Origin of radiative recombination and manifestations of localization effects in GaAs/GaNAs core/shell nanowires

• Radiative carrier recombination processes in GaAs/GaNAs core/shell nanowires grown by molecular beam epitaxy on a Si substrate are systematically investigated by employing micro-photoluminescence (mu-PL) and mu-PL excitation (mu-PLE) measurements complemented by time-resolved PL spectroscopy. At low temperatures, alloy disorder is found to cause localization of photo-excited carriers leading to predominance of optical transitions from localized excitons (LE). Some of the local fluctuations in N composition are suggested to lead to strongly localized three-dimensional confining potential equivalent to that for quantum dots, based on the observation of sharp and discrete PL lines within the LE contour. The localization effects are found to have minor influence on PL spectra at room temperature due to thermal activation of the localized excitons to extended states. Under these conditions, photo-excited carrier lifetime is found to be governed by non-radiative recombination via surface states which is somewhat suppressed upon N incorporation. (C) 2014 AIP Publishing LLC.

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NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

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