We have fabricated Au/extra-thin Si-rich SiO2 (ETSSO) film/p-Si and Au/ETSSO/n(+)-Si structures and compared their electroluminescence (EL) characteristics. It is found that for the Au/ETSSO/p-Si structure, when the forward bias (a positive voltage is applied to the p-Si substrate with respect to the Au electrode) is larger than 4 V, red light emission is observed, while under bias reverses, no light is emitted. The Au/ETSSO/n(+)-Si structure does not emit light under the forward bias (a positive voltage is applied to the Au electrode with respect to the n(+)-Si substrate), but it emits red light when the reverse bias is greater than a critical value, which correlates with the thickness of the ETSSO film. We have suggested a model for the electroluminescence mechanism of Au/ETSSO/n+-Si structures.