Vertical gradient freeze growth of GaAs with a rotating magnetic field

Pätzold, O.; Grants, I.; Wunderwald, U.; Jenkner, K.; Cröll, A.; Gerbeth, Günter

doi:10.1016/s0022-0248(02)01738-4

Cited by 47 publications

(48 citation statements)

References 11 publications

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“…In this way, natural-convection and RMF affected interfaces were obtained as explained below. In agreement with numerical studies, [7,13] the RMF induced flow is found to result in a decreased curvature of the nominally concave-shaped interface which is associated with a lowered stress level in the crystal. At a certain melt height a w-shaped interface is actually obtained as shown in Figure 2b.…”

supporting

confidence: 88%

“…Partially, the presented results were already published. [7,11] Equipment: The newly developed VGF-RMF equipment is schematically drawn in Figure 1. The furnace was especially designed for the vapour-pressure controlled VGF technique in a closed ampoule [8] under optimised thermal conditions.…”

mentioning

confidence: 99%

“…Thus, the axial temperature gradients become lower in the centre and higher in the outer part of the melt. According to the heat balance at an almost flat interface [7] …”

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New Developments in Vertical Gradient Freeze Growth

et al. 2004

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The Vertical Gradient Freeze (VGF) technique is an important method for growing high quality compound semiconductors such as GaAs. Results obtained with a novel VGF set‐up developed for the growth under influence of a rotating magnetic field (RMF) and under vapour pressure control are presented in this paper. The RMF is shown to be a powerful tool to affect the heat and mass transport within the melt in a definite way. In GaAs:Si growth, RMF induced flow results in a decreased curvature of a nominally concave‐shaped interface, i.e., it contributes to an axial heat transfer at the solid‐liquid interface. The axial dopant segregation of Ga in Ge is found to be improved under continuous RMF action due to better mixing of the melt. The set‐up also allowed to determine the influence of carbon and the arsenic vapour pressure on the dopant incorporation and crystal quality.

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New Developments in Vertical Gradient Freeze Growth

et al. 2004

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“…RMF and TMF fields are used widely for experimental studies of the influence a liquid phase motion has on heat and mass transfer during crystal growth [2,[8][9][10]11] and solidification of metal alloys. [3,4,12] In such experiments, it is necessary that all alloy components are distributed homogeneously in the melt.…”

Section: Introductionmentioning

confidence: 99%

Contactless Mixing of Liquid Metals

Nikrityuk

Eckert

Grundmann

2009

Metall Mater Trans B

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This work is devoted to the numerical study of mixing two miscible liquid metals, e.g., Sn and Pb, that are driven either separately by a rotating magnetic field (RMF), by a traveling magnetic field (TMF), or by a combination of both fields from the state of rest. The geometry studied is an enclosed cylindrical cavity with an aspect ratio equal to unity (the diameter of the cylinder is equal to its height, 2R 0 = H 0 ). The initial condition is a cylinder with the lower half filled with a melt that has two times the molecular viscosity of the liquid in the upper part of the cavity. Based on the mixture model of the two-fluid flow and the axisymmetric Navier-Stokes equations, the transient transport of momentum as well as the species for rotary and axial stirring is modeled. The numerical simulations were performed under microgravity conditions for Ekman numbers between 10 À3 and 10 À4 for the RMF-driven flow and for Reynolds numbers between 100 and 400 for TMF-driven flow that corresponded to both laminar and weak turbulent flows. The simulations analysis showed that for RMF, the rapid increase in the mixing rate occurs because of randomly appearing Taylor-Go¨rtler vortices that move up and down along the side wall of the cylinder and that dissipate in the Bo¨dewadt layers. The TMF stirring with forcing parameters that produced laminar flow offers a better mixing performance than the RMF stirring at the same magnetic field intensity. However, with an increase in magnetic forcing, the RMF and TMF lead to comparable mixing times for the same value of magnetic field induction. Additionally, we discuss different mixing scenarios that include the use of time-modulated RMF and TMF. Numerical simulations showed that the discontinuous superposition of RMF and TMF-defined as the sequential switching on and off of both fields with a well-defined period-enhances the mixing in comparison with the non-superimposed case.

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“…41,42) In the solidification of the Pb-Sn alloys under a rotating magnetic field, the forced convection significantly influenced the solidified structure and orientation of the grains. [43][44][45] The electromagnetic stirring by the rotating magnetic field promoted the columnar-to-equiaxed transition and resulted in the refinement of grains.…”

Section: Bridgman Technique and Othersmentioning

confidence: 99%

Recent Progress of EPM in Steelmaking, Casting, and Solidification Processing

et al. 2007

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Recently, twin torch plasma heating became common rather than single torch which demands anode in the tundish wall. Recent Progress of EPM in Steelmaking, Casting, and Solidification ProcessingHideyuki YASUDA, 1) Takehiko TOH, 2) Kazuhiko IWAI 3) and Kazuki MORITA 4) 1) Department of Adaptive Machine Systems, Osaka University, Suita, Osaka 565-0871 Japan.2) Technical Development Bureau, Nippon Steel Corporation, 20-1, Shintomi, Futtsu, Chiba 293-8511 Japan.3) Department of Materials, Physics and Energy Engineering, Nagoya University, Nagoya, Aichi 464-8603 Japan. 4) Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 Japan.(Received on February 13, 2007; accepted on February 22, 2007 ) This paper reviews recent trends of electromagnetic processing in steelmaking, casting and solidification processing. Electromagnetic vibration for controlling the solidified structure and application of microwave in materials processing are also presented. Aim of this paper is to prospect the recent trends in electromagnetic processing of materials.KEY WORDS: continuous casting; solidification; container-less process; electromagnetic vibration; microwave.ISIJ International, Vol. 47 (2007), No. 4, Review ment of steel cast is under trial. With AC field, the plasma arc is reciprocally moved and the fan shape plasma is obtained as a time-averaged figure. This technique may enable the loss free surface treatment of the steel semi-products. 9) BrakingThe in-mold electromagnetic braking technique started as a localized MHD application 10) to brake directly the molten steel stream discharged from the submerged entry nozzle. At that time, however, the technique had several problems concerning the stability of braking effect and the resultant metallurgical benefits. The new technique of stably controlling the molten steel flow in the mold was developed by applying a level DC magnetic field (LMF) across the mold width to discover a new function of suppressing mixing in addition to the conventional functions ensuring the slab quality. [11][12][13] The metallurgical effects of LMF are to minimize the penetration of oxide inclusions into the cast and to stabilize the steel flow in the mold so as to avoid the entrainment of liquid flux into the cast. The latter function enhanced the rapid introduction of this technique to the thin slab caster, which has high casting speed characteristics. Another application of this technology is to minimize the transition region at the ladle change by imposing a level magnetic field during the sequential casting.When an external DC magnetic field is applied to moving electrically conductive fluid, electric current is induced in the fluid. The electric current in the fluid makes a circuit to satisfy the law of conservation of electric current, according to the electrical boundary condition and generates electromagnetic braking forces on the fluid. The electric current path formed in this way contains components in the direction opposite to the one for th...

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Vertical gradient freeze growth of GaAs with a rotating magnetic field

Cited by 47 publications

References 11 publications

New Developments in Vertical Gradient Freeze Growth

New Developments in Vertical Gradient Freeze Growth

Contactless Mixing of Liquid Metals

Recent Progress of EPM in Steelmaking, Casting, and Solidification Processing

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