DISPLACEMENT OF IMPURITIES IN SI BY IRRADIATION WITH ENERGETIC H+-PARTICLE OR HE+-PARTICLE

Ion-induced displacement of impurity atoms in Si from substitutional into non-substitutional positions has been studied by He** plus or H** plus backscattering and nuclear reaction analysis in combination with the channeling technique. The impurities involved, chosen so that the influence of valence and covalent radii could be studied, were B, Ga, Ge, Sn, P, As, Sb, Bi, Se and Te in Si. Displacement is found for all elements studied except for Ge. Numbers for the displacement rates were derived from the experimental data, being lower for Sn (and Ge). The displacement of Sn atoms can be explained by size effect interactions, the displacement of group III, V and VI elements by Coulomb attraction between point defects and impurity atoms. The displacement of the group III elements is thought to be due to trapping of positively charged interstitials by the acceptor atoms, whereas displacement of group V and VI elements is due to trapping of negatively charged vacancies by the donor atoms.