EVIDENCE OF THE ORDERED GROWTH OF MONOMOLECULAR ZNTE ISLANDS IN CDTE (CD,ZN)TE QUANTUM-WELLS ON A NOMINAL (001) SURFACE/

Samples based on strained CdTe-(Cd,Zn)Te quantum wells, in which heavy -hole excitons are type I and light-hole excitons are usually type II, are studied. Fractional atomic layers of ZnTe have been inserted in C dTe wells in order to trap light-hole excitons and to confer on them a type-I character. This is checked by low-temperature reflectance and piezoreflectance measurements compared to variational calculations of exciton energies. Moreover, reference samples where integer monolayers of ZnTe have been introduced, are also investigated. Comparisons of d irect and modulated spectroscopic data of all samples provide a very s trong indication that two fractional ZnTe layers, separated by a few C dTe monolayers, tend to grow in an ordered way: successive ZnTe island s appear to avoid growing on top of each other and to adopt a staggere d lineup.