  We have investigated the photocarrier charge transport in n-type metallic
GaAs nanowires (~ 10^17 cm^-3 doping level), grown by hydride vapor phase
epitaxy (HVPE) on Si(111) substrates. Analysis of the luminescence intensity
spatial profiles for selected energies in the spectrum allows us to determine
the spatial distribution of photoelectrons, minority photoholes and electrons
of the Fermi sea as a function of distance from the light excitation spot. This
analysis shows that charge can be transported over record distances larger than
25 (micro)m at 6K, in spite of the expected localization of minority holes in
the potential fluctuations generated by statistical fluctuations of the donor
concentration. It is shown that transport is little affected by the
fluctuations because of the build up of large internal electric fields which
strongly increase the hole and electron mobilities and therefore enable
transport. Comparison of the spatial profiles of the emissions due to hot
electrons and to the Fermi sea gives evidence for at least three spatial zones,
including a zone of excess intrinsic electrons near the excitation spot and a
zone of depletion of these electrons at a distance larger than 2-10 (micro)m
depending on excitation power. The internal outward electric field increases
the kinetic energy of photoholes in the fluctuations so that after a given
distance to the excitation spot, there occurs ballistic transport over the
fluctuations.
