X-ray reflectivity and atomic force microscopy studies of MOCVD grown AlxGa1−xN/GaN superlattice structures

Abstract

The grazing incidence X-ray reflectivity (GIXR) technique and atomic force microscopy (AFM) were exploited to obtain an accurate evaluation of the surfaces and interfaces for metalorganic chemical vapor deposition grown AlxGa1−xN/GaN superlattice structures. The X-ray diffraction results have been combined with reflectivity data to evaluate the layer thickness and Al mole fraction in the AlGaN layer. The presence of a smooth interface is responsible for the observation of intensity oscillation in GIXR, which is well correlated to step flow observation in AFM images of the surface. The structure with a low Al mole fraction (x = 0.25) and thin well width has a rather smooth surface for the Rrms of AFM data value is 0.45 nm.