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Insight into the Compositional and Structural Nano Features of AlN/GaN DBRs by EELS-HAADF

Published online by Cambridge University Press:  09 May 2013

Alberto Eljarrat ,
Lluís López-Conesa ,
César Magén ,
Žarko Gačević ,
Sergio Fernández-Garrido ,
Enrique Calleja ,
Sónia Estradé  and
Francesca Peiró
Alberto Eljarrat*
Affiliation:
Laboratory of Electron NanoScopies, LENS-MIND-IN2UB, Dept. Electrónica, Universitat de Barcelona, Marti i Franqués 1, 08028 Barcelona, Spain
Lluís López-Conesa
Affiliation:
Laboratory of Electron NanoScopies, LENS-MIND-IN2UB, Dept. Electrónica, Universitat de Barcelona, Marti i Franqués 1, 08028 Barcelona, Spain
César Magén
Affiliation:
Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50018 Zaragoza, Spain Fundación ARAID, 50018 Zaragoza, Spain
Žarko Gačević
Affiliation:
Instituto de sistemas optoelectrónicos y Microtecnología (ISOM), Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
Sergio Fernández-Garrido
Affiliation:
Instituto de sistemas optoelectrónicos y Microtecnología (ISOM), Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
Enrique Calleja
Affiliation:
Instituto de sistemas optoelectrónicos y Microtecnología (ISOM), Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
Sónia Estradé
Affiliation:
Laboratory of Electron NanoScopies, LENS-MIND-IN2UB, Dept. Electrónica, Universitat de Barcelona, Marti i Franqués 1, 08028 Barcelona, Spain TEM-MAT, (CCiT), Universitat de Barcelona, Lluís Solé i Sabarís 1-3, 08028 Barcelona, Spain
Francesca Peiró
Affiliation:
Laboratory of Electron NanoScopies, LENS-MIND-IN2UB, Dept. Electrónica, Universitat de Barcelona, Marti i Franqués 1, 08028 Barcelona, Spain
*
*Corresponding author.[email protected]
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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.

Keywords

EELSHAADFIII-V nitridesDBRSTEM
Type
Materials Applications
Information
Microscopy and Microanalysis , Volume 19 , Issue 3 , June 2013 , pp. 698 - 705
Copyright
Copyright © Microscopy Society of America 2013 

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Footnotes

†

Current address: Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 57, 10117 Berlin, Germany

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