Nanometric inversion domains in conventional molecular-beam-epitaxy GaN thin films observed by atomic-resolution high-voltage electron microscopy

GaN films grown on sapphire substrates by conventional molecular-beam epitaxy were investigated by means of atomic-resolution high-voltage electron microscopy (ARHVEM). The atomic positions of Ga and N could be directly discriminated by ARHVEM to determine the polarity in GaN. It was revealed that N polarity GaN films possessed a high density of nanometric inversion domains (IDs) with Ga polarity. The ID boundary was constructed by an inversion and a c/2 translation, and formed fourfold and eightfold coordination along the boundary. (C) 2001 American Institute of Physics.