Temperature dependence of the energies and broadening parameters of the interband excitonic transitions in wurtzite GaN

We have performed contactless electroreflectance studies of the interband excitonic transitions of GaN thin films in the temperature range between 15 and 475 K. The parameters that describe the temperature dependence of the interband transition energies and the broadening function, Gamma(T), of the excitonic features are evaluated. The exciton-longitudinal optical phonon coupling constant, which is determined from an analysis of Gamma(T), is considerably larger than that for a number of the cubic III-V semiconductors.