Infrared detector with van der Waals asymmetric barrier structure and preparation method thereof

Abstract

The present invention discloses an infrared detector with a van der Waals asymmetric barrier structure and a preparation method thereof. The detector structure comprises a substrate, a dielectric layer, a graphene layer, a molybdenum disulfide layer, a black phosphorus layer, and a metal source and a drain electrode. The device preparation step is to sequentially transfer the mechanically exfoliated graphene, molybdenum disulfide and black phosphorus to a substrate with a dielectric layer, and use processes such as electron beam exposure and thermal evaporation to respectively make metal source and drain electrodes on black phosphorus and graphene, thereby forming a vertically structured van der Waals single-carrier infrared photodetector. By utilizing the rich band structure and unique physical properties of two-dimensional materials, an asymmetric barrier band structure with multi-carrier blocking is designed, which can effectively suppress dark current, thereby realizing room temperature blackbody detection, polarization detection and infrared imaging of medium-wave infrared. The detector has the characteristics of room temperature operation, multi-carrier blocking, medium-wave infrared response, high sensitivity, fast response and blackbody detection.

Description

Technical Field

[0001] The invention relates to an infrared detector with a Van der Waals asymmetric potential barrier structure, in particular to a medium-wave infrared single-carrier photoelectric detector and a preparation method thereof. Background Art

[0002] Single-carrier photodetectors are proposed to solve the problem of large dark current in infrared detectors, so that infrared detectors can work at high temperatures. The blocking layer of single-carrier photodetectors needs to strictly consider band matching and lattice matching. There is a large potential barrier in the conduction band or valence band to block the majority carriers, and a barrier close to zero is designed on the other energy band to allow the carriers on this energy band to move freely. Therefore, dark currents such as surface leakage current and majority dark current are blocked by the potential barrier, while the photocurrent is not suppressed. However, the epitaxial growth of traditional materials inevitably has lattice mismatch and interface defects, which seriously hinders the development of high-performance single-carrier photodetectors.

[0003] In order to solve the above problems, we use two-dimensional materials to construct infrared photodetectors with asymmetric barrier structures. Two-dimensional materials have rich and adjustable band structures that can meet the needs of band design, and the surface is naturally passivated to avoid the generation of leakage current. At the same time, different two-dimensional materials can be stacked arbitrarily to form lattice-matched van der Waals junctions, which are ideal materials for designing new photodetectors.

[0004] The present invention proposes an infrared detector with a van der Waals asymmetric barrier structure. The single-carrier photodetector uses black phosphorus as a narrow bandgap absorption layer, molybdenum disulfide as a multi-subsequent barrier layer, and high-mobility graphene as a contact layer. The three materials form a typical hole-blocking band structure. There is almost no barrier in the conduction band, but there is a large hole barrier in the valence band, which can block the injection of holes at the graphene end, effectively suppressing the dark current. The single-carrier photodetector achieves a medium-wave infrared response with a cutoff wavelength of 3.8 microns, and the room-temperature blackbody detectivity reaches 2.3×10 10 cm Hz 1 / 2 W -1 , and realized room temperature blackbody polarization detection and room temperature infrared imaging. At the same time, the response rate of the device reached a fast response of 73 microseconds. Summary of the invention

[0005] The present invention proposes an infrared detector with a van der Waals asymmetric barrier structure and a preparation method thereof, which realizes applications in the fields of room temperature blackbody detection, polarization detection and infrared imaging.

[0006] The above invention introduces a single-carrier barrier structure into a two-dimensional material detector. The detector is based on an optimized design of the energy band structure and utilizes the barrier layer to block majority carriers, thereby reducing dark current, thereby achieving high-sensitivity and high-speed room-temperature blackbody detection of the device.

[0007] The present invention relates to an infrared detector with a van der Waals asymmetric barrier structure and a preparation method thereof, wherein the device structure comprises:

[0008] - substrate 1,

[0009] - dielectric layer 2,

[0010] - graphene layer 3,

[0011] - a molybdenum disulfide layer 4,

[0012] - Source 5,

[0013] - Drain 6,

[0014] -Black phosphorus layer 7.

