Light-Tunable Polarity and Erasable Physisorption-Induced Memory Effect in Vertically Stacked InSe/SnS₂ Self-Powered Photodetector

Abstract

van der Waals heterojunctions with tunable polarity are being actively explored for more Moore and more-than-Moore device applications, as they can greatly simplify circuit design. However, inadequate control over the multifunctional operational states is still a challenge in their development. Here, we show that a vertically stacked InSe/SnS2 van der Waals heterojunction exhibits type-II band alignment, and its polarity can be tuned by an external electric field and by the wavelength and intensity of an illuminated light source. Moreover, such SnS2/InSe diodes are self-powered broadband photodetectors with good performance. The self-powered performance can be further enhanced significantly with gas adsorption, and the device can be quickly restored to the state before gas injection using a gate voltage pulse. Our results suggest a way to achieve and design multiple functions in a single device with multifield coupling of light, electrical field, gas, or other external stimulants.

Field Effect Transistor Gas Sensors Based on Mechanically Exfoliated Van der Waals Materials

“…Recently, several FET gas sensors have been proposed based on vdW materials, such as modified monolayer Ti 3 C 2 T x nanosheets with black phosphorus quantum dots (QDs), Ti 3 C 2 T x anchored with Pt single atoms, Ti 3 C 2 T x −ZnO hybrid structures, Ti 3 C 2 T x /WS 2 , ohmic contacted graphene with MoS 2 and black phosphorous, and Au QDs/Bi 2 S 3 . More recently, it was reported that the coupling of electrical fields and gas adsorption can be used to design memory and logical devices . More interestingly, vdW materials mechanically exfoliated from their bulk single crystals usually have flat and uniform surfaces, making them a good platform to investigate the Langmuir absorption model.…”

“…Recently, several FET gas sensors have been proposed based on vdW materials, such as modified monolayer Ti 3 C 2 T x nanosheets with black phosphorus quantum dots (QDs), 40 recently, it was reported that the coupling of electrical fields and gas adsorption can be used to design memory and logical devices. 46 More interestingly, vdW materials mechanically exfoliated from their bulk single crystals usually have flat and uniform surfaces, making them a good platform to investigate the Langmuir absorption model. Therefore, it is interesting to ask the following questions: How does an electrical field affect the gas sensing properties?…”

Direct Z‐Scheme Heterostructure of Vertically Oriented SnS2 Nanosheet on BiVO4 Nanoflower for Self‐Powered Photodetectors and Water Splitting

“…[ 1–3 ] Current studies mainly focus on field‐effect transistor (FET)‐type self‐powered photodetectors based on van der Waals heterostructure, which have been widely found in GeSe/SnS 2 , MoS 2 /SnS 2 , InSe/SnS 2, and so on. [ 4–8 ] These self‐powered photodetectors are driven by a built‐in electric field, which can achieve high responsivity beyond 10 5 mA W −1 , detectivity up to 10 10 Jones, and fast response in millisecond scale. [ 9,10 ] However, these FET‐type photodetectors suffer from several drawbacks such as: i) outputting low current in the tens to hundreds nanoampere; ii) preparing heterostructure in micron size instead of large‐area ultrathin film; iii) requiring complicated fabrication processes.…”

High-Performance Photodetectors Based on Semiconducting Graphene Nanoribbons

“…Thus, the transport current through the heterojunction will increase, leading to a higher EQE. 31 Moreover, when the device is operated under reverse bias, the EQE is further increased because the larger reverse voltage further reduces the injection barrier and enhances the electric field inside the junction making the photogenerated current increase dramatically. 32 To evaluate the response speed of the device, an oscilloscope is used to measure the photovoltage variation within a single laser pulse, as shown in Figure 4d.…”

“…Separated charges with opposite polarities will induce opposite Coulomb potentials to balance the built-in potentials in the junctions. Thus, the transport current through the heterojunction will increase, leading to a higher EQE . Moreover, when the device is operated under reverse bias, the EQE is further increased because the larger reverse voltage further reduces the injection barrier and enhances the electric field inside the junction making the photogenerated current increase dramatically .…”