  N-type doping of GaAs nanowires has proven to be difficult because the
amphoteric character of silicon impurities is enhanced by the nanowire growth
mechanism and growth conditions. The controllable growth of n-type GaAs
nanowires with carrier density as high as 1020 electron/cm3 by self-assisted
molecular beam epitaxy using Te donors is demonstrated here. Carrier density
and electron mobility of highly doped nanowires are extracted through a
combination of transport measurement and Kelvin probe force microscopy analysis
in single-wire field-effect devices. Low-temperature photoluminescence is used
to characterize the Te-doped nanowires over several orders of magnitude of the
impurity concentration. The combined use of those techniques allows the precise
definition of the growth conditions required for effective Te incorporation.
