Native point defects in yttria and relevance to its use as a high-dielectric-constant gate oxide material: First-principles study

Yttria $({\mathrm{Y}}_{2}{\mathrm{O}}_{3})$ has become a promising gate oxide material to replace silicon dioxide in metal-oxide-semiconductor devices. Using a first-principles approach the electronic structure, defect structure, and formation energy of native point defects in ${\mathrm{Y}}_{2}{\mathrm{O}}_{3}$ are studied. Vacancies, interstitials, and antisites in their relevant charge states are considered. We find that within the band gap of ${\mathrm{Y}}_{2}{\mathrm{O}}_{3}$ oxygen vacancies, oxygen interstitials, yttrium vacancies, and yttrium interstitials can be stable depending on the Fermi level and external chemical potentials. When the Fermi level is constrained to be within the band gap of silicon, oxygen vacancies are the dominant defect type under low oxygen chemical potential condition. A higher oxygen chemical potential leads to oxygen interstitials and ultimately yttrium vacancies.