GaN-Based Power HEMTs: Parasitic, Reliability and High Field Issues

This paper reviews the main mechanisms responsible for trapping and breakdown in power HEMTs based on gallium nitride. With regard to the trapping mechanisms, we describe the role of carbon and iron buffer doping compensation in determining the dynamic Ron. We also demonstrate how the use of double heterostructure without doping or a single-heterostructure with proper buffer doping compensation can effectively reduce trapping phenomena. In addition, we investigate the breakdown limits of single and double heterostructure (DH) HEMTs, by electrical and electroluminescence characterization. Results indicate that, for the devices adopting double heterostructure without doping or singleheterostructure with proper buffer doping compensation, the breakdown voltage linearly scales with the gate-drain distance, and provides information on the origin of breakdown current components for different bias levels and epitaxial structures.