The investigation of microdefects in high-purity silicon crystals by means of lithium decoration

Publisher Website
Google Scholar
Abstract
The occurrence and nature of microdefects in siliconsingle crystals have been studied by means of lithium decoration in combination with x‐ray transmission topography, ir transmission microscopy, and electrical resistivitymeasurements. The silicon crystals used were grown with the floating‐zone or the pedestal‐pulling method and contained different types of lattice defects. The Li diffusions were carried out at 400<TD <730°C. Due to precipitation the Li‐donor concentration decreased exponentially with time during annealing. The number of nucleation sites was calculated with the aid of Ham's theory. For TD =400°C precipitation took place exclusively on grown‐in lattice defects, such as dislocations and vacancy clusters. At TD =500°C vacancy‐oxygen complexes of type (V‐30) were formed in a striated distribution, which acted as nucleation sites for Li. These complexes are not formed in crystals doped with hydrogen. For TD ≥550°C the precipitation process is dominated by Li precipitation on V‐O pairs (A centers).