The polarization dependence of the photoluminescence of GaAs-AlAs supe
rlattices with different well and barrier widths has been investigated
. In wide-well superlattices (10-15 nm) the luminescence signal of fre
e excitons has the largest degree of polarization (20-25%). In short-p
eriod superlattices, however, the recombination is dominated by indire
ct, localized excitons (X-Gamma), which are exposed to anisotropic per
turbations along the [110] crystallographic axis. This results in an a
nomalous detection angle dependence of the polarization.