Interactions Between Misfit Dislocations, Surface Morphology, and Point Defects During Strain Relaxation in Semiconductor Heteroepitaxy
R. Hull
University of Virginia, Charlottesville, Virginia, 22904, USA
It is well established that relaxation of lattice-mismatch strain during heteroepitaxial growth can occur both by roughening of the epitaxial layer surface and by injection of misfit dislocations into the heteroepitaxial interface. While reasonably detailed mechanistic understanding has been developed for each of these processes, there has been relatively little quantitative treatment of the competitive or cooperative interactions between them. Further, the effects of point and planar defects upon these phenomena are not well understood.
In this presentation we describe experiments employing real time transmission electron microscope (TEM) observations during annealing and/or growth of metastably strained GeSi/Si heterostructures to elucidate and quantify the kinetic processes governing the evolution of the misfit dislocation array. Ion implantation is also used to study the effects of point defect concentrations upon misfit dislocation nucleation and propagation. Further, in-situ wafer curvature (WC) observations of stress relaxation during heteroepitaxial GeSi/Si growth are coupled with ex-situ atomic force microscopy and TEM measurements to explore and quantify the coupling between dislocation generation and the development of surface morphology. As well as providing significant practical information for design of high quality strained layer semiconductor growth, such cooperative processes can be used as a very sensitive probe for studying the fundamental properties of dislocations in semiconductors.
Our ultimate goal is to incorporate measurements of dislocation kinetics, surface morphology, point defect atmospheres and the resulting cooperative/competitive interactions between these processes into an existing simulator we have developed for predicting misfit dislocation densities generated during GexS1-x/Si growth and annealing sequences. ("Relax", preliminary version available at [1]). This should provide an invaluable tool for predictive growth and processing of strained layer heterostructures, and for exploring fundamental mechanisms of dislocation kinetics.
This work has been funded by the National Science Foundation, and by IBM, and is performed in collaboration with Jennifer Gray, Chi-Chin Wu, and John Bean (University of Virginia); Jerry Floro (Sandia National Laboratories); Eric Stach (Lawrence Berkeley National Laboratories); and Frances Ross (IBM Yorktown Heights Research Laboratories).
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