Charge Trapping in GaN Power Transistors: Challenges and Perspectives

Over the past decade, gallium nitride has emerged as an excellent semiconductor for the fabrication of power devices, to be used in energy conversion systems and switching-mode power converters. GaN and its alloys have a high breakdown field, a high saturation velocity and a wide energy gap, thus being suitable for high temperature and high voltage operation. The use of large-size silicon substrates allows large-wafer processing, with positive impact on cost reduction and yield. Further advantages will come from monolithic integration, that allows for the fabrication of fast and compact integrated circuits, all based on gallium nitride. Such integrated circuits will enable compact and high-frequency converter design, and will contribute to making gallium nitride a ubiquitous technology. This paper summarizes the most relevant properties of gallium nitride and related transistors, and describes the main challenges related to charge trapping in GaN HEMTs. Specific attention is given to the dynamic-on resistance process and to the hot-electron trapping phenomena, that have been recently investigated with the aim of ensuring reliable and high-frequency operation.