Comparison of Two Approaches to Forced Convection in Crystal Growth

Hgl -,Cd,Te and Cdl -,Zn,Te single crystals were grown by the travelling heater method (THM), applying two different techniques of artificially stirring the solution zone. Accelerated crucible rotation (ACRT) was used in a vertical growth arrangement and compared a technique with constant rotation around the horizontal axis of the ampoule. The dominant hydrodynamic mechanisms of both methods are described by the rotating disc model and are suggested to be almost identical with respect to the growth conditions at the interface. Convective flow is effectively enhanced adjacent to the growing crystal, where the matter transport is regarded as the rate-limiting step of solution growth. Inclusion density analysis by IR microscopy was used to characterise the crystals of Cdl-,Zn,Te grown at different rates. It was shown that forced convection allows an increase in the crystal growth rate from a few mm day-', typical of natural convection regimes, to more than 10 mmday-' with ACRT or horizontally rotating THM.