FuSe-TG: Monolithic Heterointegration of GeSn and SiGeSn Alloys with Silicon Platforms

半导体的未来（FuSe）项目的重点是开发基于硅、锗和锡合金的红外光传感器，这些合金都属于元素周期表的第四组。这些组iv材料具有化学兼容性，使得在单个单片芯片上集成光检测和信号处理能力（后者基于纯硅）成为可能。相比之下，目前的红外技术主要基于昂贵的材料，这些材料与硅不相容，有时甚至有毒。该基金支持由来自三所不同大学的研究人员组成的团队，以追求异质材料集成的关键科学挑战，即适应构成其晶体结构的原子块之间的大小差异。这种尺寸不匹配会导致原子错位，从而降低探测器设备的性能。解决方案需要物理学家、化学家、材料科学家和设备工程师之间的协同工作。团队的多学科特征通过围绕FuSe项目的共同设计理念整合许多不同的观点，为未来的劳动力提供了独特的教育体验。团队成员拥有非常多样化和互补的专业知识，从电路设计到全微观量子力学模拟，包括超越传统方法的新合成策略的开发。第二部分:该团队正在建立研究合作，旨在克服硅和红外GeSn或SiGeSn合金之间非常大的晶格不匹配（超过4%，限制了无缺陷生长的临界厚度为一个或两个原子单层），用于探测器和读出组件的单片集成，了解基于GeSn或SiGeSn的二极管的最终暗电流限制。并设计与这些二极管的特性和红外器件的生长相匹配的读出电路。在这些总体研究目标中，最初的团队建设工作是为了确定GeSn合金和Si衬底之间的错配位错结构，执行点缺陷的详细光谱，使用第一性原理计算理解位错和点缺陷，并消除导致暗电流的表面缺陷。在FuSe团队资助期间，该团队使用多学科方法解决了这些挑战，通过执行卢瑟福后向散射、拉曼、x射线衍射、原子力显微镜和电子显微镜研究，全面表征了合金的结构特性及其与Si的界面。特别是，后者使得确定控制应变松弛过程的位错的性质成为可能。该团队还评估了GeSn或SiGeSn合金的新型钝化介质、抗反射层和氧化物的电学和光学特性，研究人员对GeSn和SiGeSn二极管中与观察到的暗电流相关的缺陷进行了系统的光谱研究。这些初步研究以及对缺陷界面和点缺陷进行大规模第一性原理理论模拟，以解释观察到的合金器件的结构和电学性能，以及一般的团队组建活动，为未来的重点研究密集型项目奠定了基础。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。

PART I: NON-TECHNICAL SUMMARYThis Future of Semiconductors (FuSe) project focuses on developing infrared light sensors based on alloys of silicon, germanium, and tin, all of which belong to the fourth group of the Periodic Table. These group-IV materials are chemically compatible, making it possible to integrate light detection and signal processing capabilities (the latter based on pure silicon) on a single, monolithic chip. By contrast, current infrared technology is mainly based on expensive materials that are incompatible with silicon and sometimes even toxic. The grant enables the formation of a team, which consists of investigators from three different universities, to pursue key scientific challenge for the integration of heterogeneous materials is accommodating the difference in size between the atomic blocks that make up their crystal structures. This size mismatch can induce atomic misplacements that degrade the performance of detector devices. The solution requires collaborative work between physicists, chemists, materials scientists, and device engineers. The multidisciplinary character of the team provides a unique educational experience for the future workforce by integrating many different perspectives around the co-design ideas of the FuSe program. The team members have a very diverse and complementary expertise, from circuit design to fully microscopic quantum-mechanical simulations, including the development of new synthetic strategies beyond conventional methods. PART II: TECHNICAL SUMMARYThe team is building research collaborations aimed at overcoming the very large lattice mismatch between silicon and infrared GeSn or SiGeSn alloys (which exceeds 4% and limits the critical thickness for defect-free growth to one or two atomic monolayers) for monolithic integration of detectors and readout components, understanding the ultimate dark current limits of diodes based on GeSn or SiGeSn, and designing readout circuitry matched to these diode characteristics and to the growth of the infrared devices. Within these general research targets, the initial team-building effort is carried out with the purpose of determining the structure of misfit dislocations between GeSn alloys and Si substrates, performing detailed spectroscopy of point defects, understanding dislocations and point defects using first-principles calculations, and eliminating surface defects that contribute to the dark current. During the FuSe Teaming Grant period the team addresses these challenges using a multidisciplinary approach by fully characterizing the structural properties of the alloys and their interface with Si by performing Rutherford Backscattering, Raman, x-ray diffraction, atomic force microscopy, and electron microscopy studies. In particular, the latter makes it possible to determine the nature of the dislocations that control the strain-relaxation progress. The team also evaluates electrical and optical properties of novel passivating dielectrics, antireflection layers and oxides for GeSn or SiGeSn alloys, and the researchers perform systematic spectroscopy studies of defects that can be associated with observed dark currents in GeSn and SiGeSn diodes. These preliminary investigations along with large-scale first-principles theoretical simulations of the defected interfaces and point defects to interpret the observed structural and electrical properties of the alloy devices and the general team-forming activities lay the foundation for future focused, research-intense projects.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.