A van der waals heterojunction abnormal photocurrent inhibition type photodetector and application thereof

Abstract

This invention belongs to the field of two-dimensional nanomaterial photodetector technology, and relates to a van der Waals heterojunction anomalous photocurrent suppression photodetector and its application. This invention provides a van der Waals heterojunction anomalous photocurrent suppression photodetector, comprising: a substrate including a Si layer and a SiO2 layer disposed on the upper surface of the Si layer; a pair of electrodes, spaced apart on the upper surface of the SiO2 layer, forming an electrode channel; and a two-dimensional material heterojunction structure disposed within the electrode channel, including a van der Waals heterojunction formed by a MoWSe4 layer and a PdSe2 layer. This invention achieves wavelength tunability of the photoconductivity mechanism.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology of two-dimensional nanomaterials, and relates to a van der Waals heterojunction anomalous photocurrent suppression photodetector and its application. Background Technology

[0002] Photodetectors are core optoelectronic devices that convert optical signals into electrical signals. They are essential components in many fields such as optical communication, optical imaging, environmental sensing, industrial inspection, and biomedicine. As optoelectronic systems develop towards miniaturization, integration, wide dynamic range, and high sensitivity, traditional inorganic semiconductor photodetectors, limited by their photoconductivity characteristics, simple control methods, slow response speed, and low sensitivity, are gradually becoming unable to meet the development needs of next-generation optoelectronic systems.

[0003] Two-dimensional layered nanomaterials, with their atomic-level thickness, tunable band structure, strong light-matter interaction, broad spectral response, and excellent carrier transport properties, have become core sensitive materials for next-generation high-performance photodetectors. Among them, PdSe2, a transition metal chalcogenide (TMDC), is a two-dimensional material with a narrow bandgap, high air stability, broad spectral response, and in-plane anisotropy. Existing research has confirmed its intrinsic negative photoconductivity in the ultraviolet-visible band (365-660 nm), meaning that the material's conductivity decreases with increasing light intensity under illumination, providing a material basis for device design with novel photoelectric response modes. Meanwhile, MoWSe4, as a ternary alloy TMDC material, possesses unique in-plane anisotropy, making it exhibit great application potential in polarized light response.

[0004] Among them, the MoWSe4 / PdSe2 heterojunction, as a novel two-dimensional heterojunction system, possesses unique advantages in interface band matching and trap state modulation due to its intrinsic anomalous photocurrent suppression behavior. It holds promise for achieving reversible switching of the photoconductive mechanism based on the incident light wavelength, providing new device support for multifunctional integrated optoelectronic devices. However, engineering applications for this heterojunction system are still lacking, and there is an urgent need to develop dedicated photodetectors adapted to its photoelectric properties to fully unleash the technological potential of this material system and meet the development needs of integrated optoelectronic systems. Summary of the Invention

[0005] Currently, there is no dedicated photodetector design for the anomalous photocurrent suppression behavior of MoWSe4 / PdSe2 heterojunctions, nor has a standardized device fabrication method or universal application scheme based on this effect been developed. Furthermore, most current photodetectors still focus on single conductivity response characteristics and modulation methods, without exploring photoconductive mechanisms based on wavelength modulation, thus failing to achieve multi-dimensional and flexible modulation of photoelectric response characteristics. The insufficient engineering practicality and scenario adaptability of these devices result in significant technical gaps in their engineering application in core integrated optoelectronic devices such as optically controlled logic gates and low-power non-volatile optoelectronic storage. They cannot adapt to the differentiated photoelectric response modulation requirements in scenarios such as multi-state logic operations, multi-level optoelectronic storage, and neuromorphic devices. The insufficient engineering practicality and scenario adaptability of these devices make it difficult to meet the application requirements of next-generation integrated optoelectronic systems that demand multifunctional and high-precision optoelectronic devices.

