Effects of a Rotating Magnetic Field on Gas Transport During Detached Crystal Growth in Space

During the detached Bridgman growth of semiconductor crystals, the melt has a short free surface which is detached from the ampoule wall near the crystal-melt interface, thus eliminating the crystal defects caused by contact with the ampoule wall. Recent modelling has indicated that initiation and continuation of detached growth depends on the rate of transport of dissolved gas from the crystal-melt interface, where gas is rejected into the melt, to the detached free surface, where evaporating gas maintains the pressure on the free surface. Here we use numerical modelling to investigate whether the application of a rotating magnetic field increases or decreases the transport of rejected gas to the detached free surface. Unfortunately the results show that a rotating magnetic field almost always decreases the evaporation rate at the detached free surface. The exception is an insignificant increase for a short period at the beginning of crystal growth for a few circumstances. The evaporation rate decreases as the strength of the rotating magnetic field is increased.