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) are obtained on the 1 mu m gate-length devices. At 2 GHz, output power densities of 1.1 W mm(-1) and 1.02 W mm(-1) with power added efficiencies of 18.6% and 20.1% respectively are demonstrated. A dual-heat-source model is proposed for the mathematical thermal simulation of a power FET with higher accuracy. This estimates a channel temperature >300 degrees C at the maximum power output as a result of the poor thermal conductivity of the sapphire substrate. While the GaN FET's excellent power ability at high temperature has been confirmed, the thermal problem needs to be solved for realization of its full potential. (C) 1997 Elsevier Science Ltd.