| Resumo: | The effect of strain on the compositional and optical properties of a set of epitaxial single layers of InxGa12xN was studied. Indium content was measured free from the effects of strain by Rutherford backscattering spectrometry. Accurate knowledge of the In mole fraction, combined with x-ray diffraction measurements, allows perpendicular strain (e zz) to be evaluated. Optical band gaps were determined by absorption spectroscopy and corrected for strain. Following this approach, the strain free dependence of the optical band gap in InxGa12xN alloys was determined for x<0.25. Our results indicate an ‘‘anomalous,’’ linear, dependence of the energy gap on the In content, at room temperature: Eg(x)53.39– 3.57x eV. Extension of this behavior to higher concentrations is discussed on the basis of reported results
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