Layer-dependent band to band tunneling in WSe2/ReS2 van der Waals heterojunction

Abstract

Van der Waals (vdW) heterostructures are promising for building tunneling field-effect transistors (TFETs), owing to an inherent narrow vdW gap between two stacked materials induced by the dangling bond free surface. However, the band to band tunneling (BTBT) of such a vdW heterostructure TFET strongly depends on the layer-dependent band structure variation at the interface. Here, we report a first principle simulation on the BTBT transition of the monolayer ReS2 based heterostructures with monolayer and bilayer WSe2. An obvious decrease of the turn-on gate voltage from 36 V to 12 V was achieved by adding a layer of WSe2 due to the band gap narrowing and momentum conservative Γ-Γ tunneling. Under the gate voltage of 20 V with bias of 0.271 V, the upper limit of the BTBT saturate current density in bilayer WSe2 vdW heterojunction can reach 934 μA μm−1. These results show the bilayer WSe2 heterojunction could be an ideal candidate for lower power and high operating speed TFETs.