Growth Mechanism of Semipolar AlN Layers by HVPE on Hybrid SiC/Si(110) Substrates

In this work, the growth mechanism of aluminum nitride (AlN) epitaxial films by hydride vapor phase epitaxy (HVPE) on silicon carbide (SiC) epitaxial layers grown on silicon (110) substrates is investigated. The peculiarity of this study is that the SiC layers used for the growth of AN films are synthesized by the method of coordinated substitution of atoms. In this growth method, a part of the silicon atoms in the silicon substrate is replaced with carbon atoms. As a result of atom substitution, the initially smooth Si(110) surface transforms into a SiC surface covered with octahedron-shaped structures having the SiC(111) and SiC(11 (1) over bar) facets. The SiC(111)/(11 (1) over bar) facets forming the angle of 35.3 degrees with the original Si(110) surface act as "substrates" for further growth of semipolar AN. The structure and morphology of AN films are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), reflection high-energy electron diffraction (RHEED) and Raman spectroscopy. It is found that the AN layers are formed by merged hexagonal microcrystals growing in two directions, and the following relation is approximately satisfied for both crystal orientations: AlN(10 (1) over bar3) parallel to Si(110). The full-width at half-maximum (FWHM) of the X-ray rocking curve for the AlN(10 (1) over bar3) diffraction peak averaged over the sample area is about 20 arcmin. A theoretical model explaining the presence of two orientations of AN films on hybrid SiC/Si(110) substrates is proposed, and a method for controlling their orientation is presented.