Terahertz spectroscopy of optically thick multilayered semiconductor structures

Abstract

Using freely propagating terahertz radiation, we have measured the complex dielectric constant of optically thick layered materials from 0.2 THz (6.6 cm−1) to 6 THz (200 cm−1). Transmission measurements of a CdTe–adhesive–Si structure have been successfully fitted to a theoretical model over the measurement range. The accuracy of the theoretical fit shows that the technique of time-domain spectroscopy offers advantages over other spectroscopic methods in the extreme far infrared below 200 cm−1. The signal-to-noise capability of our terahertz-spectroscopy technique permits accurate measurement of power transmission coefficients less than 0.001 (absorption coefficients >5000 cm−1) and index variations larger than λ(dn/dλ) > 44, as demonstrated by the accurate fit of our data through the Reststrahlen region of CdTe.