Detecting minute amounts of nitrogen in GaNAs thin films using STEM and CBED.

Ultramicroscopy

Department of Physics, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway; Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

Published: December 2021


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Article Abstract

Nitrogen (N) is a common element added to GaAs for band gap engineering and strain compensation. However, detection of small amounts of N is difficult for electron microscopy as well as for other chemical analysis techniques. In this work, N in GaAs is examined by using different transmission electron microscopy (TEM) techniques. While both dark-field TEM imaging using the composition sensitive (002) reflections and selected area diffraction reveal a significant difference between the doped thin-film and the GaAs substrate, spectroscopy techniques such as electron energy loss and energy dispersive X-ray spectroscopy are not able to detect N. To quantify the N content, quantitative convergent beam electron diffraction (QCBED) is used, which gives a direct evidence of N substitution and As vacancies. The measurements are enabled by the electron energy-filtered scanning CBED technique. These results demonstrate a sensitive method for composition analysis based on quantitative electron diffraction.

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http://dx.doi.org/10.1016/j.ultramic.2021.113299DOI Listing

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