Convergent beam electron diffraction for strain determination at the nanoscale
Résumé
The convergent beam electron diffraction (CBED) technique has been used to quantify the strain in semiconducting GaInAs/GaAs epitaxial layers. Two different systems have been explored, a 100 nm thick GaInAs layer, in the case of very low indium content, and a 10 nm thick GaInAs layer, with 20 at.% In. We show that the direct analysis of the CBED patterns can only be achieved in the first system, provided that specimen and deposited layer thickness are close to each other. In the second system, which is the more frequent in epitaxial systems, we demonstrate that reliable measurements can still be obtained through quantitative fit performed using a CBED pattern simulation software specially developed for analysing non-inhomogeneouly strained specimens.