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 (BE-MOSCNT) outperforms the lightly-doped drain and source (LDDS) MOSCNT, in both ON and OFF regimes. The LDDS-MOSCNT 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.

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