Time-resolved study of intervalence band thermalization in a GaAs quantum well

The thermalization of optically excited cold holes in a GaAs quantum well is investigated by femtosecond two-color pump-probe measurements. Clear evidence is found for scattering from heavy-holes into the lowest light-hole band due to LO-phonon absorption. We obtain firm data on scattering times which depend strongly on lattice temperature. They vary from 230 fs at room temperature to 900 fs at T equal 05 K. The experimental data are well reproduced by numerical calculation.