A computational study of the effects of linear doping profile on the high-frequency and switching performances of hetero-material-gate CNTFETs

The effects of linear doping profile near the source and drain contacts on the switching and highfrequency characteristics for conventional single-material-gate CNTFET(C-CNTFET) and hetero-material-gate CNTFET(HMG-CNTFET) have been theoretically investigated by using a quantum kinetic model.This model is based on two-dimensional non-equilibrium Green’s functions(NEGF) solved self-consistently with Poisson’s equations.The simulation results show that at a CNT channel length of 20 nm with chirality(7,0),the intrinsic cutoff frequency of C-CNTFETs reaches up to a few THz.In addition,a comparison study has been performed between C-and HMG-CNTFETs.For the C-CNTFET,results reveal that a longer linear doping length can improve the cutoff frequency and switching speed.However,it has the reverse effect on on/off current ratios.To improve the on/off current ratios performance of CNTFETs and overcome short-channel effects(SCEs) in high-performance device applications,a novel CNTFET structure with a combination of an HMG and linear doping profile has been proposed.It is demonstrated that the HMG structure design with an optimized linear doping length has improved high-frequency and switching performances as compared to C-CNTFETs.The simulation study may be useful for understanding and optimizing high-performance of CNTFETs and assessing the reliability of CNTFETs for prospective applications.