Free and bound states of excitons in percolation cluster of ZnSe quantum dots in dielectric matrix

Two-phase systems (borosilicate glasses with ZnSe quantum dots) were studied. The results obtained provided an insight both into the mechanism of the formation of a phase percolation transition of excitons in the array of quantum dots at the critical concentration and radii and the contribution of dielectric mismatch between ZnSe and matrix to the transition. Using the above two-phase system as an example, it was found for the first time that such a complex fractal object as the percolation cluster of quantum dots had not only free (mobile) states but bound (immobile) ones well. This bound (immobile) states resemble the type-II excitons in superlattices or the impurity states in bulk semiconductors. It is shown that the polarization of the two-phase system interface is the main source of these immobile states whose energy is dependent on size of quantum dots and their average separation.