Optimization of GaN-Based High-Electron-Mobility Transistors (HEMTs) for High-Frequency Applications: A Comprehensive Study on Reliability and Performance Enhancement

Abstract

The widespread application of GaN-based high electron mobility transistors (HEMTs) in high-frequency and high-power applications still faces reliability instability. Achieving the necessary reliability is a challenging problem, primarily attributed to the elevated operational voltage and material properties. To enhance reliability, it is crucial to develop a comprehensive physical understanding of the underlying degradation mechanisms. This comprehensive thesis undertakes an in-depth exploration of trapping-related degradation in AlGaN/GaN high electron mobility transistors (HEMTs), extending and refining prior research on structural issues. The investigation encompasses a multi-faceted approach, beginning with a thorough characterization of interface and border traps using frequency-dependent C-V and G-V methods. The study then explores the influence of Al composition in AlGaN barriers on device performance, revealing insights into trap densities and their implications. A novel aspect of the research involves the application of O2 plasma treatment to mitigate volume trap states, showcasing improvements in Schottky characteristics and microwave performance. Additionally, the thesis provides a thorough analysis of Positive-Bias-Temperature Instability (PBTI) and the impact of channel back-barrier and channel thickness scaling, explaining the intricate relationship between these factors. Overall, this research significantly advances our understanding of trapping effects in AlGaN/GaN HEMTs, proposing innovative strategies to enhance device reliability and performance across various operational conditions.