High field electronic properties of SiO2

Abstract The effects of very high electric fields on the transport of electrons and holes in SiO2 are discussed. At fields above 5 × 105 V/cm, electrons emit optical phonons, which is a very efficient energy loss mechanism. Holes on the other hand form small polarons in about 10−12 s, and their mobility becomes very low, but is unaffected by field up to 5 × 106 V/cm. The field dependent generation of electron-hole pairs is fit by application of the geminate recombination theory with a distribution of thermalization distances and excitation by X-rays and bandgap radiation is discussed. The first dependent bulk recombination coefficient is discussed in terms of high field mobility of the electrons. The impact ionization of electrons in SiO2 is discussed by comparing recent results for laser-induced breakdown in SiO2 with experiments on thin films involving photocurrents, space charge buildup and prebreakdown currents, and also theoretical predictions. Below 107 V/cm the laser experiments indicate higher impact ionization rates than the thin film experiments or theory.