Ge ions of 100 keV were implanted into a 120 nm-thick SiO2 layer on n-Si at room temperature while those of 80 keV were into the same SiO2 layer on p-Si. Samples were, subsequently, annealed at 500 degreesC for 2 h to effectively induce radiative defects in the SiO2. Maximum intensities of sharp violet photoluminescence (PL) from the SiO2/n-Si and the SiO2/p-Si samples were observed when the samples have been implanted with doses of 1 x 10(16) and 5 x 10(15) cm(-2), respectively. According to current-voltage (I-V) characteristics, the defect-related samples exhibit large leakage currents with electroluminescence (EL) at only reverse bias region regardless of the type of substrate. Nanocrystal-related samples obtained by an annealing at 1100 degreesC for 4 h show the leakage at both the reverse and the forward region.