ABSTRACT
The local composition and structure of AlGaN/InGaN/AlGaN single and GaN/InGaN/GaN multiple quantum well structures was studied by energy dispersive X-ray spectroscopy and transmission electron microscopy (TEM). The In distribution was evaluated by measuring local lattice parameters from high-resolution TEM lattice fringe images, that are related to the In concentration by Vegard’s law. The investigation revealed a decreasing incorporation of In into the InGaN layer with decreasing lattice parameter of the AlGaN buffer as well as inhomogeneities of the In distribution on two different length scales. The accuracy of the evaluation method with respect to aberrations of the objective lens and sample thickness was tested by evaluating simulated images.
