High resolution electron microscopy of misfit dislocations in the GaAs/Si epitaxial interface

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Abstract
Recent studies have shown that high quality GaAs films can be grown by molecular beam epitaxy on Si substrates whose surfaces are slightly tilted from the (100) plane. In order to investigate the effect of the tilting of substrate surfaces on the formation of defects, the atomic structure in the GaAs/Si epitaxial interface has been studied with a 1-MV ultrahigh vacuum, high voltage electron microscope. Two types of misfit dislocations, one with Burgers vectors parallel to the interface and the other with Burgers vectors inclined from the interface by 45°, were found in the epitaxial interface. The observation of two cross-sectional samples perpendicular to each other has shown that the tilting of the substrate surface directly influences the formation of these two types of misfit dislocations. A possible mechanism of the reduction of threading dislocations by tilting the substrate surface is discussed based on these observations.