The crystallographic relationship between InN and its interfaces with GaN and sapphire was investigated using selected area diffraction patterns obtained with a transmission electron microscope, and was confirmed using X-ray diffraction pole figures. The lattice of InN grown on a GaN template corresponded to that of the GaN in the c-plane, while that of InN grown directly on sapphire was rotated with respect to the sapphire by 30degrees. The polarity of InN was investigated using convergent-beam electron diffraction. The InN had the same N-polarity along the growth direction as that reported for Molecular beam epitaxy growth. The growth conditions for high-quality InN with photoluminescence (PL) at room temperature, and no metal indium inclusions are described. The dependence of PL characteristics on the growth conditions was investigated. The PL peak was observed to shift to higher energies as the growth temperature rose. However, it is noteworthy that hardly any PL peak shift was observed with the measurement temperature. From the data reported up to now, uncooled and high-power operation laser diodes for optical communications systems can be expected. (C) 2004 Elsevier B.V. All rights reserved.