Polar and semipolar (1122) InAlN layers grown on AlN templates using MOVPE

We report on metalorganic vapor phase epitaxial growth of InAlN layers on (0001) and (1122) AlN templates at different temperatures (725-800 °C). The indium content (8.0-15.2%) of the (1122)InAlN layers was found to be lower compared to that for the (0001) layers (9.0-23.0%). The higher indium content of the (0001)layers was attributed to a high density of small hillocks and a larger degree of relaxation. The small hillocks on the (0001)layer surface acted as quantum-dot-like structures that caused a stronger emission at longer wavelength compared to weaker emission at shorter wavelength from a "bulk" layer underneath. A large Stokes-shift of about 300 and 480meV was observed for the (0001) and (1122) layers, respectively. The larger shift of the (1122)layers was attributed to a higher degree of localization. The larger degree of localization and higher unintentional oxygen incorporation enhanced the luminescence intensity of the (1122)layers compared to that for the (0001)layers.