STRESS-RELAXATION IN LATERALLY SMALL STRAINED SEMICONDUCTOR EPILAYERS

The stress field in laterally small strained semiconductor epilayers h as been studied by the finite element method. The reaction of the epil ayer on the substrate and the bulging-out effect caused by shear force s in the side wall boundaries play an important role. Analytical appro ximate methods are shown to be deficient. The normal stresses relax fa ster than a simple exponential with height z and virtually complete re laxation occurs at a height h(eff)approximate to root ab/2 (where a an d b are the width and length, respectively, of the parallellopipidial epilayer) which is in good agreement with recent experiments. An equiv alent lattice spacing f(m) as a function of z/ root ab is defined and calculated.