Temperature dependence of the optical properties of AlInN

Measurements of the temperature dependence of transmission have been carried out on AlInN thin films grown by reactive radio-frequency magnetron sputtering on (0001) sapphire substrates. By following a detailed procedure developed for analyzing the transmission spectra, we obtained more reliable data for the effects of temperature on the optical properties of AlInN. Two sets of temperature and photon-energy dependence of empirical formulas have been established for the absorption coefficient, bandgap, Urbach bandtail, and refractive index, which not only unify various experimental data reported in the literature but also provide a database of the optical properties of AlInN based on experimental results. It was found that the shift in the temperature dependence of the bandgap increases with the Al content and that the Urbach bandtail parameter is closely related to the structural characteristics of the AlInN thin films. These optical properties provide an experimental basis for further theoretical investigation and the design of AlInN-based devices.