B12As2 epitaxial layers grown on (0001) 6H-SiC and (1120) 6H-SiC substrates have been studied using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and synchrotron white beam x-ray topography (SWBXT) and investigated with the aid of crystal visualization software. SWBXT showed that B12As2 adopted  growth orientation, parallel to SiC, on c-plane 6H-SiC and adopted  growth orientation, parallel to SiC, on a-plane 6H-SiC. However, SWBXT also revealed the twins in both sets of the B12As2 films, consistent with the SEM observation of the surface morphology. Cross-sectional HRTEM also confirmed the presence of twins in both cases and also revealed the existence of an intermediate layer between the c-plane 6H-SiC and the B12As2 film. By correlating the HRTEM observation and crystal visualization, the atomic configurations across the twin boundaries in both samples as well as those in the intermediate layer in the c-plane sample were proposed.