Ion implantation and electron irradiation damage in unstrained germanium and silicon–germanium alloys

The possibility of making devices which use the high hole mobility of Ge and Ge-rich SiGe alloys in mainstream semiconductor technology has drawn attention to the very limited knowledge base regarding ion implantation damage and its removal in germanium. In this paper we present measurements of point defects using deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS on Ge irradiated with γ-rays from a 60Co source or MeV electrons and the ensuing defect reactions which occur during annealing. This is compared with damage induced by MeV Si implantation into Ge at low and high doses and its subsequent removal by furnace annealing. The focus of this work has been on vacancy related defects because of their technological importance. It is well known that the diffusion of both acceptors and donors is vacancy mediated in Ge and so vacancy clusters rather than interstitial clusters are expected to be the technologically significant defects in enhanced diffusion.