Composition, structure and morphology of Al1−xInxN thin films grown on Al1−yGayN templates with different GaN contents

Abstract

Four nominally Al0.85In0.15N thin films with different strains were grown simultaneously on Al1−yGayN (y = 1, 0.93, 0.87 and 0.69) templates by metal organic chemical vapour deposition. The nominal InN content of ~15% was chosen to achieve close lattice matching of Al1−xInxN with the templates of intermediate GaN molar fractions, a small tensile strain for growth on GaN, and compressive strain for the template with the lowest GaN fraction. The film deposited on GaN reveals the highest structural quality, the lowest surface roughness and a homogeneous composition with depth. For growth on the Al1−yGayN ternary templates, the film roughness and the surface pit density both increase with decreasing GaN content, in line with the roughening of the growth templates themselves. Detailed study indicates that the structural and morphological qualities of the templates influence not only the quality of the Al1−xInxN films but also their composition profile. Results suggest that surface roughness of the template and growth on the inclined facets lead to compositional gradients due to a decreased InN incorporation on these facets and to the formation of V-pits.