Nonthermalized distribution of electrons on picosecond time scale in GaAs

Abstract

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 ${10}^{14}$/${\mathrm{cm}}^{3}$ 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\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}12}$ ${\mathrm{cm}}^{2}$.