MgO epitaxy on GaN (0002) surfaces by molecular beam epitaxy

We report on the epitaxial deposition of magnesium oxide films with [111] crystallographic orientation on (0002) GaN by molecular beam epitaxy. Specifically, we use an adsorption controlled growth mechanism to initiate the growth process. Electron diffraction shows a spotty intense pattern without intensity fluctuations during growth and evidence of in-plane twinning. X-ray diffraction reveals the films to be epitaxial with full width at half maximum values of 0.3 degrees, 0.5 degrees, and 1 degrees in 2 theta, phi, and chi circles, respectively. Wet etching of the GaN surface with a HCl:HF mixture prior to growth is critical for achieving high crystalline quality. Epitaxial growth is observed between room temperature and 650 degrees C, with negligible changes in crystalline quality with increased temperature. Atomic force microscopy analysis shows grainy surfaces with feature sizes near 10 nm and rms roughness values of 1.4 A over 1 mu m(2) areas. X-ray diffraction analysis suggests MgO film stability up to 850 degrees C in ex situ air annealing. (c) 2006 American Institute of Physics.