Evidence of the ordered growth of monomolecular ZnTe islands in CdTe/(Cd,Zn)Te quantum wells on a nominal (001) surface

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Abstract
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 CdTe 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 direct and modulated spectroscopic data of all samples provide a very strong indication that two fractional ZnTe layers, separated by a few CdTe monolayers, tend to grow in an ordered way: successive ZnTe islands appear to avoid growing on top of each other and to adopt a staggered lineup.