The reduction of extended and point defects, including 8H in-grown stacking faults, basal plane dislocations (BPDs), and Z+(1/2) center, in 4H-SiC epitaxial layers was investigated. In the epitaxial growth process, a high density of 8H stacking faults was evaluated in the epilayer grown under a relatively high partial pressure of SiH_4. By decreasing the SiH_4 partial pressure or adding HC1 to the conventional gas system (H_2+SiH_4+C_3H_8), the 8H stacking fault density was considerably reduced. By using 4° off-cut 4H-SiC substrates instead of an 8° off-cut one, an extremely low BPD density in the epilayer was achieved. No deep levels other than Z_(1/2) and EH_(6/7) centers were detected in the upper half of the bandgap for epilayers grown with the addition of HCl. The Z_(1/2) center concentration was reduced to <1 × 10~(12) cm~(-3) by tuning the growth parameters, and further reduced by the post-growth processes.
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