Growth of a‐plane AlN on r‐plane sapphire by plasma source molecular beam epitaxy

Abstract

We report the epitaxial growth of a-plane AlN on r-plane sapphire (Al2O3) substrates with an AlN nucleation layer. The AlN film is identified to be non polar and of a-plane orientation (110) which follows the r-plane Al2O3. The epitaxial films of thickness 0.34 μ were grown at low temperature (650 °C) by Plasma Source Molecular Beam Epitaxy (PSMBE). Initially we deposited a thin (50 A) buffer layer of AlN on a 3 inch r-plane sapphire substrate at 400 °C in argon/nitrogen plasma followed by a 10 min annealing at 650 °C. The reflection high energy electron diffraction (RHEED) method was used for in situ structural characterization during the growth process. The a-plane growth has been confirmed by ex situ high resolution X-ray diffraction (XRD). Only the a-plane reflection peak appears at 2θ = 59.5o. The surface morphology of the films was examined by atomic force microscopy (AFM). Optical properties of the films have been studied using reflection spectroscopy in the 175–3300 nm wavelength range. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)