Low temperature characteristics of GaAs FET (3SK97, 3SK121) for UHF SQUID

The low temperature characteristics of GaAs FET (3SK97, 3SK121) were examined with respect to the usage of a GaAs FET for a preamplifier of a UHF SQUID. A diode connection of the FET was also attempted in which it was utilized as a varactor diode operating at 4.2K. A preamplifier for the UHF SQUID was successfully constructed using these FETs.