Optical properties of AlN determined by vacuum ultraviolet spectroscopy and spectroscopic ellipsometry data

Precise and accurate knowledge of the optical properties of aluminum nitride (AlN) in the ultraviolet (UV) and visible (VIS) regions is important because of the increasing application of AlN in optical and electro-optical devices, including compact disks, phase shift lithography masks, and AlN/GaN multilayer devices. The interband optical properties in the vacuum ultraviolet (VUV) region of 6–44 eV have been investigated previously because they convey detailed information on the electronic structure and interatomic bonding of the material. In this work, we have combined spectroscopic ellipsometry with UV/VIS and VUV spectroscopy to directly determine the optical constants of AlN in this range, thereby reducing the uncertainty in the preparation of the low-energy data extrapolation essential for Kramers–Kronig analysis of VUV reflectance. We report the complex optical properties of AlN, over the range of 1.5–42 eV, showing improved agreement with theory when contrasted with earlier results.