Metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are two versatile growth techniques that can readily produce multilayer structures with atomic-level precision control, which have found broad applications in technology. However, compared to MBE, MOCVD growth involves the surface reaction of metal-organic precursor compounds, which changes during film deposition. Consequently, a thorough investigation on the chemical profile layer-by-layer is critical for optimizing MOCVD film performance. Here, we examine Sb segregation in an MOCVD-grown InAs/InAs_1−xSb_x superlattice by analyzing composition and lattice strain at atomic resolution using scanning transmission electron microscopy and compare with the previously reported MBE growth results. Our findings show a different Sb profile along the growth direction in MOCVD, with the segregation coefficient being higher at the InAsSb-on-InAs interface (0.807 ± 0.021) than at the InAs-on-InAsSb interface (0.695 ± 0.009), giving rise to asymmetric composition and lattice strain profiles unlike those obtained with MBE. Furthermore, we obtain direct evidence of Sb clusters with size of ∼1–3 nm and Sb ordering within the InAs_1−xSb_x layer, which is largely absent in the reported MBE growth. These findings demonstrate the concurrent interplay between surface segregation, surface reconstruction, and surface reaction that is unique to MOCVD growth with broad implications on preparing Sb-containing quantum materials.

中文翻译：

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通过金属有机化学气相沉积生长的 InAs/InAs1−xSbx 超晶格中的锑偏析

金属有机化学气相沉积 (MOCVD) 和分子束外延 (MBE) 是两种通用的生长技术，可以轻松生产具有原子级精度控制的多层结构，已在技术中得到广泛应用。然而，与 MBE 相比，MOCVD 生长涉及金属有机前体化合物的表面反应，这在薄膜沉积过程中会发生变化。因此，逐层深入研究化学分布对于优化 MOCVD 薄膜性能至关重要。在这里，我们检查 MOCVD 生长的 InAs/InAs _{1− x} Sb _{x 中的}Sb 偏析通过使用扫描透射电子显微镜以原子分辨率分析组成和晶格应变，并与先前报道的 MBE 生长结果进行比较。我们的研究结果显示沿 MOCVD 生长方向的 Sb 分布不同，InAsSb-on-InAs 界面处的偏析系数 (0.807 ± 0.021) 比 InAs-on-InAsSb 界面处 (0.695 ± 0.009) 的偏析系数更高，从而导致与使用 MBE 获得的不对称成分和晶格应变分布不同。此外，我们获得了尺寸约为 1-3 nm 的 Sb 簇和 InAs _{1- x} Sb _x内 Sb 排序的直接证据层，这在报告的 MBE 增长中基本上不存在。这些发现证明了 MOCVD 生长所特有的表面偏析、表面重建和表面反应之间的同时相互作用，对制备含 Sb 的量子材料具有广泛的影响。