Structural characterization of InN films grown on different buffer layers by metalorganic chemical vapor deposition

InN films were grown on sapphire substrate by metalorganic chemical vapor deposition (MOCVD). Different buffer layers were used to investigate their effects on structural properties of InN films. These buffers include the nitrided treatment to the sapphire substrate, a low-temperature InN buffer layer and a thick GaN template. Symmetric high resolution X-ray diffraction (HRXRD) ω/2θ scans and asymmetric (1 0 1¯ 2) Φ scans confirmed all these InN films had a wurtzite-type structure and the in-plane orientation relationship between InN and Al2O3 was uniquely [101¯0]InN||[112¯0]Al2O3. The full-width at half maximum (FWHM) of X-ray (0 0 0 2) rocking curve decreased from 2.44° to 1.09° by inserting a low-temperature InN buffer. The narrowest FWHM of 0.36° for (0 0 0 2) rocking curve was obtained for InN film grown on a thick GaN template, whose large lateral coherence length is about 311 nm. Atomic force microscopy (AFM) images revealed that InN films without GaN buffer had a root-mean-square (RMS) roughness of 20 nm while that with a GaN template had a RMS roughness of 80 nm. So, both the low-temperature InN buffer and GaN template can improve InN film features from different aspects. It is necessary to combine the two methods to improve the quality of InN film.