The total energies and structures of a number of Be-induced defects in Si are investigated using ab initio local-density calculations. Our primary results are (1) the geometry of the isoelectronic center is found to correspond to a [111] substitutional-interstitial pair; (2) at normal doping temperatures the solubility of single Be interstitials is exceedingly low; (3) the low-energy defect spectrum includes large Be complexes containing at least one substitutional atom; and (4) the Be-Be bond in these larger complexes is metastable, while the Si-Be bond is stable for all defect configurations.

• Received 6 July 1990

DOI:https://doi.org/10.1103/PhysRevB.42.11252