Defect-engineered blue-violet electroluminescence from Ge nanocrystal rich SiO₂ layers by Er doping

Using combined microstructural and electroluminescence (EL) investigations of the Er-doped Ge-rich SiO₂ layers, it is established that the Ge-related oxygen-deficiency centers (GeODCs), which are associated with the 407 nm light emission, are situated at the Ge nanocrystal/SiO₂ interface. Electrically driven energy transfer from the Er³⁺ to GeODCs causes an increase in the 407 nm EL intensity. It reaches a maximum before quenching with increasing Er concentration due to the crystalline-to-amorphous transition of Ge nanocrystals. Ge concentration dependent quenching of the maximum EL intensity and the peak shifting toward higher Er concentration are discussed in terms of the reduction of the surface-to-volume ratio with increasing nanocrystal size.