Semiconductor nanowires (NWs) often present different structural and opto-electronic properties than their
thin film counterparts. The thinner they are, the larger these differences are. Here, we present femtosecond
transient absorbance measurements on GaAs0.8P0.2 NWs of two different diameters, 36 and 51 nm. The results
show that thinner NWs sustain a higher carrier temperature for longer times than thicker NWs. This observation
suggests that, in thinner NWs, the buildup of a hot-phonon bottleneck is easier than in thicker NWs because of
the increased phonon scattering at the NW sidewalls, which facilitates the buildup of a large phonon density.
Moreover, the important observation that the carrier temperature in thin NWs is higher than in thick NWs
already at the beginning of the hot carrier regime suggests that the phonon-mediated scattering processes
in the nonthermal regime play a major role at least for the carrier densities investigated here (8 × 1018 to
4 × 1019 cm–3). Our results also suggest that the phonon scattering at crystal defects is negligible compared
with the phonon scattering at the NW sidewalls
