Influence of diameter on temperature dynamics of hot carriers in photoexcited GaAsP nanowires

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 x 10(18) to 4 x 10(19) cm(-3)). Our results also suggest that the phonon scattering at crystal defects is negligible compared with the phonon scattering at the NW sidewalls.

Automated summary

Thinner semiconductor nanowires show easier buildup of hot-phonon bottleneck due to increased phonon scattering at the sidewalls, leading to higher carrier temperature compared to thicker nanowires. This indicates that phonon-mediated scattering processes play a major role in thin nanowires at the investigated carrier densities.