Effect of Mg2+ co-doping on the photo- and thermally stimulated luminescence of the (Lu,Gd)3(Ga,Al)5O12:Ce epitaxial films

Abstract Photoluminescence and thermally stimulated luminescence of Ce 3+ - doped (Lu,Gd) 3 (Ga,Al) 5 O 12 epitaxial films co-doped with different concentrations of Mg 2+ ions (varying from 0 to 0.09 at.%) are investigated in the 60–500 K temperature range under selective photoexcitation in the Ce 3+ - related 4f → 5d 2 and 4f → 5d 1 absorption bands and in the absorption bands arising from the 8 S 7/2 → 6 I J and 8 S 7/2 → 6 P J electronic transitions of Gd 3+ ions. Influence of Mg 2+ ions on the Ce 3+ - related photoluminescence intensity, spectrum, decay kinetics, temperature dependence of the emission intensity, and the activation energy of the luminescence thermal quenching is studied. The shortening of the luminescence decay time and simultaneous reduction of its light yield are explained by the presence of {Ce 3+ - Mg 2+ } centers in the Mg 2+ - containing films, where the luminescence optical quenching occurs in the 5d 1 excited state of Ce 3+ in these centers. Co-doping with Mg 2+ results in the reduction of the afterglow and thermally stimulated luminescence and shortening of the afterglow decay kinetics. It influences also defects creation spectra and the activation energy of the photostimulated defects creation. The optimum Mg 2+ content in the (Lu,Gd) 3 (Ga,Al) 5 O 12 :Ce epitaxial films is estimated to be around 0.005 at.%.