Phase-transition modulated, high-performance dual-mode photodetectors based on WSe₂/VO₂ heterojunctions

Photodetectors based on two-dimensional (2D) transition metal dichalcogenides (TMDs) can only be operated in a single photovoltaic or photoconductive mode, showing either high detectivity or high responsivity, but not both. An effort to develop a photodetector that can dynamically switch its working mode is indispensable for practical applications. In this article, we demonstrate a high performance, phase-transition modulated, dual-mode photodetector based on WSe₂/VO₂ heterojunction. Enabled by the insulator-to-metal transition of VO₂, the WSe₂/VO₂ heterojunction can be regulated from a type-II heterojunction to a Schottky junction, showing a tunable built-in electric field at the heterojunction interface. This resulted in the dynamic switch of carrier transport and photoresponse in the heterojunction. With this dual-mode function, the new photodetector can have both a high detectivity and a large responsivity, surpassing the current performance of single mode 2D TMDs photodetectors. With a direct laser writing and erasing technique, the photoresponse of a WSe₂/VO₂ device can be locally modulated as desired. This dual mode detection of the WSe₂/VO₂ photodetector deepens the fundamental understanding of charge transfer in heterojunctions and favors versatile applications in photodetection.