Comparison of the effects of steady ampoule rotation and magnetic fields on flow and segregation control in vertical Bridgman crystal growth

Computer simulation is conducted to compare the separate effects of steady ampoule rotation and magnetic fields, as well as their coupled effects, on flow and segregation control for vertical Bridgman (VB) crystal growth. Bot h axial and cusp fields are considered. A benchmark problem for the growth of gallium-doped germanium in a graphite ampoule is used as an example. It is found that both the magnetic fields and steady ampoule rotation effectiv ely suppress the melt flow, but that their scaling laws are different. The flow intensity decreases linearly with the rotation speed, or Ta-1/2, but q uadratically with the magnetic field, or Ha(-2). Under an axial magnetic fi eld, the effect of rotation becomes less significant due to the reduced ang ular velocity gradients. However, with a cusp field, the effect of rotation is more significant.