Modeling and analysis of intrinsic gate capacitance for carbon nanotube array based devices considering variation in screening effect and diameter

An accurate analytical model for intrinsic gate capacitance of carbon nanotube array based back-gated FET is proposed. The model accounts for electrostatic capacitive coupling between nanotubes as well as screening effect for any given number of nanotubes, their diameter, and pitch. Analysis using this model shows that as the number of nanotubes increases, although the overall electrostatic capacitance per nanotube decreases by up to 50%, the electrostatic capacitance becomes the dominant factor over the quantum capacitance. Furthermore, applicability of the proposed model in presence of practical fabrication process variations such as variation in diameter of carbon nanotubes is demonstrated using a probabilistic approach.