Infrared Quantum Materials Based on Scandium-Containing III-Nitrides

该项目通过将一种很少使用的金属（钪）整合到传统半导体中来开发新的技术上有用的材料。这种组合具有独特的发光和检测能力，对社会有广泛的好处，包括用于医学成像和太阳能电池的新型设备。这项研究旨在了解、控制和调整这些新材料的原子排列，以最大限度地吸收不可见的红外范围内的光。该项目还探讨了半导体中原子缺陷对自由电荷运动的影响。该项目还将研究与增加所有年龄段学生在传统课堂内外的学习机会的教育目标联系起来。参与该项目的研究人员和学生参加了在内部或当地学校组织的外展活动，以增加K-12学生和公众在有趣的、以项目为导向的环境中对材料科学现代科学主题的接触。为普渡大学的中学夏令营“物理Inside Out”设计了课程计划，并进行了物质基本光学特性的实验演示。为了最大限度地影响高中水平，这些活动让教师参与暑期研究。特别是，教师们正在开发以探究为基础的课程计划，将量子科学相关的概念纳入高中课程，以达到印第安纳州的标准。研究人员还为印第安纳州科学教师协会的年度会议组织了一个实践研讨会，并提供了带回家的材料。本项目为一种新型红外材料奠定了基础，该材料使用了包含IIIB族过渡金属钪的氮化半导体导带中量子化状态之间的光学跃迁。这些半导体具有独特的电子特性，使它们适合将半导体光电器件的功能推进到目前其他材料系统无法达到的光谱范围。这种创新的方法采用了一种新兴的光电材料，即与GaN晶格匹配的sc - al -氮化物的纤锌矿相，以减轻迄今为止阻碍氮化物光电子学进入红外的应变相关问题。研究工作是跨学科的，涉及材料设计和生长，加上结构和光学表征。极性和非极性ScAlN/GaN异质结构设计使用广泛的能带结构计算。为了获得最大的材料纯度和原子结构的单层控制，采用等离子体辅助分子束外延的方法在高质量的准块状GaN衬底上生长含sc材料。决定性的任务是确定满足近红外光学工艺最严格要求的外延生长条件。为了将微结构与光学和电子特性联系起来，利用高分辨率x射线衍射、先进透射电子显微镜和原子探针层析成像对半导体材料的结构进行了全面表征。利用傅里叶变换红外光谱和光致发光技术对材料的能带结构进行了实验研究。这些新兴材料的生长推动了过渡金属氮化外延的发展。未知的机制的材料生长在极性和非极性氮化镓衬底审查。这一研究也为红外光学跃迁的物理基础做出了贡献。这些红外材料有望使光电子学具有当前技术无法比拟的功能。此外，新型含sc半导体有利于其他应用，如高电子迁移率晶体管、紫外线、热电、压电和等离子体器件。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical descriptionThis project is developing new technologically useful materials by incorporating a rarely used metal (scandium) into traditional semiconductors. This combination has unique light emitting and detecting capabilities with broad benefits to society including novel devices for medical imaging and solar cells. The research aims to understand, control, and adjust the atomic arrangement of these new materials to maximize light absorption in the invisible infrared range. The project also explores the effect of atomic imperfections in the semiconductors on the movement of free electrical charge. This program also links the research with the educational goal of increasing learning opportunities for students of all ages, inside and outside the traditional classroom. The investigators and students involved in this project participate in outreach activities organized either in-house or at local schools to increase exposure of K-12 students and the general public to modern scientific topics in materials science in a fun, project-oriented environment. Lesson plans are designed and experimental demonstrations of basic optical properties of matter are built for the middle-school summer camp “Physics Inside Out” at Purdue. To maximize impact at the high-school level, the activities engage teachers in summer research. In particular, the teachers are developing inquiry-based lesson plans incorporating concepts related to quantum science into the high-school curriculum to fulfill Indiana standards. The researchers also organize a hands-on workshop with take-home materials for the annual meeting of the Hoosier Association of Science Teachers.Technical descriptionThis project sets the foundation for a novel type of infrared materials using optical transitions between quantized states in the conduction band of nitride semiconductors incorporating the group IIIB transition-metal scandium. These semiconductors have unique electronic properties that make them suitable for advancing the functionality of semiconductor optoelectronic devices into spectral ranges currently inaccessible with other material systems. The innovative approach employs an emergent optoelectronic material, the wurtzite phase of Sc-Al-nitride that is lattice-matched to GaN, to mitigate strain-related issues that have impeded progress of nitride optoelectronics into the infrared so far. The research effort is interdisciplinary and involves material design and growth, plus structural and optical characterization. Polar and nonpolar ScAlN/GaN heterostructures are designed using extensive band-structure calculations. To achieve maximum material purity and monolayer-control of the atomic structure, the Sc-containing materials are grown by plasma-assisted molecular beam epitaxy on high quality quasi-bulk GaN substrates. The decisive task is to identify the epitaxial growth conditions that satisfy the most stringent requirements imposed by near-infrared optical processes. In order to correlate microstructure with optical and electronic properties, the structure of the semiconductor materials is comprehensively characterized with high-resolution x-ray diffraction, advanced transmission electron microscopy, and atom probe tomography. The band structure of the materials is probed experimentally with Fourier transform infrared spectroscopy and photoluminescence. The growth of these emergent materials advances the state-of-the-art in transition-metal nitride epitaxy. Uncharted mechanisms of material growth on polar and non-polar GaN substrates are scrutinized. This research also contributes to the knowledge base of the physics of infrared optical transitions. These infrared materials are expected to enable optoelectronics with functionality unmatched by current technologies. Moreover, the novel class of Sc-containing semiconductors benefit other applications such as high-electron mobility transistors, ultraviolet, thermoelectric, piezoelectric, and plasmonic devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.