Indium incorporation and the optical properties of Inx Al1−x N layers (0 ≤ x ≤ 0.45) grown by metal-organic vapour phase epitaxy have been investigated simultaneously on polar (0001), untwinned semipolar (10overline 13) and nonpolar (10overline 10) AlN templates, which were prepared on planar sapphire substrates. The InN mole fraction XInN of the layers was tuned by changing growth temperature from 660°C to 860°C. XInN determined by x-ray diffraction was found to be comparable for the polar, semipolar and nonpolar surface orientations. This is consistent with comparable effective bandgap energy of the layers obtained from optical transmission measurements at room temperature. The bandgap bowing parameter was found to be strongly composition-dependent. Room-temperature photoluminescence measurements showed impurity transitions for the layers with XInN ≤ 0.2, while InAlN near-band-edge luminescence was observed for the layers with higher XInN.
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