Deep Ultraviolet Optical Anisotropy of β-Gallium Oxide Thin Films

β-Crystalline phase gallium oxide (β-Ga₂O₃) is an ultrawide bandgap material with prospective applications in electronics and deep ultraviolet (DUV) optoelectronics and optics. The monoclinic crystal structure of β-Ga₂O₃ results in optical anisotropy to incident light with different polarization states. This attribute can lead to different optical applications in the DUV. In this article, we investigated the optical properties of β-Ga₂O₃ thin films grown by pulsed laser deposition technique on sapphire substrates with different crystallographic orientations. Marked in-plane polarization anisotropy, determined by reflectance and Raman spectroscopy, was observed for β-Ga₂O₃ films deposited on an r-cut sapphire substrate. In contrast, isotropic optical properties were observed in β-Ga₂O₃ films deposited on a c-cut sapphire substrate.