Effect of back-gate on contact resistance and on channel conductance in graphene-based field-effect transistors

TL;DR

This study investigates how back-gate voltage influences contact resistance and conductance in graphene FETs, revealing the impact of contact material and doping effects on device performance.

Contribution

It provides quantitative measurements of contact resistivity for Ni and Ti contacts and explains the doping-induced double dip feature in transfer characteristics.

Findings

Contact resistivity is significant and gate-modulated.

Ni and Ti contacts show different resistivities (~7kΩ·μm² and ~30kΩ·μm²).

Doping effects cause a double dip in transfer curves.

Abstract

We study the contact resistance and the transfer characteristics of back-gated field effect transistors of mono- and bi-layer graphene. We measure specific contact resistivity of ~7kohm*um2 and ~30kohm*um2 for Ni and Ti, respectively. We show that the contact resistance is a significant contributor to the total source-to-drain resistance and it is modulated by the back-gate voltage. We measure transfer characteristics showing double dip feature that we explain as the effect of doping due to charge transfer from the contacts causing minimum density of states for graphene under the contacts and in the channel at different gate voltage.