Dopant-vacancy cluster formation in germanium

Recent experimental and theoretical studies revealed that dopants in germanium (Ge) cluster with lattice vacancies (V). The existence of these larger clusters has been recently predicted and is important as they can contribute to the low activation of dopants in Ge. With the use of electronic structure calculations we study the binding energies of clusters formed with the association of dopant atoms and vacancies. As an example of the kinetics of such clusters the diffusion of two phosporous-vacancy (P2V) clusters via the ring mechanism of diffusion in predicted. These P2V clusters are important as they can act as precursors for the formation of the larger P3V and P4V clusters. The present study provides information on the structure of clusters and is consistent with recent experimental results, which indicate that the formation of clusters in heavily doped Ge is possible. In agreement with experiment, we predict that the diffusion of P V pairs is retarded by the addition of a further P atom. (C) 2010 American Institute of Physics. [doi:10.1063/1.3361115]