A self-driven photodetector based on a SnS₂/WS₂ van der Waals heterojunction with an Al₂O₃ capping layer

Photodetectors based on two-dimensional (2D) materials have attracted considerable attention because of their unique properties. To further improve the performance of self-driven photodetectors based on van der Waals heterojunctions, a conductive band minimum (CBM) matched self-driven SnS2/WS2 van der Waals heterojunction photodetector based on a SiO2/Si substrate has been designed. The device exhibits a positive current at zero voltage under 365 nm laser illumination. This is attributed to the built-in electric field at the interface of the SnS2 and WS2 layer, which will separate and transport the photogenerated carriers, even at zero bias voltage. In addition, the Al2O3 layer is covered by the surface of the SnS2/WS2 photodetector to further improve the performance, because the Al2O3 layer will introduce tensile stress on the surface of the 2D materials leading to a higher electron concentration and smaller effective mass of electrons in the films. This work provides an idea for the research of self-driven photodetectors based on a van der Waals heterogeneous junction.