Development of GaAs JFETs for cryogenic electronic circuits

GaAs JFET with various gate sizes, which ranges from 0.5 to 200 micrometers in gate length and from 2 to 200 micrometers in gate width, are fabricated and their DC characteristics and low- frequency noise spectra are measured at low temperatures in order to develop cryogenic electronic circuits for a far-IR detector array on board a satellite such as the Japanese IR satellite. We obtained the following results from the noise measurements: (1) Noise spectra of GaAs JFETs are dominated by a 1/f noise and include some generation-recombination noises in low-frequencies. (2) The 1/f noise voltage is found to remarkably depend on both the gate length and the drain-source voltage, but the gate width and the gate-source voltage have not almost concern with the 1/f noise voltage. Therefore, we suppose that the electric field in the channel of the GaAs JFET mainly contributes to the 1/f noise. By using these characteristics, the GaAs JFET having very low power dissipation and very low noise will be designed for cryogenic readout circuits at low temperatures.