SGER: Rotating Magnetic Fields in Semiconductor Crystal Growth

对旋转磁场(RMF)作用下的两种晶体生长过程进行线性稳定性分析。这两种工艺是垂直布里奇曼法，用于生长化合物半导体的晶体，如砷化镓和磷化铟；以及垂直区熔化法，用于生长合金晶体，如各种锗和硅的混合物。在这两个过程中，浮力对流中的流体动力不稳定性会导致半导体熔体中周期性的非轴对称流动，这种流动会在晶体中产生许多缺陷。RMF可以稳定浮力对流，使流动稳定和轴对称，从而产生更好的晶体。然而，RMF也可能导致水动力不稳定。建模的目的是优化RMF对每个晶体生长过程的益处，同时避免不希望出现的RMF不稳定性。线性稳定性分析的结果将通过与定常轴对称流动向周期非轴对称流动转变的实验测量相比较来验证。结果将定义RMF的强度和频率，这将为每种工艺带来更好的半导体晶体。未来无线通信和光电子学的发展需要晶体质量的提高。

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.