Charged excitons trapped on monomolecular CdTe islands in wide ZnTe-(Zn,Mg)Te quantum wells

Optical spectroscopy at $T=2\mathrm{}\mathrm{K}$ reveals systematically a low-energy companion to the features of heavy- and light-hole excitons localized on CdTe 1-ML-high islands, buried in wide ZnTe/(Zn,Mg) Te quantum wells. These transitions are assigned to a negatively charged excitonic complex (trion) from magnetoreflectance and photoluminescence results. A mechanism of formation of the trion is proposed. A clear correlation is found between the exciton energies, which depend on the size and strain of the islands, and the trion binding energy, which varies between 1 and 3 meV.