78 nm, and the thickness of the two-dimensional indium selenide material 2 is about 68 nm.

[0051] The thickness of the source-drain electrodes 3 is about 50 - 70 nm.

[0052] The photovoltaic detector in the present invention adopts a design based on a two-dimensional molybdenum telluride and two-dimensional indium selenide heterostructure, combined with symmetric gold electrodes, to construct a basic unit for photoelectric detection. On a silicon substrate, symmetric gold electrodes are first evaporated, and then the two-dimensional molybdenum telluride and two-dimensional indium selenide materials are transferred in sequence, forming a horizontal heterojunction structure in the middle of the electrodes. Molybdenum telluride, as a narrow-bandgap material, has excellent broad-spectrum detection ability, while indium selenide, as an anisotropic material, has polarization-sensitive detection ability. The combination of the two constitutes an optoelectronic device that can simultaneously achieve broad-spectrum and polarization-sensitive detection.

[0053] The working principle of this structure is mainly based on the photovoltaic effect. Due to the difference in Fermi levels, when indium selenide and molybdenum telluride come into contact, the energy bands bend to cause a staggered band (type II) arrangement, and a built-in electric field will be formed at the junction region, with the direction pointing from indium selenide to molybdenum telluride. The built-in electric field not only enhances the light response but also suppresses the dark current to an ultra-low level of 10 -10 A.

[0054] In addition, when a forward bias is applied to the device, the direction of the applied bias electric field is the same as that of the built-in electric field, and the intensity of the built-in electric field increases as the junction region widens. This helps to separate and collect photo-generated carriers, thereby enhancing the light response.

[0055] Finally, due to the respective characteristics of indium selenide and molybdenum telluride materials, this photodetector can maintain a high and stable response under illumination of different wavelengths, and can also achieve broadband polarization-sensitive response. The overall design realizes the efficient detection of optical signals and polarization detection within a relatively wide wavelength range, and is suitable for various optoelectronic detection applications.

[0056] The specific preparation and testing processes are as follows:

[0057] Step 1: Clean the surface of the silicon substrate covered with silicon oxide, and cut the silicon substrate into a size of 1 cm × 1 cm through a cutting technique, and then perform secondary cleaning on its surface;

[0058] Step 2: Use ultraviolet lithography, electron beam evaporation, and gold film stripping processes to prepare symmetric source-drain electrodes on the silicon substrate;

[0059] Step 3: Use a high-precision spatially resolved transfer platform and mechanical cleavage and transfer techniques to transfer the two-dimensional molybdenum telluride material onto the silicon substrate, making one end connected to one side electrode and the other end extending to the middle of the device channel;

[0060] Step 4: Again, utilize the high-precision spatial resolution transfer platform and mechanical cleavage and transfer techniques to transfer the two-dimensional indium selenide material onto the silicon substrate, making one end in close contact with the two-dimensional molybdenum telluride material and the other end connected to the other electrode.

[0061] Step 6: In a room-temperature atmospheric environment, connect the probe of the probe station to the electrodes of the device. Let the signal light be modulated by a chopper and focused by an off-axis parabolic mirror, and then irradiate the detector. The optical response signal generated by the detector is amplified by a preamplifier and then input into the Meta Optoelectronic Acquisition System respectively. In addition, the modulation frequency of the chopper needs to be input into the oscilloscope as a reference signal respectively to ensure accurate recording of the response waveform and response amplitude of the device to visible and infrared radiation.

[0062] Step 7: In a room-temperature atmospheric environment, after packaging the device, connect it to a junction box, and adjust the spatial positions of the light source beam, aperture, and the device to ensure they are on a straight line. The encoded beam irradiates on the device to generate an encoded optoelectronic signal. This signal is amplified by a preamplifier and then transmitted to the optoelectronic test system workstation by a signal acquisition card. After data processing in the background, the waveform of the received encoded signal can be finally presented on the display screen.

[0063] Step 8: In a room-temperature atmospheric environment, connect the packaged device to a junction box, and adjust the spatial positions of the light source beam, aperture, imaging mask, and the device to ensure they are all on the optical path. The imaging beam passes through the aperture, off-axis parabolic mirror, and imaging mask and then irradiates on the detector. The imaging mask is fixed on a high-precision stepping motor and can move horizontally / vertically with a stepping accuracy of 0.5 mm: when the mask blocks the imaging light, the detector is not irradiated by the beam and outputs a dark current; when the mask does not block the imaging light, the detector can be irradiated by the beam and outputs a dark current and a photocurrent. The generated optoelectronic signal is amplified by a preamplifier and a lock-in amplifier in sequence and finally transmitted back to the optoelectronic imaging system workstation. After background processing, the imaging effect can be presented on the display screen.

