Resonant THz detection by periodic multi-gate plasmonic FETs

We show that a periodic multi-grated-gate structure can be applied to THz plasmonic FETs (TeraFETs) to improve the THz detection sensitivity. The introduction of spatial non-uniformity by separated gate sections creates regions with distinct carrier concentrations and velocities, giving rise to harmonic behaviors. The resulting frequency spectrum of DC voltage response is composed of enhanced and suppressed regions. In the enhanced region, the amplitude of response voltage can be enlarged up to 100% compared to that in a uniform channel device. The distribution pattern of those regions is directly related to the number of gate sections (Ns). A mapping of response amplitude in an Ns-frequency scale is created, which helps distinguish enhanced/suppressed regions and locate optimal operating parameters.

TeraFET terahertz detectors with spatially non-uniform gate capacitances

A non-uniform capacitance profile in the channel of a THz field-effect transistor (TeraFET) could significantly improve the THz detection performance. The analytical solutions and simulations of the hydrodynamic equations for the exponentially varying capacitance versus distance showed ~10% increase in the responsivity for the 130 nm Si TeraFETs in good agreement with numerical simulations. Using the numerical solutions of the hydrodynamic equations, we compared three different Cg configurations (exponential, linear and sawtooth). The simulations showed that the sawtooth configuration provides the largest response tunability. We also compared the effects of the non-uniform capacitance profiles for Si, III-V, and p-diamond TeraFETs. The results confirmed a great potential of p-diamond for THz applications. Varying the threshold voltage across the channel could have an effect similar to that of varying the gate-to-channel capacitance. The physics behind the demonstrated improvement in THz detection performance is related to breaking the channel symmetry by device geometry of composition asymmetry.