Abstract
THz emission mechanism from Indium Nitride (InN) such as drift current, diffusion current caused photocurrent surge and optical rectification effect is investigated by the setup of Time-Domain Spectroscopy in THz range (THz-TDS). We also analyzed the complex dielectric constant and complex conductivity of InN in THz radiation range. In this thesis, photocurrent surge effect is negligible when we consider THz radiation from optically excited Film surfaced InN and pyramids surfaced InN which is grown by metalorganic chemical vaper deposition (MOCVD) method. By combining the Fresnel equation, free carrier absorption and nonlinear effect (Optical rectification), we can well explain pump incident angle-, pump polarization angle- and pump power- dependence of THz electric field. In the experimental results, we found the difference between film surfaced InN and pyramids surfaced InN has the following phenomena. First, the THz radiation from pyramids surfaced InN has higher performance at the low frequency range. Second, in the pump polarization dependence, the film surfaced InN has the lowest THz generation efficiency with polarization angle at 900 (TE-wave) but the trend of pyramids surfaced InN is opposite. Third, in the pump power dependence, the THz emission from pyramids surfaced InN is easier to get saturated. After optimizing the power of THz radiation from InN surface, we can get the optimal pump incident angle ~ 550, optimal pump polarization angle ~00 (for film sample) ~900 (for pyramids sample) and the transfer efficiency can achieve the signal to noise ratio around 50.