Ab initio calculations for point defect clusters with P, As, and Sb in Si

We present results of ab initio calculations for point defect clusters with phosphorus, arsenic, and antimony in silicon, including mixed clusters. We show that these dopant species interact, modifying their diffusion and activation. Most importantly, mixed clusters can exist in similar concentrations as pure clusters, reducing the fraction of active dopants. Furthermore, we analyze the influence of cluster composition on the configurations and energetics. Phosphorus and arsenic atoms take similar roles in the cluster configurations, whereas antimony leads to different configurations. The binding to self-interstitials is weaker for As than for P and weaker for Sb than for As. The binding to a vacancy is stronger for As than for P and stronger for Sb than for As. For all clusters with one vacancy and up to four dopant atoms, the constant binding energy per dopant atom is -1.17 eV for P, -1.27 eV for As, and -1.34 eV for Sb. Finally, we derive reaction enthalpies from the calculated formation energies and discuss the implications for dopant diffusion and activation.