Structure and dislocation development in mono-like silicon

The current paper investigates the structure of low-lifetime areas observed in a < 110 >-oriented mono-like silicon ingot grown from monocrystalline seeds. These areas are related to dislocation clusters forming at seed junctions and several generation mechanisms are discussed. Dislocations generated due to physical contact between seeds could only be completely avoided by introducing gaps between the seeds. Large gaps were, however, found to suffer from alternative generation processes not found in small gaps. Dislocations generated in the seeds and in peripheral grains does not necessarily move in to the main crystal and low-lifetime areas are mainly related to dislocations generated above the seeding structure. Dislocations are found to form clusters aligning along < 111 >-directions and are proposed to happen by glide on {111}-planes from the boundary plane between two seed crystals. The extent of low-lifetime areas and corresponding dislocation clusters, for junctions containing no or small gaps, appear to mainly depend on the misorientation between seeds and by attaining sufficiently low misorientation the high bulk lifetime can be retained also at the junctions. Analysis of the misorientations along principal axes indicates that larger misorientations can be tolerated if the misorientation is limited to a single tilt axis.