ADVANCES IN DISCRETE GAAS JFETS AND SIMPLE AMPLIFIERS FOR DEEP CRYOGENIC READOUTS

The progress of the Jet Propulsion Laboratory in developing gallium ar senide junction field-effect transistors (GaAs JFETs) for application in infrared readout electronics operating below 10 Kelvin is discussed . Previously we had presented results on GaAs JFETs and shown that by using a highly isotropic HF-based etchant, the typical input leakage c urrent at 4 K can be reduced to less than 1 fA. These same devices had a low frequency noise of just under 1 mu V/Hz(1/2) at 1 Hz at 4 K, wh ile dissipating less than 1 mu W of power. In this paper we report on the fabrication of small-scale integrated circuit multiplexers and amp lifiers made using this GaAs JFET technology. Small 8x1 source-followe r-per-detector multiplexers and differential pairs have been fabricate d and are fully functional at 4 K. The input-referred noise and leakag e current is consistent with that for the discrete devices. Differenti al amplifier pairs were also measured. A systematic study of the devic e size dependence of the noise has been started, but as yet is inconcl usive.