Models for Stress and Dislocation Generation in Melt Based Compound Crystal Growth

The origin of dislocation evolution during SiC crystal growth is usually related to lattice relaxation mechanisms caused by thermal stress. In this paper we discuss dislocation generation and dislocation propagation related to doping and suppression of basal plane dislocations, the latter being of particular interest for bipolar electronic devices. We have prepared alternating p-/n-/pdoped SiC crystals using the donor nitrogen and the acceptors aluminum or boron. In addition we determined the mechanical properties of n-type and p-type SiC; in particular we measured the critical shear stress by nano-indentation on c-plane and a-plane 6H-SiC surfaces. A considerably lower basal plane dislocation density is found in aluminum as well as in boron doped p-type SiC compared to nitrogen doped n-type SiC. It is concluded that the explanation of the reduced basal plane dislocation density in p-type SiC needs the consideration of electronic as well as mechanical effects.

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The effect of interface shape on dislocation generation during crystal growth

International Communications in Heat and Mass Transfer ◽

10.1016/0735-1933(92)90084-u ◽

1992 ◽

Vol 19 (3) ◽

pp. 385-394 ◽

Cited By ~ 2

Author(s):

Ke-Ming Chen ◽

Jin-Yuan Hsieh ◽

Chi-Chuan Hwang

Keyword(s):

Crystal Growth ◽

Interface Shape ◽

Dislocation Generation

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Unsteady thermoelastic analysis of dislocation generation during Czochralski crystal growth

Journal of Crystal Growth ◽

10.1016/0022-0248(95)00002-x ◽

1995 ◽

Vol 149 (1-2) ◽

pp. 147-152 ◽

Cited By ~ 2

Author(s):

Chi-Chuan Hwang ◽

Senpuu Lin

Keyword(s):

Crystal Growth ◽

Dislocation Generation ◽

Thermoelastic Analysis ◽

Czochralski Crystal Growth

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Mechanics of shaped crystal growth from the melt

Journal of Materials Research ◽

10.1557/jmr.1996.0276 ◽

1996 ◽

Vol 11 (9) ◽

pp. 2163-2176 ◽

Cited By ~ 11

Author(s):

John C. Lambropoulos ◽

Chien-Hsing Wu

Keyword(s):

Crystal Growth ◽

Dislocation Density ◽

Growth Parameters ◽

Growth Direction ◽

Liquid Interface ◽

Dislocation Generation ◽

Crystalline Anisotropy ◽

Initial Dislocation Density ◽

Solid Liquid Interface ◽

Solid Liquid

We present the numerical formulation of the thermal stress driven steady-state dislocation generation during the growth of shaped crystals from the melt, with Czochralski (CZ) growth of solid cylinder III–V compound semiconductors as an example. We use and compare the Haasen–Alexander model, coupling dislocation multiplication and creep strain rates, and the Jordan model, based on thermoelastic stresses. Growth parameters may be chosen so as to produce an overall approximately flat interface, leading to reduced dislocation density in the majority of the crystal's cross section. Calculation of final dislocation density requires the initial dislocation density and all stress components along the solid-liquid interface, microstructural features which depend on the physical processes leading to solidification. The final dislocation density is not sensitive to the initial dislocation density along the solid-liquid interface, but strongly depends on the interface stress. Significant stress relaxation at the interface is required to produce experimentally observed “W” shaped dislocation patterns. Crystal growth direction and crystalline anisotropy couple elastic (lattice) and plastic (slip systems) crystalline anisotropy.

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3D Viscoplastic Finite Element Modeling of Dislocation Generation in a Large Size Si Ingot of the Directional Solidification Stage

Materials ◽

10.3390/ma12172783 ◽

2019 ◽

Vol 12 (17) ◽

pp. 2783

Author(s):

Maohua Lin ◽

Xinjiang Wu ◽

Xinqin Liao ◽

Min Shi ◽

Disheng Ou ◽

...

Keyword(s):

Finite Element ◽

Crystal Growth ◽

Dislocation Density ◽

Thermal Stresses ◽

High Efficiency ◽

Green Energy ◽

Dislocation Dynamics ◽

Cooling Process ◽

Dislocation Generation ◽

Large Size

Growing very large size silicon ingots with low dislocation density is a critical issue for the photovoltaic industry to reduce the production cost of the high-efficiency solar cell for affordable green energy. The thermal stresses, which are produced as the result of the non-uniform temperature field, would generate dislocation in the ingot. This is a complicated thermal viscoplasticity process during the cooling process of crystal growth. A nonlinear three-dimensional transient formulation derived from the Hassen-Sumino model (HAS) was applied to predict the number of dislocation densities, which couples the macroscopic viscoplastic deformation with the microscopic dislocation dynamics. A typical cooling process during the growth of very large size (G5 size: 0.84 m × 0.84 m × 0.3 m) Si ingot is used as an example to validate the developed HAS model and the results are compared with those obtained from qualitatively critical resolved shear stress model (CRSS). The result demonstrates that this finite element model not only predicts a similar pattern of dislocation generation with the CRSS model but also anticipate the dislocation density quantity generated in the Si ingot. A modified cooling process is also employed to study the effect of the cooling process on the generation of the dislocation. It clearly shows that dislocation density is drastically decreased by modifying the cooling process. The results obtained from this model can provide valuable information for engineers to design a better cooling process for reducing the dislocation density produced in the Si ingot under the crystal growth process.

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Montmorillonite Dendrites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052286 ◽

1974 ◽

Vol 32 ◽

pp. 454-455

Author(s):

Necip Güven ◽

Rodney W. Pease

Keyword(s):

Crystal Growth ◽

Growth Mechanism ◽

Growth Front ◽

Morphological Features ◽

Dendritic Crystal ◽

Crystal Growth Mechanism

Morphological features of montmorillonite aggregates in a large number of samples suggest that they may be formed by a dendritic crystal growth mechanism (i.e., tree-like growth by branching of a growth front).

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TEM and cathodoluminescence of precipitates in II-VI semiconductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104509 ◽

1988 ◽

Vol 46 ◽

pp. 488-489

Author(s):

Joanna L. Batstone

Keyword(s):

Crystal Growth ◽

Band Gap ◽

Local Strain ◽

Wide Band ◽

Optoelectronic Device ◽

Wide Band Gap ◽

Bulk Crystal Growth ◽

Transmission Electron ◽

Device Applications ◽

Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

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