Effect of non-strained capping layer on excess stress in strained layers

The effects of the capping-layer thickness and the discrepancy of the numbe rs of misfit dislocations at the upper and lower interfaces in capped layer on the excess stress are considered. Based on this, the formulae of excess stresses for single- and double-kink models are modified and a new formula is derived, which unifies single- and double-kink models and is valid for arbitrary capping-layer thickness. It is useful to complete the description of the formation and motion of misfit dislocations in strained layers.