The defects which were introduced into epitaxially grown 3C-type material, by implantation of 200keV N2+ or Al+ to doses of between 1013 and 1016/cm2 at temperatures ranging from ambient to 1200C, were studied by using electron spin resonance, photoluminescence and positron annihilation spectroscopy. It was found that, although hot-implantation reduced the number of paramagnetic defects and improved the crystallinity of implanted layers, it led to the simultaneous formation of vacancy clusters. Small vacancy clusters were produced mainly by low-dose (1013/cm2) implantation, and larger vacancy clusters were formed by high-dose (1015/cm2) implantation. The average size of such clusters increased with implantation temperature. Formation of the vacancy clusters was independent of the nature of the implanted ion species. All of the results were explained in terms of the migration and combination of point defects such as vacancies and interstitials during hot-implantation. In the case of high-dose Al+-implantation, additional paramagnetic defects with g = 2.0035 were formed by implantation above about 800C; thus suggesting that this defect was related to the precipitation of Al atoms. It was suggested that the g = 2.0035 defect acted as a non-radiative recombination center. This defect was thought to be unrelated to vacancy-type defects. Very large vacancy clusters were created by annealing samples which had been amorphized by high-dose (1015/cm2) implantation at room temperature, whereas such further vacancy clustering did not occur in hot-implanted samples.

H.Itoh, T.Ohshima, Y.Aoki, K.Abe, M.Yoshikawa, I.Nashiyama, H.Okumura, S.Yoshida, A.Uedono, S.Tanigawa: Journal of Applied Physics, 1997, 82[11], 5339-47