The growth,fabrication and characteristics of AlGaN/GaN PIN solar-blind ultraviolet photodetectors with back-illumination are reported.The spectral responsivity and current-voltage characteristics of photodetectors were measured by the ultraviolet spectroscopy testing system and Keithley 4 200 semiconductor characterization system,respectively.The peak responsivity of photodetectors is about 0.055 A/W at 270 nm under 2.5 V reverse bias voltage.The dark current of the 1 500 μm-diameter devices is...