The combined effects of the misfit strains, and of the strains which were caused by a neighboring defect, upon the nucleation energy of dislocation loops were calculated. Defects of various sizes, located at various distances from the loop, were considered. For very small (less than 0.5%) mismatches, and for very small defects, the activation energy was not appreciably reduced and large thicknesses were required for nucleation. At mismatches of 1% or more, and with defect sizes of 1.5nm or larger, heterogeneous nucleation at growth temperatures became possible. This was more efficient in reducing the energy when it occurred at the center of a loop. Impurities which were located within the dislocation cores could theoretically reduce the core parameter substantially and thereby reduce the activation energy. This was unlikely to occur in practice. Very large defects, such as oxide and carbide precipitates reduced the activation energy for nucleation over large distances and thereby encouraged the nucleation of several loops; thus resulting in very rapid strain relaxation. In highly mismatched (4 to 8%) layers, homogeneous nucleation occurred at 400 to 500C. It was explained why a periodic arrangement of misfit dislocations was observed only in highly mismatched layers.

Nucleation of Dislocation Loops in Strained Epitaxial Layers. U.Jain, S.C.Jain, A.H.Harker, R.Bullough: Journal of Applied Physics, 1995, 77[1], 103-9