The High-Frequency Performance of Hetero-Material-Gate CNTFETs with Gate Underlap

Abstract

For the first time, a new type of carbon nanotube field–effect transistor (CNTFET), the hetero-material-gate(HMG) with underlap, is proposed and simulated using quantum model that is based on two-dimensional nonequilibrium Green's function (NEGF) solved self-consistently with Poisson equation. The simulated results reveal that the intrinsic cutoff frequency of single-material-gate CNTFETs (C-CNTFETs) reaches up to a few THz, which is 50% higher than that of ballistic Si FETs. Furthermore, we investigate the performance of C-CNTFETs with gate underlap. The results indicate that gate underlap can improve the cutoff frequency fT and switching speed, but deteriorate Ion/Ioff ratio. To improve Ion/Ioff ratio and perfect high-frequency performance, we propose HMG-CNTFETs with underlap and evaluate frequency and switching performance. The calculated results show that, for HMG-CNTFETs, gate underlap of about 11 nm can obviously optimize Ion/Ioff ratio and achieve an ideal cutoff frequency simultaneously. Our study provide a theoretical base for optimizing high-performance of CNTFET and broadening its application.