High-performance microwave power MESFETs on GaAs/Si

The growth and fabrication of GaAs power MESFETs on high-resistivity, 3-inch diameter, float-zone Si substrates is discussed. These devices show high power-added efficiencies up to 51% and power output up to 447 mW/mm at 3 GHz. At 6 GHz power-added efficiency up to 42% and power output up to 447 mW/mm are obtained. The small-signal gain of these devices is very similar to those on GaAs substrates at 2 GHz (maximum stable gain is 18 dB), but was lower at 10 GHz (maximum available gain is 7-11 dB). Higher frequency performance in these devices is presently limited by parasitic conduction in a thin layer near the GaAs/Si interface. This has been characterized using special test structures, and possible means to overcome these problems and improve the performance are outlined.<>