Brief characterization of germanium junction field effect transistors (FETs) at 77, 4, and 1.8 K

In the case of modern infrared focal planes, one of the major problems is related to the noise contribution of the cooled, impedance-matching device used as the preamplifier stage in the detector electronics system. An ideal preamp device should have the low-noise advantages of a buried-channel device and operate isothermally with the low-temperature detector array. The Ge JFET might provide this ideal device. A testing program with Ge JFETs is discussed. It is concluded that germanium JFETs offer an attractive alternative for cryogenic preamplifier designs. They operate well with high transconductance and low noise at LHe temperatures. It is believed that these devices point the way for the development of large, integrated-array, long wavelength, infrared focal planes which incorporate germanium detectors, germanium load resistors, and germanium preamplifiers within the same monolithic structure.