Numerical solution of a Stefan-like problem in laser processing of semiconducting alloys

A theoretical model of binary alloy melting and solidification induced by p ulsed-laser irradiation is formulated using the mass and internal energy ba lances in the liquid and solid phases. The interface between the solid and liquid phases is modeled as a discontinuity surface where the mass and inte rnal energy balance conditions are expressed, together with the interface r esponse function. Both melting and solidification are considered as nonequi librium processes. The numerical solution of the mathematical model is performed using the Gal erkin finite element method in a 1D approximation and the moving boundary p roblem is solved by a front-fixing technique. The resulting set of nonlinea r algebraic equations is solved by an iterative procedure using the success ive approximation approach. In a practical application of the computational model, the phase change pro cesses in a Si-Ge system induced by XeCl excimer laser are simulated. The t emperature and concentration fields, and the position and velocity of the p hase interface are calculated in dependence on the laser energy density. Th e results show good agreement with experimental measurements by Slaoui et a l. [10]. The model can also provide some data which are difficult to be mea sured in a direct experiment. (C) 1999 IMACS/Elsevier Science B.V. All righ ts reserved.