Photoluminescence and tunneling of direct and indirect excitons of semimagnetic asymmetric double quantum wells CdSe/CdMgSe/CdMnSe

Exciton photoluminescence and reflection spectra of CdSe/CdMgSe/CdMnSe asymmetric double quantum wells with different barriers thickness were studied in strong magnetic fields for the first time. Direct excitons from the nonmagnetic CdSc and semimagnetic CdMnSe quantum wells were observed as well as a spatially indirect exciton formed by the electron in the CdSe quantum well and the heavy-hole in the CdMnSe one. The indirect exciton became observable at magnetic fields around 2 T when it was the lowest energy state of the structure. Its position shifted to lower energies with increasing magnetic field, the intensity increased drastically and the half-width decreased. Up to two LO-phonon replicas of the indirect exciton were observed. The problem of localized magnetic polarons formation is addressed. Polarization properties of the direct and indirect excitons were studied. In case of the effective tunneling of sigma(+) - polarized excitons from the CdMnSe well to the CdSe well, a change of circular polarization of the direct CdSe exciton from the negative to positive value was observed under magnetic field. Large anisotropy of the valence band of the CdMnSe quantum well was revealed by comparison of energy shifts in Faraday and Voigt magnetic field configurations. Calculations of exciton energies were performed. Calculated and experimental values were found to be in reasonable accordance.