Type-II band alignment for atomic layer deposited HfSiO₄ on α-Ga₂O₃

There is increasing interest in α-polytype Ga₂O₃ for power device applications, but there are few published reports on dielectrics for this material. Finding a dielectric with large band offsets for both valence and conduction bands is especially challenging given its large bandgap of 5.1 eV. One option is HfSiO₄ deposited by atomic layer deposition (ALD), which provides conformal, low damage deposition and has a bandgap of 7 eV. The valence band offset of the HfSiO₄/Ga₂O₃ heterointerface was measured using x-ray photoelectron spectroscopy. The single-crystal α-Ga₂O₃ was grown by halide vapor phase epitaxy on sapphire substrates. The valence band offset was 0.82 ± 0.20 eV (staggered gap, type-II alignment) for ALD HfSiO₄ on α-Ga_0.2O₃. The corresponding conduction band offset was −2.72 ± 0.45 eV, providing no barrier to electrons moving into Ga₂O₃.