We show that the detailed atomic structure of vacancy-impurity complexes in Si can be experimentally determined by combining positron lifetime and electron momentum distribution measurements. The vacancies complexed with a single impurity, $V-\mathrm{P}$ and $V-\mathrm{As}$, are identified in electron irradiated Si. The formation of native vacancy defects is observed in highly As-doped Si at the doping level of ${10}^{20}{\mathrm{cm}}^{-3\mathrm{}}$. The defects are identified as monovacancies surrounded by three As atoms. The formation of a $V-{\mathrm{As}}_3$ complex is consistent with the theoretical descriptions of As diffusion and electrical deactivation in highly As-doped Si.

• Received 1 October 1998

DOI:https://doi.org/10.1103/PhysRevLett.82.1883