Contact-induced negative differential resistance in short-channel graphene FETs

TL;DR

This paper investigates the physical origin of negative differential resistance in short-channel graphene FETs, revealing it arises from a transport mode bottleneck related to the Dirac point, with implications for device design.

Contribution

The study introduces a combined NEGF simulation and semianalytical model to explain NDR in graphene FETs, highlighting the role of the Dirac point and contact effects.

Findings

NDR occurs only in specific polarity configurations (n-p-n or p-n-p).

Transport mode bottleneck caused by the Dirac point explains NDR.

Contact-induced effects influence the NDR behavior.

Abstract

In this work, we clarify the physical mechanism for the phenomenon of negative output differential resistance (NDR) in short-channel graphene FETs (GFETs) through non-equilibrium Green's function (NEGF) simulations and a simpler semianalytical ballistic model that captures the essential physics. This NDR phenomenon is due to a transport mode bottleneck effect induced by the graphene Dirac point in the different device regions, including the contacts. NDR is found to occur only when the gate biasing produces an n-p-n or p-n-p polarity configuration along the channel, for both positive and negative drain-source voltage sweep. In addition, we also explore the impact on the NDR effect of contact-induced energy broadening in the source and drain regions and a finite contact resistance.