The field and thickness dependence of the conductivity, charge state, and electroluminescence of Si-SiO₂ structures is investigated with the aim of studying the energy-dissipation mechanisms of electrons heated by an electric field in SiO₂ films. It is shown that, as well as the previously known dissipation channels (interaction with the phonon subsystem and impact ionization in the SiO₂ volume, with characterisic energy losses ε₁<0.153 eV and ε₂>9 eV, respectively), account must also be taken of processes of defect excitation at the Si-SiO₂ boundary, which are accompanied by radiative relaxation in the electroluminescence bands and characterized by "intermediate" energy-loss values (ε₁<ε<ε₂).