Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 96: Focus Session: Semiconductor Nanophotonics - Characterization on the Atomic Scale
HL 96.3: Topical Talk
Freitag, 30. März 2012, 10:30–11:00, ER 164
Lattice parameter accomodation at the GaAs Nanowire to Silicon (111) substrate interface after Ga-assisted MBE growth — •Ullrich Pietsch1, Andreas Biermanns1, Anton Davydok1, Steffen Breuer2, Achim Trampert2, and Lutz Geelhaar2 — 1Festkörperphysik, 57068 Universität Siegen — 2Paul-Drude Institut für Festkörperelektronik, 10117 Berlin
We report on x-ray and TEM studies revealing the mechanism of lattice parameter accommodation of GaAs nanowires (NWs) grown on Si [111] substrate by Ga-assisted MBE. We show that the lattice mismatch between NW and substrate is released by a large procentage immediately after the beginning of NW growth through the inclusion of misfit dislocations. For thick NWs, the interface is rough preventing complete relaxation, whereas the release is nearly complete for thin NWs because the interface is flat. Using a nanosized x-ray beam and synchrotron radiation we could measure the residual strain and the phase composition of individual NWs. We find that even neighbouring NWs grown on the same sample under the same conditions differ significantly in their phase structure. Comparing the strains measured at a set of short nanowires of different height we are able to quantify the residual strain field close to the NW to substrate interface. It decays much faster along the interface compared to decay along the growth direction.