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Investigating surface effects of GaN nanowires using confocal microscopy at below-band gap excitation
Published online by Cambridge University Press: 09 October 2017
Abstract
We analyze the microscopic origins of subgap photoexcitations of individual gallium nitride (GaN) triangular cross-section nanowires (NWs), which are highly photoactive over a broadband spectral range. Using confocal hyperspectral photoluminescence (PL) microscopy, mid-gap states on the NWs were excited using subgap illumination, resulting in two distinct PL spectra corresponding to the polar (0001) and the semipolar $\left( {\bar 1101} \right)$ / $\left( {1\bar 101} \right)$ surfaces. Emission spectra are well represented by Gaussian functions with fitted centers of 1.99 ± 0.01 eV and 2.26 ± 0.01 eV, respectively. PL collected from the end facets exhibits interference fringes and a relative blue shift. Furthermore, the PL spectrum shifts strongly to the blue when the excitation intensity is increased. These observations are consistent with a qualitative model in which the PL results from excitation into a broad manifold of surface-associated states which are rapidly populated at a high excitation intensity and can couple to etalon modes via longitudinal photon emission.
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- Information
- Journal of Materials Research , Volume 32 , Issue 21: Focus Issue: Jan van der Merwe: Epitaxy and the Computer Age , 14 November 2017 , pp. 4076 - 4086
- Copyright
- Copyright © Materials Research Society 2017
Footnotes
Contributing Editor: Johan Brand Malherbe
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