| Summary: | Graphene on top of semiconductor builds an emerging highly sensitive photodetector with internal gain. Owing to the graphene/semiconductor interface junction, one kind of photo-excited carriers are drifted to graphene and the other carriers remain in the semiconductor. The decisive factor for the gain is the localization extent of the non-transporting carriers. Several localization strategies such as Schottky barrier regulation, introducing localized states, quantum dot confinement, and double heterojunction design are reviewed. Despite the high sensitivity, the accompanying persistent photocurrent limits the response speed. The long-wavelength light acceleration and the back-gate voltage acceleration methods are utilized to effectively eliminate the persistent photocurrent.
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