Ultrahigh efficiency obtained with GaAs-on-insulator MESFET technology

Significant results of measurement and calculation of power-added efficienc y (PAE) and drain efficiency are presented for MESFET's that use GaAs-on-in sulator. Ultrahigh PAE of 89% was obtained at 8 GHz with a gain of 9.6 dB u sing a 3-V supply. When the voltage was increased to 4 V, the peak PAE was 93% at 210 mW/mm with 9.2-dB gain. The ideal current-voltage characteristic s with practically zero leakage current and large transconductance near pin choff yielded PAE values approaching the theoretical limits of overdriven o peration, The application of conventional assumptions concerning drain effi ciency is discussed relative to devices that approach these theoretical lim its. Also discussed are the pitfalls of various figures of merit of efficie ncy when applied to these devices, Hence, there are two types of technical barriers associated with very-high-efficiency devices: the physical realiza tion and their characterization.