1.54 μm luminescence of Er-doped SiOx and GeOx thin films: A comparative study

Erbium-doped amorphous silicon oxide (SiOx:Er) and germanium oxide (GeOx:Er) thin films were prepared by evaporation on substrates maintained at 100 °C. Due to the preparation method, these samples were sub-stoichiometric involving in an excess of silicon and germanium compared to SiO2 and GeO2, respectively. The photoluminescence (PL) properties of the samples were studied in the visible and near infrared ranges for different annealing temperatures, and for different Er concentrations. Time-resolved experiments were also performed. In both types of samples, the Er-related PL bands at 0.98 μm and 1.54 μm were obtained at room temperature. The best Er-related PL efficiency was obtained for the as-deposited GeOx:Er sample and for an annealing temperature equal to around 700 °C for the SiOx:Er samples. The optimal Er concentration is equal to 2.4 at.% in GeOx:Er and only to 0.7 at.% in SiO:Er. The effective Er absorption cross section measurements are very similar for all the samples and are in agreement with those obtained in Er-doped SiO2 matrix containing silicon nanocrystals. In both cases, the high Er-related PL intensity is attributed to an indirect excitation process of Er.