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Title: Insight into the compositional and structural nano features of AlN/GaN DBRs by EELS-HAADF
Author: Eljarrat Ascunce, Alberto
López Conesa, Lluís
Magén, César
Gacevic, Zarko
Fernández-Garrido, S.
Calleja Pardo, Enrique
Estradé Albiol, Sònia
Peiró Martínez, Francisca
Keywords: Espectroscòpia d'electrons
Electron spectroscopy
Issue Date: 9-May-2013
Publisher: Cambridge University Press
Abstract: : III-V nitride ~AlGa!N distributed Bragg reflector devices are characterized by combined high-angle annular dark-field ~HAADF! and electron energy loss spectroscopy ~EELS! in the scanning transmission electron microscope. Besides the complete structural characterization of the AlN and GaN layers, the formation of AlGaN transient layers is revealed using Vegard law on profiles of the position of the bulk plasmon peak maximum. This result is confirmed by comparison of experimental and simulated HAADF intensities. In addition, we present an advantageous method for the characterization of nano-feature structures using low-loss EELS spectrum image ~EEL-SI! analysis. Information from the materials in the sample is extracted from these EEL-SI at high spatial resolution.The log-ratio formula is used to calculate the relative thickness, related to the electron inelastic mean free path. Fitting of the bulk plasmon is performed using a damped plasmon model ~DPM! equation. The maximum of this peak is related to the chemical composition variation using the previous Vegard law analysis. In addition, within the context of the DPM, information regarding the structural properties of the material can be obtained from the lifetime of the oscillation. Three anomalous segregation regions are characterized, revealing formation of metallic Al islands.
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It is part of: Microscopy and Microanalysis, 2013, vol. 19, num. 3, p. 698-705
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ISSN: 1431-9276
Appears in Collections:Articles publicats en revistes (Enginyeria Electrònica i Biomèdica)

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