Design and simulation of MOSCNT with band engineered source and drain regions

We propose a new Metal-oxide-semiconductor carbon-nanotube transistor (MOSCNT) in which source (S) and drain (D) regions are formed by band engineered multi-wall carbon nanotubes (BE-MWCNTs). The gradual potential profiles of these band-engineered S/D regions weakening the longitudinal confinements in the channel reduce the band-to-band tunneling significantly and hence eliminating the ambipolar behavior observed in other types of MOSCNTs. Such an excellent performance makes the proposed band engineered MWCNT a potential alternative to the chemically/electrostatically doped CNTs that are usually used as S/D regions in MOSCNTs. Simulations show that the proposed band engineered MOSCNT (BEMOSCNT) outperforms the lightly-doped drain and source (LDDS) MOSCNT, in both ON and OFF regimes. The LDDSMOSCNT has already proven to outperform the conventional MOSCNTs. The proposed BE-MOSCNT, in comparison with its earlier rivals, exhibits smaller subthreshold swing, smaller drain-induced barrier lowering, and lower OFF currents. Thus, in this respect, it could be more attractive to circuit designers. To simulate the device band structure and I-V characteristics, we have employed the non-equilibrium Green function (NEGF) formalism using the modified Hamiltonian and tight-binding approximation with only pz-orbitals.