An efficient structure for T-CNTFETs with intrinsic-n-doped impurity distribution pattern in drain region

Abstract

: In this paper, by using impurity distribution engineering of drain region, an efficient structure is proposedfor tunneling carbon nanotube field-effect transistors (T-CNTFETs). The drain region of the proposed structure consistsof two parts. The impurity density of the part close to the channel is intrinsic and the other is n-type with constantdensity of 1 nm −1. In conventional T-CNTFETs, heavily doped drain causes a spiky drop of potential energy aroundthe channel to drain junction resulting in a pathway for carriers in the valence band to tunnel to the conduction bandwhich means ambipolar behavior and large leakage current. The proposed structure expands the longitudinal distancebetween the bands at this junction and reduces the band-to-band tunneling (BTBT) and improves leakage current andambipolar behavior. Moreover, current ratio, delay time, power delay product, cut-off frequency, and subthreshold swingas important characteristics are enhanced so that the proposed structure can be more attractive for circuit designers.Also, design considerations for intrinsic region length were done and mentioned. To simulate the devices, self-consistentsolution of Schrodinger and Poisson equations and nonequilibrium Green’s Function method were employed