Energy band alignments between series band of Al-rich high-k materials (HfO2)(x)(Al2O3)(1-x) and beta-Ga2O3 are investigated using X-Ray Photoelectron Spectroscopy (XPS). The results exhibit sufficient conduction band offsets (1.42-1.53 eV) in (HfO2)(x)(Al2O3)(1-x)/beta-Ga2O3. In addition, it is also obtained that the value of E-g, Delta E-c, and Delta E-v for (HfO2)(x)(Al2O3)(1-x)/beta-Ga2O3 change linearly with x, which can be expressed by 6.98-1.27x, 1.65-0.56x, and 0.48-0.70x, respectively. The higher dielectric constant and higher effective breakdown electric field of (HfO2)(x)(Al2O3)(1-x) compared with Al2O3, coupled with sufficient barrier height and lower gate leakage makes it a potential dielectric for high voltage beta-Ga2O3 power MOSFET, and also provokes interest in further investigation of HfAlO/beta-Ga2O3 interface properties. (C) 2017 Elsevier B.V. All rights reserved.