A bias-switchable dual-mode photodetector based on two-dimensional van der waals p-n heterostructure and a preparation method thereof
By designing a bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure, the instantaneous switching between photovoltaic and photoconductive modes is achieved by switching the external bias polarity. This solves the adaptability problem of existing single-mode photodetectors and achieves a balance between high-speed self-driving and ultra-high sensitivity, making it suitable for multifunctional photodetector applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2026-03-05
- Publication Date
- 2026-05-29
AI Technical Summary
Existing pn junction or Schottky junction photodetectors are limited to a single operating mode and cannot dynamically switch according to the actual light signal intensity and speed requirements, making it difficult to achieve multifunctional adaptability in complex light environments.
A bias-switched dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure is designed. By combining an asymmetric work function electrode with a van der Waals pn junction, and using a Gr/2H-MoTe2/α-In2Se3/Au vertical heterostructure, the instantaneous reversible switching between photovoltaic mode and photoconductive mode is achieved by using external bias polarity switching.
It achieves dual-mode operation within a single device, possesses high-speed self-driving and ultra-high sensitivity, breaks through the trade-off between response speed and sensitivity, adapts to complex optical environments, has excellent rectification characteristics and self-powering capabilities, and is easy to scale up fabrication and array integration.
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Figure CN122121334A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photodetector technology, specifically relating to a bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure and its fabrication method. Background Technology
[0002] As a core component of optoelectronic information systems, photodetectors play an irreplaceable role in fields such as high-speed imaging, low-light detection, optical communication, remote sensing, and object recognition in complex environments. With the increasing demands for multi-scenario and multi-task detection, single-mode photodetectors are no longer sufficient to meet the stringent requirements of achieving both "high-speed response" and "ultra-high sensitivity" in practical applications.
[0003] Traditional commercial detectors based on III-V group, mercury cadmium telluride, or quantum well structures have excellent performance in specific wavelength bands, but they generally face the challenge of balancing response speed and sensitivity. Specifically, photovoltaic devices can achieve self-driving and fast response, but their sensitivity is low due to the lack of a gain mechanism; photoconductive devices have high gain and extremely high responsivity, but their response time is long, their dark current is large, and they are difficult to operate at zero bias.
[0004] Especially against the backdrop of the rapid development of two-dimensional semiconductor van der Waals heterojunctions, existing pn junction or Schottky junction photodetectors are still limited to a single working mode and cannot dynamically switch according to the actual light signal intensity and speed requirements, which seriously restricts their multifunctional adaptability in complex light environments.
[0005] Therefore, there is an urgent need to provide a novel photodetector and its fabrication method that can freely switch between high-speed self-driven and ultra-high sensitivity modes. Summary of the Invention
[0006] To address the limitation of existing pn junction or Schottky junction photodetectors to a single operating mode, this invention provides a bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure and its fabrication method. By cleverly combining an asymmetric work function electrode with a van der Waals pn junction, a vertical heterostructure of "Gr / 2H-MoTe2 / α-In2Se3 / Au" is designed. By simply changing the external bias polarity, instantaneous and reversible switching between photovoltaic (PV) mode and photoconductive (PC) mode can be achieved, providing a simple and efficient new paradigm for next-generation multifunctional and intelligent photodetectors.
[0007] The technical solution adopted in this invention is as follows:
[0008] A bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure includes, from bottom to top, an insulating substrate, a graphene (Gr) electrode, 2H-MoTe2 and α-In2Se3, and a gold source electrode and a gold drain electrode located above the insulating substrate; wherein, the gold source electrode is connected to the graphene electrode; the gold drain electrode is connected to α-In2Se3, but not connected to the graphene electrode or 2H-MoTe2; a van der Waals pn heterojunction is formed between 2H-MoTe2 and α-In2Se3.
[0009] Furthermore, ohmic contacts are formed between the graphene electrode and 2H-MoTe2, and between α-In2Se3 and the gold drain electrode.
[0010] Furthermore, the 2H-MoTe2 extends above the channel between the graphene electrode and the gold drain electrode.
[0011] Furthermore, the graphene electrode is composed of 1 to 50 layers of graphene with a thickness of approximately 2 to 17 nm.
[0012] Furthermore, the thickness of both the gold source electrode and the gold drain electrode is 10~100 nm, preferably 30~70 nm.
[0013] Furthermore, the thickness of both 2H-MoTe2 and α-In2Se3 is 1~50 nm, preferably 5~50 nm.
[0014] Furthermore, the insulating substrate is a SiO2 / Si substrate, an h-BN (hexagonal boron nitride) substrate, a sapphire substrate, or a flexible PI (polyimide) substrate.
[0015] A method for fabricating a bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure includes the following steps:
[0016] S1. Clean the insulating substrate;
[0017] S2. A gold source electrode and a gold drain electrode are prepared on the surface of an insulating substrate, and a graphene electrode is transferred over the gold source electrode.
