Physical Modeling of Gate-Controlled Schottky Barrier Lowering of Metal-Graphene Contacts in Top-Gated Graphene Field-Effect Transistors.

Ling-Feng Mao,Jin-Yan Wang,Zong-Liang Huo,Huansheng Ning

doi:10.1038/srep18307

Abstract

A new physical model of the gate controlled Schottky barrier height (SBH) lowering in top-gated graphene field-effect transistors (GFETs) under saturation bias condition is proposed based on the energy conservation equation with the balance assumption. The theoretical prediction of the SBH lowering agrees well with the experimental data reported in literatures. The reduction of the SBH increases with the increasing of gate voltage and relative dielectric constant of the gate oxide, while it decreases with the increasing of oxide thickness, channel length and acceptor density. The magnitude of the reduction is slightly enhanced under high drain voltage. Moreover, it is found that the gate oxide materials with large relative dielectric constant (>20) have a significant effect on the gate controlled SBH lowering, implying that the energy relaxation of channel electrons should be taken into account for modeling SBH in GFETs.

Highlights

The aim of this study is to provide an explanation for gate-controlled Schottky barrier of a metal-graphene transistor on a silicon substrate reported in ref
Based on the energy conservation equation with the balance assumption, a physical model is built in this work to describe the gate controlled Schottky barrier height (SBH) lowering effects in a graphene field-effect transistors (GFETs) under the saturation mode
The increases in the electron mobility and the energy relaxation (ER) time of channel electron will result in a linear increase in the reduction in the SBH according to the proposed model (Eq 19)

Summary

Introduction

The electron energy (electron temperature) can be much higher than lattice energy (lattice temperature) in semiconductor devices[9,10,11], while the energy difference between electrons and lattices is governed by the energy relaxation (ER) time[12]. Experimental results showed that the ER time in a graphene device is about 1 ps, and the electron gas temperature varies from 400 K to 700 K when the lattice temperature is 300 K in single-wall carbon nano-tubes[13]. A larger difference between the electron temperature and the lattice temperature in graphene could be found[14]

Objectives

Results

Discussion

Conclusion