| Summary: | The significant interest that SiC has attracted over the last decades, coupled with the ease of voltage control and low conduction losses of the IGBTs, have led to their development and sample fabrication. Although these devices demonstrated the advantages that SiC IGBTs can bring in High Voltage power applications, their characteristics are not yet fully understood and their structure is far from optimised. This thesis addresses specific gaps in knowledge around accurate device modelling and optimisation of SiC IGBTs considering efficiency and ruggedness.
Firstly, an experimentally validated Technology Computer-Aided Design (TCAD) model was developed to study the behaviour of SiC IGBTs in a wide range of nominal and failure conditions. To achieve good predictive capability of the TCAD model, the modelled SiC material properties and device behaviour were verified by comparing the simulation results against published experimental data. The most critical parameters for performance optimisation were identified and several optimisation trade-off relationships were studied. Additionally, the SiC IGBT structure was optimised to improve its ruggedness in regards to false turn-on, short circuit and Electromagnetic Interference (EMI). Furthermore, a novel device structure is proposed with the ability to enhance the device’s ruggedness and simplify the optimisation process without sacrificing efficiency.
The optimisation conclusions were generalised for all SiC IGBT devices rated at 10-40 kV, and specific optimisation recommendations of each voltage class were summarised. Last but not least, a behavioural model for SiC IGBT was proposed for the first time, by modifying the commonly used MOSFET behavioural model and including current- and temperature-dependence on the parasitic capacitances. Its high accuracy, convergence and speed make it an essential tool for converter-level simulations to accelerate device demand and drive commercialisation.
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