Investigations on the low-power and low-frequency noise performance of pHEMT at 4.2 K

Pseudomorphic GaAs HEMTs with a gate length of 1mum have been realized and characterized at 4.2K. For the device with a gate width of 4mm, a gate leakage current less than 1pA and a total input capacitance lower than 10pF have been obtained for any practical bias conditions. The channel resistance can be modified more than 10(9) times with a gate bias variation less than a half volt. An intrinsic voltage gain higher than 10 can be reached with a power dissipation equal to or less than 0.15mW. Under this power supply condition, equivalent input noise voltages of 8.4, 3.2 and down to 1.3nV/rootHz can be obtained at frequencies of 1, 10 and 100kHz respectively. This noise voltage has been studied as a function of the drain current. Finally, the experimental results of this work have shown that the device's noise voltage can be linked to its DC parameters.