Fluorine codoping in germanium to suppress donor diffusion and deactivation

Electronic structure calculations are used to investigate the stability of fluorine-vacancy (F(n)V(m)) clusters in germanium (Ge). Using mass action analysis, it is predicted that the F(n)V(m) clusters can remediate the concentration of free V considerably. Importantly, we find that F and P codoping leads to a reduction in the concentration of donor-vacancy (DV) pairs. These pairs are responsible for the atomic transport and the formation of D(n)V clusters that lead to a deactivation of donor atoms. The predictions are technologically significant as they point toward an approach by which V-mediated donor diffusion and the formation of inactive D(n)V clusters can be suppressed. This would result in shallow and fully electrically active n-type doped regions in Ge-based electronic devices. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3224900]