Thermal Management with AlN Passivation in AlGaN/GaN HEMTs with an Air Gap Gate for Improved RF Performance: A Simulation Study

Won, Young-Hyun; Kim, Tae-Sung; Lee, Jae-Hun; Lim, Chae-Yun; Min, Byoung-Gue; Kang, Dong-Min; Kim, Hyun-Seok

doi:10.3390/mi17010092

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Thermal Management with AlN Passivation in AlGaN/GaN HEMTs with an Air Gap Gate for Improved RF Performance: A Simulation Study

by

Young-Hyun Won

¹,

Tae-Sung Kim

¹,

Jae-Hun Lee

¹,

Chae-Yun Lim

¹,

Byoung-Gue Min

²

,

Dong-Min Kang

² and

Hyun-Seok Kim

^1,*

¹

Division of Electronics and Electrical Engineering, Dongguk University-Seoul, Seoul 04620, Republic of Korea

²

Electronics and Telecommunications Research Institute, Daejeon 34129, Republic of Korea

^*

Author to whom correspondence should be addressed.

Micromachines 2026, 17(1), 92; https://doi.org/10.3390/mi17010092 (registering DOI)

Submission received: 3 December 2025 / Revised: 3 January 2026 / Accepted: 8 January 2026 / Published: 10 January 2026

(This article belongs to the Special Issue Recent Advances in Field-Effect Transistors: Materials, Devices, and Emerging Applications)

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Abstract

This study introduces an air gap gate with AlN passivation to enhance the radio frequency (RF) performance of AlGaN/GaN high-electron-mobility transistors (HEMTs) while addressing thermal challenges. The air gap gate improves RF performance by reducing gate capacitance, resulting in a 23.9% increase in cutoff frequency (35.82 GHz) and enhancing saturation drain current and maximum transconductance by 3.7% and 10.27%, respectively, compared to a 0.15 μm planar gate baseline. However, reduced heat dissipation degrades thermal performance, as reflected in higher thermal resistance and temperature gradients. Incorporating high thermal conductivity AlN passivation mitigates these drawbacks, lowering operating temperatures and improving heat distribution, while maintaining a 17.5% cutoff frequency improvement over the baseline. These results demonstrate that the air gap gate with AlN passivation provides an effective strategy for achieving reliable, high-performance AlGaN/GaN HEMTs under high-frequency and high-power operations.

Keywords: gallium nitride; high-electron-mobility transistor; air gap gate; aluminum nitride passivation; thermal management; RF performance

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MDPI and ACS Style

Won, Y.-H.; Kim, T.-S.; Lee, J.-H.; Lim, C.-Y.; Min, B.-G.; Kang, D.-M.; Kim, H.-S. Thermal Management with AlN Passivation in AlGaN/GaN HEMTs with an Air Gap Gate for Improved RF Performance: A Simulation Study. Micromachines 2026, 17, 92. https://doi.org/10.3390/mi17010092

AMA Style

Won Y-H, Kim T-S, Lee J-H, Lim C-Y, Min B-G, Kang D-M, Kim H-S. Thermal Management with AlN Passivation in AlGaN/GaN HEMTs with an Air Gap Gate for Improved RF Performance: A Simulation Study. Micromachines. 2026; 17(1):92. https://doi.org/10.3390/mi17010092

Chicago/Turabian Style

Won, Young-Hyun, Tae-Sung Kim, Jae-Hun Lee, Chae-Yun Lim, Byoung-Gue Min, Dong-Min Kang, and Hyun-Seok Kim. 2026. "Thermal Management with AlN Passivation in AlGaN/GaN HEMTs with an Air Gap Gate for Improved RF Performance: A Simulation Study" Micromachines 17, no. 1: 92. https://doi.org/10.3390/mi17010092

APA Style

Won, Y.-H., Kim, T.-S., Lee, J.-H., Lim, C.-Y., Min, B.-G., Kang, D.-M., & Kim, H.-S. (2026). Thermal Management with AlN Passivation in AlGaN/GaN HEMTs with an Air Gap Gate for Improved RF Performance: A Simulation Study. Micromachines, 17(1), 92. https://doi.org/10.3390/mi17010092

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Thermal Management with AlN Passivation in AlGaN/GaN HEMTs with an Air Gap Gate for Improved RF Performance: A Simulation Study

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