Graphene bilayer field-effect phototransistor for terahertz and infrared detection

A graphene bilayer phototransistor (GBL-PT) is proposed and analyzed. The GBL-PT under consideration has the structure of a field-effect transistor with a GBL as the channel sandwiched between the back and the top gates. The positive bias of the back gate creates the conducting source and drain sections in the channel, while the negatively biased top gate provides the potential barrier which is controlled by the charge of the photogenerated holes. The features of the GBL-PT operation are associated with the variation in both the potential distribution and the energy gap in different sections of the channel when the gate voltages change. Using the developed GBL-PT device model, the spectral characteristics, dark current, responsivity, photoelectric gain, and detectivity are calculated as functions of the applied voltages, energy of incident photons, intensity of electron and hole scattering, and geometrical parameters. It is shown that the GBL-PT spectral characteristics are voltage tuned. The GBL-PT performance as a photodetector in the terahertz and infrared regions of the spectrum can markedly exceed the performance of other photodetectors.