Novel Optical and Electrical Transport Properties in Atomically Thin WSe2/MoS2 p-n Heterostructures

Vertically stacked Van der Waals heterojunctions of atomically thin transition metal dichalcogenides (TMDs) offer new physical properties and new strategies for designing novel device functionalities that are vastly different from homostructured TMDs. The Raman intensity is strongest and frequency difference is largest in monolayer WSe2 compared with that in few-layers, which is opposite to MoS2 and WS2. In the WSe2/MoS2 bilayer heterostructures, inefficient charge transfer quenches light emission of monolayer WSe2 but strengthens those of MoS2 monolayer. Interestingly, rectification and ambipolar effects emerge due to tunneling-assisted interlayer recombination and dual conducting channels of p-WSe2 and n-MoS2 in the heterojunctions system. Gate-induced holes tunneling also leads to a novel anti-bipolar behavior with a sharp current peak. Under light illumination, charge transfer competes with the holes tunneling between the WSe2 and MoS2 layers, which can greatly influence the electrical transport leading to the disappeared rectifying and anti-bipolar properties.