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

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.