Exciton trapping at tellurium iso-electronic centres in ZnSe-ZnTe superlattices

The photoluminescence spectra from ZnSe-ZnTe superlattices are shown to be explained by a very simple model in which excitons are formed from holes tightly localised in single ZnSe layers and from electrons in large orbits extending over several layers of both types. The results suggest that the conduction band offset is insufficiently large to localise the electrons. The holes are trapped by tellurium iso-electronic centres and, since tellurium can act as an iso-electronic trap in several II-VI compounds, this new type of excitonic behavior in superlattices may have important device implications.