Radiation-induced defects in Ge- and Sn-doped n-type Si

Because of the relatively high anneal temperature of the SnV defect, Sn-doping has been considered a better candidate for the production of radiation-hardened Si than Ge-doping. It was left, however, to be demonstrated that Sn does not introduce harmful defects. In this report we present results from recent DLTS studies of vacancy-related defects in Ge- and Sn-doped, n-type Si. SnV is found to have two acceptor levels in the upper half of the band gap; of these the mid-gap level might be harmful. GeV has only one acceptor level in the upper-half of the band gap. The GeV pair is stable to a temperature of about 320 K when singly negatively charged and unstable at room temperature when doubly negatively charged. Hence, although Ge's efficiency for trapping vacancies is small, GeV might still be stable enough to make Ge an interesting impurity with respect to radiation hardening of Si.