Hot electrons in SiO₂: ballistic to steady-state transport

We present a brief experimental and theoretical review of the properties of electron transport in thermally grown SiO2. In thick films (≳ 10 nm), steady-state transport is controlled by polar electron-phonon scattering at electric fields below 2 × 106 V/cm. At higher fields, nonpolar scattering prevents the electrons from "running away" and allows steady-state trnasport to occur at average electron energies of a few eV. In thinner films (≲ 6 nm), the "vacuum emission" technique performed at room temperature and 80 K allows the observation of ballistic transport and phonon replicas, in good agreement with Monte Carlo simulations. These results are used to investigate in detail the electron-lattice coupling constants that result from the almost ideal structural and electronic properties of thermally grown SiO2 films. © 1988.