The application of GeSn is extended to semiconductor lasers thanks to its band engineering via Sn composition and strain manipulation. As one of the strain engineering methods, thermal annealing, however, is not yet being widely adopted by the majority due to the thermal instability it induces. The thermal stability of GeSn is highly sensitive to initial material conditions, consequently thorough investigations are still demanded with different purposes. A detailed investigation on the thermal annealing effects of thick GeSn layers with a nominal 8% Sn grown on Ge-buffered Si (001) substrate by molecular beam epitaxy is presented here. Atomic force microscopy and high-resolution x-ray diffraction were used to trace the change of GeSn surface morphology and the strain relaxation after annealing. It is confirmed that the tetragonal compressive strain in GeSn, which is a proven detriment to the realisation of direct-bandgap material, can be relaxed by 90% while improving crystal quality, e.g. reduced surface roughness by appropriate annealing conditions. These findings reveal the potential of annealed GeSn to serve as a much thinner (750 nm), better lattice-matched to GeSn active layer and highly strain-relaxed platform to grow GeSn on compared to the thick Ge or the compositional-graded (Si)GeSn buffer layers, which are complicated and time-consuming in growth procedures and also securing an easier approach.

GeSn的应用由于其通过Sn成分和应变操纵的能带工程技术而扩展到了半导体激光器。然而，作为应变工程方法之一，由于其引起的热不稳定性，热退火尚未被大多数人广泛采用。GeSn的热稳定性对初始材料条件高度敏感，因此仍然需要针对不同目的进行深入研究。此处详细介绍了通过分子束外延在Ge缓冲的Si（001）衬底上生长的标称8％Sn的厚GeSn厚GeSn层的热退火效应。原子力显微镜和高分辨率X射线衍射用于追踪GeSn表面形貌的变化以及退火后的应变松弛。业已证实，GeSn中的四方压缩应变被证明对实现直接带隙材料的实现有害，可以在提高晶体质量的同时放宽90％，例如通过适当的退火条件降低表面粗糙度。这些发现表明，与厚Ge或成分梯度化的（Si）相比，退火后的GeSn的潜力更薄（750 nm），与GeSn活性层的晶格匹配更好，并且高度应变松弛的平台可以生长GeSn。 GeSn缓冲层，在生长过程中既复杂又费时，而且还确保了更简便的方法。