Determination of Nitrogen Concentration in Dilute GaNAs by STEM HAADF Z-Contrast Imaging

We determine the nitrogen concentration of GaN0.01≤x≤0.05As1−x quantum wells by evaluation of high resolution scanning transmission electron microscopy (STEM) images using a high-angle annular dark field detector. Although nitrogen has a smaller atomic number than Ga the image intensity increases with the nitrogen content. This is explained by the influence of static atomic displacements by comparison with frozen lattice simulations. The resulting nitrogen concentrations agree with high resolution X-ray diffraction measurements and strain state analysis applied to STEM images.