POWRE: Role of Temperature and Morphology in the Nucleation of Misfit Dislocations in Heteroepitaxial Films

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

The goal of this project is to enhance understanding of defects in heteroepitaxial semiconductor thin films. A fundamental issue in heteroepitaxy is the relaxation of the elastic strain induced by lattice mismatch with increasing thickness of the epitaxial film. Strain relaxation occurs either by nucleation of misfit dislocations or by morphological transformations of the surface, or a combi-nation of both. There remains a wide gap in understanding how temperature and surface mor-phology affect the nucleation of misfit dislocations in epitaxial films. Closing this gap is the cen-tral focus of the proposed research. A new 'temperature-dependent' mechanism for the nucleation of misfit dislocations in heteroepitaxial films is proposed. It leads to a cooperative nucleation of many misfit dislocations in a planar epitaxial film of a given thickness above a certain tempera-ture without any energy barrier. The proposed research focuses on how the process of misfit dis-location nucleation is influenced by changes in morphology. The analytical approach being pur-sued enables prediction of strain relaxation as a function of temperature, growth rate, misfit and morphology. %%% This is a research enhancement grant made under the Professional Opportunities for Women in Research and Education (POWRE) program. The investigator is at a critical stage of her career making a transition from a Research Specialist to the position of a Research Associate Professor. The POWRE award will enable the PI to begin a new area of research with promising ramifica-tions in technology. A duration of eighteen months will provide an opportunity to investigate and test the applicability of a novel approach advanced for understanding an outstanding issue in het-eroepitaxy. The research is expected to contribute basic materials science knowledge at a funda-mental level of special relevance to the behavior of electronic materials. The project is co-supported by the Division of Materials Research, and the MPS OMA(Office of Multidisciplinary Activities). ***