[0006] The purpose of this invention is to develop a dedicated photodetector with anomalous photocurrent suppression behavior of MoWSe4 / PdSe2 heterojunction, fill the gap in the engineering application technology of optical wavelength-controlled photoconductor switching technology in the fields of optical logic gates and low-power non-volatile optoelectronic storage, and improve the application technology system of this type of photodetector in integrated optoelectronic core scenarios.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] On one hand, the present invention provides a van der Waals heterojunction anomalous photocurrent suppression photodetector, comprising: The substrate includes a Si layer and a SiO2 layer disposed on the upper surface of the Si layer; A pair of electrodes are spaced apart on the upper surface of the SiO2 layer to form an electrode channel; A two-dimensional material heterojunction structure, disposed within the electrode channel, includes a van der Waals heterojunction formed by a MoWSe4 layer and a PdSe2 layer; wherein... The MoWSe4 layer and PdSe2 layer are stacked alternately along the thickness direction, such that the materials of any two adjacent layers in the stacking sequence are different from each other; The MoWSe4 layer and the PdSe2 layer partially overlap within the electrode channel, and the overlapping region forms a van der Waals heterojunction. One end of the MoWSe4 layer is attached to an electrode, and the other end extends into the electrode channel. One end of the PdSe2 layer is attached to another electrode, the other end extends into the electrode channel, and the other end covers the upper surface of the MoWSe4 layer.

[0009] Furthermore, the PdSe2 layer consists of 9-12 layers of PdSe2 flakes with a thickness of 5.65nm-8.98nm.

[0010] Furthermore, the MoWSe4 layer consists of 8-13 layers of MoWSe4 flakes with a thickness of 5.93nm-8.43nm.

[0011] Furthermore, the Si layer is a p-type highly doped silicon layer, and the SiO2 layer is an insulating dielectric layer.

[0012] Furthermore, the electrode has a double-layer metal structure.

[0013] Furthermore, the dual-layer metal structure includes a nickel layer as an adhesion layer and a gold layer as the main conductive layer.

[0014] Furthermore, the electrode is an interdigitated electrode.

[0015] On the other hand, a method for fabricating the van der Waals heterojunction anomalous photocurrent suppression photodetector described in this invention is provided, comprising the following steps: S1. A SiO2 layer is formed on the upper surface of the Si layer to obtain a substrate; S2. A pair of electrodes are spaced apart on the upper surface of the SiO2 layer to form an electrode channel; S3. Transfer the MoWSe4 layer into the electrode channel, so that one end of it overlaps with an electrode and the other end extends into the electrode channel. S4. Transfer the PdSe2 layer over the MoWSe4 layer, so that one end of it overlaps with another electrode and the other end extends into the electrode channel. The PdSe2 layer and the MoWSe4 layer partially overlap in the electrode channel to form a van der Waals heterojunction.

[0016] On the other hand, a method for controlling the photoconductivity mechanism of a photodetector is provided, comprising the following steps: When the incident light wavelength is 450nm, the van der Waals heterojunction anomalous photocurrent suppression photodetector described in this invention operates in anomalous photocurrent suppression mode. When the incident light wavelength is 650nm, the van der Waals heterojunction anomalous photocurrent suppression photodetector described in this invention operates in positive photoconductivity mode.

[0017] The invention also provides applications of the van der Waals heterojunction anomalous photocurrent suppression photodetector in optical logic gates, optoelectronic storage devices, low-light detection, optical wireless communication and / or laser power monitoring.

[0018] The invention also provides the application of the van der Waals heterojunction anomalous photocurrent suppression photodetector in realizing wavelength tunability of the photoconductivity mechanism.

[0019] The following points need to be explained: (1) Most traditional photodetectors only exhibit a single positive photoconductive response characteristic, that is, the bright current under illumination is greater than the dark current under dark conditions, and it increases with the increase of light intensity, which is limited by a single photoconductive response characteristic and control method. Devices that can simultaneously exhibit positive photoconductive and anomalous photocurrent suppression characteristics are extremely rare. (2) In some semiconductor materials or heterojunctions, there is a special photoelectric response phenomenon, namely light intensity-dependent anomalous photocurrent suppression behavior. This behavior is manifested as the current gradually decreases as the light intensity increases. This unique response characteristic provides a potential opportunity for the development of new photoelectric devices. However, existing conventional photodetectors have a low degree of utilization of this anomalous photocurrent suppression behavior, especially lacking a scheme to combine incident light wavelength control to achieve precise triggering and application of this characteristic, resulting in a lack of functional expansion of the device. (3) The detection performance of existing photodetectors in weak light environments is generally poor. Under low light intensity conditions, the response signal of most devices is weak, and the detectivity is difficult to reach the ideal level. This makes them difficult to apply effectively to scenarios with extremely high sensitivity requirements, such as low-light imaging and weak-light sensing, thus limiting their application in fields such as communication, biomedical imaging, and environmental sensing.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves wavelength tunability of the photoconductive mechanism. The van der Waals heterojunction anomalous photocurrent suppression photodetector of this invention exhibits drastically different photoelectric response characteristics depending on the incident light wavelength, expanding the functional diversity of optoelectronic devices and laying the foundation for the development of novel optoelectronic devices, particularly in fields such as optical logic gates and optical memories, where it has enormous application potential. Attached Figure Description

[0021] Figure 1 A schematic diagram of the setup for a photodetector.

