In this paper, by using impurity distribution engineering of drain region, an efficient structure is proposed for tunneling carbon nanotube field-effect transistors (T-CNTFETs). The drain region of the proposed structure consists of two parts. The impurity density of the part close to the channel is intrinsic and the other is n-type with constant density of 1 nm1 . In conventional T-CNTFETs, heavily doped drain causes a spiky drop of potential energy around the channel to drain junction resulting in a pathway for carriers in the valence band to tunnel to the conduction band which means ambipolar behavior and large leakage current. The proposed structure expands the longitudinal distance between the bands at this junction and reduces the band-to-band tunneling (BTBT) and improves leakage current and ambipolar behavior. Moreover, current ratio, delay time, power delay product, cut-off frequency, and subthreshold swing as 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-consistent solution of Schrodinger and Poisson equations and nonequilibrium Green’s Function method were employed.
