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 isoelectron ic indium. The layers were grown with metal-oxide chemical vapour depo sition and chemical vapour deposition methods including low temperatur e process with tertiarbutylarsine arsenic source. The critical conditi ons of misfit dislocation formation were exceeded up to 5x. The sample s were examined before and after epitaxial process with a number of di fferent X-ray topographic and diffractometric methods, including high resolution synchrotron white beam topography. The crystallographic ide ntification of the defects was supported by the numerical simulation o f topographic images. It was found that a number of threading dislocat ions, continuing in the epitaxial layer from those existing in the sub strate, did not take part in the formation of misfit dislocations desp ite 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 r ocking curves.