[0022] Figure 2A This is the output characteristic curve of the photodetector at a wavelength of 450 nm.

[0023] Figure 2B This is the output characteristic curve of the photodetector at a wavelength of 650 nm.

[0024] Figure 3 The responsivity and specific detectivity of the photodetector at a wavelength of 450 nm and under different light intensities are given.

[0025] Figure label: Figure 1 In the diagram: 100: substrate; 200: electrode; 300: two-dimensional material heterojunction structure. Detailed Implementation

[0026] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in each embodiment are conventional methods; unless otherwise specified, the reagents and materials are all commercially available.

[0027] In this embodiment of the invention, the thickness direction refers to the direction perpendicular to the upper surface of the substrate (i.e., the upper surface of the SiO2 layer).

[0028] A stacked sequence refers to the order in which MoWSe4 layers and PdSe2 layers are arranged alternately along the thickness direction. In a stacked sequence, any two adjacent layers are different from each other, meaning that MoWSe4 layers and PdSe2 layers appear alternately.

[0029] Interdigitated electrodes are specific electrode structures in which the source and drain electrodes are arranged in a finger-like, interlaced pattern, resembling the ten fingers of two hands crossed.

[0030] Example 1 This embodiment provides a van der Waals heterojunction anomalous photocurrent suppression photodetector and its fabrication method. (1) Device structure A van der Waals heterojunction anomalous photocurrent suppression photodetector (device) includes: The substrate 100 includes a Si layer and a SiO2 layer disposed on the upper surface of the Si layer; A pair of electrodes 200 are spaced apart on the upper surface of the SiO2 layer to form an electrode channel; A two-dimensional material heterojunction structure 300 is disposed in an electrode channel, including a van der Waals heterojunction formed by a MoWSe4 layer and a PdSe2 layer; wherein, the MoWSe4 layer and the PdSe2 layer are alternately stacked along the thickness direction, such that the materials of any two adjacent layers in the stacking sequence are different from each other; the MoWSe4 layer and the PdSe2 layer partially overlap in the electrode channel, and the overlapping area forms a van der Waals heterojunction; one end of the MoWSe4 layer is attached to an electrode 200, and the other end extends into the electrode channel; one end of the PdSe2 layer is attached to another electrode, and the other end extends into the electrode channel, and the other end covers the upper surface of the MoWSe4 layer. The PdSe2 layer consists of 9-12 layers of PdSe2 flakes (two-dimensional nanosheets) with a thickness of 5.65 nm-8.98 nm; the MoWSe4 layer consists of 8-13 layers of MoWSe4 flakes with a thickness of 5.93 nm-8.43 nm; the Si layer is a p-type highly doped silicon layer, and the SiO2 layer is an insulating dielectric layer; the electrode is a double-layer metal structure, which includes a nickel layer as an adhesion layer and a gold layer as the main conductive layer, and the electrode is an interdigitated electrode.

[0031] (2) Preparation method A method for fabricating a van der Waals heterojunction anomalous photocurrent suppression photodetector is provided, comprising the following steps: S1. A SiO2 layer is formed on the upper surface of the Si layer to obtain substrate 100; S2. A pair of electrodes 200 are spaced apart on the upper surface of the SiO2 layer to form an electrode channel; S3. Transfer the MoWSe4 layer into the electrode channel, with one end attached to an electrode and the other end extending into the electrode channel. S4. Transfer the PdSe2 layer above the MoWSe4 layer, so that one end of it is attached to another electrode and the other end extends into the electrode channel. The PdSe2 layer and the MoWSe4 layer partially overlap in the electrode channel to form a van der Waals heterojunction.

