DESIGN DEPENDENT CUTOFF FREQUENCY OF NANOTRANSISTORS NEAR THE ULTIMATE PERFORMANCE LIMIT

Abstract

We have studied the effect of different structural designs of double gate MOSFETs (DG–MOSFETs) and carbon nanotube field effect transistors (CNTFETs) on the cutoff frequency (fT). The effects of metallic contacts with Schottky barriers, gate work function, dual material gate (DMG), halo doped channel and lightly doped drain and source (LDDS) architectures on the fT have been investigated for DG–MOSFETs and CNTFETs and the design dependent fT for both types of transistors has been studied for the first time. The simulations are based on the Schrödinger–Poisson solvers developed for each nanotransistor separately. The ballistic limit has been studied as the ultimate performance limit of the DG–MOSFETs and CNTFETs. The results of this paper, for the first time, show how some designations used for modification of short channel effects or current–voltage characteristics affect the fT. The results revealed that the cutoff frequencies of both types of the transistors exhibit the same behavior with changing design parameters. We have shown that the Schottky barriers, parasitic capacitances and halo doping reduce the fT and have proposed the DMG and LDDS artchitectures as ways to increase the fT for DG–MOSFETs and CNTFETs for the first time.