It was shown 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.

Passivation of Oxygen Vacancy States and Suppression of Fermi Pinning in HfO2

by La Addition. D.Liu, J.Robertson: Applied Physics Letters, 2009, 94[4], 042904