Hamburg 2001 – scientific programme

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HL: Halbleiterphysik

HL 23: GaN I

HL 23.9: Talk

Tuesday, March 27, 2001, 17:30–17:45, S2

Study of the mosaicity of GaN epitaxial layer by X-ray diffraction — •Rosa Chierchia, Heidrun Heinke, Tim Boettcher, Sven Einfeldt, and Detlef Hommel — Universitaet Bremen, Kufsteiner strasse, D-28359 Bremen

GaN epitaxial layers, differing in the thickness of layer coalescence, were grown by metalorganic vapour phase epitaxy (MOVPE) and analyzed by high resolution X-ray diffraction. The layers show marked differences in the defect structure and strain state depending on the coalescence thickness. These differences are studied in detail within the model of mosaic crystals, where the defect structure is described by the lateral and vertical coherence length, tilt and twist. The lateral coherence length and the tilt of the mosaic blocks are determined by using both symmetric (00l) and asymmetric (hkl) reflections. The results of these two methods differ, which has to be explained by the different sensitivity of symmetric and asymmetric reflections for various types of defects. The twist has been determined from an extrapolation of (hkl) diffraction profile widths to those of (hk0) reflections. The results are discussed in comparison with findings of transmission electron microscopy.