  Semiconductor nanowires (NWs) have shown evidence of robust hot carrier
effects due to their small dimensions. The relaxation dynamics of hot carriers
in these nanostructures, generated by photo-absorption, are of great importance
in optoelectronic devices and high efficiency solar cells, such as hot carrier
solar cells. Among various III-V semiconductors, indium arsenide (InAs) NWs are
promising candidates for their applications in advanced light harvesting
devices due to their high photo-absorptivity and high mobility. Here, we
investigate the hot carrier dynamics in InAs-AlAsSb core-shell NWs, as well as
bare-core InAs NWs, using ultrafast pump-probe spectroscopy with widely tuned
pump and probe energies. We have found a lifetime of 2.3 ps for longitudinal
optical (LO) phonons and hot electron lifetimes of about 3 ps and 30 ps for
carrier-carrier interactions and electron-phonon interactions, respectively. In
addition, we have investigated the electronic states in the AlAsSb-shell and
found that, despite the large band offset of the core-shell design in the
conduction band, excited carriers remain in the shell longer than 100 ps. Our
results indicate evidence of plasmon-tailored core-shell NWs for efficient
light harvesting devices, which could open potential avenues for improving the
efficiency of photovoltaic solar cells.
