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

There is increasing interest in alpha-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 alpha-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 alpha-Ga0.2O3. The corresponding conduction band offset was -2.72 +/- 0.45 eV, providing no barrier to electrons moving into Ga2O3.