Formation of Ultra-High-Resistance Au/Ti/p-GaN Junctions and the Applications in AlGaN/GaN HEMTs

TL;DR

This study demonstrates that annealed Au/Ti/p-GaN Schottky junctions exhibit a dramatic increase in resistance, which enhances the performance of AlGaN/GaN HEMTs by significantly boosting gate breakdown voltage.

Contribution

It introduces a novel high-resistance Au/Ti/p-GaN junction structure and applies it to improve AlGaN/GaN HEMT gate performance.

Findings

Resistance increased by orders of magnitude after annealing.

High-resistance junctions improved HEMT gate breakdown voltage.

Deactivation of Mg observed via Raman spectroscopy.

Abstract

We report a dramatic current reduction, or a resistance increase, by a few orders of magnitude of two common-anode Au/Ti/pGaN Schottky junctions annealed within a certain annealing condition window (600 - 700 oC, 1 - 4 min). Results from similar common-anode Schottky junctions made of Au/p-GaN, Al/Ti/p-GaN and Au/Ti/graphene/p-GaN junctions demonstrated that all the three layers (Au, Ti and p-GaN) are essential for the increased resistance. Raman characterization of the p-GaN showed a decrease of the Mg-N bonding, i.e., the deactivation of Mg, which is consistent with the Hall measurement results. Moreover, this high-resistance junction structure was employed in p-GaN gate AlGaN/GaN HEMTs. It was shown to be an effective gate technology that was capable to boost the gate breakdown voltage from 9.9 V to 13.8 V with a negligible effect on the threshold voltage or the sub-threshold slope.