Optical birefringence images of dislocations in large gallium phosphide crystals

The optical birefringence induced by the strain field of a dislocation has been used to follow dislocation lines through large gallium phosphide crystals. Dislocations could be seen whether their lines were parallel to the imaging light beam or were steeply inclined to it. The images obtained so far suggest that it would be possible to resolve individual dislocations in crystals that contain ≤5 × 105 dislocations per cm2. © 1977.