The strain relaxation, depth profiles of composition and density of dislocations in GeSn epilayers were studied by using the x-ray diffraction. Regions with uniform and graded composition, different levels of strain relaxation, and dislocation density were found in the GeSn layers grown at fixed growth conditions. At the initial stage of growth, the GeSn layer is under ~8 × 10–3 compressive strain, and the Sn composition is close to the target value of 6.6%. With increasing layer thickness, the Sn content is enhanced by 0.85 ± 0.12% due to the relief of compressive strain down to ~5.0 × 10–4. The plastic strain relaxation is dominated by 60° misfit dislocations at the GeSn/Ge interface, where their density is 3 × 105 cm−1. The relaxed GeSn layer serves as a buffer for the high-quality GeSn overlayer with uniform and enhanced Sn composition. The laboratory-based x-ray diffraction is shown as a non-destructive reliable technique for strain, composition, and defects characterization, as an alternative to secondary ion mass spectrometry and transmission electron microscope techniques.

中文翻译：

---

GeSn/Ge/Si(100) 异质结构中应变弛豫、自发成分梯度和位错密度的 X 射线衍射研究

通过使用 X 射线衍射研究了 GeSn 外延层中的应变弛豫、成分的深度分布和位错密度。在固定生长条件下生长的 GeSn 层中发现了具有均匀和渐变成分、不同程度的应变松弛和位错密度的区域。在生长的初始阶段，GeSn 层处于~8 × 10-3 压缩应变下，Sn 成分接近目标值 6.6%。随着层厚度的增加，由于压缩应变降低至~5.0 × 10-4，Sn 含量增加了 0.85 ± 0.12%。塑性应变松弛由 GeSn/Ge 界面处的 60°错配位错主导，其密度为 3 × 105 cm-1。松弛的 GeSn 层用作具有均匀和增强的 Sn 成分的高质量 GeSn 覆盖层的缓冲层。