Optical anisotropy in dislocation-free silicon single crystals

The optical anisotropy in silicon single crystal was evaluated by measuring the birefringence accurately. In measurement, the use of dislocation-free silicon crystals effectively avoided the influence due to dislocation-induced birefringence. The extreme small birefringence, which was supposed to be due to the point defects, was also measured and taken into consideration, by using scanning infrared polariscope (SIRP) with high sensitivity. The random error, which may occur in 1-point measurement, was eliminated by carrying scanning measurement over the checking plane of the cuboid sample. As the result, the birefringence due to the optical anisotropy in dislocation-free silicon crystals was measured to be (3.34±0.09) × 10-6, when probing light (λ = 1.52 µm) was propagating along the [o110] direction (at the [o0] direction). The birefringences due to the optical anisotropy were also measured at other crystallographic directions with a cylindrical silicon sample.