Characterization of high-quality 4H-SiC epitaxial layers

4H-SiC epilayers grown by chemical vapor deposition were characterized by admittance spectroscopy, low-temperature photoluminescence, and deep level transient spectroscopy. The activation energies of the N donors were estimated to be 40 similar to 50meV at hexagonal and 109meV at cubic sites from admittance spectroscopy. In low-temperature photoluminescence, the N bound exciton peaks were dominant, however, free exciton peaks were also observed. DLTS measurements revealed a low concentration of electron traps (similar to 10(13)cm(-3)) for both samples grown on Si and C faces, indicating high quality epilayers independent of the substrate polarity.