Growth and characterization of AlxGa1−xN via NH3-based metal-organic molecular beam epitaxy

Growth and characterization of ammonia-based metal-organic molecular beam epitaxy (NH3-MOMBE) AlxGa1−xN epitaxial films has been conducted. AlxGa1−xN films spanning the entire range of aluminum compositions were grown on GaN templates. This is the first reported successful growth of AlxGa1−xN via NH3-MOMBE, using triethylgallium (TEGa), triethylaluminum (TEAl) and ammonia (NH3) as the precursors. These films were characterized via optical interferometry (OI), atomic force microscopy (AFM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). High-quality AlxGa1−xN films, as inferred by XRD, are achievable in films without cracking. The catalytic effect of Al on NH3 is found to play a major part in the growth rate of the AlxGa1−xN films. The excessive nitrogen produced through this catalytic effect hinders the growth rate at lower Al composition while increasing the growth rate of AlxGa1−xN (x>0.4) films. Stress in the deposited films is found to be partially relieved through surface cracking along the 〈1 1 2¯ 0〉 direction in the film. These cracks provide dislocation gettering centers, with the dislocation pit density decreasing with increasing Al composition. A basic understanding on the factors affecting the growth of AlxGa1−xN is determined and will become the basis for further investigations into the optimization of AlxGa1−xN growth.