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

## TL;DR

This paper introduces FerroHEMTs, a novel class of ferroelectric transistors with epitaxial AlScN barriers, achieving high current, high speed, and hysteretic behavior, advancing RF, mm wave, and digital electronics.

## Contribution

First demonstration of ferroelectric gating in AlScN/GaN transistors with epitaxial growth, enabling high performance and new functionalities.

## Key findings

- Achieved 4 A/mm on-current in FerroHEMTs.
- Recorded fmax > 150 GHz in ferroelectric transistors.
- Observed hysteretic Id Vgs loops with subthreshold slopes below Boltzmann limit.

## 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 fmax larger than 150 GHz observed in any ferroelectric transistor. The FerroHEMTs exhibit hysteretic Id Vgs 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.