FerroHEMTs: High-Current and High-Speed All-Epitaxial AlScN/GaN Ferroelectric Transistors
Joseph Casamento, Kazuki Nomoto, Thai‐Son Nguyen, H. Lee, Chandrashekhar Savant, Ling Li, Austin Hickman, Takuya Maeda, Jimy Encomendero, Ved Gund, Amit Lal, James C. M. Hwang, Huili Grace Xing, Debdeep Jena
Abstract
We report the first observation of ferroelectric gating in AlScN barrier wide-bandgap nitride transistors. These FerroHEMT devices realized by direct epitaxial growth represent a new class of ferroelectric transistors in which the semiconductor is itself polar, and the crystalline ferroelectric barrier is lattice-matched to the substrate. The FerroHEMTs reported here use the thinnest nitride high-K and ferroelectric barriers to date to deliver the highest on-currents at 4 A/mm, and highest speed AlScN transistors with f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</inf> > 150 GHz observed in any ferroelectric transistor. The FerroHEMTs exhibit hysteretic $I_{d}-V_{gs}$ loops with subthreshold slopes below the Boltzmann limit. A control A1N barrier HEMT exhibits neither hysteretic, nor sub-Boltzmann behavior. While these results introduce the first epitaxial high-K and ferroelectric barrier technology to RF and mm-wave electronics, they are also of interest as a new material platform for combining memory and logic functionalities in digital electronics.