The {10•0} inversion domains in GaN layers which were grown onto sapphire substrates were investigated by means of transmission electron microscopy. They were easily identified in multiple-beam dark-field images, and via convergent-beam electron diffraction. By using dark-field imaging, it was shown that the domain boundaries did not exhibit any translation in the basal plane. The atomic structure of the boundaries was determined by comparison with geometrical models. Three types of model could be used to interpret the observations. These corresponded to the Holt, Austerman-Gehman and V models. For each type of model, the boundary plane could be located in 2 positions; depending upon the cutting plane. By using the AB stacking sequences which were seen in high-resolution electron microscopic images, 2 models were identified. The atomic structure of the boundaries was then determined by comparison with simulated images. In the investigated samples, the Holt and V models were shown to exist in the 2 positions of the boundary plane. The samples which contained Holt inversion domains exhibited flat surfaces, whereas V inversion domain boundaries were observed in the centres of small pyramids (100nm-high) which protruded from the sample surface. The Holt inversion domains were always smaller (less than 20nm) and formed in quite high densities (2.5 x 1010/cm2), whereas the V inversion domains could attain 50nm; with a density that was an order of magnitude lower.

The {10¯10} Inversion Domains in GaN/Sapphire Layers - an Electron Microscopy Analysis of the Atomic Structure of the Boundaries V.Potin, G.Nouet, P.Ruterana: Philosophical Magazine A, 1999, 79[12], 2899-919