Investigations of 3C-SiC inclusions in 4H-SiC epilayers on 4H-SiC single crystal substrates

Synchrotron white beam x-ray topography (SWBXT) and Nomarski optical microscopy (NOM) have been used to characterize 4H-SiC epilayers and to study the character of triangular inclusions therein. 4H-SiC substrates misoriented by a range of angles from (0001), as well as (1 (1) over bar 00) and (11 (2) over bar 0) oriented substrates were used. For epilayers grown on substrates misoriented by 3.5 degrees from (0001) toward < 11 (2) over bar 0 >, the triangular inclusions were identified as consisting of two 3C-SiC structural configurations which are related to each other by a 180 degrees rotation about the [111] axis. The epitaxial relationships between the 3C inclusions and the 4H-SiC epilayers (or substrates) were also determined, No evidence was found for the nucleation of 3C-SiC inclusions at superscrew dislocations (along the [0001] axis) in the 4H-SiC substrates. Increasing the off-axis angle of the substrates from 3.5 to 6.5 degrees was found to greatly suppress the formation of the triangular inclusions. In the case of substrates misoriented by 8.0 degrees from (0001) toward < 11 (2) over bar 0 >, the triangular inclusions were virtually ; eliminated. The crystalline quality of 4H-SiC epilayers grown on the substrates misoriented by 8.0 degrees from (0001) was very good. For the (1 (1) over bar 00) and (11 (2) over bar 0) samples, there is no indication of 3C-SiC inclusions in the epilayers. Possible formation mechanisms and the morphology of 3C-SiC inclusions are discussed.