  The resistivity and the mobility of Carbon doped GaAs nanowires have been
studied for different doping concentrations. Surface effects have been
evaluated by comparing upassivated with passivated nanowires. We directly see
the influence of the surface: the pinning of the Fermi level and the consequent
existence of a depletion region lead to an increase of the mobility up to 30
cm^2/(V*s) for doping concentrations lower than 3*10^18 cm^-3. Electron beam
induced current measurements show that the minority carrier diffusion path can
be as high as 190 nm for passivated nanowires.
