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

In this paper, based on the simple Pz 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 Ion/Ioff ratio versus oxide thickness for switching applications of GNRFET. The results show that the edge effect changes the device specifications considerably.

Graphical abstractThe GNRFET is analyzed for its high frequency applications. The edge effect is considered, where it has significant effects on the GNRFET parameters and behavior.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We have analyzed the graphene nanoribbon FET by Non-Equilibrium Green's Function. ► The device is analyzed in the mode space with and without the edge effect. ► Cut-off frequency, gate capacitance and transconductance are calculated. ► Ion/Ioff ratio versus oxide thickness of device is examined. ► Results show that the edge effect changes the device specifications considerably.