[0015] Wherein substrate 1 is a P-type heavily doped Si substrate;

[0016] The dielectric layer 2 is SiO 2 , thickness is 280 ± 10 nm;

[0017] The thickness of the graphene layer 3 is 5 to 10 nanometers;

[0018] The thickness of the molybdenum disulfide layer 4 is 10-20 nanometers;

[0019] The metal source electrode 5 is a Cr and Au electrode, the thickness of Cr on the graphene layer is about 15 nanometers, and the thickness of Au on Cr is 75 nanometers;

[0020] The drain electrode 6 is a Cr and Au electrode, the thickness of Cr on the black phosphorus layer is about 15 nanometers, and the thickness of Au on Cr is 75 nanometers;

[0021] The thickness of the black phosphorus layer 7 is 40~150 nanometers;.

[0022] The present invention relates to an infrared detector of a Van der Waals asymmetric barrier structure and a preparation method thereof, wherein the device preparation comprises the following steps:

[0023] 1) Mechanical exfoliation is used to peel off the graphene layer from the graphite material on the SiO 2 On the dielectric layer;

[0024] 2) The molybdenum disulfide layer is peeled off from the molybdenum disulfide bulk material by mechanical peeling, and transferred to one end of the graphene layer by micro-area fixed-point transfer;

[0025] 3) The black phosphorus layer is peeled off from the black phosphorus body material by mechanical stripping, and transferred and covered on the surface of the molybdenum disulfide layer by micro-area fixed-point transfer method, and the other end is covered on the SiO 2 On the dielectric layer and avoid contact with the graphene layer;

[0026] 4) Using processes such as electron beam exposure, thermal evaporation and lift-off, chromium and gold source and drain electrodes are deposited on one end of the pre-transferred graphene layer and black phosphorus layer, respectively.

[0027] The single-carrier barrier structure designed based on two-dimensional materials does not need to consider the problem of lattice matching, and a high-quality interface can be obtained between materials. At the same time, compared with junction devices, the asymmetric barrier structure with multi-carrier blocking can obtain lower dark current at the same temperature and avoid the complex doping process in the process of constructing heterojunctions. The infrared photodetector composed of graphene, molybdenum disulfide and black phosphorus has a unique band structure. There is no electron barrier in the conduction band, but there is a large hole barrier in the valence band. By constructing a single-carrier band structure with hole blocking, the surface leakage current and multi-carrier dark current can be effectively reduced, but the photocurrent will not be suppressed. Here, the n-type doped barrier layer introduces a space charge region, resulting in the generation of defect-assisted generation-recombination current (SRH). However, it is precisely because of the introduction of the doped barrier layer that the device can work at zero bias. Using narrow-bandgap black phosphorus as the absorption layer, a wide spectral response of the mid-wave infrared and polarization detection with a high extinction ratio can be achieved. By utilizing the symmetrical barrier structure, the device achieves highly sensitive room-temperature blackbody detection and infrared imaging, and the response rate of the device reaches 73 microseconds under a 2-micron laser and 150 microseconds under a blackbody light source.

[0028] The advantages of the present invention are: based on the vertical van der Waals single carrier barrier structure, under reverse bias, the majority carriers are blocked by the hole barrier, while the photocurrent is not suppressed, effectively reducing the dark current, thereby improving the performance of the device and realizing room temperature medium-wave infrared blackbody detection. In addition, the device also has the characteristics of room temperature operation, high sensitivity, wide band, fast response, etc., and has great application prospects in blackbody detection, polarization detection, infrared imaging, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the device structure.

[0030] In the figure: 1 substrate, 2 dielectric layer, 3 graphene layer, 4 molybdenum disulfide layer, 5 source, 6 drain, 7 black phosphorus layer.

[0031] Figure 2 This is the energy band diagram of the infrared detector under illumination.

[0032] Figure 3This is the detection rate curve of infrared detector at different blackbody temperatures.

[0033] Figure 4 is the response time of the infrared detector under 900℃ black body and 2μm laser.

[0034] Figure 5 Polarization detection of infrared detector under 900℃ black body.

[0035] Figure 6 Room temperature infrared imaging of infrared detectors. DETAILED DESCRIPTION

[0036] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings:

[0037] The present invention has developed an infrared detector with a van der Waals asymmetric barrier structure. Through the unique asymmetric barrier structure design, dark current can be effectively suppressed, thereby improving the detection rate of the device, and finally realizing room temperature black body detection and infrared imaging.

