Numerical simulation of temperature and flow field in the melt for the vapour-pressure-controlled Czochralski growth of GaAs

The influence of the melt flow on the temperature field and interface during the vapour-pressure-controlled growth of GaAs was studied numerically with the commercial general-purpose program FIDAP (TM). The thermal boundary conditions for the domain of seed, crystal, boron oxide and crucible were taken from a global calculation for an equipment used at the IKZ to grow 6 " crystals. Due to the large melt volume the buoyancy forces become rather strong and have to be counteracted by reasonable rotation rates. Preliminary results have been obtained for iso- and counter-rotation showing that the flow field exhibits structures on small scales. Hi-h rotation rates are needed to counteract the buoyancy flow efficiently and to achieve a smooth flat interface. Even if the the flow structure is not resolved in detail, the interface shape can be deduced form the calculations.