The dopant fields in "uniform-diffusion-layer", "global-thermal-convection" and "precrystallization-zone" models

In the case of vertically stabilized Bridgman-Stockbarger semiconductor, cr ystal growth system, this study compares the computed dopant fields in the neighborhood of the melt/solid interface in ''uniform-diffusion-layer'', "g lobal-thermal-convection" and "precrystallization-zone" models. Using quasi -steady state approximation, this comparison is made for crystal and melt w ith thermophysical properties similar to those of gallium-doped germanium, for different Rayleigh numbers and different Schmidt numbers related to the melt/solid interface. Numerical simulations put in evidence the difference s between the computed dopant fields in the above three models. For example , the dopant concentration computed in the "precrystallization-zone" model for a volumic concentration phi = 0.055 of "solid inclusions" at the interf ace on the axis of the cylinder is five times bigger than the dopant concen tration computed in the "global-thermal-convection" model. At the same time , the percent radial segregation computed in the "precrystallization-zone" model for cp = 0.055 is considerably larger than in the "global thermal-con vection" model. Therefore, the influence of the microstructures from the pr ecrystallization-zone on the dopant dispersion in the neighborhood of the m elt/solid interface is relevant and there is no reason to ignore it in gene ral. (C) 2000 Elsevier Science Ltd. All rights reserved.