The Luminescence of Some Ternary Chalcogenides and Mixed Binary Systems of Group III-VI Compounds: The Nature of Luminescence Centres in Group III-VI Compounds

Luminescence characteristics are presented for the ternary compounds CdIn 2 S 4 and CdGa 2 S 4 and for the mixed binary systems Ga 2 S 3 -In 2 S 3 and Ga 2 S 3 -Ga 2 Se 3 . The phosphors were `self-activated' and prepared under sulphurizing conditions. At 65 °K two emission bands are observed in CdIn 2 S 4 centred at 1.42 eV and 1.65 eV respectively, and in CdGa 2 S 4 at 2.15 eV and 1.63 eV respectively. The progressive replacement of indium by cadmium at tetrahedral sites on introducing CdS into In 2 S 3 to form the spinel CdIn 2 S 4 , and the associated shifts of the luminescence spectra, suggest a model in which luminescence transitions are associated with the region of a cation vacancy. The two observed emission bands in In 2 S 3 are associated with complexes formed by neighbouring anions in the vicinity of the two types of cation vacancy site in this material, one tetrahedrally and one octahedrally coordinated. Correlation of the luminescence with change in the nature of either the cation or the anion in the mixed binary systems is an important feature in the study of group III-VI compounds.