Impact of germanium on vacancy clustering in germanium-doped silicon

Recent density functional theory calculations by Chen et al. [J. Appl. Phys. 103, 123519 (2008)] revealed that vacancies (V) tend to accumulate around germanium (Ge) atoms in Ge-doped silicon (Si) to form GeV(n) clusters. In the present study, we employ similar electronic structure calculations to predict the binding energies of GeV(n) and V(n) clusters containing up to four V. It is verified that V are strongly attracted to pre-existing GeV(n) clusters. Nevertheless, by comparing with the stability of V(n) clusters, we predict that the Ge contribution to the binding energy of the GeV(n) clusters is limited. We use mass action analysis to quantify the relative concentrations of GeV(n) and Vn clusters over a wide temperature range: V(n) clusters dominate in Ge-doped Si under realistic conditions. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3056387]