The effects of GaAs substrate misorientation upon strain relaxation in InGaAs films and multi-layers were investigated. Calculations of shear stresses due to misfit strain, resolved on the glide plane in the glide direction, revealed that the α and β 60º slip systems were affected in an almost identical fashion, for all substrate misorientation directions. It was noted that classical models for the nucleation and glide of 60º dislocations predicted that the substrate misorientation would not affect the degree of <110> asymmetry in the strain relaxation of lattice-mismatched zincblende films. Experimental results instead revealed the existence of asymmetries in strain relaxation, for partially relaxed single layers, which favoured those dislocations which were aligned with the off-cut axis. These asymmetries depended upon the substrate misorientation and the growth temperature, and were not easily explained by differences in the intrinsic core properties of α and β dislocations. In fully relaxed multi-layers (grown at lower temperatures) and in single layers (grown at higher temperatures), an epilayer tilt which increased the (111)B substrate miscut was observed. In multi-layers, this behavior was found to be related to the presence of micron-sized surface facets. Possible explanations for the results were considered to include the nucleation of partial dislocations, the interaction of gliding threading dislocations, and a strain relaxation which was predominated by back-and-forth gliding of α threading-dislocation segments. These results supported the conclusion that local surface or interface step morphologies were more important than bulk stress effects in determining misfit dislocation formation in this system.

R.S.Goldman, K.L.Kavanagh, H.H.Wieder, S.N.Ehrlich, R.M.Feenstra: Journal of Applied Physics, 1998, 83[10], 5137-49