Strain relaxation mechanism of InGaN thin film grown on m-GaN

InGaN films were grown on off-axis m -GaN substrates by metalorganic vapor phase epitaxy. Rocking curves of X-ray diffraction around c-axis revealed that In_x Ga_1-xN films incline to ±a₁ direction when the film thickness and In composition x exceed a certain critical condition. The strain relaxation mechanism by introducing a₂ and -a₃ misfit dislocations at the interface is deduced from the ±a₁ inclination. The rocking curves are reproduced fairly well by the scattering-intensity calculations according to the atomic displacements caused by an array of the misfit dislocations, whose intervals are given by an asymmetric distribution function.