Self-powered graphene phototransistor with high and tunable responsivity and detectivity

Abstract

A few layers graphene-based phototransistor was fabricated and investigated. Graphene layers were mechanically exfoliated and transferred into a p-doped Si/SiO2 substrate to fabricate a graphene field effect transistor. Gold electrodes were deposited to create a drain and source to the graphene and a back contact gate to the p-doped silicon. The device performance was examined by measuring the current-voltage characteristics in the dark and under illumination. At zero drain voltage bias and room temperature, the device operated and achieved high responsivity and detectivity on the order of 2.7 × 104 A W−1 and 5 × 1012 cm·Hz0.5/W, respectively. A ratio of 29 between the photocurrent and the dark current was achieved. The device shows an excellent tunable photoresponse as a function of the applied back-gate voltage, which indicates the domination of a photogating effect produced by the Si/SiO2 substrate.