Elastic strain in In0.18Ga0.82N layer: A combined x-ray diffraction and Rutherford backscattering/channeling study

An InGaN layer was grown by metalorganic chemical vapor deposition on a sapphire (0001) substrate using a thick (>2.2 μm) GaN intermediate layer. The In composition, which cannot be unambiguously determined by x-ray diffraction (XRD) or by photoluminescence, was determined by Rutherford backscattering (RBS). The perpendicular and parallel elastic strain of the ${\mathrm{In}}_{\mathrm{0.18}}{\mathrm{Ga}}_{\mathrm{0.82}}\mathrm{N}$ layer, $e^{\perp }\text{=+0.21\%}$ and $e^{\parallel }\text{=−0.53\%,}$ respectively, were derived using a combination of XRD and RBS/channeling. The small ratio ${\mathrm{|e}}^{\perp }{\mathrm{/e}}^{\parallel }\text{|=0.40}$ indicates that the ${\mathrm{In}}_{\mathrm{0.18}}{\mathrm{Ga}}_{\mathrm{0.82}}\mathrm{N}$ layer is much stiffer in the c-axis direction than in the a-axis direction.