Oxygen vacancies in high-k oxides

High dielectric constant (K) gate oxides such as HfO2 have suffered from charge trapping, threshold voltage shifts and a difficulty of metal or poly-Si gates to achieve band edge work function values. We investigate how these are related to the oxygen vacancies in a series of ab-initio calculations. The O vacancy is found to correlate with optical, luminescence and charge pumping spectra. The O vacancy contributes to the Fermi level pinning effect, which limits the band edge work functions. Inhibiting motion of vacancies may allow less pinning of gate electrode work functions.