Spectroscopic ellipsometry characterization of (InGa)N on GaN

Pseudodielectric function spectra of hexagonal (InGa)N epitaxial layers on GaN were obtained by spectroscopic ellipsometry and compared with photoreflection spectra. Composition and thickness of the ${\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ layers grown by metalorganic chemical vapor deposition, were varied between $\text{0.04⩽x⩽0.10}$ and 15–60 nm, respectively. The pseudodielectric function exhibits a clear maximum at the fundamental gap energy of the (InGa)N, which allows a determination of the In content via the composition dependence of that gap energy. The pseudodielectric function spectrum of a complete GaN/(InGa)N/(AlGa)N/GaN light-emitting diode structure shows maxima arising from fundamental gap interband transitions of all constituent layers including the (InGa)N active region.