QUARTER-MICROMETER LOW-NOISE PSEUDOMORPHIC GAAS HEMTS WITH EXTREMELY LOW DEPENDENCE OF THE NOISE-FIGURE ON DRAIN SOURCE CURRENT

Quarter-micrometer pseudomorphic (PM) AlGaAs-InGaAs-GaAs HEMT's 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 HEMT's with a gate width of 6 x 20 mum 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 DELTAF(min) < 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.