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Register a new userExact solution for driven oscillations in plasmonic field-effect transistors
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Authors
Dmitry Svintsov
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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.
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We introduce a fabrication method for gate-all-around nanowire field-effect transistors. Single nanowires were aligned perpendicular to underlying bottom gates using a resist-trench alignment technique. Top gates were then defined aligned to the bottom gates to form gate-all-around structures. This approach overcomes significant limitations in minimal obtainable gate length and gate-length control in previous horizontal wrap-gated nanowire transistors that arise because the gate is defined by wet etching. In the method presented here gate-length control is limited by the resolution of the electron-beam-lithography process. We demonstrate the versatility of our approach by fabricating a device with an independent bottom gate, top gate, and gate-all-around structure as well as a device with three independent gate-all-around structures with 300 nm, 200 nm, and 150 nm gate length. Our method enables us to achieve sub-threshold swings as low as 38 mV/dec at 77 K for a 150 nm gate length.
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