Aharonov-Bohm oscillations in Type-II ZnSe$_{1-x}$Te$_{x}$ excitons.

The luminescence of ZnSe$_{1-x}$Te$_{x }$has been studied extensively and it is generally accepted that the emission of this system is dominated by excitons bound to isoelectronic centers [1]. We will show that when these isoelectronic centers group into large clusters they appear to form type-II quantum dot-like structures (QDs). In such structures the hole is strongly localised within the dot while the electron is localised outside through coulombic attraction. These localised excitons are analogous to the hydrogen atom with the electron orbiting the confined hole in a `ring-like' geometry. We will show that as a result of this behaviour we observe Aharonov-Bohm (AB) oscillations in the magneto-photoluminescence of excitons bound to QDs formed with various configurations of isoelectronic centers (atoms, clusters) [2]. The behaviour of QD-like structures of different energy will be presented and it will be shown that in the case of QDs formed by larger Te-clusters the AB oscillations are preserved up to 180K. Finally, we will also present the optically detected resonance for these structures, in which a FIR laser is used to probe resonances related to the atomic-like higher order shells of the bound excitons. [1] I. L. Kuskovsky et al. Phys. Rev. B. (2001) [2] I. L. Kuskovsky et al. Cond-mat/0606752