Growth of nonpolar AlN (112¯) and (11¯00) films on SiC substrates by flow-rate modulation epitaxy

Nonpolar AlN (112¯0) and (11¯00) films were grown on SiC substrates by flow-rate modulation epitaxy (FME), wherein trimethylaluminum and NH3 were alternately supplied. FME provides both AlN (112¯0) and (11¯00) films with good crystallinity and smooth surfaces, whereas AlN (11¯00) films obtained by conventional metal-organic chemical vapor deposition exhibit poor crystallinity and rough surfaces with deep trenches consisting of (0001¯) and (11¯01) N-face microfacets. FME effectively eliminates these trenches, because the microfacets are unstable and have faster growth rates because of the enhanced migration of Al atoms in the absence of excess N surface coverage under the Al-rich condition.