Anomalous Photovoltaic Response of Graphene-on-GaN Schottky Photodiodes

Graphene has attracted great attention as an alternative to conventional metallic or transparent conducting electrodes. Despite its similarities with conventional electrodes, recent studies have shown that a single-atom layer of graphene possesses unique characteristics, such as a tunable work function and transparencies for electric potential, reactivity, and wetting. Nevertheless, a systematic analysis of graphene and semiconductor junction characteristics has not yet been carried out. Here, we report the photoresponse characteristics of graphene-on-GaN Schottky junction photodiodes (Gr–GaN SJPDs), showing a typical rectifying behavior and distinct photovoltaic and photoelectric responses. Following the initial abrupt response to UV illumination, the Gr–GaN SJPDs exhibited a distinct difference in photocarrier dynamics depending on the applied bias voltage, which is characterized by either a negative or positive change in photocurrent with time. We propose underlying mechanisms for the anomalous photoca...