Dislocation generation and propagation near the seed-crystal interface during MLEC crystal growth of sulfur-doped InP

The mechanism of dislocation generation and propagation in InP bulk crystals has been studied by controlling the shape and the growth rate of the neck. The effectiveness of deliberate necking in MLEC crystal growth of sulfur-doped InP crystals has been studied by X-ray white beam synchrotron radiation topography. For seeds oriented in the 〈100〉 direction, the twelve-fold slip systems are arrayed at 35° from the seed axis. Dislocations are observed in topographic views of the (110) cross-section of these crystals. The high density of dislocations generated at the seed-crystal interface is seen to propagate outward toward the periphery. Also seen are the striations associated with the sulfur distribution. These striations delineate the solid-melt interface as thermal excursions cause instantaneous changes in growth rate. For this study, the pulling rate was deliberately varied during growth, to determine the relationship between interface shape and dislocation density. The results show the necking process is of crucial importance to promote the growth of highly perfect InP single crystals.