Structural Evaluation of β-AlN Films Grown on Sapphire (0001) Substrates

Abstract

-AlN thin films with different thickness were grown on sapphire(0001) substrates with a smooth surface in a nitrogen atmosphere by pulsed laser deposition using a sintered AlN target, and their films were evaluated by X-ray diffraction and transmission electron microscopy. Zincblend-type -AlN with a lattice constant of 7.89 Å was epitaxially grown on sapphire(0001) near the interface with the substrate. The electron diffraction patterns of its area along the close-packed planes exhibited streaking spots caused by dislocation defects. On the other hand, with increasing film thickness, the upper area of the AlN thin films became polycrystalline, and simultaneously the streaking disappeared there. Dislocation defects near the interface might be due to a large lattice mismatch or a shift in the close-patching sequence, and they disappears in the polycrystalline area.