Characterization of Polarity of Plasma-Assisted Molecular Beam Epitaxial GaN{0001} Film Using Coaxial Impact Collision Ion Scattering Spectroscopy

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Abstract
Effects of the initial nitridation of a sapphire(0001) substrate and the thickness of a low-temperature GaN buffer layer on the polarity of GaN{0001} films grown by rf plasma-assisted molecular beam epitaxy (MBE) have been investigated by coaxial impact collision ion scattering spectroscopy (CAICISS). The volume ratios of each domain in grown GaN{0001} films, that is, (0001) and (0001̄), were evaluated by making comparisons between the experimental results of the incident angle dependences of Ga and N signal intensities and simulated ones. It was determined that the initial nitridation of a sapphire(0001) substrate increases the volume ratio of the (0001̄) domain in the grown film and, on the contrary, a thick low-temperature GaN buffer layer increases that of the (0001) domain.