Reflection X-Ray Topography of GaAs Deposited on Ge

Reflection x‐ray topography is well suited to the study of defects in epitaxial films deposited on single crystal substrates. In particular, since and Ge have lattice parameters that are almost, but not quite equal, certain reflecting planes can be used with suitable radiation to allow separate topographs of the epitaxial film and Ge substrate to be taken. In this way, the various types of defects appearing in the epitaxial film can be analyzed to show whether or not they were influenced by growth conditions or by substrate preparation. During our investigation, growth pyramids due to imperfections or contamination in the substrate, and dislocation networks, probably due to mismatch between film and substrate lattice parameters, were observed. The latter were observed in both the film and substrate, but occurred only for films more than about 2μ thick.