Role played by N and N-N impurities in type-IV semiconductors

Ab initio all-electron Hartree-Fock calculations within the molecular-cluster model are performed to analyze the role of N impurities, both isolated and complex, in type-IV semiconductors. The results are used to investigate the structural and electronic properties. For isolated impurities the N atom distorts in the direction towards a vacancy leading to a final local C 3υ symmetry. The N atom forms sp 2 bonds with the host atoms and leaves an unoccupied N lone pair. For N 2 both N atoms tend to form similar sp 2 bonds and move away from each other in the direction without N-N bond formation