Investigation of parasitic coupling of THz radiation to a large area field-effect transistor

THz radiation can couple in various undesired ways to THz detectors, e.g. through wires or contact pads, aggravating calculation of sensible values for the device responsivity. We therefore investigate coupling of THz radiation to antenna-less large area field-effect transistors with dimensions in the range of the THz spot size proving that only a very small fraction of power is coupled through the pads.