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 WS 2 /MoS 2 semiconducting heterobilayers and finite density of states of graphene electrodes. The photoresponsivity of WS 2 /MoS 2 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 2 and MoS 2 , reaching 10 3 A W −1 under an illumination power density of 1.7 × 10 2 mW cm −2 . The massive improvement in performance is due to the strong Coulomb interaction between WS 2 and MoS 2 layers. The efficient charge transfer at the WS 2 /MoS 2 heterointerface and long trapping time of photogenerated charges contribute to the observed large photoconductive gain of ≈3 × 10 4 . Laterally spaced graphene electrodes with vertically stacked 2D van der Waals heterostructures are employed for making high‐performing ultrathin photodetectors.