Heteroepitaxial GaN layers grown on sapphire by metal organic vapour phase
epitaxy (MOVPE) have been characterised by conventional transmission electron
microscopy (TEM) on planar and cross-sectional samples, Large Angle Convergent
Beam Electron Diffraction (LACBED) and by high-resolution transmission
electron microscopy (HRTEM). Hollow tubes termed nanopipes were resolved on
planar view and cross-sections of heteroepitaxial GaN. For advanced studies
of the nature of nanopipes the LACBED method was employed. The recognition
between perfect structure and screw distortion around nanopipes was
performed with high accuracy using Zone Axis LACBED images.