DFT-NEGF Study of Electron Transfer Property in Graphene Nanoribbon Double Barrier System

Abstract

Current-voltage (I – V) characteristics in armchair graphene nanoribbon (AGNR) double barrier systems (DBSs) are investigated by the density functional theory (DFT) and the non-equilibrium Green’s function (NEGF) methods. The hexagonal boron nitride (h-BN) which has an analogous structure with a graphene shows wide bandgap and becomes an electrical barrier in DBSs. The heterojunction structure of AGNR and two h-BNs with one six-membered ring width has properties as a resonant tunnelling device. Due to the resonance, sharp peaks are formed in the transmission function around the Fermi energy EF . Our previous studies have explained the origins of some peaks by solving the one-dimensional Dirac equation for massless particles. Here, by using the two-dimensional Dirac equation, we show that the remaining sharp peaks depend on the transverse nodal pattern of the wavefunction as well as the anisotropy of the Fermi velocity. Moreover, in the I – V characteristics, a flat part is formed without the negative differential resistance appearing. By partial density of state (PDOS) analysis, we reveal that the flat part in the current is caused by the fact that the peak positions in the resonance region are stable against the bias voltage.