TeraFET terahertz detectors with spatially non-uniform gate capacitances

Abstract

A non-uniform capacitance profile in the channel of a terahertz (THz) field-effect transistor (TeraFET) could improve the THz detection performance. The analytical solutions and simulations of the hydrodynamic equations for the exponentially varying capacitance vs 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 C_g 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 the amplification of boundary asymmetry by the non-uniform device geometry.