Effects of Al addition on the native defects in hafnia

Two occupied native defect bands are experimentally detected in pure HfO2. The density of states of band one in the middle of the band gap reduces drastically with the Al addition, while that of band two slightly above the valence-band maximum remains rather unaffected. We attribute the two bands to the charged oxygen vacancy, and the oxygen-interstitial-related defect states of the HfO2, respectively. We demonstrate that the added Al passivates the V-O(+) induced midgap states but has little effect on other aspects of the electronic structure of the material. (c) 2006 American Institute of Physics.