||Key word：Terahertz, GaN, refractive, conductvity, Drude model, carrier density, mobility|
We use the PC-antenna to generate the THz and study the optical properties of nonpolar GaN using Terahertz Time Domain system. In this thesis, because of the nonpolar GaN, we investigate the THz intensity data and wave shape when changing the angel between terahertz polarization and c-axis. At the same sample, we use the THz to pass the different position and research the THz intensity data and wave shape, and then we calculate the refractive index and conductivity. We investigate the factors which affect the wave shapes. The differences between samples are N/Ga ratio and N power. Using the signal of substrate and sample, we calculate the complex refractive index and conductivity. We use Drude model to obtain the parameters of carrier density and mobility by fitting experiment data. Finally, the results are compared with the previous papers. The refractive index and conductivity are near the values in previous papers.