In-situ Real-Time Observation of Sn-Rich Dots and Wires During Annealing of GeSn Epitaxial Films

Insights into the Origins of Guided Microtrenches and Microholes/rings from Sn Segregation in Germanium–Tin Epilayers

“…14,26 The recent in situ experiment under SEM and optical microscopy also provide evidence of the formation of the trenches during the annealing of the GeSn layers. 14,15 To reduce the Gibbs free energy, the Sn droplets migrate toward the supersaturated and strained GeSn epilayers and leave the strain-free and stable Ge (or low-Sn-content GeSn) layer behind (details in section 3.3). The Sn droplets and low-Sn-content trenches in GeSn can also be further verified from the EDS mapping of Ge and Sn elements in Figure 1e similar to the growth of the lateral Si nanowires by the SLS method, wherein the droplets move on the unstable Si amorphous film during annealing, resulting in the stable singlecrystal Si nanowires.…”

“…15 The higher activation energy can be attributed to the highly stable (111) surface. 15 As compared to the work reported by Ong et al, the activation energy of the Ge 0.9 Sn 0.1 sample in our work is about a quarter, indicating the lower stability of the Ge 0.9 Sn 0.1 due to the higher Sn content. Nevertheless, it is challenging to assess the activation energy of the Ge 0.885 Sn 0.115 sample due to the decrease in spot size when the annealing temperature increases.…”

“…surface with the same Sn-content of 8%. 15 The higher activation energy can be attributed to high-stability (111) surface. 15 As compared to the work reported by Eng et al, the activation energy of Ge0.9Sn0.1 sample in our work is about a quarter, indicating lower stability of the Ge0.9Sn0.1 due to the higher Sn-content.…”

“…Several studies have reported two main morphological evolutions for the phase separation process: the development of the densely-packed, isolated Sn-rich islands (droplets) [11][12][13] , and the self-assembly of surface trenches caused by the movement of Sn droplets on surfaces. [14][15][16][17] Despite the report of numerous studies in exploring the relationship between the Sn segregation and the heating temperature, strain relaxation and dislocation formation, [9][10][11][12][13][14] the fundamental mechanisms of the two abovementioned morphological evolutions remain inconclusive. Among the GeSn research communities, much effort has been focused on the growth of high quality GeSn.…”

“…The phase separation in the GeSn films caused by low thermal solubility has been observed not only during growth but also during thermal treatments. Several studies have reported two main morphological evolutions for the phase separation process: the development of the densely packed, isolated Sn-rich islands (droplets) − and the self-assembly of surface trenches caused by the movement of Sn droplets on surfaces. − Despite the report of numerous studies in exploring the relationship between the Sn segregation and the heating temperature, strain relaxation, and dislocation formation, − the fundamental mechanisms of the two abovementioned morphological evolutions remain inconclusive. Among the GeSn research communities, much effort has been focused on the growth of high-quality GeSn. , Meanwhile, there have been limited studies on the growth of GeSn layers with Sn segregation, where a systematic explanation on the mechanism is called for.…”