Reexamination of band offset transitivity employing oxide heterojunctions

Band offset transitivity is reexamined extendedly by employing oxide heterojuctions. The valence band offsets (ΔEV) at HfO2/SiO2, Al2O3/SiO2, and HfO2/Al2O3 heterojunctions are experimentally determined to be 0.81, 0.25, and 0.25 eV, respectively, by X-ray photoelectron spectroscopy. Thus, the ΔEV at HfO2/Al2O3 heterojunction is not equal to the ΔEV at HfO2/SiO2 minus the ΔEV at Al2O3/SiO2 heterostructures (0.25 ≠ 0.81 − 0.25 = 0.56), i.e., the transitivity rule fails for oxide heterojunctions. Different distributions of interfacial induced gap states at the three heterostructures contribute to this failure of transitivity rule.