Reliability Evaluation and Condition Monitoring of Wide Bandgap Devices

The reliability of power semiconductor devices is important as the device failures can lead to power converter malfunctions or power interruptions, which are not desirable in the industry because of the penalties of the maintenance cost, operation cost, and safety concerns. With low on-resistance and junction capacitance, the Wide Bandgap (WBG) devices are attractive for highefficiency and high-power-density power electronics converters in various industrial applications. However, as a relatively new technology with limited field application data, the long-term reliability of these devices is a concern for some mission-critical applications, e.g., automobile industry, aerospace application, and renewable energy systems. To understand these reliability issues, this dissertation evaluates the commercial SiC MOSFETs and GaN HEMTs in terms of their reliability and robustness. For SiC MOSFETs, a dedicated aging setup is designed, and the parameter shifts of the device over aging are studied. Both the device-related and package issues are focused, and their impacts on the device’s electrical performance are investigated, respectively. Also, targeting at the state-of-health condition monitoring of SiC MOSFETs, the aging’s effect on temperature sensitive electrical parameter (TSEP) based Tj measurement methods are evaluated. Based on the evaluation result, a new online junction temperature measurement approach is proposed and realized in an intelligent gate drive circuit for condition monitoring purposes. In terms of GaN HEMTs, device-related reliability and performance issues are studied. Specifically, the dynamic on-resistance and threshold voltage shift are successfully characterized by the proposed measurement circuits. Then their impacts on the device’s performance are investigated. The evaluation results and condition monitoring methods in this dissertation help to fully understand the physical cause of the reliability issue in WBG devices and guide the application engineers to maximize the device’s performance through proper gate drive circuit design.