Novel applications of HEMTs for future 4.2 K low-power and low-frequency cryoelectronics

Pseudomorphic (Al,In)GaAs/GaAs HEMTs have been fabricated and investigated. These devices exhibit high DC and low-frequency noise performances at 4.2 K. Neither collapse nor kink effect have been detected. Large current variation from sub-nano to milli-Ampere with good saturation behaviour has been characterised with a gate bias variation of about half a volt. Even at an extremely low-power supply of 57 pW, an intrinsic voltage gain of 160 has been reached. With a power supply smaller than 10 /spl mu/W, we obtained an equivalent input noise as small as 1.9 nV//spl radic/Hz at 1 kHz, a white noise lower than 0.5 nV//spl radic/Hz, a shot noise of 0.76 fA//spl radic/Hz,and the corresponding Hooge parameter of 5.5/spl times/10/sup -6/. Finally, a real application of this type of device in a 4.2 K preamplifier has demonstrated an equivalent input noise level of 0.12 nV//spl radic/Hz with a bandwidth of 2 MHz.