Negative Differential Resistance in Boron Nitride Graphene Heterostructures: Physical Mechanisms and Size Scaling Analysis

TL;DR

This study explores quantum transport in graphene-hBN-graphene heterostructures, revealing gate-tunable negative differential resistance caused by interference and wave vector matching, with potential applications in high-speed electronics.

Contribution

It uncovers two distinct mechanisms behind NDR in graphene-hBN heterostructures and analyzes their dependence on device parameters and scattering effects.

Findings

NDR with multiple resonant peaks observed and tunable via device dimensions.

Two mechanisms identified: Fabry-Pérot interference and wave vector matching.

Electron-phonon scattering suppresses interference-based NDR, while wave matching remains stable.

Abstract

Hexagonal boron nitride (hBN) is drawing increasing attention as an insulator and substrate material to develop next generation graphene-based electronic devices. In this paper, we investigate the quantum transport in heterostructures consisting of a few atomic layers thick hBN film sandwiched between graphene nanoribbon electrodes. We show a gate-controllable vertical transistor exhibiting strong negative differential resistance (NDR) effect with multiple resonant peaks, which stay pronounced for various device dimensions. We find two distinct mechanisms that are responsible for NDR, depending on the gate and applied biases, in the same device. The origin of first mechanism is a Fabry-P\'e like interference and that of the second mechanism is an in-plane wave vector matching when the Dirac points of the electrodes align. The hBN layers can induce an asymmetry in the current-voltage characteristics which can be further modulated by an applied bias. We find that the electron-phonon scattering introduces the decoherence and therefore suppresses first mechanism whereas second mechanism remains relatively unaffected. We also show that the NDR features are tunable by varying device dimensions. The NDR feature with multiple resonant peaks, combined with the ultrafast tunneling speed provides prospect for the graphene-hBN-graphene heterostructure in the high-performance electronics.