Ab initio calculations were carried out using a density functional theory code, to investigate the origin of the experimentally observed retardation of B diffusion in SiGe alloys. The formation energies of individual Si, B, and Ge point defects, and Si-B, Ge-B, and Si-Ge pair defects were calculated. Based on these calculations, the energetics of Si:Ge:B systems suggested that one mechanism to retard B diffusion involved the effect of Ge atoms to decrease the number of available Si self-interstitials by increasing the migration energy and, concomitantly, to increase the migration energy of B atoms. The results also showed that it was difficult for a Ge interstitial to approach a substitutional B atom, as compared with a Si self-interstitial.

First-Principles Study of the Origin of Retarded Diffusion of Boron in Silicon in the Presence of Germanium. L.Wang, P.Clancy, C.S.Murthy: Physical Review B, 2004, 70[16], 165206 (10pp)