Band Gap Behaviors of (α-GaN) / (α-AIN) Superlattice and (β-GaN)/(β- A1N) Superlattice

By using an ab initio calculation, it is found that the variation of the fundamental band gap of (α-GaN)_n / (α-AlN))_n (0001) superlattices is remarkably different from that of (β-GaN))_n / (β- A1N))_n (001) superlattices. The difference in band gap behaviors was shown to be due to the internal electric fields induced by the spontaneous polarizations in α-GaN and α-AlN. In addition, the valence-band offsets at the interfaces of these superlattices are also determined. The results are in good agreement with those available from experimental data.