Ordering and microstructures of GaN1-xAsx layers grown on (0001) GaN/sapphire substrates

Transmission electron microscope and transmission electron diffraction exam inations have been performed to investigate the ordering and microstructure s of molecular beam epitaxial GaN1-xAsx layers grown on (0001) GaN/sapphire at temperatures between 500 and 730 degrees C. We report the observation o f ordering with a space group P3m1 in the GaNAs layer grown at 730 degrees C. The GaNAs layers grown at temperatures below 600 degrees C are polycryst alline, while the 730 degrees C GaNAs layer has epitaxial relation to the G aN substrate. It is also shown that the GaNAs layers experience a structura l change from a zinc blende phase to a wurtzite phase, as the growth temper ature increases from 500 to 730 degrees C. (C) 1999 The Electrochemical Soc iety. S1099- 0062( 98) 09- 095- 6. All rights reserved.