Observation of columnar microstructure in lattice-matched InAlN/GaN grown by plasma assisted molecular beam epitaxy

Nominally lattice matched InAlN/GaN was grown by plasma-assisted molecular beam epitaxy, and the intrinsic microstructure was investigated via x-ray diffraction, transmission electron microscopy, and atom probe tomography. The InAlN showed a cellular structure, which was comprised of similar to 10 nm wide Al-rich cores and similar to 1 nm In-rich InAlN intercellular boundaries. Despite the strong laterally non-uniform In distribution, both vertical and lateral lattices are unperturbed by the cellular structure, as evidenced by strong thickness fringes in on-axis omega 2 theta high resolution x-ray diffraction scans, coherence lengths derived from on-axis (0002) and off-axis (10 (1) over bar2) omega 2 theta high resolution x-ray diffraction scans, and a modified Williamson-Hall analysis for on-axis reflections. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4725482]