Optical band gap dependence on composition and thickness of InxGa1−xN (0<x<0.25) grown on GaN

Band gap measurements have been carried out in strained and relaxed ${\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ epilayers with $\text{x<0.25.}$ Values of x were determined from x-ray diffraction of relaxed films. The lowest energy absorption threshold, measured by transmittance, was found to occur at the same energy as the peak of the photoluminescence spectrum. Bowing parameters for both strained and relaxed films were determined to be 3.42 and 4.11 eV, respectively. The dependence of the band gap shift, ${\mathrm{\Delta E}}_g,$ on strain is presented.