Numerical analysis of solute distribution and interface stabilization during experimental Bridgman growth of concentrated GaInSb alloys

Numerical simulation is used in order to study the solute segregation and morphological stability of the solid-liquid nterface during Bridgman solidification of concentrated Ga1-xInxSb(x = 0.1 and 0.2) alloys. Experimental works on the crystal growth of the concentrated GaInSb alloys by using a Bridgman-Stockbarger furnace, have shown a large increase of chemical segregations and solid-liquid interface curvature during the solidification process. These phenomena are studied by using a transient numerical modeling of the heat, momentum and mass transfer which occur during the crystal growth process. From the numerical simulation it is found a strong damping of the thermally driven convection by the solutal effect, which depends on the growth parameters. This leads to a significant increase of the radial segregation, and consequently, because of the dependency of the melting temperature on the concentration, of the interface curvature. In the case of the highly concentrated Ga0.8In0.2Sb alloy, the solutal effect is very strong and a morphological destabilization of the solid-liquid interface occurs close to the beginning of the solidification. Analytical calculations are derived by taking into account the solutal effect on the interface curvature and a semi-empirical formula which describes the evolution of the interface deflection during the growth process is proposed. It is found that the proposed formula is verified by both numerical and experimental results and can predict the occurrence of the interface morphological destabilization. Experimental and numerical results for the solute distribution in the crystals and interface deflection are compared with the analytical predictions in order to give an explanation of the physics involved during the growth of GaInSb concentrated alloys. (C) 2004 Elsevier B.V. All rights reserved.