Structural impact on the nanoscale optical properties of InGaN core-shell nanorods

Griffiths, J. T. and Ren, C. X. and Coulon, P.-M. and Le Boulbar, E. D. and Bryce, C. G. and Girgel, I. and Howkins, A. and Boyd, I. and Martin, R. W. and Allsopp, D. W. E. and Shields, P. A. and Humphreys, C. J. and Oliver, R. A. (2017) Structural impact on the nanoscale optical properties of InGaN core-shell nanorods. Applied Physics Letters, 110. 172105. ISSN 0003-6951 (https://doi.org/10.1063/1.4982594)

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Abstract

III-nitride core-shell nanorods are promising for the development of high efficiency light emitting diodes and novel optical devices. We reveal the nanoscale optical and structural properties of core-shell InGaN nanorods formed by combined top-down etching and regrowth to achieve non-polar sidewalls with a low density of extended defects. While the luminescence is uniform along the non-polar {1–100} sidewalls, nano-cathodoluminescence shows a sharp reduction in the luminescent intensity at the intersection of the non-polar {1–100} facets. The reduction in the luminescent intensity is accompanied by a reduction in the emission energy localised at the apex of the corners. Correlative compositional analysis reveals an increasing indium content towards the corner except at the apex itself. We propose that the observed variations in the structure and chemistry are responsible for the changes in the optical properties at the corners of the nanorods. The insights revealed by nano-cathodoluminescence will aid in the future development of higher efficiency core-shell nanorods.

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