Terahertz detection by high-electron-mobility transistor: Enhancement by drain bias

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Abstract
We report on a regime of operation of high-electron-mobility-transistor (HEMT) terahertz detectors, in which we apply a constant drain bias. The drain bias dependence of the gate-to-source and gate-to-drain capacitances results in a much greater asymmetry in the boundary conditions for plasma waves and greatly enhances the HEMT detector responsivity. The measured responsivity increases with the drain current by more than an order of magnitude and saturates at a saturation drain current for a given gate bias. These results confirm our model linking the responsivity increase to the drain bias dependence of the HEMT capacitances.