Advisor(s): Nancy Ma
Author(s): Xianghong Wang and Nancy Ma
Graduate Program: Mechanical Engineering
Title: Bulk Growth of Semiconductor Crystals in Static and Rotating Magnetic Fields
Abstract: Bulk semiconductor crystals can be grown from a melt whose transport can be controlled by externally-applied fields in order to optimize the properties of the crystal. Rotating magnetic fields (RMFs) are attracting a growing attraction for crystal growth technologies from the melt in recent years. An RMF is a periodic transverse magnetic field which rotates in the azimuthal direction about the centerline of the melt. An RMF is produced by a number of magnet poles which are placed at equally-spaced azimuthal positions around the crystal growth furnace and which are connected to successive phases of a multiphase AC power source. An RMF can be used to drive azimuthal and meridional flows in the melt in order to control the dopant distributions in the melt and in the crystal. Static magnetic fields can be used to provide an electromagnetic (EM) damping in the convective transport. To increase the efficiency of RMF action and the range of its possible applications in technological tasks, we numerically model the melt motion and dopant transport during the vertical Bridgman process using a submerged heater with a combination of static and rotating magnetic fields. Our primary objective is to investigate the effects of such a combination on the melt motion and concentration distribution in the crystal, and to find an optimal combination of fields that would produce a crystal with a homogeneous dopant distribution.