High responsivity electric pulse tuned mid-wave infrared photodetector and preparation method

Abstract

The application discloses a high-response electric pulse tuning mid-wave infrared photoelectric detector and a preparation method, relates to the technical field of photoelectric detection, and has the technical scheme as follows: the detector comprises a Si / SiO2 substrate, a graphene charge storage layer, an h-BN tunneling layer and a MoS2 / BP heterojunction light absorption layer. By applying positive / negative electric pulses to the substrate, the channel carrier concentration and the depletion region width are dynamically controlled, and the active tuning of the light responsivity is realized. At normal temperature, the peak response wavelength of the device is 3.6 mu m, the responsivity reaches 1.68 A / W, the cutoff wavelength is expanded to 3.9 mu m, and the unit area is only about 100 mu m square. The application solves the problems that the traditional mid-wave infrared detector depends on low-temperature refrigeration and has fixed responsivity, and is suitable for portable infrared imaging, gas sensing and other fields.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, and more specifically, to a high-response electrically pulse-tuned mid-wave infrared photodetector and its fabrication method. Background Technology

[0002] For high-performance mid-wave infrared photodetectors, commercially mature solutions are based on detectors made of mercury cadmium telluride (HgCdTe), gallium antimonide / indium arsenide (GaSb / InAs), and indium antimonide (InSb). However, these devices require liquid nitrogen temperatures, i.e., a cryogenic temperature of 70K, to function properly. Even detectors using silicon arsenide-doped (SiAs) blocking impurity band arrays have even more stringent requirements, needing to operate at an ultra-low temperature of only 4K in liquid helium. This necessitates an additional cooling system, leading to a large system size and increased manufacturing costs. Furthermore, the fixed responsivity of traditional detectors significantly limits their application flexibility and compatibility. Therefore, achieving high-responsivity, tunable electrical pulse mid-wave infrared detection at room temperature remains challenging and crucial.

[0003] Therefore, a new solution is needed to address this problem. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a high-response electrically pulse-tuned mid-wave infrared photodetector and its fabrication method, achieving mid-wave infrared detection with high responsivity, long cutoff wavelength, and small size at room temperature.

[0005] The above-mentioned technical objective of this invention is achieved through the following technical solution: A high-response electrically pulse-tuned mid-wave infrared photodetector includes a substrate, a SiO2 dielectric layer, a graphene layer, a hexagonal boron nitride (h-BN) layer, a molybdenum disulfide (MoS2) layer, a black phosphorus (BP) layer, a source electrode (Cr / Au), and a drain electrode (Cr / Au). The substrate is located at the bottom, and the SiO2 dielectric layer is disposed on its upper surface. The graphene layer partially covers the SiO2 dielectric layer. A hexagonal boron nitride layer is disposed on the graphene layer and completely covers the upper surface of the graphene layer. The molybdenum disulfide layer partially covers the hexagonal boron nitride layer. The graphene layer is not in contact with the molybdenum disulfide layer and the black phosphorus layer. The projections of the molybdenum disulfide layer and the graphene layer in the vertical direction partially overlap. The black phosphorus layer partially covers the molybdenum disulfide layer. The overlapping area of ​​the black phosphorus layer and the molybdenum disulfide layer does not overlap with the projection of the graphene layer in the vertical direction. The source electrode is located on the end of the molybdenum disulfide layer away from the black phosphorus layer, and the drain electrode is located on the black phosphorus layer.

[0006] Furthermore, the substrate is a p-type heavily doped Si substrate.

[0007] Furthermore, the SiO2 dielectric layer has a thickness of 300 nanometers.

[0008] Furthermore, the thickness of the graphene is 6 nanometers.

[0009] Furthermore, the thickness of the hexagonal boron nitride layer is 11 nanometers; the thickness of the molybdenum disulfide layer is 10 nanometers; and the thickness of the black phosphorus layer is 47 nanometers.

[0010] Furthermore, the source electrode is a Cr and an Au electrode, wherein the Cr layer on the molybdenum disulfide layer is 10 nanometers thick and the Au layer on the Cr layer is 70 nanometers thick. The drain electrode is a Cr and an Au electrode, with the Cr layer having a thickness of 10 nanometers on the black phosphorus layer and the Au layer having a thickness of 70 nanometers on the Cr layer.

