Electronic structures and band offsets of heterocrystalline superlattices (3C-AlN${)}_{3\mathit{n}}$/(2H-AlN${)}_{2\mathit{n}}$ and (3C-SiC${)}_{3\mathit{n}}$/(2H-SiC${)}_{2\mathit{n}}$ (n=1,2,3)

The electronic structures and the band offsets of heterocrystalline superlattices (3C-AlN${)}_{3\mathit{n}}$/(2H-AlN${)}_{2\mathit{n}}$ and (3C-SiC${)}_{3\mathit{n}}$/(2H-SiC${)}_{2\mathit{n}}$ (n=1, 2, and 3) are studied by ab initio calculations. The results indicate that the band lineups at both (3C-SiC)/(2H-SiC) and (3C-AlN)/(2H-AlN) interfaces are of type-II with small valence-band offsets and large conduction band offsets. The effects of lattice relaxation on the band offsets of the (3C-AlN)/(2H-AlN) system are also investigated. It is found that the band gaps of the heterocrystalline superlattices decrease rapidly with the increase of the slab thickness. This abnormal band-gap behavior is shown to be related to the internal electric fields induced by the intrinsic spontaneous polarization of the 2H structures. © 1996 The American Physical Society.