Fully combined metal-oxide-semiconductor compatible light emitting devices based on nano bi-layer structures were fabricated. The active layers are composed by silicon nitride on top or a silicon-enriched silicon dioxide film with different Si concentrations. Electro and photo luminescence spectra of the devices and the active materials are analyzed and correlated to verify if the origin of the emission is the same. Differences found between electrically and optically stimulated photo-emission in the studied region of the spectra were concluded to be due optical phenomena introduced by the gate and multi-layer configuration, meaning that the same radiative centers are stimulated optically and electrically.