The role of Ge-related oxygen-deficiency centers in controlling the blueviolet photo- and electroluminescence in Ge-rich SiO₂ via Er doping

Using combined electroluminescence (EL) and photoluminescence (PL) studies we establish that the energy transfer process from the Er³⁺ to the Ge-related oxygen-deficiency centers (GeODCs) plays the key role in enhancing the 404 nm EL intensity in Ge-rich SiO₂. Er doping induced structural modification does not appear to be relevant, which is deduced from the 404 nm PL quenching with increasing Er concentration, implying a gradual loss of GeODCs. In contrast to PL, the 404 nm EL intensity increases by 0.3% Er doping followed by a gradual decrease in intensity for higher Er concentrations, which is described in terms of a competition between the energy transfer process and the gradual segregation of Er due to the destruction of GeODCs with Er doping. This fact is further discussed in the light of ab initio molecular orbital calculations.