摘要： The unprecedented performance potential of Gallium-Nitride-on-Silicon (GaN-on-Si) High Electron Mobility Transistors (HEMTs) is seen as the key enabler for the design of power converters featuring extreme power-density figures, as demanded in next generation power electronics applications. However, unexpected loss mechanisms, i.e. dynamic Rds,on phenomena and Coss-losses, are appearing in currently available GaN transistors and are compromising their operation. In this paper, measurements of Coss-losses are performed in a dedicated calorimetric measurement setup and, through a systematic approach, the root cause of the loss mechanism is potentially identified. Afterwards, with the essential support of a manufacturer of power semiconductors, a novel transistor, featuring an enhanced multi-layer III-N buffer, is developed according to the acquired knowledge. A significant reduction in terms of Coss-losses, i.e. of soft-switching losses, and the absence of dynamic Rds,on phenomena are verified experimentally on the new device. These achievements enable a significant performance improvement for future soft-switching power converters featuring GaN-on-Si HEMTs.