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藍寶石襯底比較.pdf

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monocrystal:

300 mm and 65 kg

Numerical analysis of sapphire crystal growth by the Kyropoulos technique

Presented below are the results of numerical simulation of single leucosapphire crystal growth by the Kyropoulos method using CGSim software. It is a unique feature of the suggested approach that the computations in the crystallization zone involve the turbulent flow of the sapphire melt, laminar gas flow, and radiative heat exchange in the semi-transparent crystal including specular reflectivity at the boundaries.

Improving the hot zone of the Kyropoulos furnace to decrease thermal gradients at the crystallization front results in higher yield ratio and better crystal quality. Numerical simulation comes very helpful in the analysis and optimization of growth systems as it gives us an insight into the processes that are otherwise extremely difficult to observe or measure, such as, the temperature distributions inside the melt and growing crystal. Attempts to apply a simplified model, ignoring semitransparency of the crystal and the melt, gave physically unrealistic results for the crystalization front geometry and temperature gradients at the metl-crystal interface. In the approach developed specifically for the task, the heat fluxes obtained from the heat transfer pre-computation in the whole system were used as the thermal boundary conditions for more detailed computations in the crystallization zone including the crystal, the melt, the crucible, and the gas region around the crystal. To account for sapphire semitransparency, we used an approach developed in [2] in terms of the discrete transfer method for solving problems of the radiation transfer in axisymmetric areas of complex geometry with specular Fresnel's boundaries.

＊ Account for semitransparency and specular reflection
＊ 30% quality increase in an industrial setup
Optical properties of sapphire:
＊ transparent band is 0.5-4.5 μm with the absorption coefficient 19.26 m-1
＊ refractive index is 1.78
＊ scattering coefficient is 0

Fig. 1. Sapphire boule with a diameter up to 300 mm and weight of 65 kg grown by Monocrystal Inc. (Stavropol; Russia) using the Kyropoulos technique (left) and the sapphire crystal photo at an intermediate growth stage (right)

Fig. 2. Distributions of the temperature gradient in the crystal, the temperature in the melt and the crucible, and the flow pattern in the melt for Modification 1 (a) and Modification 2 (b)

Using the updated CGSim package, several configurations of the industrial furnace have been considered [1]. In the initial configuration (Modification 1), the melt flow had a two-vortex structure with a larger vortex occupying the melt core and a vortex of lower intensity located near the melt free surface during the lateral crystal growth and disappearing at the cylindrical growth stage, Figure 2. Such flow pattern provided direct delivery of the hot melt to the crystallization front, resulting in high temperature gradients along the melt/crystal interface. After considering several hot zone modifications, we found a furnace configuration providing one-vortex flow structure in the melt (Modification 2). Such flow pattern results in gradual cool-down of the melt as it approaches the growing crystal, thus, decreasing the temperature gradients in the crystal by up to 30%, Figure 3.

Fig. 3. Temperature gradient distribution along the crystallization front from the axis of symmetry to the periphery for Modification 1 (a) and Modification 2 (b)

The model was verified using available experimental data. A good agreement between the computational and the experimental crystallization shapes indicates that the model provides an adequate prediction of the temperature fields in the reactor.
1. "Numerical analysis of sapphire crystal growth by the Kyropoulos technique", S.E. Demina, E.N. Bystrova, M.A. Lukanina, V.V. Kalaev, V.M. Mamedov, V.S. Yuferev, E.V. Eskov, M.V. Nikolenko, V.S. Postolov, to be published in Journal of Optical Materials in 2006.
2. "Numerical solution of problems with radiation transfer in axisymmetric areas of a complex shape with specular Fresnel's", V.M.Mamedov, S.? Rukolaine, Math. Modeling, vol. 16, 10 (2004) pp.15-28

为什么国内的泡生法做不好呢？泡生法适合于大尺寸制造，却不见得是生产LED-Sapphire-substrates的最有效生长方法。现有发明可比泡生法节省成本30%以上的能够普遍掌握的方法，完全可以摆脱离开俄罗斯工程师就长不出好晶体的局面。泡生法的晶体结晶质量不一定比国内的好。

原帖由 蓝可狄光 于 2007-8-15 10:14 发表
为什么国内的泡生法做不好呢？泡生法适合于大尺寸制造，却不见得是生产LED-Sapphire-substrates的最有效生长方法。现有发明可比泡生法节省成本30%以上的能够普遍掌握的方法，完全可以摆脱离开俄罗斯工程 ...

什麽方法？

上傳附件，內有三種方法藍寶石襯底品質對比，日文版本。

[ 本帖最后由保时捷于 2007-8-15 16:25 编辑 ]

原帖由 保时捷 于 2007-8-15 16:10 发表

什麽方法？

关注ing。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。

国内有新的生长蓝宝石的方法,期待中.........................................

这么说蓝光先生已经在用“可比泡生法节省成本30%以上的能够普遍掌握的方法”，是还在实验阶段吧？

难道出了新材料,比蓝宝石更适合做衬底的新晶体?山大和上光好象在做也

原帖由 kaka 于 2007-8-21 11:13 发表
难道出了新材料,比蓝宝石更适合做衬底的新晶体?山大和上光好象在做也

碳化硅吗？北京物理所，山大晶体所做的都很不错，上光不清楚了

还是什么其他的？

比蓝宝石适合做衬底的很多，成本和技术都是要考虑的因素

江老师的硅衬底外延现在都产业化了，好像?

目前在技术上取代蓝宝石做衬底的材料很多，但如果要商业化，蓝宝石还是占有很大的优势。技术上ZnO、GaN衬底取得的效果都比蓝宝石好，只是成本比较高，一片2英寸的GaN衬底大概价格在1万美金左右，通常采用HVPE工艺生产，这个价格可是蓝宝石衬底价格的几百倍，而且其工艺复杂，对环境要求极高。

[ 本帖最后由 Joshua.Xia 于 2007-9-17 10:13 编辑 ]

是上硅所在做碳化硅，上光什么时候做过碳化硅。国内做的说不错还谈不上

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