Electrical breakdown of aluminum oxide films flanked by metallic electrodes

Breakdown characteristics of anodically grown aluminum oxide films were determined in the range of temperature 4.2–354 K, of thickness 47–187 nm, on change of polarity and for gold and aluminum electrodes. Results could be consistently interpreted with the theory of breakdown due to impact ionization by one type of carrier, presented in the prior paper. The theory ascribes breakdown events to the complex interaction of impact ionization, electron injection, hole trapping, and drift and electron trapping. The effect of trapping was found to be of primary importance, since changes in trapping properties can greatly alter the breakdown properties of aluminum oxide. The wide range of breakdown observations from 3 to 13 MV/cm was explained with changes in trapped electron charge and possibly with change in impact ionization processes, trap to band at low fields, but band to band transitions at high fields. Anomalous breakdown characteristics demonstrate that a trapped electron charge can produce protection from breakdown and that trapped electron densities can be in the low 1018/cm3 up to fields of 10 MV/cm.