  The incorporation paths of Be in GaAs nanowires grown by the Ga-assisted
method in molecular beam epitaxy has been investigated by electrical
measurements of nanowires with different doping profiles. We find that Be atoms
incorporate preferentially via the nanowire side facets, while the
incorporation path through the Ga droplet is negligible. We also demonstrate
that Be can diffuse into the volume of the nanowire giving an alternative
incorporation path. This work is an important step towards controlled doping of
nanowires and will serve as a help for designing future devices based on
nanowires.
