The distribution of alloyed atoms in semiconductors often deviates from a random distribution which can have significant effects on the properties of the materials. In this study, scanning transmission electron microscopy techniques are employed to analyze the distribution of Bi in several distinctly MBE grown GaAs_1−xBi_x alloys. Statistical quantification of atomic-resolution HAADF images, as well as numerical simulations, are employed to interpret the contrast from Bi-containing columns at atomically abrupt (001) GaAs-GaAsBi interface and the onset of CuPt-type ordering. Using monochromated EELS mapping, bulk plasmon energy red-shifts are examined in a sample exhibiting phase-separated domains. This suggests a simple method to investigate local GaAsBi unit-cell volume expansions and to complement standard X-ray-based lattice-strain measurements. Also, a single-variant CuPt-ordered GaAsBi sample grown on an offcut substrate is characterized with atomic scale compositional EDX mappings, and the order parameter is estimated. Finally, a GaAsBi alloy with a vertical Bi composition modulation is synthesized using a low substrate rotation rate. Atomically, resolved EDX and HAADF imaging shows that the usual CuPt-type ordering is further modulated along the [001] growth axis with a period of three lattice constants. These distinct GaAsBi samples exemplify the variety of Bi distributions that can be achieved in this alloy, shedding light on the incorporation mechanisms of Bi atoms and ways to further develop Bi-containing III-V semiconductors.

半导体中合金原子的分布通常偏离随机分布，这会对材料的性能产生重大影响。在这项研究中，采用扫描透射电子显微镜技术来分析几种明显MBE生长的GaAs _1−x Bi _x合金中Bi的分布。采用原子分辨率 HAADF 图像的统计量化以及数值模拟来解释原子突变 (001) GaAs-GaAsBi 界面处含 Bi 柱的对比度以及 CuPt 型有序的开始。使用单色 EELS 测绘，可以检查具有相分离域的样品中的体等离子体能量红移。这提出了一种简单的方法来研究局部 GaAsBi 晶胞体积膨胀并补充标准的基于 X 射线的晶格应变测量。此外，还利用原子级成分 EDX 映射对在切割基板上生长的单变体 CuPt 有序 GaAsBi 样品进行了表征，并估计了有序参数。最后，利用低衬底旋转速率合成了具有垂直 Bi 成分调制的 GaAsBi 合金。原子分辨率的 EDX 和 HAADF 成像表明，通常的 CuPt 型排序沿着 [001] 生长轴以三个晶格常数的周期进一步调制。这些独特的 GaAsBi 样品例证了该合金中可以实现的各种 Bi 分布，揭示了 Bi 原子的结合机制以及进一步开发含 Bi III-V 半导体的方法。