TERAHERTZ SPECTROSCOPY OF OPTICALLY THICK MULTILAYERED SEMICONDUCTOR STRUCTURES

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 lambda(dn/d lambda) > 44, as demonstrated by the accurate fit of our data through the Reststrahlen region of CdTe.