Full band calculations of low-field mobility in p-type silicon nanowire MOSFETs

The bandstructure of p-type gated Si nanowires (NWs) is calculated self-consistently using the sp³d⁵s* atomistic tight-binding (TB) model and the 2D Poisson equation. The Boltzmann transport formalism is then used for calculation of the low-field mobility. We show that the bandstructures of NWs in the [110] and [111] transport orientations change as the channel is driven into inversion, which causes a ~50% increase in their intrinsic phonon-limited hole mobility. For short channel MOSFET devices, however, the total mobility is lower that the intrinsic mobility because it is affected by the so-called “ballistic” mobility.