Frequency analysis of graphene nanoribbon FET by Non-Equilibrium Green's Function in mode space

Abstract

In this paper, based on the simple P z orbital model for the Hamiltonian of graphene nanoribbon, we have analyzed the Graphene Nanoribbon Field Effect Transistors (GNRFET). The Non-Equilibrium Green's Function (NEGF) is used to solve the Schrödinger equation self-consistently with two-dimensional (2D) Poisson equation. The Poisson equation is solved in 2D coordinates using the Finite Difference Method (FDM). In fact, we have assumed that the potential in the width of channel is invariant and the 2D Poisson equation is sufficient to be solved. The “edge effect” that is due to uncompleted bonding of atoms on the edge of the ribbon affects the GNR behavior significantly. In order to calculate the current–voltage characteristic of GNRFET, the Landauer formula is used. We have analyzed the double gate GNRFET with 10 nm channel length and source/drain doped reservoirs in the mode space for both cases, with and without the edge effect. We have computed the gate capacitance and transconductance of the device in order to calculate the intrinsic cut-off frequency and switching delay. We have also investigated the I on / I off ratio versus oxide thickness for switching applications of GNRFET. The results show that the edge effect changes the device specifications considerably.