A novel method to increase the growth rate in sublimation crystal growth of advanced materials

Sublimation crystal growth technique is widely used for the growth of optoelectronic materials, such as aluminum nitride (AIN). In this paper, an integrated model is developed to study the effects of powder geometry on crystal growth rate whereas induction heating, powder charge sublimation, vapor transport, and porosity evolution are considered. The mechanism of vapor transport is proposed by introducing a driving force arising from the temperature difference in AIN sublimation growth system. Powder porosity evolution and sublimation rate variation are predicted based on the vapor transport mechanism. In addition, a new method by optimizing the initial powder porosity and creating holes in the packed powder is proposed to increase the crystal growth rate. Simulation results for the sublimation of powder with and without central hole are presented. It is found that the powder sublimation rate is higher when hole is present. This is also validated experimentally. Effects of initial porosity, particle size and driving force on the sublimation rate are also studied. Finally, the powder geometry is optimized based on numerical simulations. The findings from this investigation can also be applied to SiC since SiC sublimation growth is similar to AIN. (c) 2006 Elsevier Ltd. All rights reserved.