Strain in AlGaN layer studied by Rutherford backscattering/channeling and x-ray diffraction

An AlGaN layer with good crystalline quality (chi(min)=2.1%) was grown by m etalorganic vapor phase epitaxy on a sapphire (0001) substrate using a GaN intermediate layer. The Al composition, which cannot be unambiguously deter mined by x-ray diffraction (XRD) or by photoluminescence, was determined by Rutherford backscattering (RBS). The perpendicular and parallel elastic st rain of the Al0.28Ga0.72N layer, e(perpendicular to) = - 0.16% and e(parall el to) = + 0.39%, respectively, were derived using XRD and RBS/channeling. The small ratio \e(perpendicular to)/e(parallel to)\ = 0.41 indicates that the Al0.28Ga0.72N lattice is much stiffer in the c-axis direction than in t he a-axis direction. A comparison of the strain data for GaN, InGaN, and Al GaN layers is presented. (C) 1999 American Vacuum Society. [S0734-211X(99)0 2404-X].