Vacancy-boron complexes in plasma immersion ion-implanted Si probed by a monoenergetic positron beam

Vacancy-type defects in plasma immersion B-implanted Si were probed by a monoenergetic positron beam. Doppler broadening spectra of the annihilation radiation were measured and compared with spectra calculated using the projector augmented-wave method. For the as-doped sample, the vacancy-rich region was found to be localized at a depth of 0-10 nm, and the major defect species were determined to be divacancy- B complexes. After spike rapid thermal annealing at 1075 °C, the lineshape parameter S of Doppler broadening spectra corresponding to the high- B-concentration region (4-30 nm) was found to be smaller than the characteristic S value obtained for defect-free Si. From a detailed analysis of the Doppler broadening spectra, the origin of the decrease in the S value was attributed to the trapping of positrons by negatively charged B clusters such as icosahedral B12.