Strain evaluation in III-V semiconductor compounds from measurement of thickness fringe displacements.

A technique has been developed for the strain analysis of strained layer heterostructures using a comparison of electron microscope images and simulated images of cleaved wedges. The technique employs the strain relaxation at the edge of the wedge sample, which as the geometry is well known, can be computed using a finite element program. The microscope images of the structure can be taken so that they are independent of the composition and only sensitive to the strain. These images change quite considerably due to a small change in strain and so by comparison between the calculated and experimental images the strain can be measured with an accuracy of about 0.01%