Impact of cation-based localized electronic states on the conduction and valence band structure of Al_1−xIn_xN alloys

We demonstrate that cation-related localized states strongly perturb the band structure of Al_1−xIn_xN leading to a strong band gap bowing at low In content. Our first-principles calculations show that In-related localized states are formed both in the conduction and the valence band in Al_1−xIn_xN for low In composition, x, and that these localized states dominate the evolution of the band structure with increasing x. Therefore, the commonly used assumption of a single composition-independent bowing parameter breaks down when describing the evolution both of the conduction and of the valence band edge in Al_1−xIn_xN.