The continued miniaturization of Si integrated devices in CMOS technology is approaching the physical limits. To meet the ITRS roadmap, novel nano-electronic devices are expected to be utilized. Graphite-related materials such as fullerenes, carbon nanotubes, and graphene have been extensively studied in recent years due to their exceptional electronic, opto-electronic, and mechanical properties. Graphene, a one-atomic carbon sheet with a honeycomb lattice, has attracted significant attention due to its unique physical properties. This material shows an extraordinarily high carrier mobility and is considered to be a potentially high speed transistor material. Graphene is a gapless material. To induce a bandgap in graphene sheets, they can be patterned into ribbons. Depending on the width and the chirality, a Graphene NanoRibbon (GNR) can have semiconducting or metallic behavior. To model transport of carriers in GNRs the Non-Equilibrium Green's Function (NEGF) formalism and an atomistic tight-binding model, which captures the granularity of the simulation domain, has been employed.
Scattering of carriers in GNRs can be due to intrinsic sources, such as acoustic and optical phonons and line-edge roughness. Extrinsic scattering sources, such as charged impurities and ripples of the substrate surface, are induced by the substrate. In order to obtain an energy bandgap larger than 0.1eV, which is essential for electronic applications, the width of the GNR must be scaled below 10nm. In this regime line-edge roughness is the dominant scattering mechanism. We model the effect of line-edge roughness using a non-perturbative approach. In this method, roughness is applied to many GNR samples using a Gaussian or exponential distribution and then a statistical averaging is performed over all these samples. In our work, the effect of roughness parameters and the role of device geometry are discussed. Depending on these parameters, carrier transport can be in the quasi ballistic, diffusive, or localization regime. Our results show that the transport gap of nanoribbons can increase due to the presence of line-edge roughness.