Diluted magnetic semiconductors as a tool for wave-function mapping in semiconductor heterostructures

Conduction and valence band edges in diluted magnetic semiconductors (e.g., Zn_{1 - x}Mn_xSe) undergo enormous Zeeman shifts when a magnetic field is applied, reaching values in excess of 100 meV at low temperatures. By performing magneto-optical studies on semiconductor heterostructures consisting of diluted magnetic and non-magnetic layers (e.g., a ZnMnSe/ZnSe superlattice), one can exploit the drastic differences in the Zeeman splitting occuring in different layers to pinpoint the localization in space of specific electronic states. In particular, we discuss the spatial localization of states whose energy exceeds the potential barriers. We illustrate this by the investigation of above-barrier excitons localized in the barriers of type-I ZnSe/ZnMnSe superlattices, and of type-I (spatially direct) excitons in ZnTe/CdMnSe and ZnMnTe/CdSe type-II superlattices. We also discuss quasi-localization of states in a single barrier.