Luminescence and absorption in InGaN epitaxial layers and the van Roosbroeck–Shockley relation

Wurtzite InxGa1−xN (0.01≲x≲0.14) films have been grown by metalorganic vapor phase epitaxy on sapphire substrates. Integrated photoluminescence intensity and line shapes have been studied as functions of temperature and alloy composition x. We compare the “effective” InGaN band gap energy assessed by photothermal deflection spectroscopy with a “mean” band gap energy calculated from room temperature photoluminescence spectra utilizing the van Roosbroeck–Shockley relation and assuming a Gaussian energy dependence of the subband gap absorption coefficient. The Stokes’ shift between band gap energy and 300 K photoluminescence peak is explained by this model.