Evidence for Resonant Tunneling of Electrons via Sodium Ions in Silicon Dioxide

Metal-oxide-silicon field-effect transistors (MOSFET's) were fabricated with ${\mathrm{Na}}^{+}$ ions in the gate oxide. Large peaks in the tunneling conductivity through the oxide were observed which are interpreted as resonant tunneling of electrons through localized ${\mathrm{Na}}^{+}$ impurities. It was demonstrated that the tunneling current was spatially localized. The temperature dependence of several peaks was measured and found to be consistent with a simple model for resonant tunneling through localized states. The position of the state in the direction of tunneling can be determined from the temperature dependence.