EFFECT OF DISORDER ON THE OPTICAL-SPECTRA OF WIDE-GAP II-VI SEMICONDUCTOR SOLID-SOLUTIONS

Experimental results on the optical properties of wide-gap II-VI semiconductor solid solutions are reviewed. The main attention is given to the effect of solution disorder on the density of states and dynamical properties of electronic excitations. The disorder of compositional, positional or structural origin causes scattering of excitons or carriers as well as exciton or carrier localization, leading to a strong modification of the density of states and dynamical properties of excitations near the band edges in solid solutions. As it is evidenced by the studies of absorption and reflection spectra the disorder at alloying produces qualitatively similar broadening of fundamental edge in solutions with substitution in anion or cation sublattices. However, the studies of recombination processes through the luminescence spectra reveal that dynamical properties of excitons are essentially different in these two classes of solutions. Whereas in solutions with anion substitution an efficient localization of excitons or holes has been observed at low temperatures the energy migration in solutions with substitution in cation sublattice is not so strongly affected by alloying. The dynamical properties and the energy spectra of localized states in II-VI solutions with anion substitution are widely discussed.