Graphene-Based Periodic Gate Field Effect Transistor Structures for Terahertz Applications

We report on theoretical investigation of graphene based Field Effect Transistor (FET) structures for resonant absorption of terahertz (THz) radiation by the plasmons excited in the high sheet concentration and high carrier mobility active layers. Metallic grating gates with varying periods were used to couple the THz radiation into the plasmons in the active region of the devices. Such grating gates not only improve the coupling by providing momentum match between the incident radiation and the plasmons but also allows the control of carrier concentration in the channel by external bias. Our studies demonstrate that the proposed periodic gate FET structures of Graphene can resonantly absorb THz radiation up to 6th harmonic at room temperature. Moreover, these structures have the advantage of tunability since the resonant absorption modes strongly depend on the sheet carrier concentration in the channel which could be controlled by gate bias.