Low Energy Methods of Mass Transfer Control during Crystal Growth in Microgravity: Rotating Magnetic Field and Vibrations

Many different techniques have been used in attempts to minimize defects in single crystal semiconductors. This study examines semiconductors grown in the presence of a rotating magnetic field (RMF). The RMF method is commonly used in metallurgy to stir an electrically conducting liquid during the casting process which can reduce the effects of buoyancy driven convection and enhance the mass transfer process. The variation of heat and mass transfer processes by RMF can be controlled by selecting a specific frequency and strength of the magnetic field. Both numerical modeling and space-based crystal growth experiments using RMF indicate that the application of RMF to solidification of semiconductors will dramatically minimize defects and inclusions.A ground based program in the Microgravity Research Division at NASA's Marshall Space Flight Center has been studying the effects of RMF on various semiconductor compounds grown by the traveling heater method (THM).

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Semiconductor Crystal Growth by the Vertical Bridgman Process With Transverse Rotating Magnetic Fields

Journal of Heat Transfer ◽

10.1115/1.2352790 ◽

2006 ◽

Vol 129 (2) ◽

pp. 241-243 ◽

Cited By ~ 5

Author(s):

X. Wang ◽

N. Ma

Keyword(s):

Magnetic Field ◽

Crystal Growth ◽

Magnetic Fields ◽

Applied Magnetic Field ◽

Rotating Magnetic Field ◽

Semiconductor Crystal ◽

Rotating Magnetic Fields ◽

Electrically Conducting ◽

Vertical Bridgman ◽

Bridgman Process

During the vertical Bridgman process, a single semiconductor crystal is grown by the solidification of an initially molten semiconductor contained in an ampoule. The motion of the electrically conducting molten semiconductor can be controlled with an externally applied magnetic field. This paper treats the flow of a molten semiconductor and the dopant transport during the vertical Bridgman process with a periodic transverse or rotating magnetic field. The frequency of the externally applied magnetic field is sufficiently low that this field penetrates throughout the molten semiconductor. Dopant distributions in the crystal are presented.

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Numerical simulation of Cz crystal growth in rotating magnetic field with crystal and crucible rotations

Journal of Crystal Growth ◽

10.1016/j.jcrysgro.2011.12.004 ◽

2012 ◽

Vol 340 (1) ◽

pp. 166-170 ◽

Cited By ~ 9

Author(s):

Xiaoming Zhou ◽

Hulin Huang

Keyword(s):

Magnetic Field ◽

Numerical Simulation ◽

Crystal Growth ◽

Rotating Magnetic Field

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Flow Control Using Alternating Magnetic Fields During Crystal Growth From a Melt

Volume 7: Fluids and Heat Transfer, Parts A, B, C, and D ◽

10.1115/imece2012-88373 ◽

2012 ◽

Author(s):

Yue Huang ◽

Kenneth E. Davis ◽

Brent C. Houchens

Keyword(s):

Magnetic Field ◽

Crystal Growth ◽

Magnetic Fields ◽

Flow Control ◽

Body Force ◽

Stokes Equations ◽

Magnetic Reynolds Number ◽

Rotating Magnetic Field ◽

Bandgap Energy ◽

Alternating Magnetic Fields

Flow control during bulk melt crystal growth is desirable for producing ternary alloy semiconductors with tunable lattice parameters and bandgap energy, providing custom materials for specific electro-optical applications. Segregation between constituent elements in the melt, be it through preferential rejection at the growth front or density variations, limits the growth rate and the uniformity in the crystal. External alternating magnetic fields are employed to stir the electrically conducting melt. While mixing is desired, turbulent flow is generally not. Precise control is required to maintain a laminar melt flow while providing sufficient mixing. Stirring via a rotating magnetic field (RMF) and a three-coil traveling magnetic field (TMF) is modeled and compared for a cylindrical melt confined in an ampule. The RMF imposes a body force in the azimuthal direction while the TMF induces primarily radial and axial body forces. The magnetic fields are effectively decoupled from the flow fields due to the small magnetic Reynolds number. Therefore, the magnetic fields are first determined using a finite element solver. The flows are then solved by a spectral element model of the Navier-Stokes equations including an electromagnetic body force term.

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