Er/Si interdiffusion effect on photoluminescent properties of erbium oxide/silicon oxide films deposited on silicon

This work studies the interdiffusion effect of Er ions in Er2O3 and Si ions in SiO2 on the photoluminescent (PL) properties of Er2O3/SiO2 films. Er2O3 layers are deposited on thermally oxidized Si substrates by reactive radio frequency magnetron sputtering. Different interdiffusion behaviors are observed by thermally treating films with rapid thermal annealing (RTA) and tube furnace annealing (TFA) at 900-1200 degrees C. Surface morphological and compositional properties are measured by optical microscopy, atomic force microscopy, and secondary ion mass spectroscopy. Surface roughness of composite films increases with the annealing temperature due to growth in grain size. The Er/Si interdiffusion across the Er2O3/SiO2 interface is observed when the annealing temperature exceeds 1000 degrees C for RTA and 900 degrees C for TFA. Thermal annealing effects in the oxygen ambient include the Er doping in the SiO2 layer, the formation of erbium silica, and the reduction of defect density. These three factors facilitate the increase of active Er ions and the enhancement of PL intensity. The PL intensity increases with the Er/Si interdiffusion thickness for RTA- and TFA-treated films. Enhancement of PL intensity with the annealing temperature is attributed to the Er/Si interdiffusion and the reduction of defect density.