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

We report the measurement of carrier concentration and mobility of metalorg anic chemical vapor deposited GaN thin films on the sapphire substrate by a n infrared reflection technique. By fitting with the experimental data we o btain all the parameters of the lattice vibration oscillators and of the pl asmon. From the plasmon frequency and the damping constant we have derived the carrier concentration and the electron mobility. The concentration agre es with the Hall data very well while the mobility values are smaller than that of the Hall measurement by a factor of about 0.5. We attribute such mo bility lowering to the increase of scattering for the electrons coupling wi th the incident photons. (C) 1999 American Institute of Physics. [S0021-897 9(99)01617-5].