Nitrogen incorporation into strained (In, Ga) (As, N) thin films grown on (100), (511), (411), (311), and (111) GaAs substrates studied by photoreflectance spectroscopy and high-resolution x-ray diffraction
We have used photoreflectance (PR) and high-resolution x-ray diffraction (HRXRD) measurements to assess the composition of InxGa1-xAs1-yNy thin films (x∼20%, y∼3%) grown by molecular beam epitaxy on GaAs substrates with different surface orientations. The aim of our work is to investigate the effect of substrate orientation on the incorporation of N and In into the films. Whereas in principle the composition of the InxGa1-xAs1-yNy films cannot be characterized by HRXRD alone because lattice spacings depend on both x and y, we show that a combined analysis of the PR and HRXRD data allows us to determine the sample composition. Our data analysis suggests that the incorporation of N in (In, Ga)(As, N) exhibits some dependence on substrate orientation, although not as strong as previously observed in Ga(As, N). We determine shear deformation potentials for our samples that are sizably different than those obtained by linearly interpolating from the values of the pure binary compounds, which has already been observed in Ga(As, N) and contradicts the currently accepted idea that only the conduction band of dilute nitrides is perturbed by N.