2, Department of Electronic and Materials Engineering, The Australian National University, Canberra, Australian Capital Territory, Australia
Like GaAs and GaSb, GaAsSb ternary alloys are not expected to show hot carrier effects. We use femtosecond pump-probe measurements (TRS: transient Rayleigh scattering) in single zinc-blende GaAs0.7Sb0.3 nanowires at both 10 K and 300 K to monitor the photoexcited carrier density and temperature as a function of time and so determine directly the energy loss rate. We confirm that hot carriers quickly thermalize to the lattice predominantly through optic phonon emission as expected. Similar measurements were performed on GaAs0.7Sb0.3-InP core-shell nanowires. While the growth of the InP shell results in substantially longer lifetimes through passivation of surface defects, we found, surprisingly, that the growth of the shell had a dramatic impact on the thermalization of the photoexcited carriers. Using TRS measurements, we monitor the density and temperature of carriers to determine the energy loss rate. At both 10 K and 300 K the optic phonon emission rate is strongly suppressed resulting in strong hot carrier effects. This is surprising since the GaAsSb nanowire core is the same in both cases. The presence of the InP shell is impacting directly the thermalization dynamics of carriers confined to the GaAsSb core.
We acknowledge the financial support of the NSF through grants DMR 1507844, DMR 1531373 and ECCS 1509706, and the financial support of the Australian Research Council.