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Al1-xInxN/GaN bilayers: Structure, morphology, and optical properties

Lorenz, K. and Magalhaes, S. and Franco, N. and Barradas, N. P. and Darakchieva, V. and Alves, E. and Pereira, S. and Correia, M. R. and Munnik, F. and Martin, R. W. and O'Donnell, K. P. and Watson, I. M. (2010) Al1-xInxN/GaN bilayers: Structure, morphology, and optical properties. Physica Status Solidi B, 247 (7). pp. 1740-1746. ISSN 0370-1972

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Abstract

High quality Al1-xInxN/GaN bilayers, grown by metal organic chemical vapor deposition (MOCVD), were characterized using structural and optical techniques. Compositional analysis was performed using Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA). The InN molar fraction x decreased approximately linearly with increasing growth temperature and ranged from x = 0.13 to 0.24. Up to x = 0.20 the layers grow pseudomorphically to GaN with good crystalline quality. These layers show a smooth surface with V-shaped pits. Two layers with InN contents around 24% showed partial strain relaxation. However, the mechanisms leading to relaxation of compressive strain are very different in the two samples grown both at similar temperature but with different growth rates. One sample shows a decreased c/a ratio, as expected for relaxation of the compressive strain, while In was shown to be homogeneously distributed with depth. The other sample started to grow with x = 0.24 but relaxed mainly by reduction of the incorporated InN content towards the lattice-match composition of x similar to 0.17. Both samples have an increased surface roughness. All samples show strong Al1-xInxN band edge luminescence with large bowing parameter and Stokes' shifts. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim