DETERMINATION OF LATTICE POLARITY FOR GROWTH OF GAN BULK SINGLE-CRYSTALS AND EPITAXIAL LAYERS

The polarity of the lattice of bulk single GaN crystals and the polari ty of homoepitaxial and heteroepitaxial-on-sapphire GaN thin films has been studied using convergent beam electron diffraction. Diffraction patterns obtained at 200 kV for the [1-100] projection of GaN were mat ched with calculated patterns. The lattice orientations of two commonl y observed bulk single-crystal facets were identified. It is shown tha t the smooth facets in single crystals correspond to the (0001), Ga-te rminated, lattice planes, whereas the rough facets correspond to the ( <000(1)over bar>), N-terminated, planes. It is also shown that metalor ganic chemical vapor deposition epitaxy retains the polarity of the su bstrate, i.e., no inversion boundaries were observed. Heteroepitaxy on sapphire is shown to grow in the (0001), Ga-terminated orientation. ( C) 1996 American Institute of Physics.