Melt flow and species transport in µg-gradient freeze growth of germanium

The result of a mug-experiment on the Gradient-Freeze growth of Ge:Zn with doping from the vapour phase shows a homogeneous distribution of the zinc in the melt, indicating the dominating role of a gravity-independent transport mechanism. This effect is investigated numerically on the basis of a global model of the growth setup. The numerical simulation includes the melt flow and the transport of the dopant taking into account buoyant and thermocapillary forces. The results confirm the minor influence of gravity on the species transport. The complete mixing of the melt can be explained by thermocapillary (Marangoni) convection only.