Abstract
The wide-bandgap ternary (AlxGa1−x)2O3 forms a heterostructure system with Ga2O3 that is attracting attention for modulation-doped field-effect transistors. The options for gate dielectric on (AlxGa1−x)2O3 are limited by the need for adequate band offsets at the heterointerface. Al2O3 deposited by atomic layer deposition (ALD) is one option due to its large bandgap (6.9 eV). We measured the valence-band offset at the Al2O3/(Al0.14Ga0.86)2O3 heterointerface using x-ray photoelectron spectroscopy (XPS). Al2O3 was deposited by ALD onto single-crystal β-(Al0.14Ga0.86)2O3 (bandgap 5.0 eV) grown by molecular beam epitaxy (MBE). The valence-band offset was determined to be 0.23 ± 0.04 eV (straddling gap, type I alignment) for ALD Al2O3 on β-(Al0.14Ga0.86)2O3. The conduction-band offset was 1.67 ± 0.30 eV, providing good electron confinement.
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