High efficiency operation of 6-H SiC MESFETs at 6 GHz

Abstract

Summary form only given. SiC MESFETs are very promising candidates for RF power amplification, due to their unique combination of high saturation velocity, high breakdown strength, and high thermal conductivity. In the present work, we demonstrate for the first time high efficiency RF power operation at 6 GHz. We have obtained power output of 35 W, with 45.5% power added efficiency at 6 GHz from a 6-H SiC MESFET operating at a drain bias of 40 V. The gate length and width were 0.5 /spl mu/m and 2 mm respectively. The corresponding power density is 1.75 W/mm and is more than a factor of 3 higher than that obtained normally in GaAs. To our knowledge, these results represent the highest power output, efficiency, and operating frequency reported to date in SiC. The power MESFETs were fabricated on high resistivity SiC substrates grown at Westinghouse. Sintered Ni ohmic contacts, mesa isolation, and channel recessing using RIE were used in device fabrication. Air-bridge source interconnects were used for large periphery devices. The fabrication and characterization of these SiC power MESFETs are presented.