Band-like Inhomogeneity in Bulk ZnGeP2 Crystals, and Composition and Influence on Optical Properties

The influence of intrinsic impurities on the formation of band-like inhomogeneities in ZGP single crystals containing two highly volatile elements has been analyzed. It has been shown that the formation of growth bands occurs due to the accumulation of binary phosphides at the crystallization front and is accompanied by the formation of pores in the near-wall region of the ingot. A connection between near-wall pore formation and the presence of growth bands in ZGP has been established. X-ray spectrometry revealed differences in the chemical compositions of “light” and “dark” growth striations, with significant deviations from stoichiometry in these regions. The dark bands exhibited a higher phosphorus content compared to the light bands and showed an increased germanium content in the light bands. Differences in the orientation of crystallographic axes were observed between the light and dark regions. It has been shown that samples containing inclusions of band-like inhomogeneity significantly distort the profile of the radiation passing through and generated in the crystal and lead to pronounced astigmatism. However, in contrast to the extremely negative influence of banded inhomogeneity on the optical properties of single crystals, the influence of growth striations on the radiation resistance of crystals is minimal.