Structural and compositional homogeneity of InAlN epitaxial layers nearly lattice-matched to GaN

A group of InAlN films was fabricated by molecular beam epitaxy and investigated by X-ray diffraction, transmission electron microscopy and element nano-analyses. All top In(x)Al(1-x)N layers have compositions around lateral lattice-matching to GaN (x ~ 0.18) and are pseudomorphic. For a growth rate of 350 nm h-1, each InAlN film separated into two sublayers with different In/Al-ratios. Micrographs reveal sharp transitions both at the InAlN/GaN and at the InAlN/InAlN interfaces. In contrast to these separated layers, an optimized epitaxy using an AlN interlayer and a lower growth rate, 100 nm h-1, enabled the fabrication of a single-phase InxAl(1-x)N layer on GaN, homogeneous on a nanoscopic scale.