Abstract
We optimized the graphene/MoS2 and graphene/WSe2 heterojunction barristors in terms of on-/off-current densities and on/off-current ratio by inserting an APTES layer which suppresses the charge puddle effect. The on-/off-current densities and on/off-current ratio were improved by a factor of 2.1/15 and 32 in the graphene/MoS2 barristor and 10/25 and 230 in the graphene/WSe2 barristor, respectively. Particularly, we reported an unusual phenomenon that on-state current density increases as the measurement temperature decreases in the graphene/WSe2 barristor. Finally, based on temperature-dependent current-voltage measurements coupled with first-principle density functional theory (DFT) calculations, we confirmed that the main operating mechanisms of graphene/MoS2 and graphene/WSe2 barristors were thermionic emission and trap-assisted tunneling processes, respectively.