High purity and semi-insulating 4H-SiC crystals grown by physical vapor transport

High purity undoped and semi-insulating vanadium doped 4H-SiC single crystals with diameters up to 50 mm were grown by the physical vapor transport method. Undoped crystals exhibiting resistivities in the 10(2) to 10(3) Omega-cm range and photoconductive decay (PCD) lifetimes in the 2 to 9 mu s range, were grown from high purity SiC sublimation sources. The crystals were p-type due to the presence of residual acceptor impurities, mainly boron. The semi-insulating behavior of the vanadium doped crystals is attributed to compensation of residual accepters by the deep level vanadium donor located near the middle of the band gap.