Advances in discrete GaAs JFETs and simple amplifiers for deep cryogenic readouts

Abstract
The progress of the Jet Propulsion Laboratory in developing gallium arsenide 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 current at 4 K can be reduced to less than 1 fA. These same devices had a low frequency noise of just under 1 µV/Hz^1/2 at 1 Hz at 4 K, while dissipating less than 1 µW of power. In this paper we report on the fabrication of small-scale integrated circuit multiplexers and amplifiers made using this GaAs JFET technology. Small 8x1 source-follower-per-detector multiplexers and differential pairs have been fabricated and are fully functional at 4 K. The input-referred noise and leakage current is consistent with that for the discrete devices. Differential amplifier pairs were also measured. A systematic study of the device size dependence of the noise has been started, but as yet is inconclusive.