K-band GaN power HFET's with 6.6 W/mm CW saturated output power density and 35% power added efficiency at 20 GHz

AlGaN/GaN heterostructure field effect transistors (HFET's) grown on SiC substrates are currently the most powerful three-terminal microwave solid state devices. While the power performance of these devices is well documented at X-band frequencies, there is growing interest in these devices at higher frequencies. In this study we characterize the power performance of GaN HFET's at 20 GHz. Our results clearly show that GaN HFET's have strong potential for power applications at K-band frequencies and beyond.