An On-Chip Amplitude and Frequency Modulating Graphene-based Plasmonic Terahertz Signal Nano-Generator

Abstract

An on-chip modulator-integrated graphene-based plasmonic nanogenerator that operates in the terahertz band is presented. The device is based on a gated High Electron Mobility Transistor (HEMT). The use of graphene as the 2-Dimensional Electron Gas (2DEG) channel allows room temperature operation of large plasmonic oscillations which are highly tunable over a broad frequency range (1 to 2 THz). By implementing asymmetric boundary conditions at the source and drain, known as the Dyakonov-Shur (DS) instability, accelerated electrons excite plasmonic waves which reflect at the drain side of the channel. This induces Surface Plasmon Polariton (SPP) waves on the gate, which results in electromagnetic radiation in the THz region. By dynamically tuning these boundary conditions, the device operates with an integrated modulator. The device is numerically modeled and analyzed using an in-house developed multi-physics finite-difference platform based on the Hydrodynamic Model (HDM) for ballistic transport and Maxwell's equations for calculating the electromagnetic fields. After steady state is reached, the numerical analysis shows a clean waveform is possible with amplitude and frequency modulation capabilities. This device offers for the first time and in a compact form factor integrated generation, modulation and radiation functionalities.