The growth temperature dependence of In aggregation in two-step MOCVD grown InN films on sapphire

摘要

Indium nitride (InN) films have been deposited on sapphire substrates at 350-500 deg C using low-pressure metalorganic chemical vapor deposition (LP-MOCVD). Increasing the growth temperature changes the structure of InN from cubic to hexagonal. At 500 deg C, no InN can be grown on sapphire due to its decomposition. The X-ray diffraction (XRD) spectra of InN films show that the diffractions from In(101) reach a maximum at 425 deg C and begin to decrease at the growth temperature higher than 425 deg C. According to the scanning electron microscope (SEM) images of InN films, the In aggregation on the surface is observed at the growth temperature of 425 deg C, which corresponds to the most intensive diffraction of In(101) in XRD spectra. In addition, the density of InN nucleation sites is reduced by increasing the growth temperature. As well as the increase of In desorption with the growth temperature, the decrease of InN nucleation sites are responsible for the most significant In aggregation at 425 deg C.