Effects of germanium doping on the behavior of oxygen and carbon impurities and impurity-related complexes in Si

The production and annealing of oxygen and carbon related defects in electron-irradiated Ge-doped Czochralski silicon have been studied by means of IR spectroscopy. The results demonstrate that the role of Ge changes with increasing Ge content. At low Ge concentrations, much less than 1020 cm−3, Ge atoms act as temporary traps for vacancies preventing their annihilation with self-interstitials. At high Ge concentrations, Ge atoms form clusters which tend to attract vacancies and self-interstitials, enhancing their mutual annihilation. As a result, for low Ge concentrations the production of oxygen-related defects (VO) and carbon-related defects (CiOi, CiOi(SiI), CiCs) tend to increase as a function of Ge content, while for high Ge concentrations tend to decrease. The annealing of the oxygen-related defects VOn (1≤n≤6) is also affected by the Ge presence. The ratio of the VO defects that convert to VO2 is reduced in Ge doped material. However, this ratio increases for the conversions VOn→VOn+1 (3≤n≤5), respectively. The annealing temperature of VO defect and the growth temperature of VO2 defect decrease versus Ge content. On the other hand, the thermal stability of the carbon-related defects was found to be insensitive to the presence of Ge. It was also found that the carbon precipitation process shows some marked differences in irradiated Ge-doped Si, in comparison with the undoped material.