Temperature dependence of the crossover between the near-infrared Er and defect-related photoluminescence bands of Ge-rich Er-doped SiO₂ layers

Temperature-dependent photoluminescence of Ge-rich SiO₂ in the presence or absence of Er shows a crossover between defect-related (15–150 K) and Er-related (150–295 K) emission within 1525 and 1440 nm. The origin of the near-infrared defect-related bands is discussed in the light of recombination of localized excitons in luminescence centers at the Ge cluster/SiO₂ interface. Time-resolved photoluminescence further enables us to illustrate the observed 1.53 um Er emission above 150 K in terms of a phonon-assisted nonradiative energy-transfer process from the luminescence centers to the Er³⁺ ions.