二元半导体合金垂直Bridgman晶体生长的热质对流Ⅱ-三段热管炉

Thermosolutal Convection during the Vertical Bridgman Directional Solidification of Binary Alloy Ⅱ-Three-zone Heat Furnace

以GeSi半导体合金为例,采用准稳态模型数值研究了垂直Bridgman三段热管炉中二元合金单晶生长过程中的热质对流现象。在原型炉计算结果的基础上,考虑坩埚传热效应对晶体生长过程的影响,分析了热质耦合、合金热物性和拉晶速度对热质对流和径向溶质分凝的影响规律。计算结果表明,在垂直Bridgman三段热管炉装置中熔体出现两个上、下对称分布的对流结构,对流驱动力分别是热边界条件不连续性和热物性不匹配引起的径向温度梯度;对于溶质稳定分布的GeSi合金系统,只有当溶质瑞利数与热瑞利数大小相近时,溶质分布才会对热质对流产生明显的抑制;在本文的计算范围内,拉晶速度对晶体生长过程中的流动没有明显影响,但对溶质分布影响明显。

The thermosolutal convection during the directional solidification of binary alloy GeSi in vertical Bridgman configuration is numerically studied by using pseudo-steady-state model.On the basis of the results of the prototype furnace,the effect of the ampoule on the heat transfer and the coupling interaction between temperature and solute gradients are taken into account.The effects of thermophysical properties of the binary alloy and the pulling rate on the thermosolutal convection and radial solute segregation are studied.Firstly,there are two distinct convection cells in the melt and the driving forces for the both cells are the discontinuity of thermal boundary conditions and the difference of the thermophysical properties between melt and crystal,respectively.Secondly,for the GeSi alloy melt with a stabilizing solute field,the solute profiles will damp the convections caused by the thermal gradient significantly only when the solute Rayleigh Number is about close to the thermal Rayleigh Number.Thirdly,within the range of the calculation parameters in this paper,the pulling rate has no significant effect on the flow,but on the solute profiles.