Abstract: A photoconductive ultraviolet detector has been fabricated on the surface of a Al_0.1Ga_0.9N film deposited by metalorganic chemical vapor deposition（MOCVD）.The UV detector presents a peak response of 1 050 A/W at wavelength of 345 nm,which indicates the band gap of the Al_0.1Ga_0.9N film was successfully regulated to 3.6 eV.Persistent photoconductivity（PPC）phenomenon was also observed in the time response measurement,appearing as prolonged response time.However,trapping effect may play an important role in reducing the carrier recombination rate and prolonging the carrier lifetime,resulting in the high responsivity in this work.Such a high responsivity UV detector has a potential application of high sensitivity detection.