Optical Characterisation of Doped Silicon Wafers Using THz Time-Domain Ellipsometry

Terahertz (THz) time-domain spectroscopic ellipsometry (TDSE) is a powerful, self-referenced, and non-destructive technique for characterizing the electrical and optical properties of a wide range of materials including semiconductors such as doped silicon wafers. By analysing the polarization changes of THz pulses reflected off the silicon samples, TDSE provides detailed information on carrier concentration, mobility, complex conductivity, and complex dielectric response. This method leverages the unique sensitivity of THz radiation to free carrier dynamics in semiconductors, enabling precise measurements of doping levels, conductivity, and hence resistivity at once. Here we show the capability of THz TDSE in distinguishing between different doping types (n-type and p-type) and concentration level, providing critical insights for semiconductor research and fast quality control in silicon wafer production.