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 (2 DEG) in the density range up to similar to 5 X 10(11) cm(-2). Two spin comp onents of optically created 2DEG are well described by Fermi-Dirac distribu tions with a common temperature but different chemical potentials, The rate of the spin depolarization of the 2DEG is found to be independent of the e lectron kinetic energy but accelerated by thermal spreading of carriers. Th is acceleration is attributed to the opening of the phase space blocking fo r the exchange-type electron spin-flip scattering with holes. (C) 1999 Else vier Science Ltd. All rights reserved.