Two emission bands are observed in the photoluminescence spectrum of ZnSe/~Zn,Mn!Se heterostructures. These bands emerge in a magnetic field and are associated with interface excitons formed as a result of a magnetic-field-induced type-I–type-II transition of the band alignment. Time-resolved measurements yield lifetimes in the ns range signifying a relatively large spatial separation of electrons and holes and hence low optical oscillator strength. These features are confirmed by a theoretical analysis of the interface exciton state revealing a reduced importance of the electron-hole Coulomb interaction in comparison with type-II excitons in quantum wells.
Rossin, V.V., Böttger, T., Henneberger, F. Type-II interface exciton in ZnSe/(Zn,Mn)Se heterostructures (1996) Physical Review B - Condensed Matter and Materials Physics, 54 (11), pp. 7682-7685. https://doi.org/10.1103/PhysRevB.54.7682