Investigation of Misfit Dislocation Sources in GaAs Epitaxial Layers

The formation of misfit dislocation was studied in GaAs homoepitaxial layers on the substrates containing considerable amount of isoelectronic indium. The layers were grown with metal-oxide chemical vapour deposition and chemical vapour deposition methods including low temperature process with tertiarbutylarsine arsenic source. The critical conditions of misfit dislocation formation were exceeded up to 5×. The samples were examined before and after epitaxial process with a number of different X-ray topographic and diffractometric methods, including high resolution synchrotron white beam topography. The crystallographic identification of the defects was supported by the numerical simulation of topographic images. It was found that a number of threading dislocations, continuing in the epitaxial layer from those existing in the substrate, did not take part in the formation of misfit dislocations despite a suitable slip system. On the other hand, the formation of misfit dislocations from small imperfections of epitaxial deposit was proved in many cases. A reasonable good quality of the layers was confirmed by the resolution of individual defects and only small broadening of rocking curves.