Strain relaxation of AlxGa1-xN epitaxial layers on GaN and SiC substrates

In this article, we present a study on strain relaxation in AlxGa1-xN layer s grown by molecular beam epitaxy (MBE) and metalorganic chemical vapor dep osition (MOCVD) on the bulk GaN single crystals (lattice mismatch of -2.5% to 0%) and on the 6H SiC crystals (lattice mismatch of 1% to 3.5%). Both sy nchrotron and X-ray tube radiation were used for diffractometry (double- an d triple-axis) and reflectivity measurements. We found that the layers on S iC relax easier than those grown on GaN. The results show that growth of Al xGa1-xN layers on GaN substrates may provide a method for producing fully s trained (i.e., unrelaxed) blue-laser structures. (C) 1999 Elsevier Science S.A. All rights reserved.