Fundamental and Technological Basis of Compliant Universal Substrates for Growing Defect Free Heteroepitaxial Films

提出的研究和教育计划的目标是：(1)开发一种可行的柔性衬底技术，该技术可用于生长具有大（15%）晶格错配和不同晶格结构的无缺陷异质外延材料；(2)了解柔性衬底的基本物理特性，并建立物理模型来定量描述衬底柔性现象。简而言之，该计划旨在建立柔性通用基板的理论和技术。作为这项研究的结果，一种或两种类型的衬底，可能是砷化镓或硅，将足以容纳各种各样的化合物半导体外延材料，包括那些没有合适的传统衬底生长的材料。所提出的兼容通用衬底基本上是由超薄（10a至100A）单晶（例如GaAs或Si）与具有大（10度）扭曲角的GaAs或Si体晶体结合而成。认为扭转边界和极薄键合层的微观结构是使结构适应异质外延层的关键。我们设想，双晶体的扭曲键合薄部分的行为有点类似于一个独立的薄模板，以实现其顺应性。我们的初步实验结果表明，InGaP， GaSb和InSb分别与GaAs失配1%，8%和15%，可以在兼容的通用衬底上无缺陷生长。该提案汇集了Lo的专业知识，Lo提出了柔顺通用衬底的概念，而Sass则对具有与柔顺通用衬底相同几何形状的双晶中包含的晶界结构进行了广泛的研究。由Lo， Sass， 3名博士生和至少4名本科生组成的研究团队将完成三项任务：基础材料研究，柔性衬底技术开发以及材料和器件演示。通过这些努力，期望建立符合通用基板的物理机制，技术和应用。几十年来，兼容的通用衬底一直是从事半导体材料和器件研究的人们的梦想。柔性通用衬底的实现将消除半导体研究中最严重的障碍之一，并显著推进微电子、光电子以及两者的集成技术。拟议的研究将大大有助于实现这一目标。

The objectives of the proposed research and education program are: (1) to develop a viable technology for compliant substrates which can be used to grow defect-free heteroepitaxial materials of large (15%) lattice mismatches and different lattice structures, and (2) to understand the underlining physics of compliant substrates and to establish a physical model to quantitatively describe the phenomenon of substrate compliance. In brief, this program aims to establish the theory and technology of compliant universal substrates. As a result of this research, one or two types of substrates, perhaps GaAs or Si, will be sufficient to accommodate a large variety of compound semiconductor epitaxial materials, including those having no proper conventional substrates on which to grow. The proposed compliant universal substrate is essentially made of an ultra thin (10 A to 100A) single crystal (e.g. GaAs or Si) bonded to a GaAs or Si bulk crystal with a large ( 10 degrees) twist angle. It is believed that the microstructure of the twist boundary and the extremely thin bonded layer play a critical role in making the structure compliant to the heteroepitaxial overlayer. We conceive that the twist bonded thin portion of the bicrystal behaves somewhat similar to a free standing thin template to achieve its compliance. Our preliminary experimental results show that InGaP, GaSb, and InSb, with 1%, 8%, and 15% mismatch to GaAs, respectively, can be grown defect-free on the compliant universal substrates. This proposal brings together the expertise of Lo, who has developed the concept of the compliant universal substrate, and of Sass, who has carried out extensive studies of the structure of grain boundaries contained in bicrystals with the same geometry as in the compliant universal substrate. The research team made of Lo, Sass, 3 Ph.D. students and at least 4 undergraduates will perform three tasks: fundamental materials research, compliant substrate technology development, and material and device demonstrations. Through these efforts, the physical mechanisms, technologies, and applications of compliant universal substrates are anticipated to be established. Compliant universal substrates have been a dream for many decades for people working on semiconductor materials and devices. The realization of compliant universal substrates will remove one of the most serious road blocks in semiconductor research and significantly advance the technologies of microelectronics, optoelectronics, and the integration of both. The proposed research will contribute substantially to achieving this goal.