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

Hiller, Kieran P and Winkelmann, Aimo and Hourahine, Ben and Starosta, Bohdan and Alasmari, Aeshah and Feng, Peng and Wang, Tao and Parbrook, Peter J and Zubialevich, Vitaly Z and Hagedorn, Sylvia and Walde, Sebastian and Weyers, Markus and Coulon, Pierre-Marie and Shields, Philip A and Bruckbauer, Jochen and Trager-Cowan, Carol (2023) Imaging threading dislocations and surface steps in nitride thin films using electron backscatter diffraction. Microscopy and Microanalysis, 29 (6). pp. 1879-1888. ISSN 1431-9276 (https://doi.org/10.1093/micmic/ozad118)

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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.

ORCID iDs

Hiller, Kieran P, Winkelmann, Aimo, Hourahine, Ben ORCID logoORCID: https://orcid.org/0000-0002-7667-7101, Starosta, Bohdan, Alasmari, Aeshah ORCID logoORCID: https://orcid.org/0000-0002-2393-6253, Feng, Peng, Wang, Tao, Parbrook, Peter J, Zubialevich, Vitaly Z, Hagedorn, Sylvia, Walde, Sebastian, Weyers, Markus, Coulon, Pierre-Marie, Shields, Philip A, Bruckbauer, Jochen ORCID logoORCID: https://orcid.org/0000-0001-9236-9320 and Trager-Cowan, Carol ORCID logoORCID: https://orcid.org/0000-0001-8684-7410;
CORE (COnnecting REpositories)