[0018] S3. 2H-MoTe2 sheets are obtained by peeling and then transferred over the graphene electrode.
[0019] S4. An α-In2Se3 sheet is obtained by peeling off the substrate and then transferred over 2H-MoTe2 and attached to the gold drain electrode to form a vertical heterostructure of "Gr / 2H-MoTe2 / α-In2Se3 / Au". After device packaging, a bias-switched dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure is obtained.
[0020] Furthermore, S4 also includes a thermal annealing step before device packaging.
[0021] Furthermore, the temperature of the heat annealing is 100~120℃, and the duration is 20~60 min.
[0022] Furthermore, in S2, the patterns of the gold source electrode and the gold drain electrode are defined using ultraviolet lithography, electron beam lithography, or a mask, and the gold source electrode and the gold drain electrode are prepared by combining electron beam evaporation, thermal evaporation, or magnetron sputtering processes.
[0023] Furthermore, in S2, the graphene electrode is transferred using polymer-assisted transfer or all-dry transfer techniques.
[0024] Furthermore, in S3 and S4, mechanical peeling or PPC / PDMS (polypropylene carbonate / polydimethylsiloxane) assisted peeling is used to peel off 2H-MoTe2 sheets and α-In2Se3 sheets.
[0025] Furthermore, in S3 and S4, a high-precision micro-transfer platform was used to transfer 2H-MoTe2 and α-In2Se3 thin films.
[0026] The beneficial effects of this invention are as follows:
[0027] 1. This invention proposes a bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure and its fabrication method. By ingeniously combining an asymmetric work function electrode with a van der Waals pn junction, a vertical heterostructure of "Gr / 2H-MoTe2 / α-In2Se3 / Au" is designed, achieving for the first time a single device with internal bias-switchable dual-mode operation. This invention does not require changing the device structure or adding a gate; it can achieve instantaneous and reversible switching between self-driven high-speed photovoltaic mode and ultra-high gain photoconductive mode simply by switching the external bias polarity. This completely breaks through the inherent trade-off between "response speed and sensitivity" that has long existed in traditional two-dimensional heterojunction photodetectors, making it a multi-functional device that greatly improves the adaptability of the device to complex optical environments.
[0028] 2. Innovative introduction of asymmetric work function electrode design: Low work function graphene and high work function gold are used as source and drain electrodes to achieve precise band alignment with the conduction band bottom of p-type 2H-MoTe2 and the valence band top of n-type α-In2Se3. Under reverse bias, the separation, injection and transport efficiency of photogenerated carriers are significantly enhanced, thereby obtaining extremely high internal gain and ultra-low noise performance in photoconductive mode. The responsivity, specific detectivity and external quantum efficiency far exceed those of two-dimensional heterojunction devices with traditional symmetric electrode structures.
[0029] 3. Achieving both ultra-low dark current and self-driving capability: With the vertically stacked 2H-MoTe2 / α-In2Se3 van der Waals pn heterojunction as the core active region, thanks to the built-in barrier of its high-quality van der Waals pn junction, the dark current in forward or zero bias mode reaches the level of femtoamperes (fA). At the same time, it has excellent rectification characteristics and open-circuit voltage, realizing true self-powered high-speed detection.
[0030] 4. Extremely simple structure and strong process compatibility: The device does not require ion doping, complex epitaxial growth or multi-gate control, and can be realized only through conventional mechanical transfer or dry transfer. It is highly compatible with existing two-dimensional material process platforms and is easy to scale up and integrate into arrays.
[0031] 5. Significant potential for multi-functional applications: The same device can dynamically select "high-speed photovoltaic mode" (suitable for high-speed imaging, optical communication, lidar, etc.) or "ultra-sensitive photoconductive mode" (suitable for extremely weak light detection, night vision, single-photon level imaging, etc.) according to actual needs, showing unparalleled performance advantages in fields such as intelligent sensing, object recognition in complex environments, and multimodal imaging. Attached Figure Description
[0032] Figure 1 This is a front view schematic diagram of the bias switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure proposed in Embodiment 1 of the present invention.
[0033] Figure 2 This is an optical microscope image of the Gr / 2H-MoTe2 / α-In2Se3 sample obtained by mechanical peeling and dry transfer in Example 1 of the present invention.
[0034] Figure 3 The linear and semi-logarithmic output curves of the bias switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure proposed in Embodiment 1 of the present invention are shown.
[0035] Figure 4 This refers to the photocurrent response of the bias switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure proposed in Embodiment 1 of the present invention, which varies with time at different wavelengths in photoconductive mode.
