ULTRAFAST RELAXATION OF HIGHLY PHOTOEXCITED CARRIERS IN P-TYPE AND INTRINSIC GAAS

The thermalization and energy relaxation of highly photoexcited carrie rs in p-type and intrinsic GaAs is investigated at room temperature us ing an ensemble Monte Carlo approach. We present an alternative model for treating carrier-carrier scattering in Monte Carlo simulations. Th e model takes into account the wave vector and frequency dependence of the dielectric function by using a screened Coulomb potential in q sp ace due to a charge moving at the velocity of the center of mass of th e interacting particles. In comparison to the statically screened mode l, the calculated effective carrier temperatures for an excitation den sity of 2 x 10(18) cm(-3) are in good agreement with the experimental results for both p-type and intrinsic GaAs. At the lower doping and ex citation density of 2.5 x 10(16) cm(-3), the dynamic and the static sc reening models result in a comparable time evolution of the carrier en ergies and band populations.