CdTe/ZnTe quantum dots - growth and optical properties

This paper gives an overview of molecular beam epitaxy growth aspects and of optical properties of CdTe quantum dots grown on ZnTe by self-assembly. It is shown that quantum dots in this material system can be obtained either by depositing CdTe at a high substrate temperature or by subjecting CdTe layer to a healing process, up to 70 s long before its capping or, eventually, by applying these two methods simultaneously. Moreover it is found, that one can also use the atomic layer epitaxy method to achieve the formation. From optical measurements performed on large quantum dot ensembles it is found out that the quantum dot emission is much broader than that from quantum wells, and that it is observable up to much higher temperatures, which indicates strong exciton localization. The latter is also evidenced by an insensitivity of the decay time of the exciton recombination (similar to300 ps) to the temperature. From the presence of a second, very long decay time (similar to5 ns) and from disappearance of the sharp lines related to recombination in single dots, the acoustic phonon scattering of excitons is found to play an important role in these quantum dot structures. From a magnetic Field dependence of the single dot emission energy, the exciton effective g-factor and spatial extension of the exciton wave function are deduced to be equal to -3 and 3 nm, respectively. Both the g-factor and the value of the diamagnetic shift are found to be independent of the energy of the quantum dot emission at B=0 T and of the in-plane symmetry of its potential. (C) 2002 Elsevier Science B.V. All rights reserved.