Relaxation mechanism of the defect-free 3C-SiC epitaxial films grown on step-free 4H SiC mesas

Cross-sectional transmission electron microscopy (TEM) was used to investigate the extended defects in 3C-SiC films deposited on atomically flat 4H-SiC mesas. The nominal layer thickness was 10 mu m and was considerably larger than the critical thickness determined by either the Matthews and Blakeslee or People and Bean models. Threading dislocation densities determined by KOH etching are far below densities typical of relaxed heteroepitaxial layers, down to as low as 10(4)cm(-2) densities found in 4H-SiC. Misfit dislocations with Burgers vectors of <11<(2)over bar>0> were observed in planes parallel to the 3C/4H SiC interface. These defects were interpreted as due to nucleation of dislocation half loops at mesa edges and glide along the 3C/4H interface.