Electrical data obtained from deep level transient spectroscopy investigations on deep defect centers in the 3C, 4H, and 6H SiC polytypes are reviewed. Emphasis is put on intrinsic defect centers observed in as‐grown material and subsequent to ion implantation or electron irradiation as well as on defect centers caused by doping with or implantation of transition metals (vanadium, titanium, chromium, and scandium).

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.

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The fabrication of 3C-SiC and 6H-SiC pn junction diodes, grown side by side on low-tilt-angle 6H-SiC substrates via a chemical vapor deposition (CVD) process, has recently been reported. Admittance spectroscopy and deep-level transient spectroscopy (DLTS) measurements were made on one of these diodes to compare the defect structure of 3C- and 6H-SiC CVD epitaxial layers grown under the same conditions. The 6H-SiC layers revealed a single minority carrier level and a deeper broad majority carrier peak. The minority level is due to the boron-related D center, whereas the broad majority level was identified as a double peak by a DLTS simulation. DLTS measurements on the 3C-SiC layers revealed only one deep level impurity consistent with the boron-related D center. Shallow donor levels observed using admittance spectroscopy correspond with the known shallow nitrogen donor in both 3C- and 6H-SiC epitaxial layers. This confirms that both 3C- and 6H-SiC polytypes were simultaneously formed on the same 6H-SiC substrate.