LAUSR

In this letter, we successfully achieved high-power radio frequency (RF) operation of AlGaN/GaN high electron mobility transistors (HEMTs) fabricated on free-standing AlN substrate at X-band. The developed HEMT on AlN substrate comprised a 200 nm thick GaN channel and AlGaN buffer with an Al composition of 30%. Thanks to high breakdown voltage of the HEMT on AlN substrate, we successfully demonstrated 15.2 W mm−1 output power density at operating voltages of 70 V even without device technologies such as source-field plate and optimization of device dimension. Our results show that the potential of GaN HEMTs on AlN substrate as next-generation high-power RF devices.