L-valley Electron Spin Dynamics in GaAs

摘要

Optical orientation experiments have been performed in GaAs epilayers withphotoexcitation energies in the 3 eV region yielding the photogeneration ofspin-polarized electrons in the satellite L valley. We demonstrate that asignificant fraction of the electron spin memory can be conserved when theelectron is scattered from the L to the $\Gamma$ valley following an energyrelaxation of several hundreds of meV. Combining these high energyphoto-excitation experiments with time-resolved photoluminescence spectroscopyof $\Gamma$ valley spin-polarized photogenerated electrons allows us to deducea typical L valley electron spin relaxation time of 200 fs, in agreement withtheoretical calculations.