Investigation of Misfit Dislocation Sources in GaAs Epitaxial Layers

The formation of misfit dislocation was studied in GaAs homoepitaxiallayers on the substrates containing considerable amount of isoelectronic in-dium. The layers were grown with metal-oxide chemical vapour depositionand chemical vapour deposition methods including low temperature processwith tertiarbutylarsine arsenic source. The critical conditions of misfit dis-location formation were exceeded up to 5 x. The samples were examinedbefore and after epitaxial process with a number of different X-ray topo-graphic and diffractometric methods, including high resolution synchrotronwhite beam topography. The crystalIographic identification of the defectswas supported by the numerical simulation of topographic images. It wasfound that a number of threading dislocations, continuing in the epitaxiallayer from those existing in the substrate, did not take part in the formationof misfit dislocations despite a suitable slip system. On the other hand, theformation of misfit dislocations from small imperfections of epitaxial depositwas proved in many cases. A reasonable good quality of the 1ayers was con-firmed by the resolution of individual defects and only smalI broadening ofrocking curves