the liquid solid interface is held at a temperature slightly higher than the melting point of the material to be crystallized while upper surface 52 of growing crystal 24 is kept at the melting point of the crystal i e 1240 u00b0 c for gallium arsenide growth since the melt is radially insulated such a temperature profile provides a strong stabilizing temperature gradient within confined melt 22 heater 14 temperature is regulated to maintain such a temperature gradient the distance between bottom surface 50 and upper surface 52 is typically of the order several mm to several cm however this distance the height of the confined melt 22 may be varied in a synchronous fashion with main heater 14 temperature if the temperature of main heater 14 is increased this separation is increased and if the heater 14 temperature is decreased so is this distance such that a stabilizing temperature gradient is maintained auxiliary heater 16 is preferably kept at a temperature higher than that of main heater 14 in order to thermally stratify top melt 20 if necessary auxiliary heater 16 can be used to melt material above main heater 14 to form top melt 20 upper surface 52 remains at a constant distance from bottom surface 50 so that the volume of confined melt 22 remains constant confined melt 22 remains unaffected by any motion of melt 20 above main heater 14 consequently a raleigh number ra h calculated based on the enclosed melt height remains constant during the growth an important advantage over czochralski and conventional vertical bridgman methods where melt height.