Electrical deactivation by vacancy-impurity complexes in highly As-doped Si

We have applied positron annihilation and Hall-effect/resistivity experiments to identify and quantify vacancy-impurity complexes formed in molecular-beam epitaxially grown Si at very high As doping levels of >10²⁰cm^-3. The results indicate that V-As₃ is the dominant vacancy defect which exists at concentrations relevant to the electrical deactivation of doping. Larger complexes, tentatively identified as V₂-As₅, are also present at high concentrations. The V-As₃ and V₂-As₅ defects are removed by annealings at 800^∘C and 900^∘C, respectively. The rapid thermal annealing leads to lowest concentrations of these deactivating defects, indicating that their formation is limited by migration processes during the cooling down.