Charge states of divacancies in self-implanted doped Si

The charge states of divacancies induced by 5 MeV self-implantation of dope d silicon were investigated by positron annihilation methods. For low dopin g concentrations, results were found to be in agreement with the prediction s of Fermi statistics. For the case of heavily boron-doped silicon (n(B) = 1 x 10(19) cm(-3)) an anomalous single-negative divacancy charge state was detected. We attribute this to the introduction of new levels in the band g ap, due to the capture of boron by divacancies, resulting in a boron-divaca ncy complex. Detailed analysis of positron annihilation spectra suggests th at the boron does not reside on a nearest-neighbor site to the divacancy. I sothermal annealing experiments yield activation energy of 0.9 +/-0.1 eV fo r migration of this defect. (C) 2001 American Institute of Physics.