Exciton orientation-to-aligument convertion in type-II GaAs/AlAs superlattices

摘要

In type-II GaAs/AlAs superlattices, the degenceracy of the el-hh1(1s) exciton radiative doublet is lifted and the two slit sublevels are dipole-active respectively along the [110]and[110]directons in the interface plane. The theory predicts an apprearance of linear polarization in the axes [110], [110] induced by the lingitudinal magnetic field, B ||[001], under circularly polarized excitation. For the first time we have observed the magnetic field effect on the photoluminescence of type-II GaAs/AlAs superlattices not only in the circular-circular and linear-linear but also in linear-circular and circular-linear configuration of the polarizer and analyzer. We have developed the exciton spin-density matrix formalism in order to calculate the polarization of the photoluminescence in longitudinal and transverse magnetic fields taking into account the excition spin relaxation and the difference between lifetimes of the optically-active and inactive sublervels. Comparison betweenb theory and experiment allows us to obtain the fine-structure and kinetic parameters of the localized e1-hh1 excitons.