Solar-blind ultraviolet photodetectors with thermally reduced graphene oxide formed on high-Al-content AlGaN layers

Solar-blind deep-ultraviolet (UV) photodetectors (PDs) with high responsivity and fast response have attracted significant attention in environmental, industrial, biological, and military applications. AlGaN is a representative semiconductor material in the field of solar-blind detection; semiconductor performance can be accelerated by combining it with high-transparency, high-stability contact electrode materials. In this study, solar-blind deep-UV metal–semiconductor–metal (MSM) PDs were fabricated based on two-dimensional reduced graphene oxide (rGO) contacts formed on various high-Al-content AlGaN semiconductors. A low dark current in the order of a few picoamperes and a fast photoresponse time of a few tens of milliseconds were confirmed. The investigation of the effects of front- and back-side illumination showed that the photocurrents and corresponding responsivities of the PDs drastically improved under back-side illumination. In detail, the peak locations of the responsivity–wavelength curves were downshifted from 290 nm with a responsivity of 0.0518 A/W for the rGO/Al0.5Ga0.5N MSM PD to 250 nm with a responsivity of 0.0113 A/W for the rGO/Al0.7Ga0.3N MSM PD under back-side illumination. These results indicate that rGO contacts on AlGaN provide a viable approach for developing solar-blind deep-UV PDs.