InN films grown on sapphire at different substrate temperatures from 550℃ to 700℃ by metalorganic chemical vapor deposition were investigated. The low-temperature GaN nucleation layer with high-temperature annealing (1100℃) was used as a buffer for main InN layer growth. X-ray diffraction and Raman scattering measurements reveal that the quality of InN films can be improved by increasing the growth temperature to 600℃. Further high substrate temperatures may promote the thermal decomposition of InN films and result in poor crystallinity and surface morphology. The photoluminescence and Hall measurements were employed to characterize the optical and electrical properties of InN films,which also indicates strong growth temperature dependence. The InN films grown at temperature of 600℃ show not only a high mobility with low carrier concentration,but also a strong infrared emission band located around 0.7 eV. For a 600 nm thick InN film grown at 600℃,the Hall mobility achieves up to 938 cm2/Vs with electron concen-tration of 3.9×1018 cm-3. The low-temperature GaN nucleation layer with high-temperature annealing (1100 ° C) was used as a buffer for the main InN layer growth. InN films grown on sapphire at different substrate temperatures from 550 ° C to 700 ° C by metalorganic chemical vapor deposition were investigated. X-ray diffraction and Raman scattering measurements reveal that the quality of InN films can be improved by increasing the growth temperature to 600 ° C. Further high substrate temperatures may promote the thermal decomposition of InN films and result in poor crystallinity and surface morphology. The photoluminescence and Hall measurements were employed to characterize the optical and electrical properties of InN films, which also indicates strong growth temperature dependence. The InN films grown at temperature of 600 ° C show not only a high mobility with low carrier concentration, but also a strong infrared emission band located around 0.7 eV. For a 600 nm thick InN film grown at 600 ° C, the Hall mobility achieves up to 938 cm2 / Vs with electron concen- tration of 3.9 × 10 18 cm-3.