IRRADIATION-INDUCED ATOMIC DEFECTS IN SIC STUDIED BY POSITRON-ANNIHILATION

The present paper reports on positron lifetime measurements on atomic defects in SiC after low-temperature (80 K) electron irradiation of lo w (0.47 MeV) and high (2.5 MeV) electron energies and doses from 1.8 x 10(17) to 1.9 x 10(19) e/cm(2) as well as after subsequent isochronal annealing up to 1900 K. For these studies the single crystals of nitr ogen doped (2-3 x 10(18) cm(-3)) SiC grown by a modified Lely techniqu e with hexagonal structure (6H polytype) were used. According to the p ositron lifetime measurements, very different types of vacancy-like po sitron traps are introduced after irradiation with electrons of either low or high energy. The formation of defect agglomerates and their de cay at high temperatures is studied during isochronal annealing and re lated to earlier studies.