Quantitative photoelastic characterization of residual strains in LEC-grown indium phosphide (100) wafers

Residual strains in a 2´´-diameter (100) wafer, sliced from a Fe-doped InP ingot grown by the liquid-encapsulated Czochralski method, have been characterized by measuring strain-induced birefringence. The authors present the quantitative photoelastic characterization of the residual strains and compare their two-dimensional distribution maps with the etch pit density distribution map to explore their origin. Their two-dimensional distribution maps exhibit eightfold rather than fourfold symmetry. From the comparison of the residual strain and etch pit distribution maps, it is found that there is an inverse correlation between them. The maximum strain value is about 5 × 10^-5 and the corresponding stress is 2.3 × 10⁶ N/m²