Ultrahigh efficiency obtained with GaAs-on-insulator MESFET technology

Significant results of measurement and calculation of power-added efficiency (PAE) and drain efficiency are presented for MESFET's that use GaAs-on-insulator. Ultrahigh PAE of 89% was obtained at 8 GHz with a gain of 9.6 dB using 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 characteristics with practically zero leakage current and large transconductance near pinchoff yielded PAE values approaching the theoretical limits of overdriven operation. The application of conventional assumptions concerning drain efficiency is discussed relative to devices that approach these theoretical limits. Also discussed are the pitfalls of various figures of merit of efficiency when applied to these devices. Hence, there are two types of technical barriers associated with very-high-efficiency devices: the physical realization and their characterization.