The correlation between structural and optical properties of indium nitride epilayer grown on gallium nitride/c-sapphire by radio frequency metal-organic molecular beam epitaxy is reported in this work. We discussed the effect of substrate temperature on the structural and optical properties of epitaxial indium nitride. The structural properties of the indium nitride films were characterized in detail using X-ray diffraction, field emission scanning electron microscopy and transmittance electron microscopy, and the electrical and optical properties were studied by Hall Effect and photoluminescence measurements. X-ray diffraction results indicated that indium nitride films were grown with a high degree of orientation along the c-axis, and their lattice constant is about 0.57 nm. Scanning electron microscopy images show that the growth of indium nitride proceeded in two-dimensional mode and the maximum thickness is about 700 nm. Our technique allowed the deposition of indium nitride at high growth rate of about 1.5 mu m/h. Optical measurements on the films revealed that a luminescence feature near-infrared emission peak is centered at 0.75 eV. The electron concentrations of the undoped films were found to range from 1.9x10(19) to 9.3x10(20) cm(-3) and the mobility varied from 30 to 464 cm(2)/V s. (C) 2012 Elsevier B.V. All rights reserved.