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Semiconductor nanowires (NWs) are characterized by an extraordinarily large surface-to-volume ratio. Consequently, surface effects are expected to play a much larger role than in thin films. Here, we review a research focused on the impact of the surface on the electrical and optical properties of catalyst-free GaN NWs with growth direction, 0001.. Using a combination of complementary experimental techniques, it has been shown that the Fermi level is pinned at the NW sidewall surfaces, resulting in internal electric fields and in full depletion for NWs below a critical diameter. Deoxidation of the surfaces unpins the Fermi level, leading to enhanced radiative recombination of excitons. Prominent absorption below the bandgap is caused by the Franz-Keldysh effect. Close to the surface, the ionization energy of donors is reduced. The consideration of surfaceinduced effects is mandatory for an understanding of the …
Cambridge University Press
Publication date: 
14 Sep 2011

Raffaella Calarco, Toma Stoica, Oliver Brandt, Lutz Geelhaar

Biblio References: 
Volume: 26 Issue: 17 Pages: 2157
Journal of materials research