Nitrogen donors and deep levels in high-quality 4H–SiC epilayers grown by chemical vapor deposition

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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 (∼1013cm−3) for both samples grown on Si and C faces, indicating high-quality epilayers independent of the substrate polarity.