Thermodynamic stability and band alignment at a metal-high-k dielectric interface

We consider theoretically a heterojunction between (110)-oriented molybdenum and (111)-oriented tetragonal polymorph of hafnia. We calculate the Schottky barrier of 2.8 eV using density functional theory, and find the near perfect "p-type alignment" in good agreement with predictions of the metal-induced gap states (MIGS) model. However, we find the interface to be unstable with respect to the formation of an unusual interface specific defect which we call the extended Frenkel pair resulting in a large additional interface dipole. This behavior is qualitatively different from that predicted by the MIGS theory, endemic to transition metal oxide contacts with most large work function metals, and has important implications for the complementary metal-oxide-semiconductor technology.