  A 20-band sp3d5s* spin-orbit-coupled, semi-empirical, atomistic tight-binding
model is used with a semi-classical, ballistic, field-effect-transistor (FET)
model, to examine the ON-current variations to size variations of [110]
oriented PMOS nanowire devices. Infinitely long, uniform, rectangular nanowires
of side dimensions from 3nm to 12nm are examined and significantly different
behavior in width vs. height variations are identified and explained. Design
regions are identified, which show minor ON-current variations to significant
width variations that might occur due to lack of line width control. Regions
which show large ON-current variations to small height variations are also
identified. The considerations of the full band model here show that ON-current
doubling can be observed in the ON-state at the onset of volume inversion to
surface inversion transport caused by structural side size variations. Strain
engineering can smooth out or tune such sensitivities to size variations. The
cause of variations described is the structural quantization behavior of the
nanowires, which provide an additional variation mechanism to any other
ON-current variations such as surface roughness, phonon scattering etc.
