Electron Channeling Contrast Imaging for epi-layer structural defect characterization
Résumé
Electron Channeling Contrast Imaging (ECCI) is a non-destructive technique that allows the characterization of dislocations and other microstructural defects using a scanning electron microscope (SEM) [1]. In particular, it is becoming increasingly popular for accurately determining the threading dislocation density created during the growth of highly lattice-mismatched semiconductors. For example, in the case of the growth of III-Vs on Silicon substrates, dislocation densities in the 5x106- 109 / cm2 range are often found in the various epilayers. Etch-pit revealing techniques is not efficient for such densities, and the use of transmission electron microscopy (TEM) techniques, although very powerful, remains cumbersome and is still a destructive process. Using a simple SEM equipped with a backscattered electron detector, it is possible to align the sample so that the electron beam is massively channeled through the crystal. In such a configuration, any deviation from a perfect crystal structure, such as the presence of a dislocation, results in a significant increase in the backscattered signal, allowing large scale imaging of individual defects that appear on the surface of the epilayer. In this presentation, we will present a historical and technical overview of this technique, as well as some detailed examples of ECCI measurements.
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