PHOTOLUMINESCENCE STUDIES OF WURTZITE TYPE W-ZNAL2S4 SINGLE-CRYSTALS

Single crystals of wurtzite-type W-ZnAl2S4 have been grown by the chem ical vapor transport technique. Structural studies of the obtained cry stals using powder X-ray diffr action analysis revealed their wurtzite structure with random distribution of cations at tetrahedral sites, w hereas optical experiments showed that the crystals obtained had a dir ect band gap of similar to 3.7 eV and exhibited a strong blue photolum inescence (PL) even at room temperature, with two different luminescen ce peaks, each of which had a different excitation band. In order to e xplain tile PL results the configuration coordinate model for the radi ative transitions inv olved in the formation of the PL bands has been proposed. The model takes into account a lattice relaxation around the deep center responsible for the blue emissions, as well as the splitt ing of the valence band of W-ZnAl2S4 caused by the effect of the noncu bic crystal field and spin-orbit interaction.