Impurity scattering induced excitonic polariton damping and its influence on the reflectance spectra of GaN epilayers

The low-temperature reflectance spectra of a number of GaN epilayers with various impurity/defect concentrations and Hall mobility are systematically investigated in this paper. The interacting excitonic polariton model, considering both excitons A and B, is employed to reproduce the measured reflectance spectra of the GaN films, leading to the determination of the damping coefficients of the propagating polaritons in the films. It is shown that the impurity scattering plays a dominant role in the damping of the excitonic polaritons in the GaN epilayers with higher impurity concentrations at low temperatures, which is additionally supported by the photoluminescence and Hall measurements.