The design of high-isolation millimeter-wave monolithic integrated switches using MOCVD-grown InGaAs/InP PIN diodes as switching devices is reported, and the impact of InGaAs PIN diode parameters on switch performance is discussed. PIN diodes made of InGaAs on InP offer several significant advantages over conventional GaAs on GaAs technology i.e. (i) compatibility with InP-based high-frequency HBT and HEMT transistors and possibility of integration on the same wafer (ii) lower turn-on voltage and smaller access resistance due to higher electron mobility and lower bandgap of InGaAs, compared with GaAs. As a result lower power consumption and better switch characteristics can be obtained. A comparative analysis of measured single- and double-diode monolithic switch characteristics is reported together with the design and fabrication details. W-band single-pole single-throw (SPST) switch using two shunt diodes demonstrated isolation in excess of 40 dB while keeping insertion loss at 1.8 dB. When compared with the single-diode SPST switch, high-isolation double-diode switch showed improvement of ON/OFF ratio by as much as 17 dB at low biasing currents (I = 0.3 mA per diode).
