FerroHEMTs: High-Current and High-Speed All-Epitaxial AlScN/GaN Ferroelectric Transistors

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(MAX) > 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 AlN 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.