We report on the design and demonstration of ultra-wide bandgap AlGaN polarization-graded field effect transistors with ultra-thin channels to enable excellent current density and high-frequency performance while significantly reducing thermal resistance. We use polarization-graded AlGaN layers and ultra-thin pseudomorphic AlGaN buffer layers to enable low thermal resistance and excellent structural quality. The polarization-graded field effect transistors (PolFETs) demonstrated here show Imax over 800mA/mm and current/power gain cutoff frequency (fT/fmax) of 26/28 GHz. Small signal modeling and analysis were used to determine parasitic/transit delays, and gate-resistance thermometry was implemented to thermally characterize AlGaN PolFET and benchmark against state-of-the-art AlGaN HEMTs. The ultra-thin AlGaN PolFET showed thermal resistance of 12 K.mm/W, representing a significant reduction from typical AlGaN transistors. These results show state-of-art combination of high current density, excellent fT-LG product for ultra-wide bandgap AlGaN transistors, and superior thermal performance, and highlight the promise of AlGaN transistors for future RF and mm-wave applications.
@article{arxiv.2512.18107,
title = {Scaled Ultra-Wide Bandgap AlGaN Polarization-Graded FET with Ultra-thin Buffer Layer},
author = {Yinxuan Zhu and Ashley Wissel-Garcia and Kidus Guye and Chandan Joishi and Can Cao and Seungheon Shin and Kyle Liddy and Emils G. B. Jurcik and Agnes Maneesha Dominic Merwin Xavier and Andrew A. Allerman and Brianna A. Klein and Andrew Amrstrong and James S. Speck and Samuel Graham and Siddharth Rajan},
journal= {arXiv preprint arXiv:2512.18107},
year = {2025}
}