Surface diffusion effects on growth of nanowires by chemical beam epitaxy

Surface processes play a large role in the growth of semiconductor nanowires by chemical beam
epitaxy. In particular, for III-V nanowires the surface diffusion of group-III species is important to
understand in order to control the nanowire growth. In this paper, we have grown InAs-based
nanowires positioned by electron beam lithography and have investigated the dependence of the
diffusion of In species on temperature, group-III and -V source pressure and group-V source
combinations by measuring nanowire growth rate for different nanowire spacings. We present a
model which relates the nanowire growth rate to the migration length of In species. The model is
fitted to the experimental data for different growth conditions, using the migration length as fitting
parameter. The results show that the migration length increases with decreasing temperature and
increasing group-V/group-III source pressure ratio. This will most often lead to an increase in
growth rate, but deviations will occur due to incomplete decomposition and changes in sticking
coefficient for group-III species. The results also show that the introduction of phosphorous
precursor for growth of InAs1−xPx nanowires decreases the migration length of the In species
followed by a decrease in nanowire growth rate.