Carrier concentration and mobility in GaN epilayers on sapphire substrate studied by infrared reflection spectroscopy

The measurement of carrier concentration and mobility of metalorganic chemical vapor deposited GaN thin films on the sapphire substrate by an infrared reflection method is described. Parameters of the lattice vibration oscillators and of the plasmon were obtained by fitting with the experimental data. A comparison of data from the Hall measurement reveals the good accuracy for the carrier concentration obtained from IR measurement while the infrared carrier mobility is lower than that from the Hall measurement by a factor of about 0.5.