GaN films with Ga-polarity were grown onto (00•1) sapphire substrates by means of plasma-assisted molecular beam epitaxy. Three types of surface reconstruction pattern, (5 x 5), (1 x 2) and (2 x 2), were observed during cooling. It was found that high-quality films were obtained when the films had the (1 x 2) pattern.

Optimization of GaN Growth with Ga-Polarity by Referring to Surface Reconstruction Reflection High-Energy Electron Diffraction Patterns. X.Q.Shen, T.Ide, S.H.Cho, M.Shimizu, S.Hara, H.Okumura, S.Sonoda, S.Shimizu: Japanese Journal of Applied Physics - 2, 2001, 40[1A/B], L23-5