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

Two of the most common dielectrics for beta-Ga2O3 are SiO2 and Al2O3 because of their large bandgaps, versatility of preparation, and thermal stability. However, because of the anisotropic properties of the ss-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/beta-Ga2O3 and Al2O3/beta-Ga2O3 heterojunctions with different beta-Ga2O3 orientations of (001), (010), and ((2) over bar 01). The bandgaps were determined to be 4.64, 4.71, and 4.59 eV for the ((2) over bar 01), (001), and (010) oriented beta-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.