Characterization of the electrical properties and thickness of thin epitaxial semiconductor layers by THz reflection spectroscopy

We have measured the dielectric properties and thickness of thin semiconduc tor epitaxy layers by the reflection of THz radiation from the surface of a two-layered semiconductor wafer. When reflecting from two interfaces the e lectromagnetic pulse has a destructive interference at a specific wavelengt h dependent on the thickness of the outer layer and its dielectric function . Near that frequency the reflection coefficient has a significant drop. By extending the incident pulse spectrum to include this interference frequen cy, a measurement of the thickness can be obtained together with a direct m easurement of the carrier number density. By this technique epitaxy layers of thickness down to 15 mum are characterized. (C) 2001 American Institute of Physics.