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HL: Halbleiterphysik
HL 43: GaN: Pr
äparation und Charakterisierung II
HL 43.7: Vortrag
Montag, 7. März 2005, 16:30–16:45, TU P164
Characterization of epitaxially laterally overgrown GaN structures by micrometer-resolved X-ray Rocking Curve Imaging — •Daniel Lübbert1,2, Tilo Baumbach1, Petr Mikulik3, Petra Pernot1,4, Lukas Helfen1,4, Stacia Keller5, and Steven DenBaars5 — 1Institut für Synchrotronstrahlung, FZK, D-Karlsruhe — 2Humboldt-Universität, D-Berlin — 3Masaryk University, CZ-Brno — 4ESRF, F-Grenoble — 5University of California, Santa Barbara, USA
Epitaxial lateral overgrowth (ELO) of GaN works by growing a nucleation layer on a substrate and covering by a mask with laterally periodic openings. Upon subsequent regrowth of GaN, dislocations from the wetting layer can propagate vertically through these mask windows, but not usually into the lateral GaN wings growing on both sides of the windows. The GaN lattice quality in ELO wings is therefore expected to be superior.
We have performed experimental investigations of the local lattice quality in ELO structures using a technique of spatially resolved X-ray diffraction named Rocking Curve Imaging. It allows to monitor the crystal lattice quality and ELO wing tilt in individual periods of the laterally periodic structure, with spatial resolution down to one micrometer. Results show a highly inhomogeneous lattice tilt distribution across the sample surface. The progressive bending of laterally overgrown areas can be analyzed, showing both concave and convex curvature of ELO wings, depending on growth conditions. Samples grown on different substrates (SiC vs. sapphire) and by different growth sequences (1S- and 2S-ELO) will be compared in view of their crystalline perfection.