Regensburg 2016 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 64: Focus Session: Semiconductor Heteroepitaxy on Nanopatterned Substrates

HL 64.2: Topical Talk

Mittwoch, 9. März 2016, 15:30–16:00, H11

Nanometer scale correlation of structural and optical properties of individual GaAs/AlGaAs nanorodsby Scanning Transmission Electron Microscope Cathodoluminescence — •Frank Bertram, Marcus Müller, Peter Veit, and Jürgen Christen — Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg

We will present a direct correlation of the luminescence with crystallographic realstructure of novel GaAs/AlGaAs coreshell nanowires using cathodoluminescence directly performed in transmission electron microscope at liquid helium temperature. The GaAs/AlGaAs coreshell NWs were produced by a unique twostep process enabling the growth of ultrathin GaAs cores. First, GaAs NWs were obtained by molecular beam epitaxy on a [111]-oriented Si. In a second step the GaAs core diameter was reduced by a reverse-reaction using in-situ thermal decomposition of the {110} side wall surfaces leading typically to a diameter down to 7 nm. Subsequently, the cores were overgrown by an AlGaAs passivation shell and a GaAs cap. TEM investigations reveal wurzite structure in the bottom part of the NW with a high density of extended defects whereas the upper part is dominated by the zincblende phase containing few twindefects. Highly spatially resolved CL measurements exhibit a blue shifted emission up to 1.66 eV as compared to bulk GaAs. In particular, we will present a detailed analysis of the impact of structural properties on the luminescence along the wire. Locally sharp emission lines originating from vicinity of twindefects within the ZB-structure indicate effective localization.