Title: EXPERIMENTAL STUDIES OF THE RECOMBINATION PROCESSES IN II-VI SEMICONDUCTORS (BULK CRYSTALS AND EPILAYERS) AT VARIABLE EXCITATION LEVELS
Authors: M.S.Brodyn, S.G.Shevel, V.V.Tishchenko (Institute of Physics of the National Academy of Sciences of Ukraine, 46 Nauky Avenue, 252022 Kyiv, Ukraine)

Low-temperature luminescence spectra under broad-scale variation of an excitation level I$_{\rm exc}$ are studied for ZnS/ZnSe single quantum wells (QW) and for CdS bulk crystals and epilayers. In the first case, the manifestations turn out to be of the heterointerface inhomogeneity - i.e. fluctuations of QW thickness. The position of the mobility edge for excitons localized by fluctuations is determined. In the second case the effect of the increase of I$_{\rm exc}$ is systematically studied not only for excitonic but also for impurity-related edge luminescence. Contrary to the earlier and commonly assumed expectations, up to the highest I$_{\rm exc}$ close to damage threshold no saturation of edge luminescence intensity was observed in bulk CdS crystals, whereas in a few thick epilayers such saturation did occur. The suggested qualitative explanation takes into account diffusion (non-diffusive transport) of carriers beyond the excited near-surface layer.

Comments: Figs. 5, Refs. 26, Tabs. 0.