Growth mechanisms and defect structures of B12As2 epilayers grown on 4Â H-SiC substrates

► Epitaxial growth of icosahedral B12As2 on c-plane 4H-SiC substrates has been analyzed. ► Twinned B12As2 was revealed on on-axis c-plane 4H-SiC substrates. ► B12As2 grown on c-plane 4H-SiC misoriented from (0001) to [1-100] is shown to be free of twinning. ► Vicinal steps formed by hydrogen etching on off-axis 4H-SiC cause the film to adopt a single orientation. ► C-plane 4H-SiC offcut toward [1-100] is a good substrate for the growth of single crystalline B12As2.