High-speed Graded-channel AlGaN/GaN HEMTs with record Power-added-efficiency >70% at 30 GHz

The authors report on highly scaled 60 nm gate length graded-channel AlGaN/GaN high electron mobility transistors (HEMTs) with a record power added efficiency (PAE) of 75% at 2.1 W/mm power density at Vdd = 10 V and the PAE of 65% at 3.0 W/mm power density at 30 GHz at Vdd = 14 V. Under two-tone power measurement, the graded-channel AlGaN/GaN HEMTs demonstrated similar power performance with peak PAE >70% at 30 GHz. This novel channel design shows great promise for high-efficiency millimetre-wave (mmW) power amplifiers up to 3 W/mm RF power density operation.