Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117, Berlin, Germany.
Nanotechnology. 2016 Aug 12;27(32):325603. doi: 10.1088/0957-4484/27/32/325603. Epub 2016 Jul 1.
In this work, we report on the spontaneous formation of ordered arrays of nanometer-sized Bi-rich structures due to lateral composition modulations in Ga(As,Bi)/GaAs quantum wells grown by molecular beam epitaxy. The overall microstructure and chemical distribution is investigated using transmission electron microscopy. The information is complemented by synchrotron x-ray grazing incidence diffraction, which provides insight into the in-plane arrangement. Due to the vertical inheritance of the lateral modulation, the Bi-rich nanostructures eventually shape into a three-dimensional assembly. Whereas the Bi-rich nanostructures are created via two-dimensional phase separation at the growing surface, our results suggest that the process is assisted by Bi segregation which is demonstrated to be strong and more complex than expected, implying both lateral and vertical (surface segregation) mass transport. As demonstrated here, the inherent thermodynamic miscibility gap of Ga(As,Bi) alloys can be exploited to create highly uniform Bi-rich units embedded in a quantum confinement structure.
在这项工作中，我们报告了由于分子束外延生长的 Ga(As,Bi)/GaAs 量子阱中横向组成调制而自发形成纳米级富铋结构的有序排列。使用透射电子显微镜研究了整体微观结构和化学分布。同步加速器 X 射线掠入射衍射提供了有关面内排列的信息，对其进行了补充。由于横向调制的垂直继承，富铋纳米结构最终形成了三维组装。虽然富铋纳米结构是通过在生长表面的二维相分离形成的，但我们的结果表明，该过程得到了 Bi 偏析的辅助，Bi 偏析比预期的要强且更复杂，这意味着存在横向和纵向（表面偏析）质量传输。如这里所示，可以利用 Ga(As,Bi) 合金固有的热力学混溶性间隙来创建高度均匀的富铋单元，这些单元嵌入在量子限制结构中。
