A first-principles calculation, based upon the local-density approximation and super-cell model, was carried out for the N substitutional impurity. Good agreement between theory and electron spin resonance data was obtained. The stable atomic geometry was found to have C3v symmetry; as indicated by electron spin resonance studies. The calculated energy difference between C3v and Td was less than 0.1eV; as compared with the experimental value of 0.073eV. The highest calculated occupied level consisted mainly of the Si dangling bond. The C3v structures for P and As were found to be unstable for the neutral and negative charge states.

M.Saito, Y.Miyamoto: Physical Review B, 1997, 56[15], 9193-6