Characterization and Control of Interfacial Structure in Type-II Superlattices and Quantum Wells

该项目研究了ii型量子阱和由分子束（MBE）、迁移增强（MEE）、外延生长的超晶格中界面结构和组成的原子尺度表征和控制。该方法强调横断面扫描隧道显微镜（STM），检查在各种生长条件下阴离子和阳离子偏析、不完全键类型选择性和动力学限制的表面粗糙度对界面完美的限制。预计界面形态（由于生长平面上的孤岛）和非均匀成分（由于混合界面键类型，交叉结合或偏析）对界面粗糙度的各自作用将完全反褶积。表征将用于识别和理解对界面键合和平面性提供最大控制的生长条件和相关现象。因此，预期可以更好地理解、控制和实现最佳ii型量子阱器件所需的结构和组成的完美性。该项目涉及材料科学中具有高技术相关性的主题领域的基础研究问题。现在有了实验工具，可以在原子水平上观察基本的表面过程，这些过程一旦得到更好的理解，就会促进基础科学和技术的进步。从研究中获得的基本知识和理解有望通过为设计和生产改进的材料和材料组合提供基本的理解和基础，从而有助于提高先进设备的性能和稳定性。该计划的一个重要特点是通过培养学生在一个基础和技术上重要的领域的研究和教育的整合。＊＊＊

This project addresses atomic-scale characterization and control of interface structure and composition in type-II quantum wells and superlattices grown by molecular-beam (MBE), and migration-enhanced (MEE), epitaxy. The approach emphasizes cross-sectional scanning tunneling microscopy (STM), examining limitations to interfacial perfection imposed by anion and cation segregation, incomplete bond type selectivity, and kinetically limited surface roughness, under a variety of growth conditions. Complete deconvolution of the respective roles of interface morphology (due to islanding in the growth plane) and inhomogeneous composition (due to mixed interface bond types, cross incorporation, or segregation) on interface roughness is expected. Characterization will be used to identify and understand growth conditions and associated phenomena which afford maximal control over interface bonding and planarity. Accordingly it is anticipated that structural and composition perfection needed for optimal type-II quantum well devices may be better understood, controlled and realized. %%% The project addresses basic research issues in a topical area of materials science with high technological relevance. Experimental tools are now available to allow atomic level observation of elementary surface processes which when better understood allow advances in fundamental science and technology. The basic knowledge and understanding gained from the research is expected to contribute to improving the perform-ance and stability of advanced devices by providing a fundamental understanding and a basis for designing and producing improved materials, and materials combinations. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. ***