Diffusion and solubility of metal impurities in germanium

硅器件的速度越来越受到硅的电荷迁移率的限制。锗较高的电荷迁移率可以大大扩展这些限制，但由于缺乏基本知识，锗对硅的商业替代受到阻碍。本项目将确定几种常见的过渡金属在单晶锗中的扩散和溶解度。选择过渡金属Fe、Co和Cr是因为它们在Si/Ge晶片的生产中以及在需要暴露于高温的器件工艺中引起严重的污染问题。扩散退火将通过炉加热和快速热处理来实现。杂质深度分布将通过放射性示踪技术和变温扩散电阻剖面测量。后一种方法还将提供有关Ge基质中杂质的电状态的数据。结果将提供重要的信息，不仅有关杂质的溶解度和扩散率作为温度的函数，但也有关的优选状态的掺入和底层的扩散机制。本提案的另一个目标是表征锗中作为扩散载体的原生点缺陷。这一目标将大大有助于与比利时根特大学的一个小组的合作，该小组是研究锗中过渡金属杂质的电学性质的专家。

The speed of silicon devices is increasingly limited bei the charge mobility of silicon. The higher charge mobility of germanium can greatly extend these limits but the commercial substitution of germanium for silicon is hindered by a lack of fundamental knowledge. The project wil dertermine the diffusion and solubility of several common transition metals in single-crystal germanium. The transition metals Fe, Co and Cr were chosen because of the serious contamination problems they cause in the production of Si/Ge wafers and in device processes where exposure to elevated temperatures ist required. Diffusion annealing will be mde by both furnace heating and rapid thermal processing. Impurity depth distributions will be measured by both radiotracer techniques and variabletemperature spreading-resistance profiling. The latter method will also provide data concerning the electric state of the impurity in the Ge matrix. The results will provide crucial information not only about the impurity solubility and diffusivity as a function of temperature but also about the preferred state of incorporation and the underlying diffusion mechanism. The characterisation of native point defects as diffusion vehicles in germanium is another goal of this proposal. This goal will be greatly helped by a cooperative effort with a group at Ghent University, Belgium, that is experts an the electric properties of transition metal impurities in Ge.