Strain relaxation in buried strained layers was investigated by using an elastic continuum model. A mixture of single dislocations located at the (lower) substrate/strained-layer interface, and dipole dislocations where one was at the lower interface and the other was at the (upper) strained-layer/capping-layer interface, was proposed. In this mixture, the dislocation distributions were denoted by a parameter which was the ratio of the density of misfit dislocations at the upper interface to that at the lower interface. In a buried strained layer, relaxation of the mean strain occurred via the introduction of 2 orthogonal arrays of a mixture of single and dipole dislocations. The total elastic energy per unit area of buried strained layer, containing 2 orthogonal arrays of a mixture of single and dipole dislocations, was calculated by considering both the free surface and interactions between dislocations. The energy depended upon the misfit-dislocation distribution. An expression for the misfit-dislocation distribution in a buried strained layer, with arbitrary strain relaxation and capping-layer thickness, was derived on the basis of energy minimization considerations. It was demonstrated that, in many buried layers of practical interest, the strain was initially relaxed by single misfit dislocations but was relaxed by a mixture of single and dipole misfit dislocations in the final stages of strain relaxation.

Strain Relaxation in Buried Strained Layers by Mixture of Single and Dipolar Dislocation Arrays. Z.Jin, S.Yang, C.Ma, S.Liu: European Physics Journal - Applied Physics, 1999, 6[3], 251-5