Quarter-micrometer low-noise pseudomorphic GaAs HEMTs withextremely low dependence of the noise figure on drain-sourcecurrent

Quarter-micrometer pseudomorphic (PM) AlGaAs-InGaAs-GaAs HEMTs with an In mole fraction of 21% have been successfully developed, fabricated, and characterized. The devices are realized in a commercial technology by using a multiple-gate-finger layout with air bridges for the interconnection of the source pads and a Si₃N₄ passivation. PM HEMTs with a gate width of 6×20 μm exhibit state-of-the-art noise figures of 0.65 and 0.82 dB with an associated gain of 14.5 and 11.5 dB at 12 and 18 GHz, respectively. The noise figure shows the lowest dependence on the drain-source current yet reported with ΔF_max<0.12 dB for a wide biasing range from 25% I_dss up to 150% I _dss at 12 GHz when I_dss=170-250 mA/mm