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

全球总能源销售中电能的份额已经达到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，根据各种情景，到2050年将达到60%以上。为了节约这种能源的资源，需要高效的电力电子解决方案，例如用于工业电力驱动、电动汽车、数据中心或可再生能源集成的电源。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进入这些电力电子变换器市场。氮化镓的特殊材料特性和异质结构使其具有高度紧凑的功率半导体。它们的特点是可实现的开关速度非常高，损耗大大降低，从而实现高效率和紧凑的转换器。然而，氮化镓半导体的高功率密度的后果也是高电场，高电流密度和相应的大热梯度在器件中。通过优化GaN外延层（GaN- epi）可以实现外延晶圆上的最佳散热，这对于实现强大的功率晶体管至关重要。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过载或短路等关键应用场景，并且必须评估发生的热诱导微结构缺陷形成。还有一些悬而未决的问题，特别是关于器件中热源的定位和动态过程中捕获效应的影响，这些问题与外延和开关的技术实现密切相关。这就是拟议的研究项目建立在DFG项目“GaN电力电子适应性电路”的初步工作基础上的地方。RuggedGaN的核心研究目标是通过开发适当优化的GaN-epi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电学，热学和微结构表征方法。

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.