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 epita xy were investigated by means of atomic-resolution high-voltage electron mi croscopy (ARHVEM). The atomic positions of Ga and N could be directly discr iminated by ARHVEM to determine the polarity in GaN. It was revealed that N polarity GaN films possessed a high density of nanometric inversion domain s (IDs) with Ga polarity. The ID boundary was constructed by an inversion a nd a c/2 translation, and formed fourfold and eightfold coordination along the boundary. (C) 2001 American Institute of Physics.