In low misfit systems (m < 1%) the elemental dislocation mechanisms could be observed over large areas; this provided information on the ways the relaxation proceeds in higher misfit hetero-epitaxial systems where large dislocation densities were rapidly generated and in which these mechanisms were not easy to discover among dislocation configurations resulting from this highly deformed state. Heteroepitaxial (GaAs/Ge, SiGe/Si, GaInAs/GaAs) and homo-epitaxial (Si/Si(As)) systems were considered in which the relaxation steps were studied: nucleation, and dislocation multiplication. The Matthews mechanism for misfit dislocation nucleation was observed in a very metastable situation. This was attributed to thermal activation of the source length rather than to the processes reported in the literature. During the development of dislocations several types of interaction occurred leading to threading segments. The very frequent occurrence of cross-slip and multiple cross-slip events allows the relaxation to proceed in spite of blocking interactions. This unexpected easy cross-slip could be related to a shrinkage of the fault ribbon close to the surface due to image forces.

Low Misfit Systems as Tools for Understanding Dislocation Relaxation Mechanisms in Semiconducting Heteroepitaxial Films. B.Pichaud, N.Burle, M.Putero-Vuaroqueaux, C.Curtil: Journal of Physics - Condensed Matter, 2002, 14[48], 13255-67