ELECTRONIC-STRUCTURE OF ALUMINUM NITRIDE - THEORY AND EXPERIMENT

We report the results of a vacuum ultraviolet (VUV) study of single crystal and polycrystalline AlN over the range 4-40 eV and compare these with theoretical optical properties calculated from first principles using an orthogonalized linear combination of atomic orbitals in the local density approximation. The electronic structure of AlN has a two-dimensional (2D) character indicated by logarithmic divergences at 8.7 and 14 eV. These mark the centers of two sets of 2D critical points which are associated with N 2p --> Al 3s transitions and Al=N --> Al 3p transitions, respectively. A third feature is centered at 33 eV and associated with N 2s --> Al 3d transitions.