Lateral Graphene-Contacted Vertically Stacked WS2/MoS2 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 WS2/MoS2 semiconducting heterobilayers and finite density of states of graphene electrodes. The photoresponsivity of WS2/MoS2 hetero-bilayer devices is increased by more than an order of magnitude compared to homobilayer devices and two orders of magnitude compared to monolayer devices of WS2 and MoS2, reaching 10(3) A W-1 under an illumination power density of 1.7 x 10(2) mW cm(-2). The massive improvement in performance is due to the strong Coulomb interaction between WS2 and MoS2 layers. The efficient charge transfer at the WS2/MoS2 heterointerface and long trapping time of photogenerated charges contribute to the observed large photoconductive gain of approximate to 3 x 10(4). Laterally spaced graphene electrodes with vertically stacked 2D van der Waals heterostructures are employed for making high-performing ultrathin photodetectors.