GeSn is a promising group-IV semiconductor material for on-chip Si photonics devices and high-mobility transistors. These devices require the use of doped GeSn regions, achieved preferably in-situ during epitaxy. From the electronic valence point of view, p-type dopants of group-IV materials include B, Al, Ga and In. The latter element has never been investigated as p-type dopant in GeSn. In this work, we explore in-situ In p-type doping of GeSn grown by MBE. We show that In acts as a surfactant during epitaxial growth of GeSn:In, accumulating on surface and inducing segregation in the form of mobile Sn-In liquid droplets, strongly affecting the local composition of the material. This work provides insights in the thermodynamic origins of this behavior, and discourages the utilization of In in GeSn-based optoelectronic devices.

中文翻译：

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Sn-In 共偏析和 In 表面活性剂在 MBE 原位掺杂 GeSn 中的作用

GeSn 是一种很有前途的 IV 族半导体材料，可用于片上 Si 光子器件和高迁移率晶体管。这些器件需要使用掺杂的 GeSn 区域，最好在外延过程中原位实现。从电子价态来看，IV族材料的p型掺杂剂包括B、Al、Ga和In。后一种元素从未作为 GeSn 中的 p 型掺杂剂进行过研究。在这项工作中，我们探索了通过 MBE 生长的 GeSn 的原位 In p 型掺杂。我们表明，In 在 GeSn:In 的外延生长过程中充当表面活性剂，在表面上积累并以可移动的 Sn-In 液滴的形式诱导偏析，强烈影响材料的局部组成。这项工作提供了对这种行为的热力学起源的见解，并阻止了在基于 GeSn 的光电器件中使用 In。