X-ray Study of Step Induced Lateral Correlation Lengths in Thin AlGaN Nucleation Layers

概要

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A 15 nm thick high temperature AlGaN nucleation layer was grown on a slightly off-oriented $c$-plane sapphire substrate by metal–organic vapor phase epitaxy. The evaluation of this layer by high resolution X-ray diffraction yields a nucleation with a threefold distribution of the rotational disorder within about 4° in the $\omega$-scan at the in-plane AlGaN$(1\bar{1}00)$ reflection, whereas the $\omega$-scan at the symmetric AlGaN(0002) reflection exhibits a very narrow correlation peak. In addition, two weaker signals could be determined in the symmetric $\omega$-scan. The positions of these minor maxima with respect to the correlation peak depend on the azimuth angle of the incident X-ray beam. Based on the determined off-orientation angle and lateral coherence lengths the phenomenon is explained in terms of a stepped sapphire surface morphology.
2010-02-25