Theoretical calculations of formation energies, binding energies of Cd-P pairs in Si, and hyperfine parameters at the Cd site were performed. The ab initio all electron full-potential linear muffin-tin orbital method based upon smooth Hankel functions, local-density-functional theory, and the super-cell technique were utilized. Cd-P pairs with different numbers of P atoms, in several charge states, were studied. In each complex, the P atom was placed at the substitutional site while Cd was localized at the substitutional or interstitial sites. It was found that substitutionals CdP0,–1 and CdP20 were stable complexes with binding energies around 0.7 to 0.8eV. The calculated electric-field gradients of these complexes at the Cd site give quadrupolar coupling constants in agreement with previous theoretical and experimental assessments. However, Cd at interstitial positions weakly binds to P for n-type samples, and gave hyperfine parameters much lower than previous tentative experimental assignations. It was found the cluster CdP3, being as stable as CdP and CdP2, could explain the origin of the third quadrupolar coupling constant found at a high P level doping. These facts suggested that segregation of P atoms around Cd could take place. Calculated charge states, transition state levels, and equilibrium concentrations were in accord with experimental measurements.

Pairing and Hyperfine Interactions of Cd-P Complexes in Silicon. R.A.Casali, M.A.Caravaca: Physical Review B, 2003, 67[15], 155207