Nonthermalized distribution of electrons on picosecond time scale in GaAs

We have observed the thermalization of conduction electrons in GaAs from a Gaussian to a Maxwell-Boltzmann distribution, by time-resolved observation of the band-to-acceptor luminescence folllowing a short (5 ps) near-resonant laser pulse of very low excitation power. At electron density less than 10¹⁴/cm³ the thermalization of the electron density distribution occurs on a time scale of 50 ps with a rate independent of density. At higher density, thermalization occurs via electron-electron scattering with a total cross section of approximately 6×{}10^-12 cm².