Band-tail model and temperature-induced blue-shift in photoluminescence spectra of InxGa1-xN grown on sapphire

A band-tail model of inhomogeneously broadened radiative recombination is presented and applied to interpret experimental, data on photoluminescence of various bulk and quantum-well epitaxial InGaN/GaN structures grown by MOCVD. The temperature dependence of the spectral peak position is analyzed according to the model, explaining the anomalous temperature-induced blue spectral shift. Significant differences are observed between epilayers grown on sapphire substrates and on GaN substrates prepared by the sublimation method. No apparent evidence of band tails in homoepitaxial structures indicates their higher crystalline quality.