Lateral Graphene-Contacted Vertically Stacked WS /MoS Hybrid Photodetectors with Large Gain.

A demonstration is presented of how significant improvements in all-2D photodetectors can be achieved by exploiting the type-II band alignment of vertically stacked WS /MoS semiconducting heterobilayers and finite density of states of graphene electrodes. The photoresponsivity of WS /MoS heterobilayer devices is increased by more than an order of magnitude compared to homobilayer devices and two orders of magnitude compared to monolayer devices of WS and MoS , reaching 10 A W under an illumination power density of 1.7 × 10 mW cm . The massive improvement in performance is due to the strong Coulomb interaction between WS and MoS layers. The efficient charge transfer at the WS /MoS heterointerface and long trapping time of photogenerated charges contribute to the observed large photoconductive gain of ≈3 × 10 . Laterally spaced graphene electrodes with vertically stacked 2D van der Waals heterostructures are employed for making high-performing ultrathin photodetectors.