FET´s and HEMT´s at Cryogenic Temperatures - Their Properties and Use in Low-Noise Amplifiers

This paper reviews the performance of a number of FET´s and HEMT´s at cryogenic temperatures. Typical d.c. characteristics and X-band noise parameters are presented and qualitatively correlated wherever possible with other technological or experimental data. While certain general trends can be identified, further work is needed to explain a number of observed phenomena. Design examples of three-stage, X-band HEMT and FET amplifiers are briefly discussed. Typical noise temperatures at 8.4 GHz areT/sub n/ = 22K, for all FET amplifiers and 11K for amplifier with HEMT´s in the input stage.