Bandstructure and orientation effects in ballistic Si and Ge nanowire FETs

Using a semi-empirical, sp/sup 3/d/sup 5/s* tight-binding approach and a 'top-of-the-barrier' ballistic FET model, we report full-band simulations of ballistic Si and Ge nanowire FETs with various channel orientations and wire diameters. We find that the nanowire FET performance displays a strong orientation and diameter dependence, and [110] is the optimum orientation for both Si and Ge nanowire FETs.