Luminescent, optical and electronic properties of La3Ta0.5Ga5.5O14 single crystals grown in different atmospheres

Abstract Luminescent, optical and electronic properties of La 3 Ta 0.5 Ga 5.5 O 14 single crystals grown in different atmospheres are presented. The absorption bands at 255, 290, 350 and 480 nm were detected; the intensity of bands increases with the concentration of oxygen in the growth atmosphere. It is shown that the shift of the fundamental absorption edge with the temperature obeys Urbach rule. The corresponding fitting allowed to estimate the slope coefficient σ =0.35, which implies self-trapping of excitons in La 3 Ta 0.5 Ga 5.5 O 14 . Calculations of the band structure, partial densities of states and reflectivity spectra were performed. The bandgap of La 3 Ta 0.5 Ga 5.5 O 14 was determined as E g =5.6 eV. The luminescence properties under UV, VUV and X-ray excitation were studied. Intrinsic emission band at 440–450 nm is attributed to the excitons self-trapped at TaO 6 molecular complexes. Extrinsic emission bands at 410, 440 and 550 nm are attributed to the emission of excitons trapped by antisite defects, F-centers and oxygen deficient oxyanionic complexes.