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

Abstract

The measurement of carrier concentration and mobility of metalorganic chemical vapor deposited GaN thin films on the sapphire substrate by an infrared reflection technique is presented. By fitting with the experimental data, all the parameters of the lattice vibration oscillators and of the plasmon are obtained. From the plasmon frequency and the damping constant, the carrier concentration and the electron mobility are derived. The concentration agrees 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. Mobility lowering are attributed to the increase of scattering for the electrons coupling with the incident photons.