NIRT: Study of Self-organization in Strained Heteroepitaxial Nanostructures: Multi-scale Modeling, Simulation and Experiment

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ABSTRACTSelf-assembled surface nanostructures hold the promise for manufacture of microelectronic devices with unprecedented performances characteristics. Potential applications include field effect transistors, quantum memory devices and solid-state lasers. Strain-driven nucleation, growth and coarsening of epitaxial islands during MBE growth, possibly with self-assembly of islands with regular arrays, offer a particularly versatile and cost-effective approach to manufacturing nanoscale devices. Recent experimental and analytical studies have revealed that appropriately controlling mismatch strain and processing conditions may influence island shapes, sizes and distributions. To exploit this phenomenon in manufacturing self-organized quantum dot arrays will require a fundamental understanding of the role of strain, surface energies, and kinetics of transport and deposition on the formation and evolution of material structures. A particular challenge is that island morphology is determined both by atomic scale phenomena, such as surface step interactions and alloy dispersion, and by long-range elastic interaction between geometric features.We propose to address this issue by developing multiple-scale models of the growth of strained semiconductor thin films. Our approach will be to use discrete-step and Monte Carlo simulations, supplemented by appropriate atomistic or continuum calculations, to model the mesoscopic processes that determine the surface energies and transport kinetics during growth. The long-range elastic interactions between surface features will be modeled rigorously using continuum finite element computations. The model will be used to predict the nucleation, evolution in shape and organization of islands, and will provide the understanding required to control and optimize processing. Modeling will be informed and guided by experimental observations of stress relaxation and surface evolution in InGaAs/GaAs and SiGe/Si.The participation of undergraduate students will be integrated into the program in two ways. First of all, the budget allows for the appointment of several undergraduate students, which will provide firsthand experience with concepts of nanotechnology for qualified students. In addition, team members will design a new course, intended for undergraduate students in materials science and mechanical engineering, to introduce students to concepts and methods in nanotechnology.