1.54 μm luminescence of Er-doped SiO x and GeO x thin films: A comparative study

Abstract

Erbium-doped amorphous silicon oxide (SiO x :Er) and germanium oxide (GeO x :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 SiO 2 and GeO 2, 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 GeO x :Er sample and for an annealing temperature equal to around 700 °C for the SiO x :Er samples. The optimal Er concentration is equal to 2.4 at.% in GeO x :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 SiO 2 matrix containing silicon nanocrystals. In both cases, the high Er-related PL intensity is attributed to an indirect excitation process of Er.