Defects in epitaxially grown 4H and 6H SiC, induced by He-implantation, were studied by using positron annihilation and deep-level transient spectroscopy. Two major annealing processes of vacancy-type defects appeared at 500 to 800C, and above 1000C, regardless of the polytype and conduction type. In n-type samples, the latter process was dominated by 2 different types of defect. In n-type 6H SiC, Z1/2 levels emerged after annealing at 800C. The Z1/2 levels disappeared around 1100C, with the appearance of E1/2 levels. The E1/2 levels eventually annealed out at 1500 to 1700C. A similar annealing behavior was observed for the corresponding levels in n-type 4H SiC: that is, RD1/2 and Z1/2 levels. Positron annihilation and deep-level data on the overall annealing behavior of vacancy-type defects were in good agreement above 800C; thus suggesting that the deep levels were related to the vacancy-type defects.

Vacancies in He-Implanted 4H and 6H SiC Epilayers Studied by Positron Annihilation. A.Kawasuso, M.Weidner, F.Redmann, T.Frank, P.Sperr, R.Krause-Rehberg, W.Triftshäuser, G.Pensl: Physica B, 2001, 308-310, 660-3