Elastic strain in InGaN and AlGaN layers

InGaN and AlGaN layers were grown on Al2O3 substrate by metalorganic chemic al vapor deposition (MOCVD) with a GaN intermediate layer. The thickness an d the composition of the layers, 270 nm In0.18Ga0.82N and 765 nm Al0.28Ga0. 72N, were determined by Rutherford backscattering (RBS). The elastic strain of these layers was determined by X-ray diffraction combined with RBS/chan neling. The results show that these layers are partially strained with a pe rpendicular strain e(perpendicular to) = + 0.21%, parallel strain e(paralle l to) = - 0.53% for the InGaN layer and e(perpendicular to) = - 0.16%, e(pa rallel to) = + 0.39% for the AlGaN layer. The signs of e(parallel to) and e (perpendicular to) of AlGaN are opposite to those of InGaN, since the latti ce mismatch between AlGaN and GaN is negative while the lattice mismatch be tween InGaN and GaN is positive. (C) 2000 Elsevier Science S.A. All rights reserved.