Electronic and optical properties of rock-salt aluminum nitride obtained from first principles

We investigated the electronic and optical properties of rock-salt aluminum nitride (AlN) using a first-principles method based on the plane-wave basis set. Analysis of the band structure shows that rock-salt aluminum nitride is a wide gap indirect semiconductor. The band gap is predicted to be 5.82 eV within the screened exchange local density approximation (sX-LDA) but to be reduced to 4.23 eV for strained rock-salt AlN corresponding to the experimental lattice constant 4.24 A. The optical properties including the dielectric function, reflectivity and energy-loss function are obtained and analyzed together with some features. The pressure coefficients of the indirect band gaps at the Gamma, X and L points are also calculated, with the value of the smallest indirect band gap determined as 31 meV GPa-1.