High-frequency and below bandgap anisotropic dielectric constants in α-(AlxGa1-x)2O3 (0 ≤ x ≤ 1)

A Mueller matrix spectroscopic ellipsometry approach was used to investigate the anisotropic dielectric constants of corundum alpha-(AlxGa1-x)(2)O-3 thin films in their below bandgap spectral regions. The sample set was epitaxially grown using plasma-assisted molecular beam epitaxy on m-plane sapphire. The spectroscopic ellipsometry measurements were performed at multiple azimuthal angles to resolve the uniaxial dielectric properties. A Cauchy dispersion model was applied, and high-frequency dielectric constants are determined for polarization perpendicular (epsilon(infinity,perpendicular to)) and parallel (epsilon(infinity,parallel to)) to the thin film c-axis. The optical birefringence is negative throughout the composition range, and the overall index of refraction substantially decreases upon incorporation of Al. We find small bowing parameters of the highfrequency dielectric constants with b(perpendicular to) = 0:386 and b(parallel to) = 0:307. Published under an exclusive license by AIP Publishing.

Automated summary

In this study, an anisotropic dielectric constant investigation of corundum alpha-(AlxGa1-x)(2)O-3 thin films was conducted using Mueller matrix spectroscopic ellipsometry in below bandgap spectral regions. The high-frequency dielectric constants and Cauchy dispersion model were applied to determine the optical properties, showing negative optical birefringence and decreased refractive index upon Al incorporation. Bowing parameters of the dielectric constants were found to be small, indicating subtle changes with composition.