Electronic Structure and Optical Properties of YAlN: A First-Principles Study

To reveal the intrinsic relationship between the electronic structure and optical properties of YxAl1-xN alloys, a comparative first-principles study for pure AlN and YxAl1-xN alloys is conducted. In light of the density functional theory, the arrangement of yttrium (Y) atoms in the AlN supercell is first investigated, which demonstrates that the structure of Y atoms distributed locally along the c-axis tends to be energetically favorable, compared with the structures of Y atoms lying on the same ab plane. The lattice parameters, bandgap, density of states, and optical constants are also calculated with varied Y concentration x. The results indicate that the lattice parameters increase with the ascending x, which demonstrates the distortion of the crystal structure. Moreover, the bandgaps of YxAl1-xN are found to be affected by the arrangement of Y atoms but generally with the same trend to become narrowed by the increase in x, respectively. The optical properties of YxAl1-xN alloy are adjustable by the Y concentration x in the low energy regime and correspond to the variation in the bandgaps. The theoretical results are likewise compared with the previously reported experimental data.