Negative capacitance overcomes Schottky-gate limits in GaN high-electron-mobility transistors

TL;DR

This paper demonstrates that using a ferroic HfO2-ZrO2 bilayer dielectric in GaN high-electron-mobility transistors enables simultaneous increase in ON current and reduction in leakage current, surpassing traditional Schottky-gate limitations.

Contribution

Introducing a ferroic HfO2-ZrO2 bilayer dielectric to overcome Schottky-gate limits in GaN HEMTs, achieving improved performance not possible with conventional dielectrics.

Findings

Increased ON current in GaN HEMTs

Reduced gate leakage current

Surpassed conventional Schottky-gate limits

Abstract

For high-electron-mobility transistors based on two-dimensional electron gas (2DEG) within a quantum well, such as those based on AlGaN/GaN heterostructure, a Schottky-gate is used to maximize the amount of charge that can be induced and thereby the current that can be achieved. However, the Schottky-gate also leads to very high leakage current through the gate electrode. Adding a conventional dielectric layer between the nitride layers and gate metal can reduce leakage; but this comes at the price of a reduced drain current. Here, we used a ferroic HfO2-ZrO2 bilayer as the gate dielectric and achieved a simultaneous increase in the ON current and decrease in the leakage current, a combination otherwise not attainable with conventional dielectrics. This approach surpasses the conventional limits of Schottky GaN transistors and provides a new pathway to improve performance in transistors based on 2DEG.