Dislocation structure of Ge crystals grown by low thermal gradient Czochralski technique

Dislocation structure of the Ge single crystals grown by Czochralski method with low thermal gradient has been studied. The selective etching technique and the X-Ray transmission and reflection topography were used. Clearly defined non-uniform dislocation distribution over the crystal cross - section is revealed. Helical dislocations and sets of prismatic dislocation loops are registered. Helical dislocations perpendicular to the ingot axis are situated near the boundary between the regions with low and high dislocation densities (102 and 103 cm−2, respectively). Their length can be as much as several millimeters. Dislocation formations lying at a 35.3° to the crystal axis along <110> directions are also observed. These formations have the shape of prism confined by {111} planes.