Inhomogeneous incorporation of in and Al in molecular beam epitaxial AlInGaN films

Plasma-induced molecular beam epitaxial AlInGaN heterostructures have been characterized by spatial resolved cathodoluminescence and x-ray energy dispersive microanalysis. Competitive incorporation of Al and In has been observed, with the formation of In-rich regions, showing enhanced luminescence around surface pinholes. These island-like In-rich regions are favored by growth at lower temperature due to the higher incorporation of indium into the alloy. The elastic strain relaxation associated to pinhole formation induces preferential local indium incorporation. The diffusion of carriers to these areas with reduced band gap enhances the luminescence emission of the quaternary film. The width and intensity of the luminescence appear to be sensitive to the mismatch between the quaternary film and the GaN layer below.