An accurate determination of barrier heights at the HfO2∕Si interfaces

X-ray photoelectron spectroscopy (XPS) combined with first principles simulations are used to investigate the band alignments of HfO2 on silicon. Our theoretical calculations predict dangling bond states originating from the partial occupancy of Hf d orbitals at a stoichiometric HfO2∕Si interface. Our band structure calculations predict that hydrogen passivation of Hf atoms at the interface as well as increased oxygen concentration at the interface remove the dangling bond states effectively. A HfSiO4∕Si interface also has no dangling bond states. Theoretically calculated valence band offsets of HfO2∕Si interface ranged from 2.69 to 3.04eV and the conduction band offsets ranged from 1.54 to 1.89eV, and they are a function of the interface coordination numbers. For the HfSiO4∕Si interface, the calculated valence and conduction band offsets are 2.69eV and 2.19eV, respectively. Experimentally measured band offsets by XPS yield a valence band offset of 3.10eV and a conduction band offset of 1.48eV for a HfO2∕Si interface, in very good agreement with theoretical results. These results suggest that HfO2 and HfSiO4 provide sufficient tunneling barriers for electrons and holes, making them suitable candidates as alternative gate dielectrics.