Band Alignment of Al₂O₃on α-(Al_xGa_1-x)₂O₃

X Ray Photoelectron Spectroscopy was used to measure valence band offsets for Al2O3 deposited by Atomic Layer Deposition on α-(AlxGa1-x)2O3 alloys over a wide range of Al contents, x, from 0.26-0.74, corresponding to a bandgap range from 5.8-7 eV. These alloys were grown by Pulsed Laser Deposition. The band alignments were type I (nested) at x >0.5, with valence band offsets 0.13 eV for x = 0.26 and x = 0.46. At higher Al contents, the band alignment was a staggered alignment, with valence band offsets of-0.07 eV for x = 0.58 and-0.17 for x = 0.74, ie. negative valence band offsets in both cases. The conduction band offsets are also small at these high Al contents, being only 0.07 eV at x = 0.74. The wide bandgap of the α-(AlxGa1-x)2O3 alloys makes it difficult to find dielectrics with nested band alignments over the entire composition range.