Oxygen-oxygen complexes and thermal donors in silicon

The suitability of several vacancy-oxygen and interstitial oxygen complexes as cores of thermal donors in silicon is examined. Tight-binding-based total-energy-minimization calculations were used in the determination of the atomic structure of the complexes. Vacancy-${\mathrm{O}}_2$ and interstitial O-O complexes are found to exhibit bistability and are the simplest structures exhibiting double-donor behavior. Atomic relaxations leading to oxygen-oxygen bonding and a threefold coordination of the oxygen atoms are critical in producing the double-donor activity.