INGAAS MICROWAVE SWITCH TRANSISTORS FOR PHASE-SHIFTER CIRCUITS

A new InGaAs insulated-Gate FET (IGFET) with 1 mum gate length and thr ee different gate widths have been designed, fabricated and characteri zed as switch devices for microwave control applications in phase shif ter circuits. The devices employed a plasma deposited silicon dioxide gate insulator and had multiple air bridged source regions. The detail s of the DC current-voltage (I-V) characteristics and small signal S-p arameter measurements up to 20 GHz are presented. The switch IGFET's h ad a drain saturation current density of 300 mA/mm gate width with bre akdown voltages of higher than 35 V. An insertion loss of 1.0, 0.6, an d 0.4 dB at 10 GHz and 1.4, 0.8, and 0.4 dB at 20 GHz have been measur ed for the 300, 600, and 1200 mum gate width IGFET's, respectively. Eq uivalent circuit models fitted to the measured S-parameters for IGFET' s yielded on-state resistances from 10.7 to 3.3 OMEGA, off-state resis tances from 734.4 to 186.8 OMEGA and off-state capacitances from 0.084 to 0.3 pF as the gate width is increased from 300 to 1200 mum. The si mulation results using IGFET models for the phase shifter circuits ind icated a maximum phase error of 0.11-degrees, 0.26-degrees, and 0.47-d egrees with 0.74, 0.96, and 1.49 dB maximum insertion loss and greater than 33, 26, and 19 dB return loss for the 11.25-degrees, 22.5-degree s, and 45-degrees phase bits, respectively, over the 9.5-10.5 GHz freq uency band.