6H- and 4H-silicon carbide for device applications

4H- and 6H-SiC crystals with the values of N_d-N_a from 5 10¹⁸ cm^-3 to less than 2 10¹⁵ cm^-3 have been grown. Material with high resistivity is of great importance for high temperature electronics and other severe environment electronics based on silicon carbide as well as nitride-based electronics. Optical absorption of the samples became significant from the values of N_d-N_a higher than 10¹⁷ cm^-3. The samples with the values of N_d -N_a higher than 10¹⁸ cm^-3 are practically nontransparent in the IR region for wavelengths higher than 2 micrometers. The samples with low N_d-N_a values are practically transparent over entire visible range and IR range up to 5 μm. Such optically transparent crystals are of great importance for radiation-hardened, high operation temperature windows and transparent substrates for optoelectronic devices. Cathodoluminescence (surface mapping and spectroscopy), PL mapping, IR absorption/reflection spectroscopy, X-ray topography and optical microscopy have been employed for investigations of the 4H- and 6H-SiC crystals grown by sublimation method and results of the investigations are compared