β-Ga2O3 orientation dependence of band offsets with SiO2 and Al2O3

Two of the most common dielectrics for β-Ga2O3 are SiO2 and Al2O3 because of their large bandgaps, versatility of preparation, and thermal stability. However, because of the anisotropic properties of the β-polytype, it is necessary to understand differences in band alignment for the different crystal orientation. Using x-ray photoelectron spectroscopy, we performed a comparative study of the band alignment of SiO2/β-Ga2O3 and Al2O3/ β-Ga2O3 heterojunctions with different β-Ga2O3 orientations of (001), (010), and (2¯01). The bandgaps were determined to be 4.64, 4.71, and 4.59 eV for the (2¯01), (001), and (010) oriented β-Ga2O3 substrates, respectively. The valence band offsets for SiO2 on these three orientations were 1.4, 1.4, and 1.1 eV, respectively, while for Al2O3, the corresponding values were 0.0, 0.1, and 0.2 eV, respectively. The corresponding conduction band offsets ranged from 2.59 to 3.01 eV for SiO2 and 2.26 to 2.51 eV for Al2O3.