Correlation between microstructural and electroluminescent properties of Ge–SiO2 composite films

Ge nanocrystal (nc-Ge) embedded Si oxide films were deposited on p-type Si substrates using the RF magnetron sputtering technique with a Ge–SiO2 composite target. Films were annealed in a nitrogen ambient for 30 min at 300–1000 °C with an interval of 100 °C. The average sizes of nc-Ge in films were evaluated to be 3.9–6.1 nm with the increasing annealing temperature (Ta) in the range of 600–1000 °C from X-ray diffraction (XRD) results. The changes of the content of various Ge oxides with Ta were determined by the results of X-ray photoelectronic spectra (XPS). One peak of 510 nm (2.43 eV) was observed in the electroluminescence (EL) measurements, and the EL intensity changed a lot with the peak position unchanged for samples annealed at different temperatures. The quantum confinement (QC) effect and luminescence centers (LCs) are discussed based on the correlation between the EL characteristics and the change of the structure of the films annealed at different temperatures.