Identification of Vacancy-Impurity Complexes in Highly n-Type Si

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-P and V-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 10²⁰cm^-3. The defects are identified as monovacancies surrounded by three As atoms. The formation of a V-As₃ complex is consistent with the theoretical descriptions of As diffusion and electrical deactivation in highly As-doped Si.