Efficient white electroluminescence (EL) is obtained from metal-oxynitride-oxide-silicon (MONOS) structures with a silicon-rich SiO 2 -SiON interface as an active layer. Samples containing only silicon show white EL under a constant current excitation of 500 μA. The EL spectra consist of three main bands associated with the neutral oxygen vacancy at 430 nm, Eδ′ centers at about 550 nm, and nonbridging oxygen hole centers peaking at 650 nm. After Gd co-doping into the SiO2:Si-nc layer, the light emitted from the MONOS structure observed by the naked eye is clearly white, but the constant current needed for the EL excitation is reduced five times. A fourfold increase in the external EL power efficiency after Gd co-doping (up to 3× 10-4 %) is observed. © 2009 The Electrochemical Society.