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-Ga2O3 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 × 105. 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.