Detecting minute amounts of nitrogen in GaNAs thin films using STEM and CBED
Vatanparast, Maryam; Shao, Yu-Tsun; Rajpalke, Mohana; Fimland, Bjørn-Ove; Reenaas, Turid Dory; Holmestad, Randi; Vullum, Per Erik; Zuo, Jian Min
Journal article, Peer reviewed
Published version
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https://hdl.handle.net/11250/2988511Utgivelsesdato
2021Metadata
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Sammendrag
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.