High-precision determination of lattice constants and structural characterization of InN thin films

Abstract

X-ray diffraction and Rutherford backscattering/channeling were used to characterize the crystalline quality of an InN layer grown on Al2O3(0001) using metal-organic chemical-vapor deposition. A full width at half maximum of 0.27° from an InN(0002) ω scan and a minimum yield of 23% from channeling measurements show that this 480-nm-thick InN layer grown at low temperature (450°C) has a relatively good crystalline quality. High-resolution x-ray diffraction indicates that the InN layer contains a small fraction of cubic InN, besides the predominant hexagonal phase. From this InN sample, the lattice constants a=0.35376nm and c=0.57064nm for the hexagonal InN and a=0.4986nm for the cubic InN were determined independently. 2θ∕ω-χ mapping and a pole figure measurement revealed that the crystallographic relationship among the cubic InN, the hexagonal InN, and the substrate is: InN[111]‖InN[0001]‖Al2O3[0001] and InN{110}‖InN{112¯0}‖Al2O3{101¯0}, and that the cubic InN is twinned. Photoluminescence measurements indicate that the band-gap energy of this sample is approximately 0.82eV.