The authors report on detection of terahertz radiation by high electron mobility nanometer transistors. The photovoltaic type of response was observed at the frequency range, which is far above the cutoff frequency of the transistors. The experiments were performed in the temperature range from . The resonant response was observed and was found to be tunable by the gate voltage. The resonances were interpreted as plasma wave excitations in the gated two-dimensional electron gas. The minimum noise equivalent power was estimated, showing possible application of these transistors in sensing of terahertz radiation.
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The criterion separating the resonant detection/emission nature from the nonresonant one is the so-called quality factor, namely, , where is the excitation frequency and denotes the electron momentum relaxation time. If the condition is fulfilled, the plasma oscillations are overdamped; consequently, the response is nonresonant, exhibiting smooth function of frequency and the gate voltage. In opposite case, when the quality factor becomes much larger than 1, a spectrally narrow plasmon resonance peak should be clearly resolved—see Refs. 2 and 3.
