Development of ultra-broadband terahertz time-domain ellipsometry

摘要

We developed a reflection type ultra-broad band terahertz time-domain spectroscopic ellipsometry covering the frequency range from 0.5 to 30 THz. The system utilizes two nonlinear optical crystals of GaP and GaSe as terahertz and mid-infrared sources, respectively, and employs a detector based on a photoconductive antenna switch using a low temperature grown GaAs (LT-GaAs) epitaxial layer transferred on Si substrate. By switching the emitter, the measurable frequency range can be easily changed from the 0.5-7.8 THz range to the 7.8-30 THz range without additional optical alignment. We measured the dielectric function of a p-type InAs wafer and the complex optical conductivity of an indium tin oxide (ITO) thin film. The obtained carrier density and the mobility of the ITO thin film show good aggreement with that obtained by the Hall.