Vacancy-Nitrogen Complexes in Float-Zone Silicon

The influence of nitrogen on vacancy reactions during float-zone (FZ) crystal growth and during subsequent inert diffusion steps in the range from 650 to 1000°C was investigated. Using platinum diffusion for characterization, much higher concentrations of vacancies were found in nitrogen-doped crystals than in crystals not intentionally doped with nitrogen. A likely reason is that nitrogen forms complexes with vacancies which immobilize them but which can be broken up and decorated by platinum interstitials. During inert anneals the vacancy-nitrogen complexes were found to transform into defects which are not as easily decorated by platinum atoms. This result was also confirmed by experiments in which the temperature of the platinum-diffusion process was varied from 680 to 800°C.