Defect structure study of epitaxial InN films by transmission electron microscopy and X-ray diffraction

The structural and morphological properties of InN epilayers grown on Si(1 1 1) substrates by plasma-assisted molecular beam epitaxy were studied. The mosaic characteristics such as grain size, twist and tilt angles were extracted by performing symmetric and asymmetric rocking curves and reciprocal space mapping. According to X-ray diffraction analysis, the dislocation densities reduced from 1×1011 to 2.27×1010 cm−2, when the substrate temperature was increased from 440 to 525 °C. Edge-type dislocation densities estimated both by fitting the FWHM of ω-scans of various lattice planes based on cosine theorem of spherical trigonometry and by grazing incidence (1 1 2¯ 0) diffraction agree with plan-view transmission electron microscopy (TEM) results. Surface morphology revealed grains with flat or terrace-like features separated by deep trenches. Faceted pits associated with screw-type threading dislocations are observed and their densities are in good consistence with the results obtained from X-ray diffraction. Improved film quality is achieved by applying highest growth temperature within InN dissociation limit.