Abstract
Examination of breakdown observations in oxides roughly thicker than 10 nm shows that the impact ionization-recombination (IIR) model interprets fast breakdowns on constant voltage tests by the growth of positive charge at the cathode at fields larger than a critical field Fr . Breakdown events of longer duration at fields slightly below the critical field can be observed on constant current tests. Such breakdown cannot be explained by the IIR model. It is suggested that it results from changes produced in the oxide prior to the breakdown by the generation of a large density of electron trap states of the order of 1019 cm−3. The mechanism of such breakdowns has not been identified yet. Resonant tunneling via trap states near the cathode, or degradation of the injection barrier, or transition of the oxide from an insulating to a conducting state may be processes producing breakdown in constant current tests.