学术文献库

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.