Effect of germanium doping on the annealing characteristics of oxygen and carbon-related defects in Czochralski silicon

Abstract

This paper is devoted to the annealing studies of defects produced in carbon-rich Ge-doped Czochralski-grown Si (Cz-Si) by 2 MeV electron irradiation. The annealing temperature of vacancy-oxygen (VO) complexes, carbon interstitial-oxygen interstitial (CiOi), and carbon interstitial-carbon substitutional (CiCs) pairs as well as the formation temperature of vacancy-two oxygen (VO2) complexes are monitored as a function of Ge concentration. It has been established that the annealing of CiOi and CiCs defects remains practically unaffected by the Ge presence, whereas the annealing temperature of VO defects and the formation temperature of VO2 complexes are substantially lowered at Ge concentrations larger than 1×1019 cm−3. The hydrostatic component of elastic strains introduced by Ge atoms in the Si crystal lattice was calculated. It appears to be very small, at least insufficient to exert a pronounced effect upon the annealing behavior of radiation-produced defects. This conclusion is in line with what is observed for the CiOi and CiCs species. In the case of VO, whose annealing process in Cz-Si is concurrently conducted by two reaction paths VO+Oi→VO2 and VO+SiI→Oi, we suggest that the latter reaction in Ge-doped Cz-Si is enhanced by emitting self-interstitials (SiI) from loosely bound self-interstitial clusters predominantly formed around Ge impurity atoms. As a result, the liberation of self-interstitials at lower annealing temperatures leads to an enhanced annealing of VO defects. An enhanced formation of VO2 complexes at lower temperatures is also discussed in terms of other reactions running in parallel with the reaction VO+SiI→Oi.