Modeling of carrier density and quantum capacitance in graphene nanoribbon FETs

Gate voltage control of carrier density and quantum capacitance is an important step for understanding the device physics and assessing the performance of nanoscale transistors. In this paper, we present a simple phenomenological model for the carrier density and quantum capacitance of graphene nanoribbon field-effect transistors as functions of gate voltage, Fermi level position and temperature. Quantum capacitance is calculated from the broadened density of states incorporating the presence of electron-hole puddles and possible finite lifetime of electronic states through a Gaussian broadening distribution. Thin gate-insulators of high-κ dielectric constant are used in our calculations in order to approach the quantum capacitance limit.