Luminescence properties of Sn2P2Se6 crystals

A large family of Sn2yPb2(1−y)P2S6xSe6(1−x) semiconductor-ferroelectric crystals were obtained by the Bridgman technique. The photoluminescence properties of the Sn2yPb2(1−y)P2S6xSe6(1−x) family crystals strongly depend on their chemical composition, excitation energy and temperature. The influence of the Pb → Sn and S → Se isovalent substitutions on the luminescence properties of a crystal with the Sn2P2Se6 basic composition was investigated. A broad emission band observed in the Sn2P2Se6 crystal with a maximum roughly at 600 nm (at T = 8.6 K) was assigned to a band-to-band electron-hole recombination, whereas broad emission bands, peaked near 785 nm (at T = 8.6 K) and 1025 nm (at T = 44 K) were assigned to an electron-hole recombination from defect levels localised within the bandgap. Possible types of recombination defect centres and specific mechanisms of luminescence in the Sn2P2Se6 semiconductor-ferroelectric crystals were considered and discussed on the basis of the obtained results and the referenced data.