HIGH-POWER ALGAN GAN HEMTS FOR MICROWAVE APPLICATIONS/

AlGaN/GaN power HEMTs were fabricated and characterized. Gate-to-drain breakdown voltages up to 230 V and channel currents >300 mA mm(-1) ar e obtained on the 1 mu m gate-length devices. At 2 GHz, output power d ensities of 1.1 W mm(-1) and 1.02 W mm(-1) with power added efficienci es of 18.6% and 20.1% respectively are demonstrated. A dual-heat-sourc e model is proposed for the mathematical thermal simulation of a power FET with higher accuracy. This estimates a channel temperature >300 d egrees C at the maximum power output as a result of the poor thermal c onductivity of the sapphire substrate. While the GaN FET's excellent p ower ability at high temperature has been confirmed, the thermal probl em needs to be solved for realization of its full potential. (C) 1997 Elsevier Science Ltd.