RF Power Performance of Sc(Al,Ga)N/GaN HEMTs at Ka-Band

• Published in: IEEE electron device letters Vol. 41; no. 8; pp. 1181 - 1184
• Main Authors: Green, Andrew J., Moser, Neil, Miller, Nicholas C., Liddy, Kyle J., Lindquist, Miles, Elliot, Michael, Gillespie, James K., Fitch, Robert C., Gilbert, Ryan, Walker, Dennis E., Werner, Elizabeth, Crespo, Antonio, Beam, Edward, Xie, Andy, Lee, Cathy, Cao, Yu, Chabak, Kelson D.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-08-2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: dispersion; Extremely high frequencies; Gallium nitride; GaN; HEMT; HEMTs; High electron mobility transistors; large-signal; Logic gates; Maximum power; MODFETs; Molecular beam epitaxial growth; Performance evaluation; Radio frequency; ScAlGaN; ScAlN; Semiconductor devices; small-signal
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2020.3006035

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.