[0036] Figure 5 The device responsivity and specific detectivity of the bias switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure proposed in Embodiment 1 of the present invention under photoconductive mode and illumination with different wavelengths of light;
[0037] Figure 6 The curves showing the photocurrent variation over time of the bias switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure proposed in Embodiment 1 of the present invention under 450 nm light illumination at different optical power densities.
[0038] Figure 7 The It curves of the bias switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure proposed in Embodiment 1 of the present invention under photovoltaic mode and illumination with different wavelengths of light;
[0039] Figure 8 The device responsivity and specific detectivity of the bias switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure proposed in Embodiment 1 of the present invention under photovoltaic mode and illumination of different wavelengths of light;
[0040] Figure 9 The responsivity and specific detectivity of the bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure proposed in Embodiment 1 of this invention are shown under 450 nm light illumination and different voltages (-1 V, 0 V and 1 V).
[0041] Figure 10 This is a comparison of the responsivity and rise time of the bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure proposed in Embodiment 1 of the present invention with the reported results of existing photodetectors based on two-dimensional materials. Detailed Implementation
[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Although limited embodiments are described below, the components of the embodiments of the present invention described and illustrated in the accompanying drawings can be arranged and designed in various different configurations.
[0043] Example 1
[0044] This embodiment provides a bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure, as shown in the following structure. Figure 1 As shown, the structure includes, from bottom to top, an insulating substrate, a graphene electrode, 2H-MoTe2, and α-In2Se3, as well as a gold source electrode and a gold drain electrode located above the insulating substrate. 2H-MoTe2 represents MoTe2 in a semiconductor state, and α-In2Se3 represents In2Se3 with an α-polarization direction. The gold source electrode is connected to the graphene electrode. The gold drain electrode is connected to α-In2Se3 but not to the graphene electrode or 2H-MoTe2. A van der Waals pn heterojunction is formed between 2H-MoTe2 and α-In2Se3. Ohmic contacts are formed between the graphene electrode and 2H-MoTe2, and between α-In2Se3 and the gold drain electrode.
[0045] In this embodiment, the insulating substrate is a 300 nm thick SiO2 / Si substrate with dimensions of 2 cm × 2 cm; the graphene electrode is 12 nm thick graphene; the gold source electrode and the gold drain electrode are both 50 nm thick; the 2H-MoTe2 is 15 nm thick; and the α-In2Se3 is 18 nm thick.
[0046] The fabrication method of the bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure specifically includes the following steps:
[0047] S1. Cleaning the insulating substrate: The SiO2 / Si substrate is ultrasonically cleaned with acetone, isopropanol and deionized water for 10 min in sequence, dried with nitrogen, and then placed on a hot plate at 100 ℃ for 5 min to remove surface organic matter and moisture.
[0048] S2. Use ultraviolet lithography to define the patterns of gold source electrode and gold drain electrode on the surface of insulating substrate. Use thermal evaporation to deposit gold source electrode and gold drain electrode. Then, use dry transfer to cover the gold source electrode with a single layer of graphene to form a low work function graphene electrode. The channel length between the graphene electrode and the gold drain electrode is controlled at 5~20μm to ensure that there is no short circuit between the two electrodes.
[0049] S3. 2H-MoTe2 sheets are obtained by mechanical exfoliation. Using a high-precision micro-transfer platform (transfer accuracy <1 μm), the sheets are transferred and covered on top of the graphene electrode, extending partially into the channel region to ensure that 2H-MoTe2 and α-In2Se3 can form an effective stack, i.e., a van der Waals pn heterojunction, and to ensure that α-In2Se3 does not come into contact with the graphene electrode.
[0050] S4. Continue by peeling and transferring the α-In₂Se₃ sheet using the same platform, covering one side of it over 2H-MoTe₂ and overlapping the other side over the gold drain electrode, forming a vertical heterostructure of "Gr / 2H-MoTe₂ / α-In₂Se₃ / Au". Figure 2 As shown, the device is annealed in a vacuum environment at 120℃ for 30 min to remove interface bubbles and optimize the contact. The device is protected by standard semiconductor packaging process (PDMS protection or epoxy resin cover plate) and external electrodes are brought out. Finally, a bias-switched dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure is obtained.
[0051] The photoelectric performance of the bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure obtained in this embodiment is tested below.
[0052] 1) Dark Environment Testing
[0053] Linear and semi-logarithmic output curves in the dark were tested using a Keithley 4200-SCS probe station at room temperature, and the results are as follows. Figure 3 As shown, the bias switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure obtained in this embodiment has ultra-low dark current and high rectification ratio.
