First-principles calculation of the interaction between nitrogen atoms and vacancies in silicon

Stability of several states of nitrogen in silicon were investigated by the first-principles calculation. A single nitrogen at a split interstitial site and bond center site is more stable than that at a tetrahedral and hexagonal site. A nitrogen pair is more stable than the single nitrogen at the split interstitial site by 4.3 eV, which indicates that the nitrogen pair exists even near the melting temperature of silicon. Binding energy between the nitrogen pair and two vacancies indicates that a complex consisting of the nitrogen pair and two vacancies can exist at the temperature of the void aggregation as far as considering thermal equilibrium. Formation of the complex can affect the concentration or the diffusibility of the vacancy.