Theoretical Analysis and Experimental Optimization of Graphene/TMD Heterojunction Barristors

摘要

We optimized the graphene/MoS_2 and graphene/WSe_2 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/MoS_2 barristor and 10/25 and 230 in the graphene/WSe_2 barristor, respectively. Particularly, we reported an unusual phenomenon that on-state current density increases as the measurement temperature decreases in the graphene/WSe_2 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/MoS_2 and graphene/WSe_2 barristors were thermionic emission and trap-assisted tunneling processes, respectively.