Accurate characterization of doped semiconductors with terahertz spectroscopy

The Characterization of the material optical properties with terahertz time domain spectroscopy is usually formulated as an optimization problem with an objective function representing the deviation of the theoretical scattering parameters from the measured ones. Both the magnitude and phase of the scattering parameters are utilized. For samples of unknown thickness, false estimation of the thickness limits the accuracy of the results. We propose an accurate optimization technique that predicts the actual thickness by solving only one optimization problem. Our technique is also efficient compared to other techniques that solve N expensive optimization problems. Dispersive dielectric models are embedded for accurate parameter extraction of a sample with unknown thickness. For doped semiconductors we utilize the surface Plasmon Polariton behavior for accurately estimating the doping level of semiconductor sample of unknown characteristics. By estimating the frequency at which the negative permittivity exists, we can accurately estimate the doping level of the semiconductor. Our technique has been demonstrated to be efficient and accurate through a number of examples.