Solute segregation in directional solidification of GaInSb concentrated alloys under alternating magnetic fields

Numerical simulations of the vertical Bridgman solidification of Ga1-xInxSb concentrated alloys are performed by using the commercial codes FIDAP((R)) and FLUENT(R). The transient axi-symmetric simulation of heat, mass and species transport during highly doped (x = 0.2) crystal growth, shows a strong solute effect on the melt convection. The thermally driven flow is damped by the heavier solute (InSb) rejected at the solid-liquid interface. A diffusive transport regime is established in the melt a short time after the beginning of solidification and as a consequence, the radial segregation increases. This leads to a significant increase of the interface curvature because of the melting point dependency on the interface composition. Finally, the crystals are not chemically homogeneous with large variations of InSb concentration on the axial and radial directions. In order to improve the chemical homogeneity of highly doped Ga1-xInxSb crystals, it is proposed to apply an alternating magnetic field in the vicinity of the solid-liquid interface. The magnetic parameters for which an optimal level of convection arises in the melt are derived from the numerical simulation. It is shown that during solidification under optimized electromagnetic stirring, the radial segregation and interface deflection can be maintained at low values. (C) 2004 Elsevier B.V. All rights reserved.