An embedded quantum wire mode of dielectric breakdown

The reverse gate bias current-voltage characteristics of n(+) polycrystalli ne-Si/SiO2/p-Si tunnel structures containing nanoscale quantum wires embedd ed in ultrathin oxide layers are analyzed using a three-dimensional quantum mechanical scattering calculation. By varying wire. geometry, our model ca n qualitatively reproduce experimental current-voltage characteristics for ultrathin oxides having undergone soft breakdown or breakdown. We find that low-bias current densities can be greatly enhanced by resonant tunneling, and that this mechanism is highly temperature dependent. We demonstrate tha t funneling of wave functions into quantum wires results in highly efficien t localized conduction paths which contributes to dramatic current increase s in the direct tunneling regime. We also explain how quantum wires which e xtend partially into the oxide layer from the SiO2/p-Si interface can be us ed to model soft breakdown current-voltage characteristics. (C) 1999 Americ an Institute of Physics. [S0003-6951(99)02804-1].