The dependence of the single-crystalline yield on the thermal field during physical vapour transport growth of SiC was investigated systematically. It is shown that the development of a flat faceted growth interface improves crystal quality but restrains enlargement of the single-crystalline part in the grown SiC boules. A highly convex interface shape allows effective enlargement but leads to enhanced generation of defects. Modifications of the growth process were made to separately control the thermal field at the periphery of the growing SiC boules and in the central area. With proper tailoring of the temperature gradient, an enlargement of the single-crystalline part from 35 to 45 mm in diameter was achieved within one growth run. The idea can be extended to larger diameters as well. (C) 2003 Elsevier B.V. All rights reserved.