Band alignment of grafted monocrystalline Si (001)/fl-Ga2O3 (010) p-n heterojunction determined by X-ray photoelectron spectroscopy

Beta -phase gallium oxide (fl-Ga2O3) research has gained accelerated pace nowadays. However, the high acceptor activation energy obstructs the development of homojunction bipolar devices employing fl-Ga2O3. The recently demonstrated semiconductor grafting technique provides an alternative and viable approach towards latticemismatched fl-Ga2O3-based p -n heterojunctions with high quality interfaces. Understanding and quantitatively characterizing the band alignment of the grafted heterojunctions is crucial for future bipolar device development employing the grafting method. In this work, we present a systematic study of the band alignment in the grafted monocrystalline Si/fl-Ga2O3 heterostructure by employing X-ray photoelectron spectroscopy (XPS). The band diagrams were constructed using two individual methods, the core level peak method and the valence band spectrum method, by utilizing the different portions of the measured data. Both methods resulted in an identical band alignment within the error range, which is also consistent with the prediction from the electron affinity values of Si and fl-Ga2O3. The study suggests that the interface defect density in grafted Si/fl-Ga2O3 heterostructures is at a sufficiently low level such that Fermi level pinning at the interface has been completely avoided and the universal electron affinity rule can be safely employed to construct the band diagrams of grafted monocrystalline Si/fl-Ga2O3 heterostructures.