Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 55: GaN: preparation and characterization II
HL 55.2: Vortrag
Freitag, 29. Februar 2008, 10:45–11:00, ER 164
Influence of Si and Mg on the growth mechanism of GaN nanorods on Si (111) — •Florian Furtmayr1, Christoph Stark1, Martin Stutzmann1, Martin Eickhoff1, Jordi Arbiol2, and Joan Ramon Morante2 — 1Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany — 2TEM-MAT, Serveis Cientificotecnics, Universitat de Barcelona, Barcelona, CAT, Spain
The self assembled growth of GaN nanorods (NRs) on Si (111) substrates without the use of extrinsic catalysts by PAMBE under nitrogen-rich conditions is investigated. A thin amorphous silicon nitride layer is formed in the initial stage of the growth which impedes nucleation on the substrate surface at high growth temperatures, preventing the formation of a wetting layer. Investigation of the nucleation process by SEM reveals a nucleation diameter of (12 ± 3) nm and a non-linear dependence of the nucleation density on the growth time. The observation of the low lateral growth rate of 1.7 Å/min and the homogeneous NR height distribution indicate strong desorption from the NR sidewalls, which inhibits diffusion transport to the top surface. The incorporation of Mg leads to a decrease of the nucleation time and to an increase of the lateral growth rate. In the case of Si-doping the increase of the lateral growth rate is smaller, but the rod morphology is changed to widening cones for high Si fluxes. We discuss these results in terms of the growth kinetics and show that during growth the presence of a Ga droplet on the NR top surface is very likely. PL spectroscopy as well as HRTEM have been employed.