Noise measurements on silicon J-FETs at low temperature using a very high Q superconducting resonator

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Abstract
Noise voltage and noise current measurements have been carried out at different temperatures on two kinds of low‐noise silicon J‐FET at moderately high frequencies up to 100 kHz. We have made careful noise current measurements by constructing a very low‐loss superconducting resonator working in the kHz frequency range, whose quality factor reaches 3×105. At 10 kHz, the measured noise energy lies between 1.1 and 1.8×10−24 W/Hz for both types of transistors, but the ratio between the noise voltage and the noise current exhibits pronounced differences depending on the device under test.