Construction of a Fully Transparent Back-Illuminated Ga₂O₃ Polarization Detection Experimental System for Non-Line-of-Sight Communication Applications

To meet the urgent demand for high-performance photodetectors in emerging solar-blind ultraviolet communication applications, this study systematically designed and implemented a fully transparent β-Ga₂O₃ solarblind photodetector based on a back-illumination architecture. The device was fabricated using RF magnetron sputtering to epitaxially grow highquality β-Ga₂O₃ films (~300 nm thickness, bandgap ~4.98 ± 0.05 eV) on double-polished sapphire substrates, with indium tin oxide (ITO) interdigitated electrodes forming efficient quasi-Ohmic contacts with ntype Ga₂O₃. The core advantage of this design lies in exploiting the high deep-UV transmittance of double-polished sapphire substrates, enabling incident photons to completely bypass the UV-absorbing ITO electrodes and eliminate photon loss caused by electrode shadowing effects in conventional front-illumination configurations. Consequently, the device demonstrates exceptional optoelectronic performance: a maximum responsivity of 0.46 A/W corresponding to an external quantum efficiency of 222.4%, an outstanding UV/visible rejection ratio of 1.2×10⁴, a minimum noise equivalent power of 1.52 pW/Hz1/2, and a peak specific detectivity of 1.39×10¹¹ Jones, with fast response times of 24 μs (rise) and 1.24 ms (decay). Building upon this high-performance detector platform, we further explored its multifunctional application potential by constructing polarization detection systems that exploit the intrinsic lattice anisotropy of monoclinic β-Ga₂O₃, and successfully demonstrating a nonline-of-sight (NLOS) UV communication system that validates highfidelity information transmission in complex scattering channels. This research provides effective physical insights and experimental foundations for developing next-generation Ga₂O₃-based optoelectronic devices with integrated high sensitivity, polarization resolution, and NLOS communication capabilities, showing promising applications in secure communications and polarization imaging.