MULTIPLICATION OF DISLOCATIONS IN SI1-XGEX LAYERS ON SI(001)

A mechanism describing how dislocations in epitaxial layers multiply is presented. It is shown that a single threading dislocation can give rise to an array of dislocation sources, where each source generates a separate dislocation loop perpendicular to the primary misfit dislocation. The conditions controlling the activation of these sources are discussed in detail. Most notably, it is demonstrated that a minimum layer thickness, referred to as the "multiplication thickness," is required to accommodate the cross-slip processes that are necessary for source activation. An experimental value of 0.67-mu-m for the multiplication thickness h(x) is measured from a single Si0.87Ge0.13 layer on Si(001), and a general expression for h(x) is developed. The dislocation patterns produced by this mechanism are also considered, as are the implications of such a mechanism in light of the established view of strain relaxation.