Temperature and gate effects on contact resistance and mobility in graphene transistors by TLM and Y-function methods

TL;DR

This study investigates how temperature and gate voltage influence contact resistance and mobility in graphene transistors, using TLM and Y-function methods to improve understanding and device performance.

Contribution

It demonstrates the complementary use of TLM and Y-function methods for accurate contact resistance evaluation and explores temperature effects on mobility and resistance.

Findings

Gate voltage modulates contact and channel resistance similarly.

Raising temperature reduces carrier mobility.

Eliminating contact resistance nearly doubles mobility.

Abstract

The metal-graphene contact resistance is one of the major limiting factors toward the technological exploitation of graphene in electronic devices and sensors. A high contact resistance can be detrimental to device performance and spoil the intrinsic great properties of graphene. In this paper, we fabricate graphene field-effect transistors with different geometries to study the contact and channel resistance as well as the carrier mobility as a function of gate voltage and temperature. We apply the transfer length method and the y-function method showing that the two approaches can complement each other to evaluate the contact resistance and prevent artifacts in the estimation of the gate-voltage dependence of the carrier mobility. We find that the gate voltage modulates the contact and the channel resistance in a similar way but does not change the carrier mobility. We also show that the raising temperature lowers the carrier mobility, has negligible effect on the contact resistance, and can induce a transition from a semiconducting to a metallic behavior of the graphene sheet resistance, depending on the applied gate voltage. Finally we show that eliminating the detrimental effects of the contact resistance on the transistor channel current almost doubles the carrier field-effect mobility and that a competitive contact resistance an be achieved by the zig-zag shaping of the Ni contact.