NONEQUILIBRIUM HOLE RELAXATION DYNAMICS IN AN INTRINSIC SEMICONDUCTOR

The thermalization dynamics of photoexcited nonequilibrium holes is se lectively investigated in intrinsic bulk GaAs using a high sensitivity two-wavelength pump-probe technique. The carriers are photoexcited cl ose to the bottom of their respective bands and hole heating is follow ed by monitoring the absorption saturation due to filling of higher-en ergy states. The characteristic thermalization time is measured to inc rease only slightly from similar to 120 to similar to 170 fs as carrie r density decreases from 7x10(17) to 2x10(16) cm(-3), indicating that hole heating is dominated by hole-optical-phonon scattering. These res ults are in good agreement with a simulation of the carrier relaxation based on numerical resolution of the carrier Boltzmann equations incl uding interaction of holes with LO and TO phonons.