Abstract

To enable the computer-aided design of vertically stacked two-dimensional (2D) van der Waals (vdW) heterostructure devices, we here introduce a non-equilibrium first-principles simulation method based on the multi-space constrained-search density functional formalism. Applying it to graphene/few-layer hBN/graphene field-effect transistors, we show that the negative differential resistance (NDR) characteristics can be produced not only from the gating-induced mismatch between two graphene Dirac cones in energy-momentum space but from the bias-dependent energetic shift of defect levels. Specifically, for a carbon atom substituted for a nitrogen atom (CN) within inner hBN layers, the increase of bias voltage is found to induce a self-consistent electron filling of in-gap CN states, which in turn changes voltage drop profiles and produces symmetric NDR characteristics. With the CN placed on outer hBN layers, however, the pinning of CN states to nearby graphene significantly modifies device characteristics, demonstrating the critical impact of atomic details for 2D vdW devices.

Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call