[0038] The specific steps are as follows:

[0039] 1. Substrate selection

[0040] Heavily doped p-type silicon is used as the substrate, SiO 2 The thickness of the dielectric layer is about 280±10 nanometers.

[0041] 2. 2D Material Transfer

[0042] The three two-dimensional materials, graphene layer, molybdenum disulfide layer and black phosphorus layer, were peeled off in sequence by mechanical peeling, and then transferred to SiO2 in sequence by fixed-point transfer in a nitrogen box. 2 On the dielectric layer, the graphene layer is at the bottom, the molybdenum disulfide layer covers one end of the graphene layer, one end of the black phosphorus layer covers the molybdenum disulfide layer and the other end is partially covered on the SiO 2 The dielectric layer is on the substrate and has no contact with the graphene layer.

[0043] 3. Source and drain preparation

[0044] Electron beam exposure is used to precisely position and expose the electrode pattern, and then PMMA developer is used for development. Thermal evaporation technology is used to prepare metal electrodes, with 15 nanometers for chromium and 75 nanometers for gold. Finally, the metal film is peeled off by soaking in acetone solution for 10 minutes to obtain metal source and drain electrodes.

[0045] 4. Three kinds of van der Waals asymmetric barrier structure infrared detectors with different structural parameters were prepared. Device 1, in which the substrate is a P-type heavily doped Si substrate; the dielectric layer is SiO 2, with a thickness of 280±10 nanometers; the thickness of the graphene layer is 5 nanometers; the thickness of the molybdenum disulfide layer is 10 nanometers; the metal source is Cr and Au electrodes, the thickness of Cr on the graphene layer is about 15 nanometers, and the thickness of Au on Cr is 75 nanometers; the thickness of the black phosphorus layer is 40 nanometers; the metal drain is Cr and Au electrodes, the thickness of Cr on the black phosphorus layer is about 15 nanometers, and the thickness of Au on Cr is 75 nanometers. Device 2, in which the substrate is a P-type heavily doped Si substrate; the dielectric layer is SiO 2 , with a thickness of 280±10 nanometers; the thickness of the graphene layer is 7.5 nanometers; the thickness of the molybdenum disulfide layer is 15 nanometers; the metal source is Cr and Au electrodes, the thickness of Cr on the graphene layer is about 15 nanometers, and the thickness of Au on Cr is 75 nanometers; the thickness of the black phosphorus layer is 95 nanometers; the metal drain is Cr and Au electrodes, the thickness of Cr on the black phosphorus layer is about 15 nanometers, and the thickness of Au on Cr is 75 nanometers. Device 3, in which the substrate is a P-type heavily doped Si substrate; the dielectric layer is SiO 2 , with a thickness of 280±10 nanometers; the thickness of the graphene layer is 10 nanometers; the thickness of the molybdenum disulfide layer is 20 nanometers; the metal source is Cr and Au electrodes, the thickness of Cr on the graphene layer is about 15 nanometers, and the thickness of Au on Cr is 75 nanometers; the thickness of the black phosphorus layer is 150 nanometers; the metal drain is Cr and Au electrodes, the thickness of Cr on the black phosphorus layer is about 15 nanometers, and the thickness of Au on Cr is 75 nanometers. The devices with three structural parameters have similar optoelectronic properties, and the performance indicators are as follows Figure 3 , Figure 4 , Figure 5 and Figure 6 shown.

[0046] 5. Figure 1 This is a schematic diagram of the device structure, where: 1 substrate, 2 dielectric layer, 3 graphene layer, 4 molybdenum disulfide layer, 5 drain, 6 source, 7 black phosphorus layer.

[0047] 6. Figure 2 This is the energy band diagram of the infrared detector under light. Graphene, molybdenum disulfide and black phosphorus have almost no electron barrier in the conduction band, but a large hole barrier in the valence band. When light shines on the surface of the device, electron-hole pairs are generated in the absorption layer black phosphorus. Under the action of the external bias, the electrons are collected by the anode along the conduction band, and the holes are directly collected by the cathode, while the holes in the graphene are blocked by molybdenum disulfide.

