Passivation of oxygen vacancy states and suppression of Fermi pinning in HfO2 by La addition

We show that group III elements such as La, Y, Sc, and Al can passivate adjacent oxygen vacancies in HfO2 and ZrO2 by shifting the vacancy gap state up into the conduction band. The shift arises from the outward relaxation of the cations around the vacancy due to its positive charge, becoming a closed shell configuration. La substitution at Hf sites in HfO2 suppresses Fermi level pinning because its holes offer a deeper sink for electrons generated by the vacancy than transfer to the metal gate.