  Scaling of semiconductor devices has reached a stage where it has become
absolutely imperative to consider the quantum mechanical aspects of transport
in these ultra small devices. In these simulations, often one excludes a
rigorous band structure treatment, since it poses a huge computational
challenge. We have proposed here an efficient method for calculating full
three-dimensionally coupled quantum transport in nanowire transistors including
full band structure. We have shown the power of the method by simulating hole
transport in p-type Ge nanowire transistors. The hole band structure obtained
from our nearest neighbor sp3s* tight binding Hamiltonian agrees well
qualitatively with more complex and accurate calculations that take third
nearest neighbors into account. The calculated I-V results show how shifting of
the energy bands due to confinement can be accurately captured only in a full
band full quantum simulation.
