We review recent progress in the development of grating-gate plasmonic THz detectors based on InGaAs-channel high-electron- mobility transistors for fast, highly sensitive, room-temperature-operating THz detection. First, a 2D diffraction grating structure, instead of the conventional 1D grating structure, was proposed for realization of polarization-independent detection and was experimentally demonstrated to alter the polarization characteristic of output photoresponse drastically. Second, it was demonstrated that a new way to read the output photovoltage from the gate of a detector simultaneously enables the scaling of the photovoltage with the active area size and the impedance matching with 50-Ω interconnection systems, which were the main issues in the conventional drain-readout configuration. Third, a significant enhancement of the photovoltage was observed at a positive gate bias voltage application in the gate-readout configuration, due to the “3D rectification effect" originating from the heterobarrier between the InGaAs channel layer and InAlAs spacer/carrier-supply/ barrier layers.
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