Linear and circular polarizations of exciton luminescence in GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells

The cw, linearly and circularly polarized photoluminescence excitation spectra (${\mathit{P}}_{\mathrm{lin}}$ and ${\mathit{P}}_{\mathrm{cir}}$), are studied for (e1:hh1) excitons of undoped GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells. Monitoring in the high-energy range of the luminescence, pronounced 1S and 2S polarization-preserving bands are observed. They are shown to be due to LA-phonon-assisted relaxation of delocalized excitons. For the low-energy range ${\mathit{P}}_{\mathrm{lin}}$∼0 and a circular polarization reversal is observed, resulting from exciton-exciton scattering.