Abstract

Relaxation of photoexcited nonequilibrium carriers in semiconductors has been extensively investigated using time-resolved femtosecond techniques. These investigations have however focused on hot-electron relaxation dynamics and little is known on hole scattering processes. The different approach of cold-carrier investigation has been recently applied to this problem and it has been shown that hole thermalization can thus be selectively studied in direct gap intrinsic semiconductors using a femtosecond high-sensitivity two-color absorption saturation technique [1]. This is based on the fact that because of the larger k-space spreading of the heavy-hole distribution as compared to the electron one, the transient transmission change (ΔT/T) due to filling of large momentum states (i.e., for large probe photon excess energy) predominantly contains information on heavy-hole thermalization making possible investigation of cold-hole heating dynamics [1]. In contrast to carrier cooling, heating of cold-carriers by phonons is strongly dependent on the lattice temperature (the efficiency of phonon absorption is proportional to their occupation number) which permits separation of carrier-phonon interaction from other scattering processes. We have exploited this temperature dependence to perform the first direct investigation of hole-optical phonon interactions in bulk GaAs.

© 1996 Optical Society of America