Imaging threading dislocations and surface steps in nitride thin films using electron backscatter diffraction

Kieran P Hiller, Aimo Winkelmann, Ben Hourahine, Bohdan Starosta, Aeshah Alasmari, Peng Feng, Tao Wang, Peter J Parbrook, Vitaly Z Zubialevich, Sylvia Hagedorn, Sebastian Walde, Markus Weyers, Pierre-Marie Coulon, Philip A Shields, Jochen Bruckbauer, Carol Trager-Cowan

Research output: Contribution to journalArticlepeer-review

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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 post-processing 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.
Original languageEnglish
Pages (from-to)1879-1888
Number of pages10
JournalMicroscopy and Microanalysis
Volume29
Issue number6
Early online date8 Nov 2023
DOIs
Publication statusPublished - 31 Dec 2023

Keywords

  • SEM
  • nitrides
  • thin film semiconductors
  • extended defects
  • dislocations
  • EBSD

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