The cryogenic multiplexer and shift register for submillimeter-wave digital camera

We have been developing cryogenic readout integrate circuits using SONY GaAs JFETs for large format arrays of high impedance type detectors especially for submillimeter/terahertz astronomy. The GaAs JFETs manufactured by SONY CO. Ltd have excellent static properties at less than 1 K. Besides, these JFETs have good performance for electrical switches; they have very low gate capacitance (<50 fF), low on resistance (∼10 kΩ), and high off resistance (>100 TΩ). To realize a cryogenic readout system for submillimeter-wave/terahertz camera, we designed multiplexers with sample-and-holds and shift registers. We report the first test results of each circuit and show prospect of a cryogenic multiplex system for a submillimeter-wave/terahertz digital camera.