Modeling 15nm graphene FET with contact resistance effects using channel segmentation technique

Abstract

Graphene Field Effect Transistor (GFET) which is scaled down to 15nm is modeled by integrating the effects of contact resistance. The effect of contact resistance cannot be neglected as the device is scaled down. As the contact resistance is directly related to the device drain current, increase in contact resistance results in reduced current flow. In this paper contact resistance formula with respect to sheet resistance, resistivity of the graphene under source-drain contacts and channel length is derived. It is known that Gold (Au) offers lesser contact resistance due to its lower sheet resistivity. Hence the derived formula is validated by proving that the contact resistance of Gold(Au) is lesser than other metals. The derived formula provides easier contact resistance calculation by replacing the sheet resistivity of different materials. A comparative study is made by having different metals as contacts and the total contact resistance offered by each metal is estimated. The model that has been developed to incorporate the contact resistance is used to determine drain current, which is computed by analyzing the channel potential and electric field. A novel method is adopted to analyze the channel potential by segmenting the channel. This method is key feature in modeling a purely ballistic transport at 15nm channel length. The ballistic structure resulted in lower channel potential drop due to the reduced scattering of electrons. Mobility which is considered to be a key factor of Graphene is being analyzed with respect to carrier concentration, conductivity and temperature. The realized mobility is found to be higher of 2497 cm /Vs. Simulation of a digital application-GFET Inverter with lesser fall time is presented in this paper.