Medium-power GaAs field-effect transistors

Results on medium-power GaAs m.e.s.f.e.t.s. are described. Output powers as high as 300 mW at 9 GHz at 1 dB gain compression with a linear gain of 5.2 dB and drain efficiency of 30% have been obtained with single-cell m.e.s.f.e.t.s. At 4 GHz, a power output of 665 mW at 1 dB gain compression, a linear gain of 8 dB and a drain efficiency of 44.5% were realised with a 3-cell m.e.s.f.e.t. Two-tone intermodulation characteristics at 4 GHz are also described. A major innovation has been the use of a high-resistivity chromium-doped epitaxial GaAs buffer layer to isolate the device active region from the bulk-grown substrate.