Molybdenum Trioxide Gates for Suppression of Leakage Current in InAlN/GaN HEMTs at 300{\deg}C

TL;DR

This study demonstrates that MoO₃ gates significantly reduce leakage current in InAlN/GaN HEMTs at high temperatures, enabling high ON/OFF ratios and advancing high-temperature GaN electronics.

Contribution

The paper introduces MoO₃ as an effective gate material for high-temperature HEMTs, showing improved leakage suppression and device stability after oxidation treatment.

Findings

Leakage reduced over 60 times after Mo oxidation

High ON/OFF ratio of 1.2 x 10⁸ at 25°C

Operation up to 500°C with passivation

Abstract

Because high electron mobility transistors (HEMTs) often exhibit significant gate leakage during high-temperature operation, the choice of Schottky metal is critical. Increased gate leakage and reduced ON/OFF ratio are unsuitable for the design of high-temperature electronics and integrated circuits. This paper presents high-temperature characteristics of depletion-mode molybdenum trioxide (MoO${_3}$)-gated InAlN/GaN-on-silicon HEMTs in air. After a room temperature oxidation of the Mo for 10 weeks, the leakage of the HEMT is reduced over 60 times compared to the as-deposited Mo. The use of MoO${_3}$ as the Schottky gate material enables low gate leakage, resulting in a high ON/OFF current ratio of 1.2 x 10${^8}$ at 25{\deg}C and 1.2 x 10${^5}$ at 300{\deg}C in air. At 400{\deg}C, gate control of the InAlN/GaN two-dimensional electron gas (2DEG) channel is lost and unrecoverable. Here, this permanent device failure is attributed to volatilization of the MoO${_3}$ gate due to the presence of water vapor in air. Passivation of the device with SiN enables operation up to 500{\deg}C, but also increases the leakage current. The suppression of gate leakage via Mo oxidation and resulting high ON/OFF ratio paves the way for viable high-temperature GaN-based electronics that can function beyond the thermal limit of silicon once proper passivation is achieved.