Photoluminescence spectra of ZnAl₂Se_4-4xS_4xsingle crystals

Single crystals of ZnAl2Se4-4xS4x quaternary solid solution were grown by the chemical transport reaction method. The ZnAl2Se4-4xS4x single crystals were found to have a defect chalcopyrite structure in the region of 0.0≤x≤0.2 and a cubic spinel in the region of 0.8≤x≤1.0. It was also shown in these regions that the lattice constants and optical energy gaps depend on a composition x. A miscibility region existed in the region of 0.2<x<0.8. The photoluminescence spectra for the crystals with 0.0≤x≤0.2 and 0.8≤x≤1.0 showed a strong blue emission band and a weak broad emission band due to donor-acceptor pair recombination at low temperatures. A simple energy band scheme for the radiative mechanism in the ZnAl2Se4-4xS4x was proposed on the basis of our experimental results along with the measurements of thermoluminescence and photo-induced current transient spectroscopy.