Experimental investigation of inclusion of hexagonal GaN phase-domain by varying nitrogen-beam direction to a < 111 > axis in MBE growth of cubic GaN

Crystalline quality of cubic phase (c-) GaN epilayers on (0 0 1) GaAs has b een systematically investigated by varying nitrogen (N-) beam direction in molecular beam epitaxy. In this study, the N-beam was obliquely incident to the surface normal. The N-beam direction during both buffer layer and epil ayer depositions could approximate either c-GaN[1 1 1]A or c-GaN[1 1 1]B. I n the c-GaN epilayers grown with different N-beam directions, the c-GaN dom ain or hexagonal (h-) GaN domain showed the tilt and the mosaicity. From th e X-ray rocking curves, the extraordinary c-GaN domains and the h-GaN domai ns were tilted by influence of oblique incidence of the N-beam. The phase p urity of c-GaN domain became high when the N-beam direction was along a c-G aN[1 1 1]A direction during both the buffer layer and the epilayer depositi ons. In order to understand the difference in crystalline quality with chan ge in the N-beam direction, we took account of stack of the Ga and N precur sors on (1 1 1)A (or ((1) over cap 1 1)B) c-GaN facet. It is considered tha t the difference of the crystalline quality result from the polarity of the facets. (C) 2001 Published by Elsevier Science B.V.