GOALI: Zintl Engineering of Epitaxial Ceramic Films on Gallium Nitride

该项目由材料研究部电子与光子材料（EPM）和陶瓷（CER）项目共同资助。非技术描述：在过去的几十年里，硅一直是半导体工业中几乎所有微电子设备的衬底。由于需要更快的设备速度，业界正在考虑化合物半导体，如氮化镓，它具有更高的电子迁移率。因此，需要新的介电层材料来实现基于氮化镓的电子器件。本研究项目正在探索在氮化镓上生长晶体稀土氧化物薄膜的方法，这些薄膜与氮化镓的晶格非常匹配，并使氮化镓成为可行的衬底。由于氮化镓和稀土氧化物具有不同类型的化学键，因此本研究正在探索连接键类型并迫使氧化物生长为二维层的界面层。学术研究人员与氮化镓技术领导者半透明公司之间的合作将帮助研究生了解开发可行新技术所涉及的因素。此外，研究人员还参与了一个名为“爱丽丝梦游仙境”的推广项目，旨在吸引女高中生学习物理科学和工程。这些学生和当地高中的物理教师在德克萨斯大学奥斯汀分校度过暑假，在一个支持性的环境中参与研究。技术细节：本研究项目的首要目标是发现、理解和描述导致氧化镧、氧化钆和氧化铒在wurtzitic GaN（0001）上形成的过程。本研究推进了精确界面工程的方法，并阐明了由族1或族2元素和族13-15元素组成的金属间化合物（称为“Zintl化合物”）在改变表面能以促进润湿和指导氧化物在GaN上[111]生长方向方面的作用（0001）。该研究得益于基础设施、相关研究的相邻性、学术研究人员和工业合作伙伴在原子控制生长、材料表征、表面化学、第一性原理建模和电学表征方面带来的专业知识和互补技能。基础研究的具体重点领域包括：1)发现在GaN（0001）表面外延生长晶体、c型La、Gd和Er氧化物薄膜的方法；2)阐明了导致半导体异质外延氧化的潜在界面化学；3)探索结构-性能-生长关系，使结果可以扩展到其他氧化物半导体系统。本研究采用分子束外延和原子层沉积技术生长外延结构；第一性原理密度泛函理论（DFT）方法来识别合适的金属间化合物，并模拟氧化物-氮化镓界面的原子结构、电学和电子性质；以及非原位透射电子显微镜（TEM）和电测量来验证模型预测并建立结构-性能关系。

This project is jointly funded by the Electronic and Photonic Materials (EPM) and Ceramic (CER) Programs in the Division of Materials Research. NON-TECHNICAL DESCRIPTION:Silicon has been the substrate of almost all microelectronic devices for the semiconductor industry over the last several decades. Motivated by the need for faster device speeds, the industry is considering compound semiconductors, such as gallium nitride, which have higher electron mobility. Accordingly, new dielectric layer materials that enable gallium nitride-based electronic devices are needed. This research project is exploring approaches to growing crystalline rare earth oxide films on gallium nitride that are well-matched to the crystal lattice of gallium nitride and make gallium nitride a viable substrate. Because gallium nitride and the rare earth oxides have different types of chemical bonding, this research is exploring interfacial layers that bridge the bonding types and force the oxide to grow as a two-dimensional layer. The partnership between academic researchers and Translucent, Inc., a technology leader in gallium nitride, will help graduate students appreciate the factors involved in developing a viable new technology. As well, the researchers are engaging in an outreach program (called "Alice in Wonderland") that is aimed at attracting female high-school students to the physical sciences and engineering. These students and physics instructors in local high schools are spending their summers at the University of Texas at Austin participating in research within a supportive environment.TECHNICAL DETAILS: The overarching objectives of this research project are to discover, understand and describe processes that lead to the formation of crystalline lanthanum, gadolinium, and erbium oxides on wurtzitic gallium nitride, GaN (0001). This research advances methods for precise interface engineering and elucidates the role of intermetallic compounds (called "Zintl compounds"), comprised of Group 1or 2 elements and Group 13-15 elements, in altering the surface energy to facilitate wetting and direct the [111] growth direction of the oxides on GaN (0001). The research benefits from the infrastructure, adjacency of related research, and expertise and complementary skills the academic researchers and the industrial partner bring in atomically controlled growth, materials characterization, surface chemistry, first-principles modeling and electrical characterization. Specific focus areas for the fundamental studies include: 1) discovery of approaches to grow crystalline, C-type La, Gd and Er oxide films epitaxially on GaN(0001) surfaces; 2) elucidation of the underlying interface chemistry responsible for oxide on semiconductor heteroepitaxy; and 3) exploring the structure-property-growth relationships so the results can be extended to additional oxide-semiconductor systems. The research uses molecular beam epitaxy and atomic layer deposition techniques to grow the epitaxial structures; first-principles density functional theory (DFT) approaches to identify suitable intermetallic compounds and to model the atomic structure, electric and electronic properties of the oxide-gallium nitride interface; and ex situ transmission electron microscopy (TEM) and electrical measurements to validate model predictions and establish structure-property relations.