RF Power Performance of Sc(Al,Ga)N/GaN HEMTs at Ka-Band
Andrew J. Green, Neil Moser, Nicholas C. Miller, Kyle J. Liddy, Miles Lindquist, Michael Elliot, J. Gillespie, Robert Fitch, Ryan Gilbert, Dennis E. Walker, Elizabeth Werner, Antonio Crespo, Edward Beam, Andy Xie, Cathy Lee, Yu Cao, Kelson D. Chabak
Abstract
We report the RF power results of Sc(Al,Ga)N/GaN high electron mobility transistors (HEMTs). We show dc, small-signal RF and load-pull performance at 30 GHz with two barrier alloys-a ternary of ScAlN and a quaternary of ScAlGaN. The active layers are grown by molecular beam epitaxy on a GaN-on-SiC template. The Sc(Al,Ga)N HEMTs with 120 nm gate length achieve transconductance >700 mS/mm and >70 GHz cutoff frequency. The quaternary ScAlGaN sample shows reduced current collapse during pulsed I-V and load-pull characterization. The ScAlGaN HEMT delivers 5.77 W/mm output power (VD = 20 V) and 47% power-added efficiency (VD = 15 V) when tuned for maximum power and efficiency, respectively.