Nanoplasmonically Enhanced High-Performance Metastable Phase α-Ga₂O₃ Solar-Blind Photodetectors

In this work, nanoplasmonically enhanced α-Ga₂O₃ solar-blind photodetectors with an interdigital structure were fabricated on sapphire. By introducing Al nanoparticles (NPs) onto the device surface, the photodetector obtained a significant increase in responsivity at the solar-blind region, and the response peak located at 244 nm reached 3.36 A/W under an applied voltage of 5 V. Compared with the responsivity at 320 nm, the response ratio exceeds 240, demonstrating a superior solar-blind cut-off edge. It also presents that the photocurrent was dramatically increased under 254 nm ultraviolet irradiation for the enhanced device while the dark current remains below 1 pA at 20 V. To explicitly elucidate the enhancement effects by Al NPs under ultraviolet illumination, Kelvin probe force microscopy was employed and directly revealed the physical mechanism of surface plasmon oscillation, which promoted the formation of localized electric fields on α-Ga₂O₃. In addition, we illustrated the effects of interdigital spacing on device performances through experimental measurements and theoretical calculations. These results not only provide direct evidences for Al nanoplasmonic enhancement on the α-Ga₂O₃ device but also facilitate design and fabrication of solar-blind photodetectors.