Anisotropic optical properties of a-axis AlN films: a spectroscopic ellipsometry study

Abstract

We report the uniaxial anisotropic optical constants of wurtzite-type a-axis oriented AlN films deposited on Si (100) using DC reactive magnetron sputtering as a function of growth temperature (Ts, 35 to 600 °C) using the spectroscopic ellipsometry (SE) technique. The thickness and roughness of these films are determined from the regression analysis of SE data, which are corroborated using TEM and AFM techniques. Highly oriented a-axis AlN film grown at 400 °C, exhibits high n and low k at 210 nm (deep-UV region) with small birefringence (−0.01) and dichroism (0.03) near the band edge. All these AlN films exhibit transparent nature from near-infrared (NIR) to 354 nm, where optical band gap energies vary between 5.7 to 6.1 eV.