[0064] Example 1: Device Fabrication and Structure Verification

[0065] 1. Substrate treatment:

[0066] Use a silicon substrate 4 (with a thickness of 0.5 mm) covered with silicon oxide (with a thickness of 300 nm), and cut it into a size of 1 cm × 1 cm.

[0067] Ultrasonically clean it with acetone and isopropyl alcohol for 10 minutes in sequence. After drying with nitrogen, enhance the surface hydrophilicity through oxygen plasma treatment (power 50 W, time 5 minutes).

[0068] 2. Electrode preparation:

[0069] Define symmetric electrode patterns on the silicon substrate using ultraviolet lithography;

[0070] Deposit a gold layer by electron beam evaporation, and then perform a lift-off process (soak in acetone for 1 hour) to form symmetric electrodes 3 (thickness 50 nm) with a spacing of 5 μm.

[0071] 3. Material transfer:

[0072] Transfer of two-dimensional molybdenum telluride 1 (MoTe2): Use mechanical cleavage technology to exfoliate a single-layer film (thickness 78 nm ± 5 nm) from a bulk MoTe2 crystal, and transfer it to the left side of a silicon substrate through a high-precision transfer platform (positioning accuracy ±0.1 μm), ensuring that one end is in contact with the left electrode and the other end extends to the middle of the channel.

[0073] Transfer of two-dimensional indium selenide 2 (In2Se3): Similarly, exfoliate an In2Se3 film (thickness 68 nm ± 5 nm), transfer it to the right side of the silicon substrate, and make one end in contact with the right electrode and the other end form a tight heterojunction interface with the MoTe2 film.

[0074] Verify the material thickness by atomic force microscopy (AFM) (MoTe2: 78 nm ± 3 nm, In2Se3: 68 nm ± 3 nm). Confirm that there is no significant material mixing at the heterojunction interface through Raman spectroscopy (excitation wavelength 532 nm) (the characteristic peaks of MoTe2 are located at 172 and 232 cm -1 , and the characteristic peaks of In2Se3 are located at 88, 104, 181, and 197 cm -1 ).

[0075] Figure 4 This is the optical response of the photovoltaic photodetector in the embodiments of the present invention at different wavelength bands. As Figure 4 shown, under visible-infrared (638 nm, 940 nm, and 1550 nm) light illumination, the photocurrents are 42 nA, 43 nA, and 1.1 nA respectively. It can be seen that the photocurrent pulse signal is stable and repeatable, showing a stable broadband response.

[0076] The thickness of the silicon substrate covered with silicon dioxide is 0.5 mm, the thickness of the two-dimensional molybdenum telluride material is about 78 nm, the thickness of the two-dimensional indium selenide material is about 68 nm, and the electrode thickness is 60 nm. As Figure 5 shown, under illumination at 638 nm and 1550 nm, the anisotropy ratios (PR, defined as I ph-max / I ph-min ) of the indium selenide / molybdenum telluride heterojunction device are 1.40 and 1.07 respectively. The relatively low anisotropy ratio at 1550 nm is attributed to the relatively low light absorption rate (~5%) of indium selenide beyond the cut-off wavelength of ~894.3 nm. Generally speaking, the indium selenide / molybdenum telluride heterojunction device has important potential in broadband polarization-sensitive detection.

[0077] AsFigure 6 As shown in Figure 2, under 638nm, 940nm and 1550nm light, the response rate of the InSe / MoTe heterostructure device is 0.005-4.6A / W, and the specific detection rate is (0.006-6.7)×10 9 Jones, demonstrated high-performance broadband photodetection capabilities.

[0078] Imaging test: Using a 520nm laser light source, the mask (patterns "SIOM" and "M") are projected onto the detector surface. The stepper motor controls the mask movement (accuracy 0.5mm). After the output signal is processed by a lock-in amplifier, the imaging result shows that the pattern outline is clear and the signal-to-noise ratio is >20dB ( Figure 7 a, 7b). The results show that the detector of this embodiment has stable photoelectric polarization detection performance and imaging capability.

[0079] Optical communication test: InSe / MoTe heterostructure device is used as signal receiver to transmit ASCII code via visible-infrared light. Figure 7 Figure c shows the input signal of the letter "HIAS" encoded by the two-state photocurrent ("1" and "0" represent the "ON" and "OFF" states, respectively). The received 4-bit signal presents a perfect square wave, which matches the original input signal well, ensuring high-quality reproduction of information transmission. This verifies the high reliability of the device in optical communications.

[0080] 1. Specific application fields or related products of the present invention.

[0081] Aiming at the current needs of complicated photoelectric detection environment, refined target identification, and integrated communication perception, the present invention is based on a simple gold-anisotropic material / narrow bandgap material-gold symmetrical electrode device structure, and selects the wide-band absorption characteristics of narrow-bandgap molybdenum telluride and the anisotropic lattice structure of indium selenide to simultaneously realize broadband and light polarization-sensitive photoelectric detection at the device level; in addition, by constructing a type II heterostructure, the built-in electric field is used to suppress dark current, and the separation and transport efficiency of photogenerated carriers are improved in coordination with the bias electric field, so as to realize high-performance photoelectric detection. It provides a good solution for target identification in complex environments and multifunctional applications of photoelectric devices.

