Ultra-Wide Bandgap AlGaN Heterostructure Field Effect Transistors with Current Gain Cutoff Frequency Above 85 GHz

TL;DR

This paper presents ultra-wide-bandgap AlGaN PolFETs with a record current gain cutoff frequency above 85 GHz, achieved through innovative epitaxial growth and device scaling, promising advancements in millimeter-wave electronics.

Contribution

The paper introduces a novel design of UWBG AlGaN PolFETs with record high-frequency performance and low contact resistance, demonstrating a significant advancement over previous UWBG transistor technologies.

Findings

Cutoff frequency above 85 GHz achieved

Contact resistance reduced below 1 ohm.mm

State-of-the-art high-frequency performance demonstrated

Abstract

We report the design and demonstration of ultra-wide-bandgap (UWBG) AlGaN polarization-graded field-effect transistors (PolFETs) that achieve a current-gain cutoff frequency above 85 GHz and a current density exceeding 1.3 A/mm. Ultra-thin channel and buffer layers were grown epitaxially on AlN substrates, and a reverse-graded AlGaN contact layer was incorporated to reduce the contact resistance to below 1 ohm.mm. With aggressively scaled device dimensions, the AlGaN PolFETs exhibit state-of-the-art high-frequency performance for UWBG transistors. Small-signal modeling reveals both parasitic and transit delays, confirming the benefits of reduced access resistance and enhanced intrinsic transconductance. These results establish a new performance benchmark for UWBG AlGaN devices and demonstrate their strong potential for next-generation millimeter-wave electronics.