Revolutionizing Power Electronics with a Gallium Nitride Monolithic Bidirectional Switch

Smart power electronic design aims to make energy conversion more climate-friendly by optimizing efficiency. This reduces energy loss and heat production, cutting down on energy consumption and emissions of harmful substances. One of the key elements to reach that goal is to reshape power converter design by using an innovative switch designed in a cutting-edge GaN power electronics technology. 

The superior material properties of GaN compared to Si for power applications have yielded power devices such as the GaN high-electron-mobility transistor (HEMT) that are now in the market. The GaN HEMTs enable faster switching combined with low on-resistance and are becoming a serious competitor for Si-based power devices. A bidirectional switch (BDS), capable of conducting current and block voltage in both polarities is conventionally made by connecting discrete components either back-to-back or in an antiparallel way. Yet, a high-power on-chip bidirectional switch that offers a high blocking voltage with current-handling capability is not available to date. The GaN-based BDS featuring 4-quadrant operation could further revolutionize power electronics with its compact design, outshining traditional antiparallel switches.  

The objective of this PhD is to improve the bidirectional switches already available in imec’s GaN technologies, with a focus on the switching operation and reliability of the device. The candidate will be expected to study and optimize the different design options of the BDS in imec’s GaN technologies. Several device metrics such as on-state resistance, blocking voltage and switching efficiency need to be balanced against each other. Furthermore, the gate driving procedure is quite challenging because two identical or non-identical isolated gate signals need to be provided depending on the switching topology. Therefore, the study needs to be extended to design a suitable monolithically integrated gate driver with a high-power BDS. Overall, the student will be expected to gain a deep fundamental understanding of the device operation, reliability and related integrated driver design. 

This research gives an opportunity to have an in-depth understanding of device design, circuit design and prototyping activities. It also encompasses the examination of how processing technology and device design interacts with device operation. The PhD student joins a team with over a decade of experience in processing, simulation, and characterization of GaN switches in a top-notch environment. The student will receive training by highly skilled professionals and will be embedded in the GaN device team.  Typical tools that will be used by the student include probe stations for on-wafer electrical characterization, software tools for data analysis (Python), for device design and circuit simulation (Cadence) and Technology-CAD software (Synopsys).