Efficient white electroluminescence (EL) is obtained from metal-oxynitride-oxide-silicon (MONOS) structures with a silicon-rich SiO2-SiON interface as an active layer. Samples containing only silicon show white EL under a constant current excitation of 500 mu A. The EL spectra consist of three main bands associated with the neutral oxygen vacancy at 430 nm, E-delta(') 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 3x10(-4)%) is observed.