Graphene nanoribbon phototransistor: Proposal and analysis

We consider a concept of a graphene nanoribbon phototransistor (GNR-PT) based on an array of GNRs operating as a photodetector of far-infrared (FIR) and terahertz (THz) radiation. The photodetector has the structure of a GNR field effect transistor with the back and relatively short top gates. To calculate the GNR-PT characteristics, we develop an analytical model of the device. This model generalizes the model we proposed previously by accounting for the possibility of not only the thermionic regime but also the tunneling regime of the GNR-PT operation. Using the developed model, we derive analytical formulas for the source-drain current as a function of the intensity and frequency of the incident radiation and bias voltages, and estimate the detector responsivity. The obtained formulas can be used for detector optimization by varying the dark current, photoelectric current gain, and voltage control of the spectral properties. The dependences of the absorption edge on GNR width and bias voltages can be utilized for the development of multicolor voltage tunable FIR/ THz photodetectors.