An InGaN layer was grown by metalorganic chemical vapor deposition on a sapphire (0001) substrate using a thick (>2.2 mu m) 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 In0.18Ga0.82N layer, e(perpendicular to) = + 0.21% and e(parallel to) = -0.53%, respectively, were derived using a combination of XRD and RBS/channeling. The small ratio \e(perpendicular to)/e(parallel to)\ = 0.40 indicates that the In0.18Ga0.82N layer is much stiffer in the c-axis direction than in the a-axis direction. (C) 1999 American Institute of Physics. [S0003-6951(99)01703-9].