Enhanced Photoresponse in Interfacial Gated Graphene Phototransistor With Ultrathin Al2O3 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 1.4 × 10
⁴
A/W. The temporal measurements unveil a fast photoresponse speed with a rising time of 2 μs. 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.