Energy band alignments of Al₂O₃-HfO₂/Al₂O₃ nanolaminates-SiO₂-p-type Si structures

The energy band alignments of Al₂O₃-HfO₂/Al₂O₃ nanolaminates-SiO₂-p-type Si structures were constructed based on the measurement of the band parameters by reflection electron energy-loss spectroscopy and x-ray photoelectron spectroscopy. The valence band offset at HfO₂/Al₂O₃ interface was obtained to be 0.17±0.05eV, while the valence band offset of 0.98±0.05eV was observed at HfO₂/SiO₂ interface. The binding energy shifts in the structures indicate that band bending occurs due to Fermi level alignment built by charge transfer across heterojunctions. From the schematic band diagrams of the structures, it is suggested that more negative charges are present on HfO₂-side, which also means there are more negative charges in HfO₂/Al₂O₃ nanolaminates, causing upward band bending in the middle part of the structures.