[0032] Specifically, such as Figure 1 As shown, the fabrication method of the van der Waals heterojunction anomalous photocurrent suppression photodetector includes the following steps: Step 1: Material Preparation and Verification. Few-layer MoWSe4 and PdSe2 two-dimensional nanosheets were prepared using a mechanical exfoliation method. The number of layers in the prepared MoWSe4 and PdSe2 nanosheets was confirmed using atomic force microscopy (AFM). The MoWSe4 nanosheets (MoWSe4 sheets) had approximately 8-13 layers, corresponding to a thickness of approximately 5.93 nm-8.43 nm; the PdSe2 nanosheets (PdSe2 sheets) had approximately 9-12 layers, corresponding to a thickness of approximately 5.65 nm-8.98 nm.

[0033] Step 2: Fabrication of Substrate 100 and Electrode 200. The Si / SiO2 substrate is rigorously cleaned to remove surface contaminants. After wafer dicing, the surface is cleaned with propanol, then with deionized water, and finally dried using a nitrogen gun to obtain a clean silicon substrate 100. Using physical vapor deposition or other suitable thin film deposition techniques, a 5nm thick nickel (Ni) layer as an adhesion layer and a 50nm thick gold (Au) layer as an electrode conductive layer are sequentially deposited on the cleaned Si / SiO2 substrate. Pre-defined interdigitated electrodes (5 pairs of interdigitated fingers, 5µm finger width, and 5µm finger spacing) are then fabricated using electron beam lithography and thermal evaporation processes to obtain a device substrate with electrode structures.

[0034] Step 3: Construction of the MoWSe4 / PdSe2 van der Waals heterojunction. First, the MoWSe4 two-dimensional nanosheets obtained in Step 1 were precisely transferred to the surface of the device substrate prepared in Step 2, ensuring good contact between the MoWSe4 nanosheets and the source / drain electrodes. Second, using a dry transfer process, the PdSe2 two-dimensional nanosheets obtained in Step 1 were precisely stacked on specific regions of the MoWSe4 nanosheets, thereby constructing the MoWSe4 / PdSe2 van der Waals heterojunction. After the stacking was completed, the target photodetector was finally fabricated. Raman spectroscopy was used to characterize the prepared MoWSe4 and PdSe2 two-dimensional nanosheets and the MoWSe4 / PdSe2 van der Waals heterojunction to confirm the successful construction of the heterojunction structure.

[0035] Step 4: Photodetector performance testing. The prepared MoWSe4 / PdSe2 van der Waals heterojunction photodetector (van der Waals heterojunction anomalous photocurrent suppression photodetector) was subjected to current-voltage (IV) and polarization characteristics tests to evaluate its electrical performance.

[0036] like Figure 2A , Figure 2B As shown, the photoelectric response of the photodetector was tested under specific wavelength illumination. When the incident light wavelength was 450 nm, the photodetector exhibited an anomalous photocurrent suppression phenomenon, meaning that the output current of the device gradually decreased as the light intensity increased. When the incident light wavelength was 650 nm, the photodetector exhibited a positive photoconductivity effect, meaning that the output current of the device increased significantly as the light intensity increased. These response characteristics under different wavelengths of illumination clearly demonstrate that the photoconductivity mechanism of this photodetector can be effectively controlled by the incident light wavelength.

[0037] Based on the differences in characteristics between the two photoelectric response modes, their application scenarios exhibit differentiated adaptability. The 450nm wavelength, with its anomalous photocurrent suppression effect, possesses the core potential to construct optical control logic gates, multi-level optoelectronic storage, and integrated sensing-memory-computing architectures; while the 650nm wavelength, relying on the high linearity conversion characteristics of the positive photoconductivity effect, can be efficiently applied to high-speed optical control and metering scenarios such as optical wireless communication modulation or laser power precision monitoring.

[0038] Step 5: Performance parameter analysis of the photodetector Responsivity is defined as photocurrent ( ) and incident light power ( The ratio of light to electrical signals indicates the efficiency of the detector in converting light signals into electrical signals.

[0039]

[0040] in, Photocurrent, The current under light, Dark current, The power of the light incident on the effective area of ​​the detector.

[0041] Specific detectability ( () is an indicator for measuring the ability of a detector to detect weak signals.

[0042]

[0043] in, For responsiveness, The effective photosensitive area of ​​the detector. Dark current, is the elementary charge.

[0044] Mastering the two core performance parameters, responsivity and specific detectivity, allows for accurate evaluation of the detector's ability to efficiently convert optical signals into electrical signals, and also enables the quantification of its limit threshold for capturing weak optical signals. This provides crucial information for subsequent optimization of device structures and selection of suitable photoelectric detection systems.

