Band Offsets for Atomic Layer Deposited HfSiO4 on (Al0.14Ga0.86)2O3

There is increasing interest in (AlxGa1-x)(2)O-3/Ga2O3 metal-oxide semiconductor field effect transistors, but there is little information on appropriate gate dielectrics for the (AlxGa1-x)(2)O-3. A potential candidate is HfSiO4 deposited by Atomic Layer Deposition (ALD), which should mitigate disruption to the surface. The valence band offset of the HfSiO4/(Al0.14Ga0.86)(2)O-3 heterointerface was measured using X-Ray Photoelectron Spectroscopy. The single-crystal beta-(Al0.14Ga0.86)(2)O-3 was grown by Molecular Beam Epitaxy. The bandgap of the HfSiO4 was determined by Reflection Electron Energy Loss Spectroscopy to be 7.0 +/- 0.35 eV, while high resolution XPS data of the O 1s peak and onset of elastic losses was used to establish the (Al0.14Ga0.86)(2)O-3 bandgap as 5.0 +/- 0.30 eV. The valence band offset was 0.42 eV +/- 0.10 eV (straddling gap, type I alignment) for ALD HfSiO4 on beta-(Al0.14Ga0.86)(2)O-3. The conduction band offset was 1.58 +/- 0.35 eV, providing good electron confinement. (C) 2018 The Electrochemical Society.