Investigations of GaN-based vertical field effect transistors for applications in high-power electronics

在本项目中，将研究常断电流孔径垂直场效应晶体管概念(CAVET)，用于基于III-N族半导体的电子功率器件的分析、外延、加工和表征。本项目的目的是研究垂直晶体管，以便在比硅器件和横向GaN基器件更高的水平上提高关键器件参数的导通电阻和击穿电压。与以前的工作不同，这将使用外延方法来定义孔径。对于所需的缺乏缺陷的厚的GaN漂移层，我们将根据我们长期使用这种方法的经验，进行氢化物气相外延(HVPE)生长。在这些先进的低缺陷密度衬底上，实际的器件结构将通过金属有机气相外延(MOVPE)进行生长，使用所需的电流孔层的选择性区域外延，以便将横向结构化过程中产生的任何缺陷降至最低。在工艺方面，需要分析和执行垂直结构和复杂的工艺流程，以探索垂直晶体管在电流流动和击穿稳定性方面的全部潜力。应研究与凹坑孔径相结合的新的常关概念。全器件模拟ATIAF将指导和支持外延生长和器件加工。将特别关注所需的兴奋剂概况。将进行结构和电气表征，以了解这种用于高压操作的新型设备的前景和局限性。该工作计划由乌尔姆大学、弗莱堡大学和弗劳恩霍费尔宇航联合会的小组共同制定和执行。这些小组的背景结合了该项目在半导体外延、加工、建模和表征方面所需的深入专业知识。

In this project, normally-off current aperture vertical field effect transistor concepts (CAVET) will be investigated for the analysis, epitaxy, processing, and characterization of electronic power devices based on group III-N semiconductors. The aim of this project is to investigate vertical transistors in order to enhance the key device parameters on-state resistance and breakdown voltage on a higher level than in Si devices and lateral GaN-based devices. In contrast to previous work this shall be accomplished using epitaxial approaches for the definition of the aperture. For the required thick defect-poor GaN drift layer, hydride vapor phase epitaxial (HVPE) growth will be performed and analyzed based on our long-standing experience of this method. On these advancedlow defect density substrates, the actual device structures will be grown by metalorganic vapor phase epitaxy (MOVPE) using selective area epitaxy for the required current aperture layers in order to minimize any defect generation during lateral structurization. On the processing side, vertical structuring and complex process flows need to be analyzed and performed in order to explore the full potential of the vertical transistor in terms of current flow and breakdown stability. Novel normally-off concepts in combination with the CAVET aperture shall be investigated. Full device simulations atIAF will guide and support epitaxial growth and device processing. Particular focus will be put on the required doping profiles. Structural and electrical characterization will be performed to understand the prospects and limitations of this new class of devices for high-voltage operation. The work program is defined and executed jointly by groups at the University of Ulm, University of Freiburg and Fraunhofer IAF. The background of the groups combines the required in-depth expertise for this project in terms of semiconductor epitaxy, processing, modeling and characterization.