Electronic-structure and total-energy calculations are reported for the vacancy and the substitutional and interstitial S, Se, and Te impurities in Si. We identify several mechanisms of impurity-impurity interactions. This theoretical study also serves to determine the dominant defect site of chalcogen pairs as two substitutionals.

• Received 5 January 1987

DOI:https://doi.org/10.1103/PhysRevLett.58.1456