The recently developed precession electron diffraction (PED) technique in scanning transmission electron microscopy (STEM) has been used to elucidate the local strain distribution and crystalline misorientation in CMOS fabricated strained Ge micro disk structure grown on Si substrate. Such structures are considered to be a compact optical source for the future photonics due to the specific undercut for direct bandgap behaviour under strain. In this study, the strain maps are interpreted and compared with a finite element model (FEM) of the strain in the investigated structure. Results demonstrate that the SiN used as a stressor on top of the Ge disk induces an in-plane strain ϵxx of a maximum value of almost 2 % which is also confirmed by FEM simulations. This tensile strain can reduce the difference between the direct and indirect bandgaps leading to direct bandgap radiative transitions, with the potential for applications in strained Ge lasers.
@article{arxiv.1906.02484,
title = {Strain analysis of Ge micro disk using precession electron diffraction},
author = {Aneeqa Bashir and Ross. W. Millar and Kevin Gallacher and Douglas. J. Paul and Amith. D. Darbal and Robert Stroud and Andrea Ballabio and Jacopo Frigerio and Giovanni Isella and Ian MacLaren},
journal= {arXiv preprint arXiv:1906.02484},
year = {2020}
}