[0082] 2. Relevant evidence of the technical effects obtained by the embodiments of the present invention.

[0083] The present invention uses indium selenide with anisotropic crystal structure and molybdenum telluride with narrow band gap, and combines the symmetrical electrode structure of gold / indium selenide / molybdenum telluride / gold to achieve broadband (520nm-1550nm), high sensitivity (0.005-4.6A / W, (0.006-6.7)×10 9Jones), polarization response (PR = 1.4, @638 nm). This is mainly due to the inherent properties of the material itself and the constructed type-II heterojunction device structure, which uses the built-in electric field to suppress the dark current and cooperates with the bias electric field to improve the separation and transport efficiency of photo-generated carriers, achieving high-performance photodetection. Figure 7 The results show that the indium selenide / molybdenum telluride heterostructure photodetector has polarization-sensitive detection ability and broad prospects in the practical applications of visible-infrared imaging and optical communication.

[0084] As mentioned above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A photovoltaic photodetector, characterized in that, Comprising: A silicon substrate (4) covered with silicon dioxide; A pair of gold electrodes (3) symmetrically disposed on the silicon substrate (4); A two-dimensional molybdenum telluride material (1) and a two-dimensional indium selenide material (2) disposed on the silicon substrate (4) and between a pair of gold electrodes (3), and a horizontal heterojunction structure is formed in the channel region between the electrodes by the two-dimensional molybdenum telluride material (1) and the two-dimensional indium selenide material (2); One end of the two-dimensional molybdenum telluride material (1) is connected to one side electrode, and the other end extends to the middle of the channel region; One end of the two-dimensional indium selenide material (2) is connected to the other side electrode, and the other end forms a heterojunction interface with the two-dimensional molybdenum telluride material (1); The heterojunction is a type-II energy band structure, suppressing dark current through the built-in electric field, and synergistically acting with an external bias electric field to achieve wide-spectrum response and light polarization-sensitive detection in the wavelength band of 520 nm to 1550 nm.

2. The photovoltaic photodetector according to claim 1, wherein The anisotropy ratio (PR) of the photocurrent is 1.40 ± 0.05 (@638 nm); the responsivity is 0.005 A / W to 4.6 A / W; the specific detectivity is 0.006 × 10^9 Jones to 6.7 × 10^9 Jones.

3. The photovoltaic photodetector according to claim 1, characterized in that, The thickness of the silicon substrate (4) covered with silicon dioxide is 0.5 mm to 0.6 mm.

4. The photovoltaic photodetector according to claim 1, characterized in that, The thickness of the two-dimensional molybdenum telluride material (1) is 78 nm ± 5 nm, and the thickness of the two-dimensional indium selenide material (2) is 68 nm ± 5 nm.

5. The photovoltaic photodetector according to claim 1, characterized in that, The thickness of the gold electrode (3) is 50 nm to 70 nm.

6. The photovoltaic photodetector according to claim 1, characterized in that, The two-dimensional molybdenum telluride material (1) is p-type doped, and the two-dimensional indium selenide material (2) is n-type doped. The two contact to form a pn junction structure, and the direction of the built-in electric field of the pn junction points from indium selenide to molybdenum telluride.

7. A method for preparing a photovoltaic photodetector according to any one of claims 1-6, characterized in that, Including the following steps: S1: Cleaning the silicon substrate covered with silicon dioxide; S2: Preparing symmetric gold electrodes (3) on the silicon substrate through ultraviolet lithography, electron beam evaporation and lift-off processes; S3: Transferring the two-dimensional molybdenum telluride material (1) onto the silicon substrate (4) by using a mechanical cleavage technique, controlling its thickness to be 78 nm ± 5 nm, and connecting one end of the material to one side electrode and the other end extending to the middle of the channel region; S4: Transferring the two-dimensional indium selenide material (2) onto the silicon substrate (4) by using a mechanical cleavage technique, controlling its thickness to be 68 nm ± 5 nm, and connecting one end of the material to the other side electrode and the other end forming a heterojunction interface with the two-dimensional molybdenum telluride material (1).

8. The manufacturing method of the photovoltaic photodetector according to claim 6, characterized in that, In the step S2, the thickness of the gold electrode (3) is controlled to be 50 nm to 70 nm through the electron beam evaporation process.

9. The manufacturing method of the photovoltaic photodetector according to claim 6, characterized in that, In the steps S3 and S4, the mechanical cleavage technique includes controlling the number of layers of the two-dimensional material and performing edge flattening treatment.

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