Enhanced Photoresponse in Interfacial Gated Graphene Phototransistor With Ultrathin Al 2 O 3 Dielectric

An interfacial-gated graphene phototransistor sensitized by silicon substrate with an ultrathin 3-nm Al 2 O 3 dielectric layer is demonstrated. When applying gate voltages larger than a certain threshold, the phototransistor exhibits a photo-induced switching-on behavior, giving rise to its capacity of detecting light with the ultralow power of 470 pW, with a high responsivity of $\textsf {1.4} \times \textsf {10}^{\textsf {4}}$ A/W. The temporal measurements unveil a fast photoresponse speed with a rising time of $2~\mu \text{s}$ . The novel channel on-state trigged by light was not observed in a control device with 16-nm Al 2 O 3 . The difference of transfer characteristics in the dark and under illumination is assigned mainly to the photo-assisted modification of the silicon depletion region.