Electronic structure of thin heterocrystalline superlattices in SiC and AlN

The spontaneous polarization, the valence band offset, and the quantum confinement effect for thin SiC and AlN cubic/hexagonal heterocrystalline superlattices are studied by use of a full potential linear muffin-tin orbital method (FP-LMTO). We find that the polarization is screened and suppressed while the length of the cubic region grows. The band offsets do not change with layer thickness. For thin superlattices, the quantum confinement effects dominate and result in a band gap which stays larger than the gap of the bulk cubic structure. Furthermore, the energy levels of the bound states in the quantum well resemble the pattern of the energy levels of conventional III-V based quantum wells and superlattices but at a much smaller length scale, which is due to the higher quantum well depth and the larger effective masses in SiC and AlN systems.