A near-thermal-equilibrium process has been used to grow 15R-SiC bulk single crystals by the modified Lely method. The 15R-SiC growth can only be stabilized if stoichiometric SiC source material is used. Crystals grown on the Si-face at temperatures between 2150 degreesC and 2180 degreesC are free of inclusions of different polytypes and without micropipes. The incorporation of nitrogen and boron depends on the polarity of the seed crystal face. Three deep defect centers (W-1, W-2,W-3) have been observed by deep level transient spectroscopy (DLTS) in 15R-SiC crystals.