Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 33: Quantum wires: preparation and characterization

HL 33.6: Vortrag

Mittwoch, 25. März 2009, 15:30–15:45, BEY 81

In-situ study of catalyst-induced GaN nanowire nucleation — •Caroline Chèze^1,2, Lutz Geelhaar^1,2, Achim Trampert¹, Oliver Brandt¹, and Henning Riechert^1,2 — ¹Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin — ²Formerly at Qimonda, 81730 Munich, Germany

We investigated in situ the nucleation of Ni-seeded GaN nanowires (NWs) grown on C-plane sapphire by molecular beam epitaxy (MBE). The crystal structure was probed by reflection high-energy electron diffraction (RHEED), and simultaneously the incorporated amount of Ga was monitored by line-of-sight quadrupole mass spectrometry (QMS). Additionally, some samples were investigated by transmission electron microscopy (TEM). During growth three different RHEED patterns appear subsequently, and each of them is accompanied by a change in the Ga incorporation behavior. We explained these three different nucleation phases as follows: first an accumulation of Ga into Ni seeds, then a drastic change in the orientation of the seed structure probably corresponding to a phase change induced by Ga incorporation, and finally growth of GaN below the seeds. The comparison of the QMS profiles for the first phase with and without Ni showed that Ga incorporation into the Ni seeds is not the growth limiting step. Moreover the tilt of the seed crystal structure in the second phase suggests a bulk diffusion process of Ga into the Ni seeds. Last the observation of a clear RHEED pattern during the whole nucleation is a strong evidence for the vapor-solid-solid mechanism (VSS).