[0045] like Figure 3 As shown, the device of this invention exhibits extremely excellent detection performance in the near-infrared band. Although the device performance degrades somewhat with increasing optical power density, it still maintains an excellent level at key operating points. Particularly noteworthy is its performance at a wavelength of 450 nm and an optical power density of 127.32 µW / mm². 2 Under illumination conditions, this photodetector exhibits a responsivity as high as 43.6 A / W and an efficiency of 8.96 × 10⁻⁶. 10 Jones's specific detectivity. This result fully demonstrates that the detector possesses excellent photoelectric conversion efficiency and weak signal recognition capability.

[0046] It should be understood that the disclosed invention is not limited to the specific methods, schemes, and substances described, as these are all subject to variation. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of the invention, which is limited only by the appended claims.

Claims

1. A van der Waals heterojunction anomalous photocurrent suppression photodetector, characterized in that, include: The substrate includes a Si layer and a SiO2 layer disposed on the upper surface of the Si layer; A pair of electrodes are spaced apart on the upper surface of the SiO2 layer to form an electrode channel; A two-dimensional material heterojunction structure, disposed within the electrode channel, includes a van der Waals heterojunction formed by a MoWSe4 layer and a PdSe2 layer; wherein... The MoWSe4 layer and PdSe2 layer are stacked alternately along the thickness direction, such that the materials of any two adjacent layers in the stacking sequence are different from each other; The MoWSe4 layer and the PdSe2 layer partially overlap within the electrode channel, and the overlapping region forms a van der Waals heterojunction. One end of the MoWSe4 layer is attached to an electrode, and the other end extends into the electrode channel. One end of the PdSe2 layer is attached to another electrode, the other end extends into the electrode channel, and the other end covers the upper surface of the MoWSe4 layer.

2. The van der Waals heterojunction anomalous photocurrent suppression photodetector according to claim 1, characterized in that, The PdSe2 layer consists of 9-12 layers of PdSe2 flakes with a thickness of 5.65nm-8.98nm.

3. The van der Waals heterojunction anomalous photocurrent suppression photodetector according to claim 1, characterized in that, The MoWSe4 layer consists of 8-13 layers of MoWSe4 flakes with a thickness of 5.93nm-8.43nm.

4. The van der Waals heterojunction anomalous photocurrent suppression photodetector according to claim 1, characterized in that, The Si layer is a p-type highly doped silicon layer, and the SiO2 layer is an insulating dielectric layer.

5. The van der Waals heterojunction anomalous photocurrent suppression photodetector according to claim 1, characterized in that, The electrode has a double-layer metal structure.

6. The van der Waals heterojunction anomalous photocurrent suppression photodetector according to claim 5, characterized in that, The dual-layer metal structure includes a nickel layer as an adhesion layer and a gold layer as the main conductive layer.

7. The van der Waals heterojunction anomalous photocurrent suppression photodetector according to claim 1, characterized in that, The electrode is an interdigitated electrode.

8. The method for fabricating a van der Waals heterojunction anomalous photocurrent suppression photodetector according to any one of claims 1-7, characterized in that, Includes the following steps: S1. A SiO2 layer is formed on the upper surface of the Si layer to obtain a substrate; S2. A pair of electrodes are spaced apart on the upper surface of the SiO2 layer to form an electrode channel; S3. Transfer the MoWSe4 layer into the electrode channel, so that one end of it overlaps with an electrode and the other end extends into the electrode channel. S4. Transfer the PdSe2 layer over the MoWSe4 layer, so that one end of it overlaps with another electrode and the other end extends into the electrode channel. The PdSe2 layer and the MoWSe4 layer partially overlap in the electrode channel to form a van der Waals heterojunction.

9. A method for controlling the photoconductivity mechanism of a photodetector, characterized in that, Includes the following steps: When the incident light wavelength is 450 nm, the van der Waals heterojunction anomalous photocurrent suppression photodetector according to any one of claims 1-7 operates in anomalous photocurrent suppression mode. When the incident light wavelength is 650 nm, the van der Waals heterojunction anomalous photocurrent suppression photodetector according to any one of claims 1-7 operates in positive photoconductivity mode.

10. The application of the van der Waals heterojunction anomalous photocurrent suppression photodetector according to any one of claims 1-7 in optical logic gates, optoelectronic storage devices, low-light detection, optical wireless communication and / or laser power monitoring.

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