Band Structure Effects on the Scaling Properties of [111] InAs Nanowire MOSFETs

We have investigated the scaling properties of [111] InAs nanowire MOSFETs in the ballistic limit. The nanowire band structure has been calculated with an sp³d⁵ s* tight-binding model for nanowire diameters between 2 and 25 nm. Both the effective band gap and the effective masses increase with confinement. Using the atomistic dispersion relations, the ballistic currents and corresponding capacitances have been calculated with a semianalytical model. It is shown that the InAs nanowire MOSFET with diameters scaled below 15-20 nm can be expected to operate close to the quantum capacitance limit, assuming a high-kappa dielectric thickness of 1-1.5 nm. We have also investigated the evolution of f_t and the gate delay, both showing improvements as the device is scaled. The very small intrinsic gate capacitance in the quantum limit makes the device susceptible to parasitic capacitances.