Resonant coupling of terahertz electro-magnetic waves and 2-dimensional surface plasmons can be exploited to develop chip-based detectors able to perform spectroscopy. The plasma response of a 2-dimensional electron gas can be tuned by a set of periodic lateral gates. A plasmonic terahertz detector that integrates a voltage-controlled planar barrier into a grating gated GaAs/AlGaAs high electron mobility transistor was fabricated and experimentally characterized. The plasmonic response at fixed grating gate voltage has a full width at half-maximum of 40 GHz at ~405 GHz. Substantially increased responsivity is achieved by introducing an independently biased narrow gate that produces a lateral potential barrier electrically in series with the resonant grating gated region.
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