Solid-State and Nanotechnology
Gallium Nitride and other emerging semiconductors for next generation power conversion
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Widebandgap (WBG) semiconductors present a pathway to push the limits of power conversion efficiency beyond that available from Silicon (Si)-based devices, enabling significant energy savings. Recent progress in Gallium Nitride (GaN)-based power electronic devices has been compelling. Reducing conversion losses is not only critical for minimizing consumption of limited resources, it simultaneously enables new compact architectures, the basis for a new industry offering increased power conversion performance at reduced system cost. This is because GaN devices enable power electronics with 1) higher efficiency at higher frequency of operation and 2) higher efficiency over a wider range of operating temperature, compared with what is possible with Si, which is approaching its physical material limit in power conversion. High efficiency operation at higher operating frequency reduces the size, weight and cost of the overall system by reducing the size of the passive components and the heat sink. GaN-based Photovoltaic (PV) inverters have achieved efficiency above 98% at a pulse-width modulation frequency of 50 kHz (vs. 96% with Si at 15 kHz), reducing loss by 50%, thereby shrinking the PV inverter size by 40%. Research has already commenced on utilizing the unique bidirectional nature of current transport and voltage blocking available in GaN-based devices, leading to the development of bidirectional switches with a single transistor, effecting at least 50% reduction of components on a chip. All these innovations have resulted in new possibilities with circuit architecture, and opening hitherto unavailable prospects for integration to further enhance the efficiency and add portability to existing applications. While Lateral GaN devices are more matured in technology and have entered the medium power conversion market (up to 10 kW), Vertical GaN devices are evolving to address high power conversion (10 kW-10 MW). The novelty of the device design can be extended beyond GaN to other wider bandgap materials like Gallium Oxide, Aluminum Nitride and Diamond for more futuristic power electronic applications.
It is always exciting to be at the beginning of a new technological revolution, which has tremendous ecological impact. WBG electronics offers just this opportunity both with its promise of superior solutions to pressing problems while simultaneously opening the possibilities of providing functionality that we have not even thought of.
Srabanti Chowdhury received her B.Tech in Radiophysics and Electronics from Institute of Radiophysics and Electronics, India and her M.S (2008) and PhD (2010) in Electrical Engineering from University of California, Santa Barbara. In her PhD. work she developed GaN-based vertical devices for power conversion and demonstrated the first vertical GaN power device (CAVET) with a record high breakdown field. After her PhD she joined Transphorm, a California-based company to develop and commercialize GaN based devices for power electronics application where she led the development of 1.2KV GaN-on-Si devices. She has authored and coauthored over 12 journal publications and presented in over 15 conferences. She has over 12 patents on Gallium Nitride based devices and technologies. In her current role as an assistant professor in the school of Electrical Computer and Energy Engineering at Arizona State University (since March'13) she continues to develop solid-state devices to enable efficient power conversion. Besides Gallium Nitride, her research group also focuses on Diamond and Gallium Oxide materials for power and other emerging electronics.