Optimization of Hot-Zone Design through CFD Analysis for Kyropoulos Sapphire Single Crystal Grower

Abstract

Sapphire (Al2O3) wafers are used as an important substrate for the production of blue Light Emitting Diodes (LED) and the LED’s performance largely depends on the quality of the sapphire single crystals. There are several crystal growth methods for sapphire crystals and the Kyropoulos method is an efficient way to grow large diameter and high-quality sapphire single crystals with low dislocation density. During Kyropoulos growth, crystal growth begins from the seed at the top by slowly decreasing the temperature of heater, and the quality of the single crystals is largely influenced by the convection of the molten sapphire. The convection of molten sapphire is mainly influenced by the Hot-zone geometry such as crucible shape, heater arrangements and temperature distribution. In this study, Computational Fluid Dynamics (CFD) simulations were performed in order to optimize the Hot-zone of a Kyropoulos grower for producing high quality sapphire single crystals.