SGER: Rotating Magnetic Fields in Semiconductor Crystal Growth

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Linear stability analyses will be developed for two crystal growth processes with rotating magnetic fields (RMF). The two processes are the Vertical Bridgman process, which is used to grow crystals of compound semiconductors, such as gallium-arsenide and indium-phosphide, and the Vertical Zone Melting process, which is used to grow alloyed crystals, such as various mixtures of germanium and silicon. In both processes, hydrodynamic instabilities in the buoyant convection can lead to periodic, nonaxisymmetric flows in the molten semiconductor, and such flows produce many defects in the crystal. An RMF can stabilize the buoyant convection so that the flow is steady and axisymmetric, leading to much better crystals. However, the RMF can also lead to a hydrodynamic instability. The object of the modeling is to optimize the benefits of the RMF for each crystal growth process while avoiding the undesirable RMF instability. The results of the linear stability analyses will be validated by comparison to experimental measurements of the transitions from steady axisymmetric flows to periodic nonaxisymmetric flows. The results will define the strength and frequency of the RMF which will lead to much better semiconductor crystals for each process. Improvements in crystal quality are needed for future advances in wireless communications and optoelectronics.