Step bunching mechanism in chemical vapor deposition of 6H– and 4H–SiC0001

Step bunching in chemical vapor deposition of 6H– and 4H–SiC on off-oriented 0001 faces is investigated with cross-sectional transmission electron microscopy. On an off-oriented (0001) Si face, three Si–C bilayer-height steps are the most dominant on 6H–SiC and four bilayer-height steps on 4H–SiC. In contrast, single bilayer-height steps show the highest probability on a (0001̄) C face for both 6H– and 4H–SiC epilayers grown with a C/Si ratio of 2. 0. The increase of C/Si ratio up to 5. 0 induces the formation of multiple-height steps even on a C face. The bunched step height corresponds to the unit cell or the half unit cell of SiC. The mechanism of step bunching is discussed with consideration of surface formation processes.