Imaging Threading Dislocations and Surface Steps in Nitride Thin Films Using Electron Backscatter Diffraction
K.P. Hiller1, A. Winkelmann1,2, B. Hourahine1, B. Starosta1, A. Alasmari1, P. Feng3, T. Wang3, P.J. Parbrook4, V.Z. Zubialevich4, S. Hagedorn5, S. Walde5, M. Weyers5, P.-M. Coulon6,7, P.A. Shields6, J. Bruckbauer1, and C. Trager-Cowan1
Published in:
Microsc. Microanal., vol. 29, no. 6, pp. 1879–1888, doi:10.1093/micmic/ozad118 (2023).
Abstract:
Extended defects, like threading dislocations, are detrimental to the performance of optoelectronic devices. In the scanning electron microscope, dislocations are traditionally imaged using diodes to monitor changes in backscattered electron intensity as the electron beam is scanned over the sample, with the sample positioned so the electron beam is at, or close to the Bragg angle for a crystal plane/planes. Here, we use a pixelated detector instead of single diodes, specifically an electron backscatter diffraction (EBSD) detector. We present postprocessing techniques to extract images of dislocations and surface steps, for a nitride thin film, from measurements of backscattered electron intensities and intensity distributions in unprocessed EBSD patterns. In virtual diode (VD) imaging, the backscattered electron intensity is monitored for a selected segment of the unprocessed EBSD patterns. In center of mass (COM) imaging, the position of the center of the backscattered electron intensity distribution is monitored. Additionally, both methods can be combined (VDCOM). Using both VD and VDCOM, images of only threading dislocations, or dislocations and surface steps can be produced, with VDCOM images exhibiting better signal-to-noise. The applicability of VDCOM imaging is demonstrated across a range of nitride semiconductor thin films, with varying surface step and dislocation densities.
1 Advanced Materials Diffraction Lab, Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, UK
2 Academic Centre for Materials and Nanotechnology, AGH University of Krakow, Kraków 30-055, Poland
3 Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, UK
4 Tyndall National Institute, University College Cork, Cork T12 R5CP, Ireland
5 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, D-12489 Berlin, Germany
6 Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK
7 CNRS-CRHEA, Université Côte d’Azur, 06560 Valbonne, France
Keywords:
SEM, nitrides, thin film semiconductors, extended defects, dislocations, EBSD
© The Author(s) 2023. Published by Oxford University Press on behalf of the Microscopy Society of America.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
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