Band offsets of wide-band-gap oxides and implications for future electronic devices

Abstract

Wide-band-gap oxides such as ${\mathrm{SrTiO}}_3$ are shown to be critical tests of theories of Schottky barrier heights based on metal-induced gap states and charge neutrality levels. This theory is reviewed and used to calculate the Schottky barrier heights and band offsets for many important high dielectric constant oxides on Pt and Si. Good agreement with experiment is found for barrier heights. The band offsets for electrons on Si are found to be small for many key oxides such as ${\mathrm{SrTiO}}_3$ and ${\mathrm{Ta}}_{\mathrm{2}}{\mathrm{O}}_5$ which limit their utility as gate oxides in future silicon field effect transistors. The calculations are extended to screen other proposed oxides such as ${\mathrm{BaZrO}}_3.$ ${\mathrm{ZrO}}_2,$ ${\mathrm{HfO}}_2,$ ${\mathrm{La}}_{\mathrm{2}}{\mathrm{O}}_3,$ ${\mathrm{Y}}_{\mathrm{2}}{\mathrm{O}}_3,$ ${\mathrm{HfSiO}}_4,$ and ${\mathrm{ZrSiO}}_4.$ Predictions are also given for barrier heights of the ferroelectric oxides ${\mathrm{Pb}}_{\text{1−x}}{\mathrm{Zr}}_x{\mathrm{TiO}}_3$ and ${\mathrm{SrBi}}_{\mathrm{2}}{\mathrm{Ta}}_{\mathrm{2}}{\mathrm{O}}_9$ which are used in nonvolatile memories.