Effect of composition on the band gap of strained InxGa1−xN alloys

The band gap of pseudomorphically strained InxGa1−xN alloys has been measured using optical absorption spectroscopy. X-ray diffraction measurements indicated that the in-plane lattice parameter of the InxGa1−xN film equaled that of the underlying GaN layer. For strained InxGa1−xN, it was determined that the band gap shift versus composition is given by dEg/dx=−4.1 eV for x<0.12. Our results contradict some recent reports that InxGa1−xN has a relatively small bowing parameter. Possible reasons for the discrepancies are discussed.