Lattice location of implanted Co in heavily doped $$n^+$$ n + - and $$p^+$$ p + -type silicon

Abstract

We have studied the influence of electronic doping on the preferred lattice sites of implanted \({^{61}\text{Co}}\), and the related stabilities against thermal annealing, in silicon. Using the \(\beta ^-\) emission channeling technique we have identified Co on ideal substitutional (ideal S) sites, sites displaced from bond-centered towards substitutional (near-BC) sites and sites displaced from tetrahedral interstitial towards anti-bonding (near-T) sites. We show clearly that the fractions of Co on these lattice sites change with doping. While near-BC sites prevail in \(n^+\)-type Si, near-T sites are preferred in \(p^+\)-type Si. Less than \(\sim\)35% of Co occupies ideal S sites in both types of heavily doped silicon, showing that the majority of implanted Co forms complex defect structures. Implantation-induced defects seem to getter more efficiently Co in lightly doped n-type than in heavily doped \(n^+\)- or \(p^+\)-type silicon. The formation of CoB pairs in \(p^+\)-type silicon and its possible influence on the lattice sites is discussed.