Giant responsivity of a new optically controlled graphene UV-phototransistor using graded band-gap ZnMgO gate

Abstract In this work, a new Ultraviolet Optically Controlled Graphene Field-Effect Transistor (UV-OC-GFET) based on Graded Band-Gap (GBG) ZnMgO photosensitive-gate is proposed. The device drain current model is numerically developed by self-consistently solving the Schrodinger/Poisson equations based on non-equilibrium Green's function (NEGF) formalism. The influence of GBG strategy with different profiles on the device sensing performances is analyzed. Our investigation reveals that the use of both GBG ZnMgO photo-gate and graphene nanoribbon channel offers the dual-benefit of improved electric field distribution in the photosensitive layer and enhanced drain current. This leads to outperforming the device Figure of Merits (FoMs). In this context, it is found that the proposed UV sensor with optimized band-gap profile exhibits giant responsivity exceeding 1.5 × 106 A/W with superb detectivity of 7 × 1014 Jones, far surpassing that of the conventional Si-channel based phototransistors. Therefore, this innovative strategy based on graphene nanoribbon channel combined with GBG sensitive-gate pinpoints a new path towards achieving high-performance visible-blind UV-phototransistor, making it a potential alternative photoreceiver for chip-level optical communication and optoelectronic applications.