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

根据2050年达到60%或更高的各种情景，电能在全球能源销售总额中的份额已经达到25%(2019年)，并将在未来几年继续大幅增加，以实现二氧化碳减排目标。为了节约使用这种能源，需要高效的电力电子解决方案，例如用于工业电力驱动、电子机动性、电源例如数据中心或用于整合可再生能源。基于宽带隙半导体材料氮化镓(GaN)的功率晶体管正越来越多地打入电力电子转换器的这些市场。GaN的特殊材料特性和所使用的异质结构导致了本质上高度紧凑的功率半导体。它们的特点是具有极高的可实现开关速度和极大降低的损耗，从而实现高效和紧凑的转换器。然而，GaN半导体的高功率密度也会导致器件中的高电场、高电流密度和相应的大温度梯度。通过优化GaN外延层(GaN-Epi)可以实现最佳的外延片散热，这是实现坚固的功率晶体管的关键。为了评估GaN功率晶体管器件的稳健性，必须通过适当的电气测试程序来保证关键的应用场景，如过载或短路，并且必须评估发生的热诱导微结构缺陷形成。对于器件中热源的局部化和动态过程中捕获效应的影响，尤其是与外延和开关的技术实现密切相关的问题，还存在一些悬而未决的问题。这就是拟议的研究项目建立在DFG项目“用于GaN电力电子的适配电路”的前期工作的基础上。RuggedGaN的中心研究目标是通过开发具有更好散热性能的适当优化的GaN-外延半导体衬底来提高GaN基功率器件的稳健性，并提供工艺和器件鉴定所需的基于电、热和微结构的表征方法。

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.