35 GHz GaAs power MESFETs and monolithic amplifiers

GaAs MESFETs optimized for power operation at 35 GHz are described. Various doping levels and potential barrier layers at the interface between the buffer and the active layers were studied. The best power performance was obtained from an FET on a very heavily doped active layer. A device on an AlGaAs heterobuffer had further improved output power. The best devices delivered output power densities of 0.8 W/mm with 23% efficiency, 0.71 W/mm with 34% efficiency, and 0.61 W/mm with 41% efficiency. Monolithic power amplifiers with a 400- mu m FET generated 200 mW of output power. These amplifiers were monolithically power combined, resulting in 600 mW of output power at 34 GHz.<
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