We report on the optical studies of exciton broadening mechanisms and exciton spin dynamics in diluted magnetic semiconductor GaAs/AlGaAs/ZnSe/ZnCdMnSe heterovalent double quantum wells (QWs) grown by molecular-beam epitaxy. The heterovalent interface manifests itself in the fluctuations of the interface dipole moment and, hence, in an enhanced inhomogeneous broadening of the excitonic emission, as well as in generation of type-II localized excitons. Microphotoluminescence measurements indicate that these fluctuations occur on the scale less than $1\mu \text{m}$. The rise curves of circular polarization of the excitonic emission are measured in an external magnetic field. The kinetics of the exciton spin polarization is strongly affected by the strength of electronic coupling between the GaAs/AlGaAs and ZnSe/ZnCdMnSe QWs, as well as by the factor of the exciton inhomogeneous broadening. Depending on these parameters, the relaxation time of the net spin polarization in the structures varies from the values shorter than 20 ps up to $\sim 9\text{ns}$.

• Received 3 March 2008

DOI:https://doi.org/10.1103/PhysRevB.77.235310