Evidence of phase separation in cubic InxGa1−xN epitaxial layers by resonant Raman scattering

Phase separation effects in cubic InxGa1−xN epitaxial layers were investigated by means of resonant Raman scattering. The alloy epilayers were grown by radio-frequency plasma-assisted molecular beam epitaxy on GaAs (001) substrates. The results, which are confirmed by x-ray diffractometry (XRD) experiments, show the presence of In-rich inclusions in c-InGaN layers with x=0.19 and 0.33. In-rich inclusions were also found by XRD in a lower In-content layer with x=0.07. Compositional inhomogeneity of about 10% was observed through selective resonances of localized regions in the In-rich separated inclusions. We find that the In-rich separated phase has nearly the same composition in all analyzed samples (x≅0.8).