Substrate Engineering of β-Ga2O3 Thin Films on Off-Axis Sapphire for Polarization-Sensitive Solar-Blind UV Photodetector and Encrypted Communication

The solar-blind ultraviolet (UV) spectrum (200-280 nm) offers a unique advantage for secure optical communication due to its negligible background. However, conventional solar-blind systems face limitations in communication distance and channel capacity, constrained by low photodetector responsivity and reliance on intensity modulation. This study addresses these challenges by ing polarization-sensitive detection through anisotropic β-Ga₂O₃ thin films. In this work, we demonstrate films grown via plasma-enhanced chemical vapor deposition (PECVD) on off-aixs sapphire substrates exhibited high crystallinity and optical absorption anisotropy, as confirmed by X-ray diffraction and UV-vis spectroscopy. Metal-semiconductor-metal (MSM) photodetectors fabricated from these films achieved a high responsivity of 16 A/W at 254 nm and demonstrated polarization-sensitive characteristics. Capitalizing on this anisotropy, we implemented a prototype UV-encrypted communication system, showcasing enhanced information capacity through polarization-state modulation. By implementing substrate engineering, this study establishes an innovative pathway to advance solar-blind optoelectronic systems. The developed strategy significantly improves both responsivity and polarization sensitivity in solar-blind UV detection, while simultaneously addressing the critical demands for high-security communication in military and space applications.