A pseudomorphic MODFET structure with excellent linear power performance at mm-wave range

The design, fabrication, and excellent linear power performance at the millimeter-wave frequency range of a modified InGaAs channel pseudomorphic MODFET structure are reported. This structure replaced the conventional n/sup +/ AlGaAs carrier supply layer with an n/sup +/ GaAs carrier supply layer. g/sub m/ was improved at high gate bias due to the superior carrier transport property of n/sup +/ GaAs compared to that of n/sup +/ AlGaAs. This g/sub m/ improvement results in relatively flat and broad f/sub T/ and f/sub max/ versus gate bias curves. Consequently, record high P/sub 1db/ of 0.68 W/mm with G/sub 1dB/ of 12.9 dB and power-added-efficiency of 45% was achieved at 25 GHz on a 0.33- mu m*120- mu m device. The P/sub out/ at maximum-power-added-efficiency point was as high as 0.81 W/mm with 10.9-dB gain and power-added efficiency of 59%.<
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