NITROGEN DONORS AND DEEP LEVELS IN HIGH-QUALITY 4H-SIC EPILAYERS GROWN BY CHEMICAL-VAPOR-DEPOSITION

4H-SiC epilayers grown by chemical vapor deposition were characterized by Hall effect, admittance spectroscopy, low-temperature photoluminescence, and deep level transient spectroscopy (DLTS). The nitrogen (N) donor activation energies were estimated as 45-65 meV at hexagonal and 105-125 meV at cubic sites from Hall effect investigations in agreement with the data taken by 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 cm high-quality epilayers independent of the substrate polarity. (C) 1995 American Institute of Physics.