[0054] 2) Photoconductivity mode test
[0055] Multi-wavelength lasers of 450 nm, 637 nm, 830 nm, and 1060 nm were selected, modulated by a chopper, and focused by an off-axis parabolic mirror into the bias-switchable dual-mode photodetector channel based on a two-dimensional van der Waals pn heterostructure obtained in this embodiment. Under a reverse bias voltage of -1 V, the device is in photoconductive mode. The photocurrent signal obtained from the test is amplified by a low-noise preamplifier (SR570) and then read by a lock-in amplifier (SR830) or a data acquisition card.
[0056] according to Figure 4 The photocurrent response of different wavelengths over time is shown, and Figure 6 The photocurrent versus time curves shown, under 450 nm light illumination at different optical power densities, demonstrate that the bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure obtained in this embodiment possesses a time-resolved optical response; combined with... Figure 5 The device responsivity and specific detectivity under different wavelengths of light illumination shown in this embodiment demonstrate that the bias-switched dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure obtained in this embodiment can generate significant photoconductivity gain under reverse bias, achieving ultra-high sensitivity.
[0057] 3) Photovoltaic mode test
[0058] The same test environment as the photoconductivity mode test was used. Under a forward bias of 1 V, the device was in photovoltaic mode.
[0059] according to Figure 7 The It curves shown are for illumination at different wavelengths (three sets of data were repeated for each wavelength to verify stability and repeatability), and Figure 8 The device responsivity and specific detectivity under different wavelengths of light irradiation are shown in the figure. It can be seen that the bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure obtained in this embodiment has millisecond-level response speed and broadband self-driving capability.
[0060] 4) Dual-mode switching verification and performance comparison
[0061] The same test environment as the photoconductivity mode test was used. Under the same optical power density, the bias-switched dual-mode photodetector based on the two-dimensional van der Waals pn heterostructure obtained in this embodiment was biased with -1 V, 0 V (in self-driven mode), and +1 V, respectively, and the changes in key parameters such as responsivity and response time were recorded.
[0062] according to Figure 9 The responsivity and specific detectivity under 450 nm light illumination and different voltages shown in the figure demonstrate that the bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure obtained in this embodiment can achieve dynamic switching between high speed and ultra-high sensitivity.
[0063] The responsivity and rise time of the bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure obtained in this embodiment are compared with the reported results of existing photodetectors based on two-dimensional materials. Figure 10 As shown, this demonstrates that the detector in this embodiment has superior performance.
[0064] The above embodiments are only for illustrating the principles and advantages of the present invention, and are not intended to limit the present invention. They are only for helping to understand the principles of the present invention. The scope of protection of the present invention is not limited to the above configurations and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the disclosed technology without departing from the essence of the present invention, but they are still within the scope of protection of the present invention.
Claims
1. A bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure, characterized in that, The structure includes, from bottom to top, an insulating substrate, a graphene electrode, 2H-MoTe2 and α-In2Se3, and a gold source electrode and a gold drain electrode located above the insulating substrate. The gold source electrode is connected to the graphene electrode. The gold drain electrode is connected to α-In2Se3 but not to the graphene electrode or 2H-MoTe2. A van der Waals pn heterojunction is formed between 2H-MoTe2 and α-In2Se3.
2. The bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure according to claim 1, characterized in that, Ohmic contacts are formed between the graphene electrode and 2H-MoTe2, and between α-In2Se3 and the gold drain electrode.
3. The bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure according to claim 2, characterized in that, The 2H-MoTe2 extends above the channel between the graphene electrode and the gold drain electrode.
4. The bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure according to claim 2, characterized in that, The graphene electrode is composed of 1 to 50 layers of graphene.
5. The bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure according to claim 2, characterized in that, The thickness of both the gold source electrode and the gold drain electrode is 10~100 nm.
6. The bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure according to claim 2, characterized in that, The thicknesses of both 2H-MoTe2 and α-In2Se3 are 1~50 nm.
7. The bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure according to claim 2, characterized in that, The insulating substrate is a SiO2 / Si substrate, an h-BN substrate, a sapphire substrate, or a flexible PI substrate.
8. A method for fabricating a bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure, characterized in that, Includes the following steps: S1. Clean the insulating substrate; S2. A gold source electrode and a gold drain electrode are prepared on the surface of an insulating substrate, and a graphene electrode is transferred over the gold source electrode. S3. 2H-MoTe2 sheets are obtained by peeling and then transferred over the graphene electrode; S4. An α-In2Se3 sheet is obtained by peeling off, and then transferred over 2H-MoTe2 and overlapped over the gold drain electrode to form a vertical heterostructure of "Gr / 2H-MoTe2 / α-In2Se3 / Au". After device packaging, a bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure as described in any one of claims 2 to 7 is obtained.
9. The fabrication method of the bias-switchable dual-mode photodetector based on a two-dimensional van der Waals pn heterostructure according to claim 8, characterized in that, S4 also includes a thermal annealing step before device packaging, with a temperature of 100~120℃ and a duration of 20~60 min.