Improving GaN power transistor ruggedness by novel GaN-epi-wafers with improved thermal capabilities

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The share of electrical energy in total energy sales worldwide is already 25% (2019) and will continue to increase significantly in the coming years to achieve the CO2 reduction targets, according to various scenarios up to 60% and more in 2050. For the resource-saving use of this energy, highly efficient power electronic solutions are needed, e.g. for industrial electric drives, for electromobility, for power supplies e.g. of data centers or for the integration of renewable energies. Power transistors based on the wide-bandgap semiconductor material gallium nitride (GaN) are increasingly making inroads into these markets for power electronic converters. The special material properties of GaN and the heterostructures used result in inherently highly- compact power semiconductors. These are characterized by very high achievable switching speeds with drastically reduced losses, thus enabling highly efficient and compact converters. However, the consequences of the high power density of GaN semiconductors are also high electric fields, high current densities and correspondingly large thermal gradients in the device. Optimal heat dissipation across the epi-wafer is essential for the realization of robust power transistors and can be achieved by optimizing the GaN epitaxial layers (GaN-Epi). For the evaluation of the robustness of GaN power transistor devices, critical application scenarios such as overload or short circuit have to be guaranteed by appropriate electrical test procedures, and the occurring thermally induced microstructural defect formations have to be evaluated. There are open questions, especially regarding the localization of heat sources in the device and the influence of trapping effects during dynamic processes, which are closely linked to the epitaxy and the technological implementation of the switches. This is where the proposed research project builds on the preliminary work in the DFG project "Adapted circuitry for GaN power electronics". The central research objective of RuggedGaN is to increase the robustness of GaN-based power devices by developing appropriately optimized GaN-epi semiconductor substrates with improved heat dissipation, and to provide the electrical, thermal and microstructure-based characterization methods required for process and device qualification.