Growth - related formation mechanism of I3 - type basal stacking fault in epitaxially grown hexagonal Ge - 2H

The hexagonal-2H crystal phase of Ge recently emerged as a promising direct bandgap semiconductor in the mid-infrared range providing new prospects of additional optoelectronic functionalities of group-IV semiconductors (Ge and SiGe). The controlled synthesis of such hexagonal(2H)Gephaseis a challenge that can be overcome by usingwurtziteGaAsnanowires as a template. However, depending on growth conditions, unusual basal stacking faults (BSFs) of I3-type are formed in themetastable2H structure. The growth of such core/shell heterostructures has been observed in situ and in real-time by means of environmental transmission electron microscopy using chemical vapor deposition. The observations provide direct evidence of a step-flow growth of the Ge-2H epi layer and reveal the growth-related formation of I3-BSF during unstable growth. Their formation conditions are dynamically investigated. Through these in situ observations we can propose a scenario for the nucleation of I3-type BSFs that is likely valid for any metastable hexagonal 2H or wurtzite structures grown on m-plane substrates. Conditions are identified to avoid their formation for the perfect crystalline synthesis of SiGe-2H. This dataset contains all the original scanning and transmission electron microscopy images and videos, and the atomic models that our results and understanding of the I3 defects are based on.