Thick 4H-SiC Epitaxial Growth and Defect Reduction for Very High Voltage Bipolar Devices

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 HCl to the conventional gas system (H 2 +SiH 4 +C 3 H 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.