Femtosecond hole thermalization in bulk GaAs

Ultrafast hole relaxation dynamics is selectively investigated in intrinsic bulk GaAs using a high sensitivity two-wavelength pump-probe technique. Nonequilibrium carriers are photoexcited close to the bottom of their respective bands and hole heating is followed by monitoring the transient bleaching of optical transitions involving higher momentum states. Hole heating is found to be dominated by hole-phonon interactions with a thermalization time of the order of 150 fs for carriers densities in the 1017 cm−3 range.