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P型锗单晶作为空间太阳电池外延层的衬底片,对其电阻率均匀性的一致性有着极高的要求。在直拉法锗晶体生长中,固液界面即为结晶前沿的等电阻面、等杂质浓度面。因此固液界面的形状和晶体中径向电阻率均匀性直接相关,对晶体质量有重大影响。因此要提高外延层衬底片质量就是要控制晶体生长过程中的固液界面形状。晶体生长系统的热场分布和晶体生长工艺参数影响着固液界面的形状。本文结合数值模拟对影响固液界面形状的因素进行了研究,在TDR-Z80炉中进行的晶体界面实验、高电阻率均匀性单晶生长实验和数值模拟结果基本一致。同时对低位错锗单晶电阻率均匀性进行了表征与研究。优化工艺前的电阻率均匀性大于15%。优化工艺后获得的相对平坦固液界面极大的提高了径向电阻率均匀性,并且可控制在5%以内。
P-type germanium single crystal as a space solar cell epitaxial layer of the substrate, the uniformity of its resistivity has a very high demand. In Czochralski law germanium crystal growth, solid-liquid interface is the front of the crystallization of the isoelectric resistance surface, and other impurity concentration surface. The shape of the solid-liquid interface is therefore directly related to the uniformity of the radial resistivity of the crystal, which has a significant effect on the crystal quality. Therefore, to improve the quality of the epitaxial layer of the substrate sheet is to control the crystal growth process solid-liquid interface shape. The thermal field distribution and crystal growth parameters of the crystal growth system affect the shape of the solid-liquid interface. In this paper, the factors influencing the shape of the solid-liquid interface are studied in combination with the numerical simulation. The experimental results of the crystal interface and the experiment of single crystal growth with high resistivity uniformity in the TDR-Z80 furnace are basically the same. At the same time, the homogeneity of low dislocation germanium single crystal was characterized and studied. The uniformity of resistivity before optimization is greater than 15%. The relatively flat solid-liquid interface obtained after the optimization process greatly improves the radial resistivity uniformity and can be controlled within 5%.