H-related defect complexes in HfO2: A model for positive fixed charge defects

Abstract

Based on first-principles theoretical calculations, we investigate the hydrogenation effect on the defect properties of oxygen vacancies ${\mathrm{(V}}_{\mathrm{O}})$ in ${\mathrm{HfO}}_2.$ A defect complex of $V_{\mathrm{O}}$ and H behaves as a shallow donor for a wide range of Fermi levels, with a positive charge state, and this complex is energetically stable against its dissociation into $V_{\mathrm{O}}$ and H. We suggest that the $V_{\mathrm{O}}–\mathrm{H}$ complex is responsible for the formation of positive fixed charges, which neutralize negative fixed charges during the postannealing process of ${\mathrm{SiO}}_x/{\mathrm{HfO}}_2$ stack.