Polar oxide/semiconductor heterojunction: MgO (111)/SiC (0001)

Abstract

The layered structures of polar oxides (i.e., metal/oxygen/metal/oxygen/…) can be utilized to engineer the atomic structures and thus tailor the electronic properties of polar oxide/semiconductor interfaces, including the band offsets between the technologically important MgO and SiC for complementary metal–oxide–semiconductor and spintronic devices. However, the growth of atomically flat polar oxide MgO films with arbitrary thickness has been hindered by polarity issues. In this study, we analyze the interfacial structure and band alignment of MgO (111) thin films deposited on 6h-SiC (0001) by the molecular beam epitaxy method. An epitaxial growth of the MgO (111) thin film on SiC is demonstrated. We show that the interface is O-terminated by atomic-scale scanning transmission electron microscopy measurements. The insulating characteristics are preserved in the vicinity of the interface according to electronic structure calculations. X-ray photoelectron spectroscopy measurements show that the valence band offset is approximately 1.6 eV. Electronic structure calculations for a realistic model constructed using the atomically resolved electron microscopy images show an excellent agreement between the calculated and measured valence band offsets, further confirming the validity of the developed atomic interface model. These findings pave the way for further advancements in MgO-based electronic devices, considering the ability to tailor the interface atomic structure, which could be employed to engineer the overall electronic properties at the interface, including the valence band offset.