A three-dimensional simulation of electrostatic characteristics for carbon nanotube array field effect transistors

We, in this paper, study the electrostatic characteristics and the gate capacitances for carbon nanotube (CNT) array field effect transistors (FETs). The explored CNT-array FET is with three configurations of gate electrode, the top gate, the wrap around gate, and the bottom gate. Taking the pitch distance of structures and the gate length of CNT FET into consideration, a three-dimensional (3D) electrostatic simulation are performed by using an adaptive finite volume method, where different gate capacitance are calculated and compared. It is found that there is at least a 20% difference in calculating the gate capacitance between the 2D and 3D modeling and simulations. Our 3D simulation shows that a wrap around gate gives the largest gate capacitance among structures. A bottom gate possesses the weakest gate controllability. Effects of the pitch distance and the gate length on the gate capacitances of CNT-array FET are investigated. Results of the 3D electrostatic simulations can be applied to estimate the magnitude of the on-current of CNT FETs.