[0011] The above-described method for fabricating a high-response electrically pulse-tuned mid-wave infrared photodetector includes the following steps: S1, Substrate pretreatment: Select a SiO2 dielectric layer / substrate composite substrate and perform ultrasonic cleaning of the surface with acetone and ethylene glycol in sequence; S2, Two-dimensional material transfer: a. The graphene layer, hexagonal boron nitride layer, molybdenum disulfide layer, and black phosphorus layer were exfoliated from the bulk crystal using a polydimethylsiloxane (PDMS) mechanical exfoliation method. b. Using a dry transfer technique on a fixed-point transfer platform, the graphene layer, hexagonal boron nitride layer, molybdenum disulfide layer, and black phosphorus layer are sequentially transferred to the substrate according to the positional relationship described in claim 1, ensuring that: The graphene layer is partially covered by a SiO2 dielectric layer, and the hexagonal boron nitride layer completely covers the graphene layer. The molybdenum disulfide layer is partially covered by a hexagonal boron nitride layer, and partially overlaps with the graphene layer in the vertical projection. The black phosphorus layer is partially covered by a molybdenum disulfide layer, and the overlapping area is not in contact with the graphene layer when projected perpendicularly. S3, Electrode fabrication: a. The source and drain regions are patterned at the end of the molybdenum disulfide layer away from the black phosphorus layer and on the surface of the black phosphorus layer, respectively, by electron beam lithography (EBL); b. Electron beam evaporation (EBE) is used to deposit metal, and a 10 nm thick Cr layer and a 70 nm thick Au layer are grown sequentially in the patterned region to form the source and drain.

[0012] In summary, the present invention has the following beneficial effects: 1) High responsivity: The peak response wavelength of the mid-wave infrared at room temperature is 3.6 μm, and the responsivity reaches 1.68 A / W (commercial products are about 1 A / W).

[0013] 2) Long cutoff wavelength: The response cutoff wavelength is extended to 3.9 μm, covering the typical mid-wave infrared band.

[0014] 3) Small size and low cost: Unit device area ~100 μm² (commercial products ~1 mm²), and no cryogenic cooling system required.

[0015] 4) Dynamic adjustability: The photocurrent can be adjusted in real time by electrical pulses to adapt to the needs of complex detection scenarios. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the detector structure in this invention; Figure 2 This is a flowchart of the detector manufacturing process in this invention; Figure 3 This is a functional relationship between the responsivity and wavelength of the detector in different conductance states in this invention; Figure 4 This is a schematic diagram of a blackbody testing system; Figure 5 This is a schematic diagram of a Fourier transform infrared spectroscopy testing system. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] Example 1: Device fabrication and working principle integration: 1. Device fabrication process, such as Figure 2 As shown, Substrate pretreatment: P-type heavily doped Si substrate (1) is thermally oxidized to form a 300 nm SiO2 dielectric layer (2), and then cleaned for later use.

[0019] Two-dimensional material transfer: Graphene (3), h-BN (4), MoS2 (5), and black phosphorus (6) are transferred sequentially to ensure that the interlayer projection relationship conforms to claim 1.

[0020] Electrode fabrication: Cr / Au source (7) and drain (8) are formed by EBL and EBE processes.

[0021] 2. The electrical pulse tuning and photoelectric response mechanism were verified using the detector with the above-mentioned layered structure. Positive pulse modulation (+5 V applied to the substrate). Longitudinal electric field formation: When a positive pulse is applied to the substrate (1), a vertically upward longitudinal electric field is generated at the Si / SiO2 interface.

[0022] FN tunneling and carrier separation: Electrons generated by ionization in the channel (MoS2 / BP heterojunction) pass through the 11 nm thick h-BN layer (4) through the FN tunneling effect and enter the graphene layer (3) for storage; holes are trapped in the channel due to the barrier.

[0023] Electrical conductivity and depletion region changes: According to the formula σ = nqμ, the decrease in channel electron concentration (n) leads to a decrease in electrical conductivity (σ). At this time, the electron concentration of the MoS2 layer (5) decreases, the width of the depletion region of the black phosphorus layer (6) shrinks, the number of excitable BP covalent bonds in the heterojunction decreases, and the photocurrent weakens.

