Identifying threading dislocation types in ammonothermally grown bulk α-GaN by confocal Raman 3-D imaging of volumetric stress distribution

• Published in: Journal of crystal growth 2018-10, Vol.499, p.47-54, Article 47
• Main Authors: Holmi, J.T., Bairamov, B.H., Suihkonen, S., Lipsanen, H.
• Format: Article
• Language: English
• Subjects: 00-01; 99-00; A1. Confocal Raman spectroscopy; A1. Dislocation types; A1. Stress distribution; A1. Three-dimensional (3-D) imaging; A2. Ammonothermal crystal growth; B1. Bulk hexagonal GaN
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2018.07.024

•First confocal Raman 3-D imaging study of dislocations in ammonothermal α-GaN.•Non-destructive all-optical volumetric Raman imaging characterization of dislocations.•Edge a-type threading dislocation identified from its volumetric stress distribution.•Effects of threading dislocation types on Raman shift discussed in detail. This study demonstrates all-optical Raman scattering study of dislocations in ammonothermally grown α-GaN crystal and identifies an edge a→-type threading dislocation (TD) using a confocal Raman 3-D imaging technique. These findings make possible the characterization of volumetric stress field and low TD density distributions over a large area on bulk α-GaN single crystal. The dislocation type effects on Raman shift are also discussed in detail (in order to identify the edge a→-type and mixed a→+c→-type TDs, and theorize the invisibility of the screw c→-type TDs). Authors are not aware of any previous reports using the confocal Raman 3-D imaging to identify the edge a→-type and mixed a→+c→-type TDs.