X-Ray Topographic Analysis of Misfit Dislocation Distribution in InGaAs and GeSi/Si Partially Relaxed Heterostructures

摘要

InGaAs/GaAs and SiGe/Ge partially relaxed heterostructures have been characterized by high resolution X-ray diffraction and by X-ray double crystal topography in order to evaluate the degree of strain release and the distribution of misfit dislocations. X-ray topography evidences a rapid decrease of the average length of misfit dislocation segments with the increase of the density of misfit dislocations both in InGaAs and GeSi/Si structures. For a comparable amount of strain release, SiGe/Si heterostructures exhibit shorter misfit dislocation lengths with respect to InGaAs/GaAs heterostructures. The analysis of the dislocation network in the samples with lower dislocation density evidence dislocation blocking and cross slip mechanisms. In comparison with single heterostructures, composition graded InGaAs/GaAs heterostructures exhibit longer misfit dislocation segments. A simple model to evaluate the threading dislocation density in a completely not destructive way is proposed.