Positron lifetime spectroscopy was used to study native vacancy defects in semi-insulating silicon carbide. The material was shown to contain (i) vacancy clusters consisting of 4 to 5 missing atoms and (ii) Si-vacancy-related negatively charged defects. The total open volume bound to the clusters anticorrelated with the electrical resistivity in both as-grown and annealed materials. The results suggested that Si-vacancy-related complexes electrically compensated the as-grown material, but migrated to increase the size of the clusters during annealing; leading to a loss of resistivity.

Clustering of Vacancy Defects in High-Purity Semi-Insulating SiC. R.Aavikko, K.Saarinen, F.Tuomisto, B.Magnusson, N.T.Son, E.Janzén: Physical Review B, 2007, 75[8], 085208 (8pp)