We have investigated the growth structure and their optical properties of Wurzite AlN nanowires grown on sapphire (0002) substrates by chemical vapor deposition at various temperatures. The morphology, and structure were characterized by scanning and transmission electron microscopy, X-ray diffraction, and Raman analysis. Blue shift to shorter wavelength was observed in Raman spectrum when reaction temperature was increased. Emission characteristics were slightly altered by temperature effect due to defects of impurities and vacancies introduced during chemical reactions. Band to band excitonic feature at 6.12eV at room temperature was first reported in this study by the methods of optical measurements of cathodoluminescence, and photoluminescence. Two defect related transmissions around 2.95eV and 4.85eV were also observed as well, and a band gap structure of AlN nanowires was suggested in this report.
