Thermosolutal convection and solute segregation during the vertical Bridgman growth of Hg_1-xCd_xTe single crystals

The mechanism for thermosolutal convection and the coupling effects of flow, temperature and solute fields during the vertical Bridgman growth of Hg_1-xCd_xTe single crystals have been numerically analyzed. The calculations take into account the thermophysical properties and their dependence on temperature and composition. The results show that there are two main thermal convection cells in the melt caused by two temperature gradients during the growth of Hg_1-xCd_xTe single crystals. The stabilizing axial solute gradient in the melt will significantly damp the thermal convection cells when the absolute value of the solute Rayleigh number is close to the value of the thermal Rayleigh number. When there is a large solute gradient in the melt, the thermosolutal convection will become unstable, and the upper flow cell will evolve into a two-cell flow pattern. During the growth of Hg_1-xCd_xTe single crystals, the radial solute segregation in the melt develops non-monotonically with two minima values. Thus, the methods that solely aim at either damping or enhancing the thermosolutal convection are not always able to improve the radial solute segregation.