Hartree-Fock Cluster Investigation of Locations for Erbium in Silicon

Using the Hartree-Fock Cluster Procedure, we have investigated three locations hexagonal and tetrahedral interstitial (H$_{i}$ and T$_{i})$ and substitutional (S) for Er$^{3+}$ in Silicon including relaxation effects of the Si neighbors of Er$^{3+}$. Our results for the binding energies show that S is the most stable site for Er$^{3+}$, in contrast with the results from the most recent channeling measurements,\footnote{M. B. Huang et al., Appl. Phys. Lett. 81, 2734 (2002)} which can best be explained assuming that Er$^{3+}$ is at T$_{i}$ site. Possible reasons for the difference will be suggested. Magnetic hyperfine fields obtained for the Er nucleus at various sites will be discussed.