DEFECTS IN CZOCHRALSKI-GROWN SILICON-CRYSTALS INVESTIGATED BY POSITRON-ANNIHILATION

Positron lifetime and Doppler broadening experiments were performed on Czochralski-grown silicon crystals. A monoenergetic positron beam was also used to measure the diffusion length of positrons in the wafer. From the measurements, it was observed that the value of diffusion len gth of positrons decreased at the region where microdefects were forme d during the crystal growth process. It was also found that the line s hape parameter S decreased and the lifetime of positrons increased at the region. These results can be attributed to the annihilation of pos itrons trapped by vacancy oxygen complexes which are formed in associa tion with the microdefects.