Highly Sensitive, Ultrafast, and Broadband Photo-Detecting Field-Effect Transistor with Transition-Metal Dichalcogenide van der Waals Heterostructures of MoTe and PdSe.

Recently, van der Waals heterostructures (vdWHs) based on transition-metal dichalcogenides (TMDs) have attracted significant attention owing to their superior capabilities and multiple functionalities. Herein, a novel vdWH field-effect transistor (FET) composed of molybdenum ditelluride (MoTe ) and palladium diselenide (PdSe ) is studied for highly sensitive photodetection performance in the broad visible and near-infrared (VNIR) region. A high rectification ratio of 6.3 × 10 is obtained, stemming from the sharp interface and low Schottky barriers of the MoTe /PdSe vdWHs. It is also successfully demonstrated that the vdWH FET exhibits highly sensitive photo-detecting abilities, such as noticeably high photoresponsivity (1.24 × 10 A W ), specific detectivity (2.42 × 10 Jones), and good external quantum efficiency (3.5 × 10 ), not only due to the intra-TMD band-to-band transition but also due to the inter-TMD charge transfer (CT) transition. Further, rapid rise (16.1 µs) and decay (31.1 µs) times are obtained under incident light with a wavelength of 2000 nm due to the CT transition, representing an outcome one order of magnitude faster than values currently in the literature. Such TMD-based vdWH FETs would improve the photo-gating characteristics and provide a platform for the realization of a highly sensitive photodetector in the broad VNIR region.