An investigation was made of Al- and B-implanted 4H-type samples by using secondary ion mass spectroscopy, low-temperature photoluminescence, Hall-effect and positron annihilation spectroscopy methods. In B-implanted samples, marked diffusion was observed towards the inside and surface during post-annealing at 1700C. This did not occur in Al-implanted samples. A luminescence at 427.2nm, which was independent of the dopant species and the annealing temperature, originated from the so-called D1 centre which was introduced by implantation and post-annealing. The positron lifetime (216ps) in both Al and B as-implanted samples was in good agreement with the theoretical lifetime (214ps) for positrons which were localized at a Si-C di-vacancy. The positron lifetimes of post-annealed samples (148, 147, 149ps) were located between that for a virgin sample (144ps) and the theoretical lifetime of a positron which was localized at a C vacancy (153ps). It was proposed that a defect of di-interstitial or di-vacancy type predominated in post-annealed samples.

Electrical and Structural Properties of Al and B Implanted 4H-SiC. Y.Tanaka, N.Kobayashi, H.Okumura, R.Suzuki, T.Ohdaira, M.Hasegawa, M.Ogura, S.Yoshida, H.Tanoue: Materials Science Forum, 2000, 338-342, 909-12