InGaAs switch transistors for microwave control applications

InGaAs insulated-gate FETs (IGFETs) with 1.2 μm gate lengths have been designed, fabricated and characterized as switch devices for microwave control applications in switched and phase shifter circuits. The devices employed a plasma deposited silicon dioxide gate insulator and had multiple airbridged source regions. The control voltage was applied to the gate through a on chip 5 current kΩ mesa resistor to RF isolate the device from the gate supply. The effect of increased gate leakage current on device performance due to the leakage path created by the gate bias resistor is discussed. Three different gate widths of 300 μm, 600μm and 1200μm were investigated to examine the tradeoff between low on state and high off state capacitance. The DC current-voltage (I-V) characteristics as well as small signal scattering parameter (S-parameter) measurement results from 2-20 GHz are presented. The equivalent circuit models of the InGaAs switch FET fitted to the experimentally measured S-parameters are also given