Interface chemistry and electrical characteristics of 4H-SiC/SiO₂ after nitridation in varying atmospheres

SiC/SiO₂ is a prototypical wide-bandgap semiconductor/dielectric interface, which represents the challenges faced by many such material systems. A multitude of different defects leads to unacceptably large defect densities near the SiC conduction band and management of interfacial defects still remains a topic of lively discussion and current interest.
Advanced X-ray spectroscopy methods can probe chemical states at interfaces, and X-ray Photoelectron Spectroscopy (XPS) in particular can deliver great insight into interfaces as it combines both qualitative and quantitative information on elemental distributions, chemical environments, and valence states. Here, we present a systematic study of the 4H-SiC/SiO₂ interface in industrially manufactured samples with a particular focus on the effects of nitridation in a variety of atmospheres, to reduce interface defect states. Clear differences are found in both spectroscopy and electrical behaviour after high temperature treatments in N₂, NO, NH₃ and NO+NH₃ atmospheres. Core level spectra give a complete picture of chemical environments present in the oxide and carbide layers as well as at the interface providing insight into defect states and how they are compensated by nitridation.