Optical properties of InN films grown by pressurized-reactor metalorganic vapor phase epitaxy

InN thin films have been grown using a pressurized-reactor metalorganic vapor phase epitaxy system at 500-700 C under the pressure of 2.1 × 10⁵ Pa. Photoluminescence (PL), optical reflectance and transmission measurements were performed at room temperature. We found that optical properties of these as-grown films strongly depend on the growth temperature. By analyzing the reflectance spectra, it is found that the calculated carrier concentrations of the films increased with decreasing growth temperature. Room-temperature photoluminescence spectra show that the films grown at temperatures higher than 575 C have strong emission peaks at 0.68-0.75 eV, while those grown at temperatures lower than and equal to 575 C have negligible emission. The quenching of the emission is attributed to the existences of cubic InN and a high-density of nonradiative recombination centers in the films grown at low growth temperature region. Especially for the case of high temperature growth, the growth temperature dependence of the absorption-edge energy shows a similar tendency with that of the PL peak energy, both blue-shifted with decreasing the growth temperature possibly due to the well-known Burstein-Moss effects. From these results, an optimum growth temperature of 675 C in the pressurized growth could be obtained.