Design of InAlAs/InGaAs PHEMTs and small-signal modeling from 0.5 to 110 GHz

90-nm T-shaped gate InP-based In0.52Al0.48As/In0.6Ga0.4 As pseudomorphic high electron mobility transistors were designed and fabricated with a gate-width of 2 x 30 mu m, a source-drain space of 2.5 mu m, and a source-gate space of 0.75 mu m. DC, RF and small-signal model characterizations were demonstrated. The maximum saturation current density was measured to be 755 mA/mm biased at V-gs = 0.6 V and V-ds = 1.5 V. The maximum extrinsic transconductance was measured to be 1006 mS/mm biased at V-gs = -0.1 V and V-ds = 1.5 V. The extrapolated current gain cutoff frequency and maximum oscillation frequency based on S-parameters measured from 0.5 to 110 GHz were 180 and 264 GHz, respectively. The inflection point (the stability factor k = 1) where the slope from - 10 dB/decade (MSG) to -20 dB/decade (MAG) was measured to be 83 GHz. The small-signal model of this device was also established, and the S-parameters of the model are consistent with those measured from 0.5-110 GHz.