Near-Infrared Photoluminescence in Mo-Doped Single Crystals of CuAlS 2

Near-infrared photoluminescence (PL) spectra were measured at 6 K in single crystals of CuAlS 2 doped with different amounts of Mo. A fine-structure PL emission was observed around 1,600 nm (0.775 eV) in both lightly and heavily doped crystals. The emission was tentatively assigned to the ligand-field transition in 4d 3 -manifold of Mo 3+ ions taking into account the reported PL spectrum in Nb 2+ (4d 3 )-doped GaAs. On the other hand, a broad emission band around 1,500 nm (0.826 eV) was only observed in heavily-doped crystals and was tentatively assigned to an intra-center transition of the Mo 2+ –X complex.