Carrier-carrier scattering in photoexcited intrinsic GaAs quantum wells and its effect on femtosecond plasma thermalization

When a nonthermal electron-hole plasma is excited close to the band edge of the intrinsic GaAs quantum well by a short laser pulse, the plasma thermalization occurs within about 200 fs [Knox et al., Phys. Rev. Lett. 56, 1191 (1986)]. According to previous Monte Carlo simulations, this fast process is due to carrier-carrier (c-c) scattering. Our work finds that c-c scattering causes much slower thermalization than the observed one. This conclusion is drawn from the Monte Carlo simulation with revised c-c scattering rates as well as from the molecular-dynamics simulation of many-body Coulomb kinetics, and the problem of explaining the rapid thermalization thus reappears. The c-c scattering rates derived by us are four times smaller than those used in previous simulations. In contrast to similar studies of bulk semiconductors we find a remarkably faster thermalization in the Monte Carlo simulation than in the molecular-dynamics simulation. The effect is ascribed to the breakdown of the Born-approximation treatment of binary collisions in the Monte Carlo method.