Band offset determination for amorphous Al2O3deposited on bulk AlN and atomic-layer epitaxial AlN on sapphire

Abstract

Valence and conduction band offsets of atomic layer deposition (ALD) Al2O3 deposited on bulk AlN crystals were determined using x-ray photoelectron spectroscopy to be ΔEV = 0.75 eV and ΔEC = -1.45 eV, with a measured energy gap of the Al2O3 film of 6.9 eV. In addition, crystalline AlN deposited by atomic layer epitaxy on sapphire was evaluated, resulting in a valence band offset of ΔEV = -0.75 eV and a conduction band offset of ΔEC = 3.25 eV due to the wider bandgap of the crystalline Al2O3 substrate compared to amorphous ALD Al2O3. Both heterojunctions exhibited type-II behavior and similar valence band offsets.