Free-fall grown single crystals, doped with Te, were investigated by using X-ray projection topography and high-resolution triple-crystal diffractometry. It was shown that a large part of the samples grown without contacting the crucible was of quite high perfection. It was striation-free and only a few dislocation lines were present. However, it was found that large micro-defects (exceeding 1μm in diameter) were present at a density of about 4 x 104/cm3. The number of small micro-defects (smaller than 1μm in diameter) was still considerably lower than that in terrestrially-grown samples. A twin boundary was found between the free-fall grown part, and the part which was grown in contact with the ampoule walls. Besides the twin, it was found that dislocations at a density of up to about 104/cm3 were generated. The end part of the ingot contained dislocations, with a density greater than 106/cm3, which were introduced due to high thermal stresses in the final stage of crystallization.

The Perfection of Space-Grown GaSb Studied by X-Ray Topography and High-Resolution Diffractometry. A.E.Voloshin, A.A.Lomov, T.Nishinaga, P.Ge, C.Huo: Journal of Crystal Growth, 2002, 236[4], 501-10