Structural analysis of N-polar AlN layers grown on Si (111) substrates by high resolution X-ray diffraction

Crack-free high quality N-polar AlN epitaxial layers were grown on Si (111) substrates by plasma-assisted molecular beam epitaxy in the temperature range of 780–880 °C. The streaky 1×3 reflection high energy electron diffraction pattern was observed at room temperature for all AlN samples indicating N-polarity of epilayers. The polarity of samples was also confirmed by KOH etching studies. Structural properties of as-grown samples were carried out by high resolution X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The Williamson-Hall plots of the rocking curves widths were employed in order to study the mosaicity, dislocation density, and level of stress as a function of growth temperature. The 250 nm thick AlN sample grown at 830 °C yields the best crystalline quality, smooth surface morphology, and smallest root mean square roughness. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)