Czochralski growth of Ga1−xInxSb single crystals with uniform compositions

Severe macrosegregation tends to develop along Ga1−xInxSb alloy crystals grown by the conventional Czochralski process. Failure to eliminate macrosegregation by floating-crucible Czochralski has been attributed to InSb back diffusion from the floating crucible. In the present study Ga1−xInxSb crystals were grown from the growth melt in a floating crucible having a unique bottom tube that was wide to let the replenishing melt in the outer crucible pass through easily but long to suppress back diffusion. Ga1−xInxSb crystals with a uniform composition of 1 mol% InSb were grown as targeted. However, crystals of about 2 mol% InSb were grown when 4 mol% InSb was targeted. By using Bi1−xSbx as a model material, it was found that hydrodynamic instability caused the problem-the denser growth melt mixed with the lighter replenishing melt during or even before crystal growth. A new double-crucible Czochralski process was thus developed, with an upper chamber for the growth melt and a lower chamber for the replenishing melt. The slightly higher gas pressure in the lower chamber caused replenishing through a long capillary tube that suppressed mixing between the melts. Single crystals of Ga1−xInxSb were grown with uniform compositions up to 4.5 mol% InSb.