A broadband self-powered UV photodetector of a β-Ga2O3/γ-CuI p-n junction

The symmetric Ti/Au bi-layer point electrodes have been successfully patterned on the β -Ga 2 O 3 films which are prepared by metal–organic chemical vapor deposition (MOCVD) and the γ -CuI films which are prepared by spin-coating. The fabricated heterojunction has a large open circuit voltage ( V oc ) of 0.69 V, desired for achieving self-powered operation of a photodetector. Irradiated by 254-nm ultraviolet (UV) light, when the bias voltage is –5 V, the dark current ( I dark ) of the device is 0.47 pA, the photocurrent ( I photo ) is –50.93 nA, and the photo-to-dark current ratio ( I photo / I dark ) reaches about 1.08 × 10 5 . The device has a stable and fast response speed in different wavelengths, the rise time ( τ r ) and decay time ( τ d ) are 0.762 s and 1.741 s under 254-nm UV light illumination, respectively. While the τ r and τ d are 10.709 s and 7.241 s under 365-nm UV light illumination, respectively. The time-dependent ( I – t ) response (photocurrent in the order of 10 −10 A) can be clearly distinguished at a small light intensity of 1 μW⋅cm −2 . The internal physical mechanism affecting the device performances is discussed by the band diagram and charge carrier transfer theory.