Microscopic models of impurities in silicon

The study of electronic structure of insulated and complex puntual impurities in silicon responsible by the appearing of deep energy levels in the forbiden band of semiconductor, is presented. The molecular cluster model with the treatment of surface orbitals by Watson sphere within the formalism of Xα multiple scattering method, was used. The electronic structures of three clusters representative of perfect silicon crystal, which were used for the impurity studies, are presented. The method was applied to analyse insulated impurities of substitutional and interstitial hydrogen (Si:H and Si:Hi), subtitutional and interstitial iron in neutral and positive charge states (Si:Fe0,+, Si:Fe0,+) and substitutional gold in three charge states(Si,Au-,0,+). The thetraedic interstitial defect of silicon (Si:Sii) was also studied. The complex impurities: neighbour iron pair in the lattice (Si:Fe2), substitutional gold-interstitial iron pair (Si:AusFe) and substitutional boron-interstitial hydrogen pair (Si:BsHi), were analysed. (M.C.K.)