[0048] 7. Figure 3 This is the detection rate curve of the infrared detector at different blackbody temperatures. The device exhibits excellent room temperature blackbody detection capability, with a detection cutoff wavelength of 3.8 microns and a peak detection rate of 2.3 × 10 10 cm Hz 1 / 2 W -1 .

[0049] 8. Figure 4 It is the response time of the infrared detector under 900℃ black body and 2 micron laser. The rising edge time is defined as the time required for the photocurrent to increase from 10% to 90%, and the falling edge time is defined as the time required for the photocurrent to decrease from 90% to 10%. Under 2 micron laser, the rising edge time of the device is 73μs and the falling edge time is 77μs. Under 900℃ black body light source, the -3dB response frequency is 2.3 kHz, and the corresponding -3dB response time under black body is 150μs.

[0050] 9. Figure 5 It is the polarization detection of infrared detector under 900℃ black body. Under the black body light source without polarization, half-wave plate and polarizer are placed in the light path respectively. By modulating the black body light source, the photocurrent under different polarization angles is recorded on the phase lock, and finally the extinction ratio of the device under the black body light source is about 3.5. It shows that the device can achieve high-performance polarization detection without external optical lens.

[0051] 10. Figure 6 It is the room temperature infrared imaging of the infrared detector. A U-shaped heating tube with a blackbody-like light source is used as the imaging target, which is focused on the detector through a lens. A germanium filter is placed in front of the detector, and the detection target is scanned line by line by controlling the two-dimensional mobile platform, and the light intensity of each pixel is collected and recorded by the computer, and finally a high-resolution infrared image is formed. Without the help of a phase-locked amplifier, a high-resolution room temperature infrared image is obtained, indicating that the detector has good detection performance.

Claims

1. An infrared detector with a van der Waals asymmetric barrier structure, comprising a substrate (1), SiO 2 Dielectric layer (2), graphene layer (3), molybdenum disulfide layer (4), source electrode (5), black phosphorus layer (7), drain electrode (6), Features: The structure of the detector is as follows: there is SiO on a P-type Si substrate (1) 2 The dielectric layer (2) and the graphene layer (3) are partially covered on the SiO 2 On the dielectric layer (2), a molybdenum disulfide layer (4) is covered on one end of the graphene layer (3), a source electrode (5) is provided on the other end of the graphene layer (3), and a black phosphorus layer (7) is covered on the molybdenum disulfide layer (4) and the SiO2 layer not in contact with the graphene layer (3). 2 The dielectric layer (2) is partially covered, and the black phosphorus layer (7) and the graphene layer (3) are not in contact, and the drain electrode (6) is located on the black phosphorus layer (7); The substrate (1) is a P-type heavily doped Si substrate; The SiO 2 The dielectric layer (2) has a thickness of 280±10 nanometers; The thickness of the graphene (3) is 5 to 10 nanometers; The thickness of the molybdenum disulfide (4) is 10-20 nanometers; The source electrode (5) is a Cr and Au electrode, the thickness of Cr on the graphene layer is 15 nanometers, and the thickness of Au on the Cr is 75 nanometers; The thickness of the black phosphorus layer (7) is 40-150 nanometers; The drain electrode (6) is a Cr and Au electrode, the thickness of Cr on the black phosphorus layer is 15 nanometers, and the thickness of Au on the Cr is 75 nanometers.

2. A method for preparing an infrared detector having a van der Waals asymmetric barrier structure as claimed in claim 1, Features The following steps are involved: 1) Peel off the graphene layer from the graphite material by mechanical peeling (3) 2 On the dielectric layer (2); 2) peeling off the molybdenum disulfide layer (4) from the molybdenum disulfide bulk material by a mechanical peeling method, and transferring it to one end of the graphene layer (3) by a micro-area fixed-point transfer method; 3) peeling off the black phosphorus layer (7) from the black phosphorus body material by a mechanical peeling method, and transferring and covering the surface of the molybdenum disulfide layer (4) by a micro-area fixed-point transfer method, ensuring that the black phosphorus layer (7) and the graphene layer (3) are not in contact; 4) Depositing a chromium source electrode (5) and a gold drain electrode (6) on one end of the pre-transferred graphene layer (3) and the black phosphorus layer (7) respectively by using processes such as electron beam exposure, thermal evaporation and lift-off.

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