The role of charge trapping in AlGaN/GaN-on-Si HEMT based power switches

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GaN is a promising wide-bandgap compound semiconductor with outstanding physical properties especially for high voltage applications. Therefore, AlGaN/GaN-on-Si based power switches are predicted to supersede the prevalent role of modern silicon based transistors in fast-switching and high-efficient power conversion systems. This work is addressing two main obstacles for a future market launch, device reliability and dynamic switching behavior. The emphasis is put on localization and identification of charge trapping effects that deteriorate static and dynamic device parameter and impair system performance and device reliability. For a definition of critical areas in the device regarding charge trapping, the work is comparing different bias conditions, device designs, process parameter, and epitaxial properties. Most severe influence of trapping effects is found in the area of the semiconductor surface. By introducing a bilayer passivation with increased dielectric strength and an adjusted field plate design, the improved devices showed an immaculate dynamic behavior. A compromise of charge compensation and charge trapping is defining the optimal carbon doping level of the buffer.