Exact solution for driven oscillations in plasmonic field-effect transistors

TL;DR

This paper presents an exact analytical solution for driven oscillations in plasmonic field-effect transistors, revealing the role of evanescent plasma waves and boundary conditions in shaping detector responsivity spectra.

Contribution

It provides a novel exact solution for driven oscillations in plasmonic FETs with realistic contacts, bridging previous approximate models and full-wave simulations.

Findings

Evanescent plasma waves significantly influence responsivity spectra.

Boundary conditions interpolate between open-circuit and short-circuit regimes.

Resonant fringes are present in photovoltage in both boundary limits.

Abstract

High-mobility field effect transistors can serve as resonant detectors of terahertz radiation due to excitation of plasmons in the channel. The modeling of these devices previously relied either on approximate techniques, or complex full-wave simulations. In this paper, we obtain an exact solution for driven electrical oscillations in plasmonic field-effect transistor with realistic contact geometry. The obtained solution highlights the importance of evanescent plasma waves excited near the contacts, which qualitatively modify the detector responsivity spectra. We derive the boundary condition on the ac floating electrodes of plasmonic FET which interpolates between open-circuit (Dyakonov-Shur) and short-circuit (clamped voltage) boundary conditions. In both limits, the FET photovoltage possesses resonant fringes, however, the absolute value of voltage is greater in the open-circuit regime.