Quantitative characterization of residual strains in gallium phosphide (100) wafers

Residual strains in thin GaP (100) wafers, sliced from crystalline ingot grown by the liquid-encapsulated Czochralski method, have been first characterized by measuring strain-induced birefringence. The absolute values of the residual strain components ‖Sr−St ‖, ‖Syy−Szz ‖, and 2‖Syz ‖ are quantitatively characterized. It is found that their two-dimensional distribution maps exhibit fourfold symmetry and that most of wafers exhibit U- or M-shape distributions along diametric directions, but some wafers with a low level of strains exhibit distorted-shape distributions. The maximum strain value attains to the order of 10−4 and the corresponding stress is about 7.5×106 N/m2.