First-Principles Study of Er Location in Er-Si Systems with Oxygen Co-Dopants

Using the Hartree-Fock cluster procedure, we are investigating possible models for the Er$^{3+}$ ion in silicon with oxygen co-dopants[1]. We are examining first the Hi (hexagonal interstitial) site with six O atoms in the intrabond regions of the six Si-Si bonds for this center[2], allowing for relaxation in positions of the O and Si atoms. The aim of this study is to see if the presence of the O atoms is indeed able to change the situation of a maximum in the potential surface for Er$^{3+}$ found from our recent investigations of the Er-Si system without co-dopants to a minimum in the co-doped Oxygen system. Results for the Er$^{3+}$ potential curve for the Hi center and the geometries of the Si and O atoms will be presented. [1] F. d'Acapito, S. Mobilio, S. Scalese, A. Terrasi, G. Franz\'{o} and F. Priolo, Phys. Rev. B 69, 153310 (2004) and references therein. [2] J.D. Carey, J. Phys. Condens. Matter 14, 8537 (2002)