Defect states in the high-dielectric-constant gate oxide LaAlO3

We present calculations of the energy levels of the oxygen vacancy, Al-La antisite, and oxygen interstitial defects in LaAlO3 using density functional methods that do not need an empirical band gap correction. The levels are aligned to those of the Si channel using the known band offsets. The oxygen vacancy gives an energy level near the LaAlO3 conduction band and above the Si gap. It is identified as the main electron trap and the cause of instability. The Al-La antisite gives a state near midgap, neutral when empty, which would be an important trap, with no counterpart in HfO2. (c) 2006 American Institute of Physics.