Numerical study on the radial dopant distribution in micro-pulling-down crystal growth

To improve the dopant homogeneity in the radial direction, the micro-pulling-down apparatus was modified for Ce-doped Y3Al5O12 (Ce3+:YAG) crystal growth. Two effective crucible variants, diffusion-channel and multi-channel crucibles, were adopted to alleviate the inhomogeneity of dopant concentration in the radial direction. In the diffusion-channel model, two different inclination angles were investigated. The results demonstrate that the radial dopant distribution at the melt-crystal interface (i.e., the growth front) is improved notably by using the diffusion-channel crucible. Furthermore, the better radial distribution is achieved with the larger inclination angle. In the multi-channel model, more capillary-channels result in a smaller inflow velocity from every single capillary-channel with the same growth rate. Therefore, the effect of inflow on the dopant distribution is reduced, and thus the radial dopant homogeneity is improved apparently. Besides, although the symmetry of concentration distribution along the azimuthal direction is broken in the multi-channel model, the whole homogeneity of dopant at the melt-crystal interface is ameliorated.