Insights were obtained into the deactivation mechanisms of group-V donors in heavily doped Si. Based upon ab initio calculations, a 3-step model was suggested for the donor deactivation. In highly n-type Si grown at low temperatures, in the absence of excess native point defects, an intrinsic limit seemed to arise in part from donor deactivating distortions of the Si lattice in the proximity of 2 or more donor atoms that shared close sites. Also, donor dimers played an important part in the deactivation at high doping concentrations. While the dimers constituted a stable or metastable inactive donor configuration, the lattice distortions lowered the donor levels gradually below the impurity band in degenerate Si. On the other hand, it was found that, in general, none of the earlier proposed deactivating donor pair defects was stable at any position of the Fermi level. The lattice distortions could be viewed as a precursor to Frenkel pair generation and donor-vacancy clustering process (step 2) that accounted for deactivation at elevated temperatures and longer annealing times. Ultimately, and most prominently in the case of the large Sb atoms, precipitation of the donor atoms could set in as the last step of the deactivation process chain.

Highly n-Doped Silicon - Deactivating Defects of Donors. D.C.Mueller, W.Fichtner: Physical Review B, 2004, 70[24], 245207 (8pp)