Growth pressure dependence of residual strain and threading dislocations in the GaN layer

We investigated the generation of threading dislocations (TDs) and the relaxation of the compressive strain in the GaN/sapphire (0001) grown by metalorganic chemical vapor deposition. With decreasing the growth pressure, the a-axis lattice constant of GaN film and the width of the (002) and the (101) rocking curve increases. This indicates that the density of TDs in GaN epilayers increases with the lattice constant a of GaN film. The fact that the width of the (101) rocking curves increases much more than that of the (002) rocking curve indicates that the residual strain in GaN on sapphire reduces mainly by generating the edge-type TDs. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)