NUMERICAL-STUDIES OF FEMTOSECOND CARRIER DYNAMICS IN GAAS

We present simulations of 2-eV femtosecond differential transmission experiments in GaAs. Electron and heavy-, light-, and split-off-hole dynamics are calculated by an ensemble Monte Carlo method. To account for valence-band nonparabolicity and anisotropy, a 30-band kp method is used to determine hole band structure, optical matrix elements, density of states, and Bloch overlap factors. Using the distribution functions obtained from the Monte Carlo simulations, we calculate the differential transmission and compare directly with experimental spectra. We show that the inclusion of both collisional broadening during photoexcitation and holes is essential to reproduce accurately the experimental results. We also discuss the effects of intervalley and carrier-carrier scattering in these measurements. © 1990 The American Physical Society.