Evaluation of valence band offset and its non-commutativity at all oxide alpha-Cr2O3/beta-Ga2O3 heterojunction from photoelectron spectroscopy

We have investigated the non-commutativity of the band offset in RF magnetron sputter deposited all oxide epitaxial alpha-Cr2O3/beta-Ga2O3 heterojunction (HJ). The core-level x-ray photoelectron spectroscopy technique has been employed to probe the electronic structure of the interface formed between alpha-Cr2O3 and beta-Ga2O3. Valence and conduction band offsets of 2.6 +/- 0.2 and 0.9 +/- 0.2 eV, respectively, for alpha-Cr2O3/beta-Ga2O3 HJ have been determined from Kraut's method. These values are different from those reported for beta-Ga2O3/alpha-Cr2O3 HJ, thus indicating that the alpha-Cr2O3/beta-Ga2O3 HJ does not follow the band commutativity with respect to the growth sequence of the constituting layers forming the HJ. Furthermore, the band alignment at alpha-Cr2O3/beta-Ga2O3 HJ is still type-II like beta-Ga2O3/alpha-Cr2O3 HJ but with lower band offset values. Therefore, this HJ would also be able to confine the electrons and holes in beta-Ga2O3 and alpha-Cr2O3 layers, respectively, with lower turn on voltage.