Self-healing thermal annealing: surface morphological restructuring control of GaN nanorods

Michelle Conroy, Haoning Li, Vitaly Z. Zubialevich, Gunnar Kusch, Michael Schmidt, Timothy Collins, Colm Glynn, Robert W. Martin, Colm O'Dwyer, Justin D. Holmes, Peter J. Parbrook, Michael D. Morris

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)
25 Downloads (Pure)


With advances in nanolithography and dry etching, top-down methods of nanostructuring have become a widely used tool for improving the efficiency of optoelectronics. These nano dimensions can offer various benefits to the device performance in terms of light extraction and efficiency, but often at the expense of emission color quality. Broadening of the target emission peak and unwanted yellow luminescence are characteristic defect-related effects due to the ion beam etching damage, particularly for III–N based materials. In this article we focus on GaN based nanorods, showing that through thermal annealing the surface roughness and deformities of the crystal structure can be “self-healed”. Correlative electron microscopy and atomic force microscopy show the change from spherical nanorods to faceted hexagonal structures, revealing the temperature-dependent surface morphology faceting evolution. The faceted nanorods were shown to be strain- and defect-free by cathodoluminescence hyperspectral imaging, micro-Raman, and transmission electron microscopy (TEM). In-situ TEM thermal annealing experiments allowed for real time observation of dislocation movements and surface restructuring observed in ex-situ annealing TEM sampling. This thermal annealing investigation gives new insight into the redistribution path of GaN material and dislocation movement post growth, allowing for improved understanding and in turn advances in optoelectronic device processing of compound semiconductors.
Original languageEnglish
Pages (from-to)6769-6775
Number of pages7
JournalCrystal Growth and Design
Issue number12
Early online date31 Oct 2016
Publication statusPublished - 7 Dec 2016


  • nanolithography
  • nanostructuring
  • nanorods
  • thermal annealing
  • self-healing
  • gallium nitride
  • cathodoluminescence hyperspectral imaging
  • micro-Raman


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