Electroluminescence (EL) in an electrolyte-insulator-semiconductor system is used to study oxide layers in Si-SiO₂-Si₃N₄ and Si-SiO₂ structures prepared using various techniques. The EL spectra of all the structures contained the 2.7-eV emission band characteristic of the radiative relaxation of excited sililene centers. A comparative study of the conditions conducive to the formation of such luminescence centers in various structures containing SiO₂ layers was made, and their nature was refined.