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

TL;DR

This study uses density functional theory to show that rotational misalignment of hBN tunnel barriers in graphene/hBN/graphene heterostructures significantly reduces interlayer coupling, impacting device performance.

Contribution

It provides the first detailed theoretical analysis of how rotational misalignment affects interlayer coupling in van der Waal's heterostructures, specifically in tunnel FETs.

Findings

Rotational misalignment reduces interlayer coupling.

Weakened coupling may influence device characteristics.

Simulation results applicable to various van der Waal's heterostructures.

Abstract

Van der Waal's heterostrucutures allow for novel devices such as two-dimensional-to-two-dimensional tunnel devices, exemplified by interlayer tunnel 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 device characteristics. In this work, by using density functional theory methods, we consider a reduction in tunneling due to weakened coupling across the rotationally misaligned interface between the channel layers and the tunnel barrier. As a prototypical system, we simulate the effects of rotational misalignment of the tunnel barrier layer between aligned channel layers in a graphene/hBN/graphene system. We find that rotational misalignment between the channel layers and the tunnel barrier in this van der Waal's heterostructure can significantly reduce coupling between the channels by reducing, specifically, coupling across the interface between the channels and the tunnel barrier. This weakened coupling in graphene/hBN/graphene with hBN misalignment may be relevant to all such van der Waal's heterostructures.