The asymmetric band structure and electrical behavior of the GdScO3/GaN system

III–V nitrides are interesting materials for a very wide variety of electronic and optoelectronic devices. In this study, their interaction with GdScO3 (GSO), a ternary rare earth oxide, is investigated for MOS applications. We compare pulsed laser deposited amorphous and crystalline epitaxial GdScO3 in terms of their band alignment with the underlying GaN substrate and the resulting electrical characteristics of the MOS stack. The crystal structure of GdScO3 and GaN is investigated by means of x-ray diffraction, showing that crystalline oxide is growing epitaxially on GaN. X-ray photoelectron spectroscopy analysis shows a staggered band alignment with a GdScO3-GaN valence band offset of 3.6–3.7 eV, which is reflected in a very asymmetric current-voltage behaviour of the MOS capacitors: breakdown at positive bias, significantly earlier for the crystalline oxide (around 5 MV/cm) compared to the amorphous oxide (around 8 MV/cm), and no breakdown up to a field of −14 MV/cm at negative bias. Transmission elec...