Terahertz carrier dynamics and dielectric properties of GaN epilayers with different carrier concentrations

Using terahertz time-domain spectroscopy, we measured the complex conductivity and dielectric function of n-type GaN with various carrier concentrations on sapphire substrate. The measured complex conductivity, which is due to the free carriers, is well fitted by simple Drude model. The contribution from the lattice vibration to the complex dielectric function increases with the decrease in free carrier concentration. A better fitting of the frequency-dependent complex dielectric response was obtained by considering both of the Drude and the classical damped oscillator model. (C) 2009 American Institute of Physics. [doi:10.1063/1.3212966]