DISSERTATION DEFENSE
Sajal Islam, Interdisciplinary Materials Science
*under the supervision of Ron Schrimpf and Josh Caldwell
“Enhancing Reliability in Ga₂O₃, GaN and SiC Wide-Bandgap Semiconductor Devices through Structural Design Improvement and Radiation Effects Analysis”
12.16.25 | 11:00 am | ISDE Conference Room | Zoom
Wide bandgap semiconductor technologies, such as gallium oxide (Ga₂O₃), gallium nitride (GaN), and silicon carbide (SiC), have transformed power electronics by offering higher breakdown fields, faster switching, and improved efficiency compared to silicon. Each material has unique advantages and tradeoffs that make it suitable for specific applications. Ga₂O₃ has the widest bandgap, enabling ultra-high-voltage operation and compact devices, but suffers from poor thermal management. GaN, with its high electron mobility and low switching losses, is ideal for high-frequency, high-efficiency systems that require compact design and fast operation. SiC, with excellent thermal conductivity and high breakdown field, is preferred for high-temperature, high-power applications such as automotive and grid-level conversion. Material selection depends on factors such as performance requirements, operating conditions, process maturity, and system-level design goals. These considerations motivate the need to continuously improve the performance and reliability of wide bandgap devices across all material platforms, forming the foundation of this dissertation.
Power devices such as diodes and MOSFETs remain vulnerable when operated in radiation environments such as space. High-energy ions and particles present in cosmic and solar radiation can induce single-event effects (SEE), a type of radiation effect caused by an energetic particle hitting the sensitive part of the device. Among SEE, single event leakage current (SELC) and single event burnout (SEB) are among the most critical for wide bandgap power devices. To prevent such failures, devices in space operate at significantly derated voltages, which limits power density and efficiency, and makes it essential to understand the underlying mechanisms of these phenomena and develop strategies to enhance device robustness.
In this dissertation, I present a comprehensive experimental study of wide bandgap devices across Ga₂O₃, GaN, and SiC technologies to investigate how structural optimization, epitaxial design, and termination engineering improve reliability and radiation hardness. For Ga₂O₃ and GaN, optimizing the device structure through increased epitaxial thickness, improved edge termination, and improved anode and passivation materials enhanced reverse voltage blocking performance and radiation tolerance. For SiC, detailed experimental analysis and modeling of heavy-ion-induced failures advanced the understanding of how epitaxial doping influences SEB and SELC thresholds in high-voltage devices up to 10 kV.
The dissertation establishes the relationships among ion range, linear energy transfer (LET), and SEB thresholds, clarifying how these parameters interact with device design and epitaxial structure. The collective results reveal the key design dependencies governing radiation-induced degradation across multiple wide bandgap material systems and guide the development of next-generation high-reliability power devices optimized for extreme environments such as space and defense applications.