Photo-induced excitonic spin dynamics in GaAs

The dynamics of the optical orientated excitonic spins in semiconductor quantum wells has been investigated using opposite circular polarizations of the photoluminescence (PL) caused by the spin-dependent phase-space filling. The PL excitonic spin polarization estimated from the two different polarization conditions is found to strongly depend on the strength of the electric bias as well as on the size of the wells. With an increase of the electric bias field, the excitonic PL spin polarization increases, giving a maximum value of 90 % at the fields higher than 2.5 V. However, the PL spin polarization decreases with increasing the size of the well as well as increasing crystal temperature. The results as well as possible reasons responsible for the effects are discussed.