Quantitative photoelastic measurement of residual strains in undoped semi-insulating gallium arsenide

A new quantitative photoelastic method has been developed to measure residual strains in undoped semi-insulating (001) GaAs substrates for integrated circuits. The absolute values of the shear strain ‖exy‖ and the difference of the expansion and contraction strains ‖eyy−exx‖ existing in the (001) substrate plane are quantitatively determined by using the present method. Their two-dimensional distribution maps are demonstrated to exhibit fourfold symmetries rotating 45° to each other. The absolute values are found to be of the order of 10−5 at the substrate edges.