[0024] Negative pulse modulation (-5 V applied to the substrate). Reverse electric field and electron backflow: The negative pulse on the substrate generates a downward electric field, and the electrons stored in the graphene layer (3) tunnel back into the channel through the h-BN layer.

[0025] Increased conductivity and enhanced photoresponse: The increased channel electron concentration significantly increases conductivity. Meanwhile, the high electron concentration of the MoS2 layer (5) expands the depletion region of the black phosphorus layer (6), improves the excitation efficiency of BP covalent bonds, and enables rapid separation of photogenerated electron-hole pairs under the built-in electric field, resulting in a significant increase in photocurrent.

[0026] 3. Mid-wave infrared light absorption mechanism Covalent electron excitation: When irradiated with mid-wave infrared light (3.6 μm), photon energy excites boron (B)-phosphorus (P) covalent electrons in the depletion region of the MoS2 / BP heterojunction, generating photogenerated carriers.

[0027] Built-in electric field drive: The built-in electric field of the heterojunction drives electrons to the MoS2 layer and holes to the black phosphorus layer, which are output through the source (7) and drain (8) respectively to form photocurrent.

[0028] Example 2, Performance Testing Method: Figure 3 A schematic diagram of a blackbody radiation testing system is shown. The blackbody can be adjusted to the desired temperature via a temperature control system, thus determining the corresponding radiation effect. The output signal frequency of the phase-locked loop (PLL) controls the chopping frequency. When the chopped blackbody radiation strikes the device surface, it generates a photocurrent signal with the same frequency as the chopping. This signal is then amplified by a preamplifier and used as the input to the PLL. In this way, the input and output frequencies of the PLL are the same, and the phase difference is effectively locked, allowing for the accurate reading of the photoresponse at a specific frequency.

[0029] Last use Figure 4 The Fourier transform infrared spectrometer test system shown converts the net photocurrent in the time domain of the device for blackbody chopping into a relative intensity distribution in the frequency domain.

[0030] Methods for calculating blackbody response. The total incident power of blackbody radiation on the device surface can be calculated using the following formula: (1) α is the modulation factor, ε is the average emissivity of the blackbody radiation source, and σ is the Stefan-Boltzmann constant. T is the temperature of the blackbody radiation source, T0 is the temperature of the test environment, A is the area of ​​the blackbody radiation source, An is the area of ​​the device, and L is the distance between the photodetector and the aperture.

[0031] The formula for blackbody radiative responsivity is (R blackbody ): (2) I ph It is the blackbody radiation light response current.

[0032] The response spectrum obtained by Fourier transform infrared spectroscopy is only a relative response spectrum. The response spectrum measured by Fourier transform infrared spectroscopy is an isopower curve, where the radiant power is equal at any wavelength. After calibrating the blackbody response, the responsivity of the photodetector's response spectrum can be obtained. The relative response spectrum R'(λ) is obtained through Fourier transform infrared characteristic analysis: (3) Because blackbody radiation has a continuous spectrum and the emissivity is different for each wavelength, the blackbody light signal generated by the photodetector is the sum of the signals generated by radiation at each wavelength: (4) Blackbody responsivity (R) of infrared photodetectors blackbody ) and peak response rate (R (λp) The ratio of R'(λ) to the blackbody spectral emissivity R'(λ) is a constant, known as the g factor. The g factor can be calculated from the measured R'(λ) and the blackbody spectral emissivity λ(λ). Therefore, by calculating the g factor, the peak responsivity R(λ) can be obtained. p ): or (5) Where h is Planck's constant, c is the speed of light in a vacuum, λ is the photon wavelength, and λ is the electron bandwidth.

[0033] Performance test results: The electrical conductivity state of a device can be changed by applying an electrical pulse, and then the photoresponse of the device can be obtained by illuminating it with a radiation source. Figure 5The figure illustrates the functional relationship between responsivity and wavelength under different conductance states of the device. It is clearly observed from the figure that the device exhibits significant mid-infrared detection performance, with a peak response wavelength at 3.6 μm and a cutoff wavelength reaching 3.9 μm. The peak responsivity shows a clear positive correlation with the conductance state: as the conductivity increases from 1.4 μS to 6 μS, the responsivity at the characteristic wavelength of 3.6 μm significantly increases from 0.39 A / W to 1.68 A / W, an increase of more than four times. This excellent tunable conductance characteristic, combined with the device's non-volatile storage feature, provides a new technical path for realizing integrated detection-storage-computation functionality in the mid-infrared band.

