POSITRON-ANNIHILATION STUDIES OF DEFECTS IN 3C-SIC HOT-IMPLANTED WITHNITROGEN AND ALUMINUM IONS

Monoenergetic positron beams were used to study defects introduced in cubic silicon carbide (3C-SiC) by implantation of 200 keV-N-2(+) and A l+ at temperatures from room temperature (RT) to 1200 degrees C at dos es of 10(13) and 10(15)/cm(2). It is found from Doppler broadening spe ctra of annihilation gamma-rays obtained by varying the incident posit ron energy that hot-implantation gives rise to clustering of vacancies , whereas it suppresses amorphization and diminishes the thickness of damaged layers. The average size of such clusters increases with incre asing implantation dose and temperature. Vacancy clustering by hot-imp lantation can be interpreted by the combination of vacancies during im plantation. Vacancy type defects in the low-dose (10(13)/cm(2)) implan ted samples are found to be removed by annealing at 1400 degrees C, wh ereas large vacancy clusters still remain after 1400 degrees C anneali ng in the high-dose (10(15)/cm(2)) implanted samples. It is also deriv ed from the depth profile of positron diffusion length that positron s cattering centers are produced after annealing at 1400 degrees C in al l implanted samples.