Nonequilibrium hole relaxation dynamics in an intrinsic semiconductor

Abstract

The thermalization dynamics of photoexcited nonequilibrium holes is selectively investigated in intrinsic bulk GaAs using a high sensitivity two-wavelength pump-probe technique. The carriers are photoexcited close to the bottom of their respective bands and hole heating is followed by monitoring the absorption saturation due to filling of higher-energy states. The characteristic thermalization time is measured to increase only slightly from \ensuremath{\sim}120 to \ensuremath{\sim}170 fs as carrier density decreases from 7\ifmmode\times\else\texttimes\fi{}${10}^{17}$ to 2\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$, indicating that hole heating is dominated by hole--optical-phonon scattering. These results are in good agreement with a simulation of the carrier relaxation based on numerical resolution of the carrier Boltzmann equations including interaction of holes with LO and TO phonons. \textcopyright{} 1996 The American Physical Society.