THEORETICAL COMPARISON OF THE STABILITY CHARACTERISTICS OF CAPPED AND UNCAPPED GEXSI1-X STRAINED EPILAYERS

A theoretical comparison of the stability characteristics of capped and uncapped GexSi1-x strained layers is performed, using exact expressions for the energy of orthogonal, periodic arrays of misfit dislocations in both cases. The critical thickness of a capped layer is predicted to be between two and four times larger than that of an uncapped layer which has the same lattice misfit with its substrate, Experimentally determined values of the critical layer thickness of capped layers are in good agreement with the theory presented. Equilibrium dislocation density and rate of plastic flow are predicted to be considerably reduced in a capped layer in comparison with an uncapped layer of the same thickness and misfit.