Theory of the Thermal Stability of Silicon Vacancies and Interstitials in 4H–SiC

This paper presents a theoretical study of the electronic and dynamic properties silicon vacancies self-interstitials in 4H–SiC using hybrid density functional methods. Several pending issues, mostly related to thermal stability this defect, are addressed. The site vacancy carbon-related antisite-vacancy (CAV) pair interpreted as unique bistable defect. It possesses metastable negative-U neutral state, which “disproportionates” into VSi+ or VSi?, depending on location Fermi level. introduces (?/+) transition, calculated at Ec?1.25 eV, determines temperature threshold for annealing VSi CAV n-type material due level crossing effect. Analysis configuration coordinate diagram allows us conclude that anneals out two stages—at low temperatures (T?600 °C) via capture mobile species (e.g., self-interstitials) higher (T?1200 dissociation VC CSi defects. Si interstitial (Sii) is also with q=+1 q=+3 states. These only paramagnetic states maybe explains why it escaped detection, even p-type where migration barriers least 2.7 eV high.