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

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 $1×1019cm−3$⁠. 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 $VO+SiI→Oi$⁠.