  Effective electron mobilities are obtained by transport measurements on InAs
nanowire field-effect transistors at temperatures ranging from 10-200 K. The
mobility increases with temperature below ~ 30 - 50 K, and then decreases with
temperature above 50 K, consistent with other reports. The magnitude and
temperature dependence of the observed mobility can be explained by Coulomb
scattering from ionized surface states at typical densities. The behaviour
above 50 K is ascribed to the thermally activated increase in the number of
scatterers, although nanoscale confinement also plays a role as higher radial
subbands are populated, leading to interband scattering and a shift of the
carrier distribution closer to the surface. Scattering rate calculations using
finite-element simulations of the nanowire transistor confirm that these
mechanisms are able to explain the data.
