Ge/Si（001）衬底上GeSn外延层的工程应变弛豫
Engineering strain relaxation of GeSn epilayers on Ge/Si(001) substrates
摘要：
本文报道了在Ge/Si（001）衬底上用分子束外延生长GeSn外延层时，应变弛豫程度的控制机理。它表明，通过适当地控制下面的Ge缓冲层的厚度和生长配方，完全应变和高度弛豫的GeSn外延层可以得到，没有显着的Sn偏析。GeSn外延层的应变弛豫由Ge缓冲层的穿透位错介导，穿过Ge-GeSn界面传播。通过Benediktovich等人开发的方法系统地估计合金外延层和Ge缓冲层中的穿透位错密度。Benediktovitch，A. Zhylik，T. Ulyanenkova，M. Myronov，A. Ulyanenkov（2015），J.Appl.Cryst.48，655-665]支持了这一观察，并且还揭示了在Ge-GeSn界面处没有产生额外的位错。再加上最近报道的技术，以逮捕位错传播的GeSn外延层，这些结果预示着非常好的实现高度松弛的GeSn外延层，非常令人垂涎的发展GeSn基发射器。
英文摘要：
A mechanism of controlling the degree of strain relaxation in GeSn epilayers, grown by molecular beam epitaxy on Ge/Si(001) substrates, is reported in this work. It is demonstrated that by suitably controlling the thickness and the growth recipe of the underlying Ge buffer layer, both fully-strained and highly-relaxed GeSn epilayers can be obtained, without significant Sn segregation. The strain relaxation of the GeSn epilayer is mediated by threading dislocations of the Ge buffer layer, propagating across the Ge-GeSn interface. Systematic estimation of the threading dislocation density in both the alloy epilayer and the Ge buffer layer, by the approach developed by Benediktovich et al. [A. Benediktovitch, A. Zhylik, T. Ulyanenkova, M. Myronov, A. Ulyanenkov (2015), J. Appl. Cryst. 48, 655-665] supports this observation, and also reveals that no additional dislocations are generated at the Ge-GeSn interface. Together with recently reported techniques to arrest dislocation propagation in GeSn epilayers, these results bode extremely well for realization of highly-relaxed GeSn epilayers, much coveted for development of GeSn-based emitters.
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