First principles study on electronic and optical properties of Al_xGa_1−xN and In_yGa_1−yN

The band structure, density of states of Al_xGa_1−xN and In_yGa_1−yN was performed by the first-principles method within the local density approximation. The calculated energy gaps of the AlN, Al_0.5Ga_0.5N, GaN, In_0.5Ga_0.5N and InN were 5.48, 4.23, 3.137, 1.274 and 0.504 eV, which were in agreement with the experimental result. The dielectric functions, absorption coefficient and loss function were calculated based on Kramers–Kronig relations. Further more, the relationships between electronic structure and optical properties were investigated theoretically. For Al_xGa_1−xN and In_yGa_1−yN materials, the micromechanism of the optical properties were explained.