Carbon vacancy in SiC: A negative-U system
Institut für Festkörpertheorie und Theoretische Optik, Friedrich-Schiller-Universität, D-07743 Jena, Germany
Accepted: 19 September 1998
Total-energy and electronic-structure calculations are performed within density-functional theory in the local-density approximation for charged C and Si vacancies in cubic SiC. We find a pronounced Jahn-Teller distortion with a symmetry lowering for neutral and negatively charged C vacancies. Consequently, from the total energies as well as from the order of the vacancy levels (+/++) and (0/+) we derive a negative-U behaviour for the carbon vacancy. The formation energies are studied vs. composition and sample doping.
PACS: 61.72.Ji – Point defects and defect clusters / 71.55.Cn – Elemental semiconductors
© EDP Sciences, 1998