OPTICAL-PROPERTIES OF DILUTED MAGNETIC SEMICONDUCTOR QUANTUM STRUCTURES

Conduction and valence band edges in diluted magnetic semiconductors u ndergo enormous Zeeman shifts when a magnetic field is applied, reachi ng values in excess of 100 meV at low temperatures. These Zeeman shift s can thus have profound consequences on the properties of DMS/non-DMS heterostructures, since they provide the opportunity of tuning their band alignment by varying an applied field. This leads to a variety of entirely new effects, and also provides a powerful tool for probing t he effect of band alignment on the properties of semiconductor heteros tructures in general. We illustrate this with several examples. First, using the ZnSe/ZnMnSe system, we discuss the creation of a spatial sp in modulation (spin superlattice). Second, we use the drastic differen ces in the Zeeman splitting occurring in different layers of a DMS/non -DMS superlattice in order to pinpoint the localization in space of th e specific electronic states involved in optical transitions. We illus trate this by investigating the localization of above-barrier states i n type-I ZnSe/ZnMnSe superlattices, and of spatially-direct (type-I) e xcitons which occur in ZnTe/CdMnSe and ZnMnTe/CdSe type-II superlattic es. Finally, we exploit Zeeman tuning to demonstrate the confinement e ffects which occur in a single quantum barrier.