Width-Dependent Characteristics of Graphene Nanoribbon Field Effect Transistor for High Frequency Applications

A numerical simulation based on self-consistent solution of non-equilibrium Green's function (NEGF) formulism and Poisson equation has been developed in order to investigate the width-dependent characteristics of GNR FETs in two GNR families (3p,0) and (3p+1,0). On-state characteristics such as transfer characteristics, transconductance, gate capacitance, intrinsic cut-off frequency and intrinsic gate-delay time have been studied. We found that while the maximum intrinsic cut-off frequency of both GNR families are increased by increasing the GNR width, GNR(3p,0) shows superior performance such as more than twice larger intrinsic cut-off frequency at lower gate voltages, higher drive current and lower intrinsic gate-delay time, indicating GNR(3p,0) a more preferable attribute than GNR(3p+1,0) for high frequency applications.

I. Introduction

Graphene is a promising material for next-generation electronics due to its exceptional properties such as high thermal conductivity, large carrier motilities, high carrier concentration and atomically thin planar structure [1]. It has been predicted by ITRS [2] that the graphene material can continue the improvement of switching speed with low switching power consumption at the same time. A narrow graphene (~1-3 nm) in the form of armchair-edge nanoribbon can result in energy gap of several hundred meV, making it applicable for logic operation [3]. For narrow strip of graphene nanoribbon (GNR), the controlling width is very important as removing or adding one atom along the ribbon can significantly change the bandgap and effective mass of GNR and consequently alter GNR FET characteristics. As the precise control of GNR width in nanometer range is an unsolved technical problem, the atomistic quantum-based simulation can accurately describe the width dependent performance of GNR FETs [4] for future nanoelectronics. Figure 1.

Schematic of DG GNR FET with two insulator layers of hfo2 and hbn.