DFT Simulations of Inter-Graphene-Layer Coupling with Rotationally Misaligned hBN Tunnel Barriers in Graphene/hBN/Graphene Tunnel FETs

摘要

Van der Waal's heterostrucutures allow for novel devices such astwo-dimensional-to-two-dimensional tunnel devices, exemplified by interlayertunnel FETs. These devices employ channel/tunnel-barrier/channel geometries.However, during layer-by-layer exfoliation of these multi-layer materials,rotational misalignment is the norm and may substantially affect devicecharacteristics. In this work, by using density functional theory methods, weconsider a reduction in tunneling due to weakened coupling across therotationally misaligned interface between the channel layers and the tunnelbarrier. As a prototypical system, we simulate the effects of rotationalmisalignment of the tunnel barrier layer between aligned channel layers in agraphene/hBN/graphene system. We find that rotational misalignment between thechannel layers and the tunnel barrier in this van der Waal's heterostructurecan significantly reduce coupling between the channels by reducing,specifically, coupling across the interface between the channels and the tunnelbarrier. This weakened coupling in graphene/hBN/graphene with hBN misalignmentmay be relevant to all such van der Waal's heterostructures.