Highly Polarization-Deep-Ultraviolet-Sensitive β-Ga 2 O 3 Epitaxial Films by Disrupting Rotational Symmetry and Encrypted Solar-Blind Optical Communication Application.

Ultrawide bandgap semiconductor β-Ga 2 O 3 (4.9 eV), with its monoclinic crystal structure, exhibits distinct anisotropic characteristics both optically and electrically, making it an ideal material for solar-blind polarization photodetectors. In this work, β-Ga 2 O 3 epitaxial films were deposited on sapphire substrates with different orientations, and the mechanisms underlying the anisotropy of these epitaxial films were investigated. Compared to c-plane sapphire, the lattice mismatch between m- or r-plane sapphire and β-Ga 2 O 3 is more pronounced, disrupting the rotational symmetry of the films and rendering them anisotropic. Thanks to the improved anisotropy, the polarization ratio of the photodetector based on β-Ga 2 O 3 films grown on r-plane substrates is 0.24, nearly ten times higher than that on c-plane substrates. Finally, by utilizing these polarization-sensitive photodetectors, we developed an encrypted solar-blind ultraviolet optical communication system. Our work provides a new approach to facilitate the fabrication and application of high-performance polarization-sensitive solar-blind photodetectors.