New Frontiers of Wide-Bandgap Semiconductors-Based Power Electronics: Novel Architectures and Reliability

The increasing demand for energy-efficient technologies has elevated the role of power electronic devices as essential components in modern applications, including renewable energy systems, industrial automation, consumer electronics, and electric vehicles. Wide-bandgap (WBG) semiconductor-based power devices, such as Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs), have emerged as key enablers of improved energy efficiency, reduced losses, and enhanced system performance. However, the growing reliance on GaN HEMTs in critical applications raises significant concerns regarding their long-term reliability, as failures can compromise overall system performance. This thesis investigates two primary aspects of GaN HEMT reliability that critically affect their operational lifetime and performance. First, the impact of packaging-induced stress on GaN HEMTs is examined through micro-Raman spectroscopy, which quantifies localized residual stress at the GaN layer and GaN/Si interface. A comparative analysis of packaged and bare devices provides insights into the effects of stress distribution on device reliability. Second, the thesis explores the behavior of dynamic ON-resistance under thermal and thermomechanical stress during operation. Advanced techniques such as high-speed infrared imaging and scanning vibrometry are employed to analyze the thermal and mechanical responses of GaN HEMTs under power cycling conditions. The findings offer a comprehensive understanding of the reliability challenges faced by GaN HEMTs, contributing to the development of more reliable GaN-based power devices. By addressing both packaging-induced stress and thermomechanical effects on dynamic ON-resistance, this research provides valuable insights into enhancing the lifetime and performance of GaN HEMTs for deployment in critical applications.