Ion-channeling studies of cubic GaN and InxGa1-xN on GaAs substrates

Rutherford backscattering (RBS), dechanneling and angular scan measurements with 2 MeV He-4(+) ions have been performed to investigate molecular-beam epitaxially (MBE)-grown cubic GaN and InxGa1-xN layers on semi-insulating GaAs (001) substrates. The thickness of the epitaxial layers and the In concentration were determined by RES, the crystalline quality by ion-channeling measurements. The predominant defect type was determined to be dislocations. Due to the lack of a perfect crystal we used an approximation for the minimum yield given by Lindhard and Barrett to normalize the measured minimum yields. The determined concentration of dislocations varies between 6 x 10(10) and 2.2 x 10(11) cm(-2). Furthermore, a mosaic spread of crystallites was detected with angular scan measurements. Both the concentration of dislocations and the distribution of crystallite orientations do not show a significant dependence on the In concentration. (C) 1999 Elsevier Science B.V. All rights reserved.