GOALI: Charge Transfer in Semi-Insulating GaN

技术描述：尽管GaN被有效地用于照明应用，但一些电子器件需要高电阻率材料。GALI项目的目标是研究和了解用于实现绝缘GaN的缺陷之间的电荷转移机制，并评估有意杂质对晶体质量的影响。具体地说，电子顺磁共振(EPR)谱被用来探测有意添加的铁杂质和本征施主之间的电荷转移。EPR测量提供了铁和施主缺陷的指纹，并与光激发相结合，用于监测各种电荷交换过程。此外，还利用光学吸收光谱探测了Fe杂质的几种不同的电荷状态以及其他潜在的缺陷中心，并用X射线衍射法对晶体的整体质量进行了评估。这些实验主要针对该项目的工业合作伙伴Kyma Technologies通过氢化物气相外延生长的块状掺铁衬底。然而，其他研究包括与其他生长技术生长的样品进行比较，如高压溶液，并掺杂不同的补偿杂质，以便确定稳定的绝缘氮化物衬底的最佳生长参数。非技术描述：通过直接探测GaN中的缺陷获得的洞察力为改进的生长技术提供了输入，从而可以实现未来电力电子所需的高质量、高阻材料。通过与行业合作者的互动，学生们获得了课堂环境中无法获得的科学观点。此外，正在为从事这项研究的一名研究生提供与Kyma的暑期研究体验，并计划至少由Kyma科学家举办一次研讨会。这两个课程都旨在向学生介绍与材料生长和设备开发相关的实际问题。在大学预科阶段，PI在系内一位同事组织的为期一周的高中物理桥研讨会上，下午就与GaN器件有关的口语主题进行了演讲。

Technical Description: Although GaN is effectively used in lighting applications, some electronic devices require high resistivity material. The goal of this GOALI project is to investigate and understand charge transfer mechanisms among the defects used to achieve insulating GaN and to assess the influence of the intentional impurities on crystal quality. Specifically, electron paramagnetic resonance (EPR) spectroscopy is used to probe charge transfer between the intentionally added Fe impurities and intrinsic donors. The EPR measurements provide a fingerprint of the Fe and donor defects, and, combined with photo-excitation, are used to monitor various charge exchange processes. Additionally, several different charge states of the Fe impurity as well as other potential defect centers are probed with optical absorption spectroscopy, and overall crystal quality is assessed with x-ray diffraction. The experiments primarily address bulk Fe-doped substrates grown by hydride vapor phase epitaxy at Kyma Technologies, the industrial collaborator of this project. However, additional studies include comparisons with samples grown by other growth techniques, such as high pressure solution, and doped with different compensating impurities so that optimal growth parameters for stable insulating nitride substrates may be determined.Non-technical Description: The insights gained by directly probing defects in GaN provide input for improved growth techniques, so that high-quality, high-resistivity material needed for future power electronics can be realized. By interacting with the industrial collaborators, students gain a view of science not available in a classroom setting. Furthermore, a summer research experience with Kyma is being offered to one of the graduate students working on this research, and at least one seminar by a Kyma scientist is planned. Both are intended to introduce students to the practical issues associated with material growth and device development. At the pre-college level, the PI gives an afternoon presentation on colloquial topics related to GaN devices at the week-long high-school Physics Bridge workshop organized by a colleague in the department.