Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 33: Quantum wires: preparation and characterization
HL 33.9: Vortrag
Mittwoch, 25. März 2009, 16:30–16:45, BEY 81
In-situ RHEED study on the morphology of MBE-grown GaN nanowires — •Matthias Knelangen, Achim Trampert, Lutz Geelhaar, and Henning Riechert — Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
GaN nanowires are defect-free, quasi 1-dimensional nanocrystals. Although the fabrication of nanowires is well established, there is still a lack of understanding of the initial nucleation and the catalyst-free self-organized growth mechanism. In this work, we will present an in-situ RHEED study of the nucleation process of GaN nanowires growth on Si (111) substrates.
If GaN growth is initiated directly on Si, the RHEED pattern turns faint and blurry, characteristic for the formation of an amorphous SixNy layer. After GaN nucleation, the RHEED spots are broadened, indicating a tilt of the wires with respect to the substrate. The superposition of two different azimuthal RHEED patterns and the independence to substrate rotation demonstrate the loss of in-plane orientation.
When growing on a smooth AlN buffer, the RHEED shows a clear transition from the AlN reflection pattern to a GaN transmission pattern. The two characteristic azimuths do correspond, showing the epitaxial alignment between AlN and GaN. HRTEM images show that the AlN layer relaxes by formation of misfit dislocations. The GaN/AlN interface is defect-free, so there is no plastic relaxation in the nanowires. Additional ex-situ TEM and XRD experiments will complement this RHEED study to investigate the overall strain of GaN and AlN.