Spin polarization of an optically pumped electron gas

Time-resolved optical-pumping experiments on p-type GaAs quantum wells are applied to study the spin polarization of a two dimensional electron gas (2DEG) in the density range up to similar to 5 X 10(11) cm(-2). Two spin components of optically created 2DEG are well described by Fermi-Dirac distributions with a common temperature but different chemical potentials, The rate of the spin depolarization of the 2DEG is found to be independent of the electron kinetic energy but accelerated by thermal spreading of carriers. This acceleration is attributed to the opening of the phase space blocking for the exchange-type electron spin-flip scattering with holes. (C) 1999 Elsevier Science Ltd. All rights reserved.