Photoluminescence studies of indium nitride films grown on oxide buffer by metalorganic molecular-beam epitaxy

We have investigated the effects of III/V ratio on the properties of InN films grown on sapphire substrates with oxide buffer by metalorganic molecular-beam epitaxy. The structural, optical and electrical properties of the InN films were investigated by X-ray diffraction, scanning electron microscopy, Hall-effect and temperature-dependent photoluminescence (PL) measurements. Near-infrared emission peaks between 0.74 and 0.78 eV were observed. On increasing the III/V flux ratio, the PL emission peak red-shifted that is related to the reduction in carrier concentration. In addition, the PL spectra show an abnormal behavior with increase in temperature. The temperature-dependence PL spectra exhibit blue-shift as the temperature increased up to 150 K and then red-shift, reflecting a competition between the blue-shift induced by thermal screening and the red-shift induced by electron–phonon interaction.