Isochronal annealing and the evolution of electron- and proton-induced defects in semi-insulating 4H-type material were investigated by means of positron annihilation. Positron lifetime and Doppler broadening measurements were performed in order to investigate the thermal stability of the radiation-induced defects, and possible clustering mechanisms during isochronal annealing. The as-grown samples contained vacancy-type defects which exhibited a positron lifetime of about 248ps (mean lifetime of 142ps). The observed lifetimes suggested the existence of complexes having a divacancy nature. The concentration of these defects was of the order of 3 x 1016/cm3. A value of 138ps was deduced for the bulk lifetime. The mean lifetime exhibited an increasing dependence upon the radiation dose. The grown-in defects were found to be stable even at 1600C. The annealing behaviour of irradiated semi-insulating samples was quite different to that observed in n-type or p-type samples.

Microstructural Evolution of Radiation-Induced Defects in Semi-Insulating SiC during Isochronal Annealing W.Puff, A.G.Balogh, P.Mascher: Materials Science Forum, 2000, 338-342, 965-8