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

Abstract

We present calculations of the energy levels of the oxygen vacancy, ${\mathrm{Al}}_{\mathrm{La}}$ antisite, and oxygen interstitial defects in $\mathrm{La}\mathrm{Al}{\mathrm{O}}_3$ 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 $\mathrm{La}\mathrm{Al}{\mathrm{O}}_3$ conduction band and above the Si gap. It is identified as the main electron trap and the cause of instability. The ${\mathrm{Al}}_{\mathrm{La}}$ antisite gives a state near midgap, neutral when empty, which would be an important trap, with no counterpart in $\mathrm{Hf}{\mathrm{O}}_2$ .