  Efficient doping of semiconductor nanowires remains a major challenge towards
the commercialization of nanowire-based devices. In this work we investigate
the growth regimes and electrical properties of MBE-grown p- and n-type gallium
phosphide nanowires doped with Be and Si respectively. Electrical conductivity
of individual nanowires is quantitatively studied via atomic force microscopy
supported with numerical analysis. Based on conductivity measurements, we
provide growth strategies for achieving the doping level up to 5E18 and 2E19
$cm^{-3}$ for GaP:Si and GaP:Be nanowires respectively, which is high enough to
be demanded for technological applications.
