Poisson's ratio of GaAs

Most epitaxial layer growth involves mismatch between layer and growth substrate, even in the case of nearly lattice matched systems such as GaAs/AlAs. The accurate determination of layer thicknesses and stoichiometry in single and multi-layer heterostructures by x-ray diffraction requires knowledge of the elastic properties of the layers so that accurate account can be taken of strain effects. A novel technique has been developed which allows Poisson's ratio to be determined by measuring a semiconductor sample in both the pseudomorphic and completely relaxed states. The relationship between the two strain states determines the material's Poisson ratio and this has been found to be 0.320/spl plusmn/0.001 for GaAs.