In-Plane Homojunctions and Their Dominant Effects on Charge Transport in Vertical van der Waals Heterostructures

We report, for the first time, the direct observation of in-plane (lateral) homojunctions in vertical van der Waals heterostructures and their dominant effect on charge transport properties. Particularly, with an all-van der Waals metal-semiconductor vertical Schottky junction (MoS2/beta-In2Se3) as a model system, we use scanning gate microscopy to directly visualize the inplane homojunction in the MoS2 channel, the formation of which is a result of charge transfer between MoS2 and beta-In2Se3, as supported by numerical simulations and electrical transport measurements. Importantly, we find that this gate-tunable in-plane junction controls the vertical Schottky junction characteristics under the forward-bias condition. This is in contrast to the common assumption that the charge transport across the vertical heterojunction interface is the dominant process. Our findings are universally relevant in vertical van der Waals heterostructures where the charge transfer occurs across the interface, providing new insight into the underlying charge transport process in these heterostructures.