Defect structures of B₁₂As₂ epilayers grown on c-plane and a-plane 6H-SiC substrates

B₁₂As₂ epitaxial layers grown on (0001) 6H-SiC and (112̄0) 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 structure visualization software. SWBXT showed that B ₁₂As₂ adopted [111] growth orientation, parallel to [0001]_SiC, on c-plane 6H-SiC and adopted [101̄] growth orientation, parallel to [112̄0 ]_SiC, on a-plane 6H-SiC However, SWBXT also revealed 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, the latter being consistent with the result reported by Michael etc[1]. By correlating the HRTEM observations and crystal structure visualization, the atomic configurations across the twin boundaries in both samples as well as those in the intermediate layer in the c-plane sample are proposed.