[0034] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A high-response electrically pulse-tuned mid-wave infrared photodetector, characterized in that: The structure includes a substrate (1), a SiO2 dielectric layer (2), a graphene layer (3), a hexagonal boron nitride layer (4), a molybdenum disulfide layer (5), a black phosphorus layer (6), a source electrode (7), and a drain electrode (8). The substrate (1) is located at the bottom, and the SiO2 dielectric layer (2) is disposed on its upper surface. The graphene layer (3) partially covers the SiO2 dielectric layer (2). The hexagonal boron nitride layer (4) is disposed on the graphene layer (3) and completely covers the upper surface of the graphene layer (3). The molybdenum disulfide layer (5) partially covers the hexagonal boron nitride layer (4). On the boron layer (4), the graphene layer (3) is not in contact with the molybdenum disulfide layer (5) and the black phosphorus layer (6). The projection of the molybdenum disulfide layer (5) and the graphene layer (3) in the vertical direction partially overlaps. The black phosphorus layer (6) partially covers the molybdenum disulfide layer (5). The overlapping area of ​​the black phosphorus layer (6) and the molybdenum disulfide layer (5) does not overlap with the projection of the graphene layer (3) in the vertical direction. The source electrode (7) is located on the end of the molybdenum disulfide layer (5) away from the black phosphorus layer (6). The drain electrode (8) is located on the black phosphorus layer (6).

2. The detector according to claim 1, characterized in that: The substrate (1) is a P-type heavily doped Si substrate.

3. A detector according to claim 1, characterized in that: The SiO2 dielectric layer (2) has a thickness of 300 nanometers.

4. A detector according to claim 1, characterized in that: The thickness of the graphene (3) is 6 nanometers.

5. A detector according to claim 1, characterized in that: The thickness of the hexagonal boron nitride layer (4) is 11 nanometers; The thickness of the molybdenum disulfide layer (5) is 10 nanometers; The thickness of the black phosphorus layer (6) is 47 nanometers.

6. A detector according to claim 1, characterized in that: The source electrode (7) is a Cr and Au electrode, with Cr having a thickness of 10 nanometers on the molybdenum disulfide layer (5) and Au having a thickness of 70 nanometers on the Cr. The drain electrode (8) is a Cr and Au electrode, with a thickness of 10 nanometers on the black phosphorus layer (6) and a thickness of 70 nanometers on the Cr.

7. A method for fabricating a high-response electrically pulse-tuned mid-wave infrared photodetector as described in claims 1-7, characterized in that: Includes the following steps: S1, Substrate pretreatment: Select a SiO2 dielectric layer (2) / substrate (1) composite substrate, and perform ultrasonic cleaning of the surface with acetone and ethylene glycol in sequence; S2, Two-dimensional material transfer: a. Using polydimethylsiloxane (PDMS) mechanical exfoliation method, graphene layer (3), hexagonal boron nitride layer (4), molybdenum disulfide layer (5), and black phosphorus layer (6) were exfoliated from the bulk crystals respectively. b. Using a dry transfer technique on a fixed-point transfer platform, the graphene layer (3), hexagonal boron nitride layer (4), molybdenum disulfide layer (5), and black phosphorus layer (6) are sequentially transferred to the substrate according to the positional relationship described in claim 1, ensuring that: The graphene layer (3) partially covers the SiO2 dielectric layer (2), and the hexagonal boron nitride layer (4) completely covers the graphene layer (3). The molybdenum disulfide layer (5) partially covers the hexagonal boron nitride layer (4) and partially overlaps with the graphene layer (3) in the vertical projection. The black phosphorus layer (6) is partially covered by the molybdenum disulfide layer (5), and the overlapping area is not in contact with the graphene layer (3) by perpendicular projection. S3, Electrode fabrication: a. The source (7) and drain (8) regions are patterned on the end of the molybdenum disulfide layer (5) away from the black phosphorus layer (6) and on the surface of the black phosphorus layer (6) by electron beam exposure (EBL); b. Electron beam evaporation (EBE) is used to deposit metal, and a 10 nm thick Cr layer and a 70 nm thick Au layer are grown sequentially in the patterned region to form the source (7) and drain (8).

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