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Modelling and Characterization of GaN-HEMTs under Stress Conditions in Power Electronic Systems

Subject Area Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
Term since 2021
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 462842520
 
GaN power HEMTs are being used in an increasing number of applications due to their excellent dynamic properties and the associated possibility of lower losses and the use of smaller passive components. However, the use of GaN HEMTs requires a good understanding of the devices, particularly with regard to long-term stability and overload characteristics, which can lead to potential performance degradation. Transistor parameters degrade with increasing lifetime due to short-term overload conditions. In particular, changes in on-resistance, threshold voltage and leakage current occur. This can be relevant to the application. For example, in the case of the threshold voltage, instabilities are observed depending on the conditions previously applied, even if these are well within the acceptable operating range, which can affect the short-circuit behavior. This raises questions about device robustness, long-term stability and safe operating range, which are critical for efficient and reliable use over the lifetime of e.g. inverters. This is becoming increasingly important as GaN HEMTs are pushed to their performance limits while failures must be avoided. The main objective of this project is to develop methods to characterize the time- and temperature-dependent transistor parameters during operation, including threshold voltage shift, dynamic on-resistance, breakdown voltage and leakage current, and then to implement these parameters in a compact model for circuit simulation. The focus here is on application-oriented characterization. A wide temperature range is analyzed, e.g. from -40°C to 175°C. In addition, the degradation of the device under overload conditions is examined and the effects of degradation on the long-term stability and reliability, on the safe operating area and on the reliable gate control of the transistor is evaluated. This is valuable information for gate driver design to achieve stable und reliable operation with considering the overload detection and protection. In addition, electrothermal simulation is performed to predict the safe operating area, taking into account time-dependent threshold voltage instability and other degradation-related effects. Predicting this behavior requires an accurate modeling with high spatial resolution over the entire active device area. We therefore use a 3D numerical simulator developed specifically for this task.
DFG Programme Priority Programmes
 
 

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