Bulk AlN-SiC mixed single crystals are prepared by sublimation growth employing pure AlN or mixed AlN-SiC sources and 6H-SiC seed crystals. As the growth temperature is increased from 1900 to 2050 degrees C, using seeds with different off-axis orientations, inclined up to 42 degrees from the basal plane toward the (0 1 - 1 0)-plane, or using different source materials, crystals with different Si/C contents are obtained. Dependent on the Si and/or C content, crystal coloration changes from yellowish to greenish to blackish. Modification in crystals' coloration and corresponding changes in below band-gap optical absorption and cathodoluminescence spectra are discussed. (C) 2010 Elsevier B.V. All rights reserved.